CA2566367A1 - Filter cake degradation compositions and associated methods - Google Patents
Filter cake degradation compositions and associated methods Download PDFInfo
- Publication number
- CA2566367A1 CA2566367A1 CA002566367A CA2566367A CA2566367A1 CA 2566367 A1 CA2566367 A1 CA 2566367A1 CA 002566367 A CA002566367 A CA 002566367A CA 2566367 A CA2566367 A CA 2566367A CA 2566367 A1 CA2566367 A1 CA 2566367A1
- Authority
- CA
- Canada
- Prior art keywords
- filter cake
- composition
- fluid
- enzyme
- precipitation
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 239000012065 filter cake Substances 0.000 title claims abstract description 119
- 239000000203 mixture Substances 0.000 title claims abstract description 77
- 230000015556 catabolic process Effects 0.000 title claims abstract description 56
- 238000006731 degradation reaction Methods 0.000 title claims abstract description 56
- 238000000034 method Methods 0.000 title claims abstract description 46
- 108090000790 Enzymes Proteins 0.000 claims abstract description 101
- 102000004190 Enzymes Human genes 0.000 claims abstract description 101
- 238000001556 precipitation Methods 0.000 claims abstract description 79
- 208000005156 Dehydration Diseases 0.000 claims abstract description 37
- 239000000654 additive Substances 0.000 claims abstract description 36
- 230000000996 additive effect Effects 0.000 claims abstract description 32
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 32
- 230000000593 degrading effect Effects 0.000 claims abstract description 19
- 239000012530 fluid Substances 0.000 claims description 42
- 239000003795 chemical substances by application Substances 0.000 claims description 26
- HPALAKNZSZLMCH-UHFFFAOYSA-M sodium;chloride;hydrate Chemical class O.[Na+].[Cl-] HPALAKNZSZLMCH-UHFFFAOYSA-M 0.000 claims description 18
- 150000003839 salts Chemical class 0.000 claims description 13
- 239000002253 acid Substances 0.000 claims description 10
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 9
- 239000004382 Amylase Substances 0.000 claims description 6
- 238000005553 drilling Methods 0.000 claims description 6
- URAYPUMNDPQOKB-UHFFFAOYSA-N triacetin Chemical compound CC(=O)OCC(OC(C)=O)COC(C)=O URAYPUMNDPQOKB-UHFFFAOYSA-N 0.000 claims description 6
- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 5
- 150000007524 organic acids Chemical class 0.000 claims description 5
- 238000012856 packing Methods 0.000 claims description 5
- 239000002738 chelating agent Substances 0.000 claims description 4
- -1 microbiocides Substances 0.000 claims description 4
- 239000002243 precursor Substances 0.000 claims description 4
- 229920001503 Glucan Polymers 0.000 claims description 3
- UXDDRFCJKNROTO-UHFFFAOYSA-N Glycerol 1,2-diacetate Chemical compound CC(=O)OCC(CO)OC(C)=O UXDDRFCJKNROTO-UHFFFAOYSA-N 0.000 claims description 3
- 108010031186 Glycoside Hydrolases Proteins 0.000 claims description 3
- 102000005744 Glycoside Hydrolases Human genes 0.000 claims description 3
- 108090000604 Hydrolases Proteins 0.000 claims description 3
- 102000004157 Hydrolases Human genes 0.000 claims description 3
- 230000000844 anti-bacterial effect Effects 0.000 claims description 3
- 239000003899 bactericide agent Substances 0.000 claims description 3
- 239000008139 complexing agent Substances 0.000 claims description 3
- 239000004088 foaming agent Substances 0.000 claims description 3
- 235000013773 glyceryl triacetate Nutrition 0.000 claims description 3
- 230000003641 microbiacidal effect Effects 0.000 claims description 3
- 239000004094 surface-active agent Substances 0.000 claims description 3
- 229960002622 triacetin Drugs 0.000 claims description 3
- IKCQWKJZLSDDSS-UHFFFAOYSA-N 2-formyloxyethyl formate Chemical compound O=COCCOC=O IKCQWKJZLSDDSS-UHFFFAOYSA-N 0.000 claims 2
- 238000005755 formation reaction Methods 0.000 abstract description 31
- 239000000243 solution Substances 0.000 description 27
- 238000012360 testing method Methods 0.000 description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 21
- 229920002472 Starch Polymers 0.000 description 19
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 18
- 230000000694 effects Effects 0.000 description 18
- 230000035699 permeability Effects 0.000 description 18
- 235000019698 starch Nutrition 0.000 description 18
- 239000008107 starch Substances 0.000 description 17
- 239000012267 brine Substances 0.000 description 16
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 11
- 239000011148 porous material Substances 0.000 description 10
- ZCYVEMRRCGMTRW-UHFFFAOYSA-N 7553-56-2 Chemical compound [I] ZCYVEMRRCGMTRW-UHFFFAOYSA-N 0.000 description 8
- 229910052740 iodine Inorganic materials 0.000 description 8
- 239000011630 iodine Substances 0.000 description 8
- 239000011780 sodium chloride Substances 0.000 description 8
- 108010075550 termamyl Proteins 0.000 description 8
- 230000008901 benefit Effects 0.000 description 7
- 239000002244 precipitate Substances 0.000 description 7
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 6
- 239000007787 solid Substances 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- 230000036619 pore blockages Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- UXVMQQNJUSDDNG-UHFFFAOYSA-L Calcium chloride Chemical compound [Cl-].[Cl-].[Ca+2] UXVMQQNJUSDDNG-UHFFFAOYSA-L 0.000 description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000012141 concentrate Substances 0.000 description 3
- 239000013505 freshwater Substances 0.000 description 3
- 238000002347 injection Methods 0.000 description 3
- 239000007924 injection Substances 0.000 description 3
- 239000007788 liquid Substances 0.000 description 3
- 235000005985 organic acids Nutrition 0.000 description 3
- 238000010998 test method Methods 0.000 description 3
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 230000001427 coherent effect Effects 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 239000000839 emulsion Substances 0.000 description 2
- 230000002255 enzymatic effect Effects 0.000 description 2
- 230000005484 gravity Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000007062 hydrolysis Effects 0.000 description 2
- 238000006460 hydrolysis reaction Methods 0.000 description 2
- 239000012528 membrane Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- FJWLWIRHZOHPIY-UHFFFAOYSA-N potassium;hydroiodide Chemical compound [K].I FJWLWIRHZOHPIY-UHFFFAOYSA-N 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- OVSKIKFHRZPJSS-UHFFFAOYSA-N 2,4-D Chemical compound OC(=O)COC1=CC=C(Cl)C=C1Cl OVSKIKFHRZPJSS-UHFFFAOYSA-N 0.000 description 1
- JGJDTAFZUXGTQS-UHFFFAOYSA-N 2-(2-formyloxyethoxy)ethyl formate Chemical compound O=COCCOCCOC=O JGJDTAFZUXGTQS-UHFFFAOYSA-N 0.000 description 1
- GJCOSYZMQJWQCA-UHFFFAOYSA-N 9H-xanthene Chemical compound C1=CC=C2CC3=CC=CC=C3OC2=C1 GJCOSYZMQJWQCA-UHFFFAOYSA-N 0.000 description 1
- 229920000945 Amylopectin Polymers 0.000 description 1
- 229920000856 Amylose Polymers 0.000 description 1
- 235000019890 Amylum Nutrition 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 150000001450 anions Chemical class 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 230000004071 biological effect Effects 0.000 description 1
- 238000009835 boiling Methods 0.000 description 1
- 239000000872 buffer Substances 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 239000001110 calcium chloride Substances 0.000 description 1
- 229910001628 calcium chloride Inorganic materials 0.000 description 1
- 235000011148 calcium chloride Nutrition 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 238000004925 denaturation Methods 0.000 description 1
- 230000036425 denaturation Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001952 enzyme assay Methods 0.000 description 1
- 235000013305 food Nutrition 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000004676 glycans Chemical class 0.000 description 1
- 230000003301 hydrolyzing effect Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 230000002779 inactivation Effects 0.000 description 1
- 230000002427 irreversible effect Effects 0.000 description 1
- 230000002045 lasting effect Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000000178 monomer Substances 0.000 description 1
- 229910000402 monopotassium phosphate Inorganic materials 0.000 description 1
- 125000001483 monosaccharide substituent group Chemical group 0.000 description 1
- 229920000642 polymer Polymers 0.000 description 1
- 229920001282 polysaccharide Polymers 0.000 description 1
- 239000005017 polysaccharide Substances 0.000 description 1
- 239000011541 reaction mixture Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000012085 test solution Substances 0.000 description 1
- 239000012130 whole-cell lysate Substances 0.000 description 1
- 229920001285 xanthan gum Polymers 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/52—Compositions for preventing, limiting or eliminating depositions, e.g. for cleaning
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/02—Well-drilling compositions
- C09K8/04—Aqueous well-drilling compositions
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
- C09K8/60—Compositions for stimulating production by acting on the underground formation
- C09K8/62—Compositions for forming crevices or fractures
- C09K8/66—Compositions based on water or polar solvents
- C09K8/68—Compositions based on water or polar solvents containing organic compounds
-
- C—CHEMISTRY; METALLURGY
- C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
- C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
- C09K2208/00—Aspects relating to compositions of drilling or well treatment fluids
- C09K2208/18—Bridging agents, i.e. particles for temporarily filling the pores of a formation; Graded salts
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Enzymes And Modification Thereof (AREA)
- Processing Of Solid Wastes (AREA)
- Filtering Materials (AREA)
Abstract
The present invention relates to removal of filter cakes in subterranean formations. More particularly, the present invention provides filter cake degradation compositions and methods of degrading filter cakes. The present invention provides methods of degradation a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising: contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component;
and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake. The present invention also provides filter cake degradation compositions comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake. The present invention also provides filter cake degradation compositions comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
Description
FILTER CAKE DEGRADATION COMPOSITIONS AND ASSOCIATED METHODS
BACKGROiTND
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In general, filter cakes are residues deposited on the walls of subterranean well bores as a result of various subterranean operations such as drilling, completion, and work-over operations. Such filter cakes are often tough, dense, substantially water insoluble, and usually capable of reducing the permeability of a surface on which they have formed. In general, filter cakes may prevent a fluid used in subterranean operations from being lost into the formation. Filter cakes also may prevent solids from entering the pores of the formation, thus preventing damage to the conductivity of the formation. Eventually, for a subterranean formation or portion of a subterranean formation to produce, the filter cake is often removed from the walls of the well bore.
Filter cakes are desirable, at least temporarily, in subterranean operations for several reasons. For instance, a filter cake may be used in a fluid-loss control operation. In such an operation, a filter cake may act to localize the flow of a servicing fluid and minimize undesirable fluid loss into the formation matrix. This is an important function of a filter cake because if too much fluid is lost the conductivity or permeability of the formation may be damaged. A filter cake also may add strength and stability to the formation surfaces on which the filter cake forms. For example, one type of drilling fluid, commonly referred to as a "drill-in fluid," may be used to drill a well bore while minimizing the damage to the permeability of the producing zone. Drill-in fluids may include a fluid-loss additive (e.g., starch) and a bridging agent to block fluid entry into formation pores (e.g., calcium carbonate). Typically, a drill-in fluid forms a filter cake on the walls of the well bore that prevents or reduces fluid loss during drilling, and upon completion of the drilling operation, stabilizes the well bore during subsequent completion operations. The filter cake may be beneficial to other well bore operations, for example, hydraulic fracturing, and gravel packing.
In general, filter cakes include bridging agents that block formation pores and fluid-loss additives that, inter alia, bind the bridging agents to the well bore and further inhibit fluids from entering the formation. The fluid-loss additive component of a filter cake generally should form a coherent membrane so that the filter cake maintains its integrity.
Although useful, the coherent membrane oftentimes can make it difficult to remove the filter cake from the face of the formation when it is desirable to do so. Typical fluid-loss additives include starches (e.g., xanthan, amylose, and/or amylopectin) and typical bridging agents include salts (e.g., calcium carbonate andlor sodium chloride). Starch is a polysaccharide that comprises monosaccharide units linked by glycosidic bonds, e.g., a-1,4 glucosidic bonds and a-1,6 glucosidic bonds. In addition, filter cakes commonly include drilled solids, weighting agents, and viscosifying polymers that have been used to viscosify fluids used in some subterranean operations. Although some fluids used in well bore operations do not form filter cakes, these fluids may create conditions analogous to those found within filter cakes, e.g., by plugging formation pores. Therefore, the term "filter cake" when used herein also refers to these conditions.
Although desirable for a certain amount of time or during a certain operation, to produce the desirable fluids from the formation, at some point the filter cake generally may need to be removed. Accordingly, some subterranean fluids may comprise an additional component that is capable of degrading the fluid-loss additive of the filter cake. Such components include acids, enzymes, and oxidizers.
Although enzymes may be useful for degrading the fluid-loss additive component of a filter cake, enzymes may be unstable at certain elevated temperatures like those frequently encountered in some subterranean operations. At sufficiently high temperatures, enzymes can undergo irreversible denaturation (i. e., conformational alteration entailing a loss of biological activity). Enzymes also may be intolerant to the salt concentrations commonly found in well bores. In addition, the combination of salt concentration and temperature may cause enzymes to coagulate and precipitate as shown in Figure 1. Typical enzymes often produce this damaging precipitate at the enzyme concentrations, salinity, and temperatures needed to effectively remove the filter cake. This sort of precipitation is particularly problematic with filter cakes because the gelatinous precipitate may clog formation pore throats, which can decrease the permeability of the formation and ultimately reduce production from the formation.
SUMMARY
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In one embodiment, the present invention provides a method of degrading a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising:
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component; and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
In one embodiment, the present invention provides a filter cake degradation composition comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the embodiments that follows.
BRIEF DESCRIPTION OF THE FIGURES
A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings. The patent or application file contains at least one figure executed in color. Copies of this patent or patent application publication with color figures) will be provided by the Office upon request and payment of the necessary fee.
FIGURE 1 illustrates an embodiment of a precipitated enzyme.
FIGURE 2 illustrates a graph of the change in permeability possible if using certain methods of the present invention.
FIGURE 3 illustrates a graph of the change in permeability with a comparative test sample.
While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown in the figures and are herein described. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In general, the present invention provides filter cake degradation compositions and methods of degrading the fluid-loss additive components of filter cakes. In certain embodiments, the methods of the present invention degrade at least a portion of the fluid-loss additive component of a filter cake in a subterranean formation. The term "degrade," as used herein, refers to at least a partial degradation of the fluid-loss additive component of the filter cake, e.g., by hydrolysis. In certain embodiments, the methods of the present invention also may comprise degradation of bridging agents from a filter cake in a subterranean formation.
In certain exemplary embodiments, the methods of the present invention compromise the integrity of the filter cake to a degree at least sufficient to allow any pressure differential between formation fluids and the well bore to induce flow from the formation.
The filter cake degradation compositions of the present invention comprise precipitation resistant enzymes. Suitable precipitation resistant enzymes should be capable of hydrolyzing starch and should be resistant to precipitation under conditions sometimes found in subterranean well bores, e.g., elevated temperatures. Precipitation resistant enzymes suitable for use in the methods of the present invention generally catalyze the hydrolysis of the fluid-loss additive component of a filter cake, e.g., by chemically removing any of the linkages between the monomers of a starch molecule. In certain embodiments, the precipitation resistant enzymes include hydrolase enzymes of enzyme classification (E.C.) number 3.2, according to the Recommendations of the Nomenclature Committee of the International Union of Biochemistry on the Nomenclature and Classification of Enzymes. In certain embodiments of the present invention, glycosidase enzymes (E.C. 3.2.1) may be used.
In certain exemplary embodiments, the precipitation resistant enzymes include a-amylase enzymes (E.C. 3.2.1.1), J3-amylase enzymes (E.C. 3.2.1.2), glucan 1,4-a-glucosidase enzymes (E.C. 3.2.1.3), or combinations thereof. Examples of suitable precipitation resistant enzymes that are commercially available, include, but are not limited to, Liquezyme~ X
(Novozymes A/S of Bagsaerd, Denmark) and Optisize HT (Genencor International, Palo Alto, California). The precipitation resistant enzymes of the present invention should resist precipitation in temperatures ranging from about 10°C (50°F) to about 150°C (327°F) and pHs ranging from about 2 to about 11. In addition, the precipitation resistant enzymes should resist precipitation at salt concentrations of up to at least about 2.5 molar;
and may resist precipitation at salt concentrations up to at least 5 molar. The term "salt"
refers to salts of monovalent cations and anions. A person of ordinary skill in the art, with the benefit of this disclosure, will recognize how the valency of the salt will affect molarity and ionic strength.
In certain exemplary embodiments, the precipitation resistant enzymes of the filter cake degradation compositions of the present invention are capable of degrading starch without precipitation in saturated brines (e.g., sodium chloride) at a temperature up to about at least 90°C.
The precipitation resistant enzymes may be present in the compositions of the present invention in an amount sufficient to degrade at least a desired portion of a filter cake. In some exemplary embodiments, the precipitation resistant enzymes may be present in an amount in the range of from about 10 kilo novo units (~ to about 150 KNU. One KNU
is defined as the quantity of enzyme which degrades 4.87 grams of starch (Merck, soluble amylum, Erg. B6, Batch No.: 6380528), at pH 5.6, and at a temperature of 37°C.
The filter cake degradation compositions of the present invention may be used in any form including a solid, a liquid, an emulsion, or a combination thereof. The precipitation resistant enzymes in the compositions of the present invention also may be used as, or with, encapsulated particles, particles that are impregnated on a carrier, solids, liquids, emulsions, or mixtures thereof. The filter cake degradation compositions may be designed to have a delayed effect on a portion of a filter cake, for instance, when the process will involve a long pump time and consequently it is necessary to delay the enzymatic action of the precipitation resistant enzymes. Examples of delayed forms include encapsulated embodiments and solid embodiments. If immediate enzymatic action is desired, a liquid form may be preferable, e.g., in an aqueous solution. In certain embodiments of the present invention, the precipitation resistant enzymes in the filter cake degradation compositions may be spray-dried, freeze-dried, or the like. In certain embodiments, cells capable of producing the precipitation resistant enzymes that have been lyophilized may provide the precipitation resistant enzymes. In certain embodiments, the precipitation resistant enzymes of the present invention may be provided, inter alia, in a purified form, in a partially purified form, as whole cells, as whole cell lysates, or any combination thereof. One of ordinary skill in the art with the benefit of this disclosure will be able to determine the appropriate form for a given application.
In certain embodiments of the present invention, the filter cake degradation compositions of the present invention may comprise other additives, including, but not limited to, glycerol, bactericides, microbiocides, surfactants, chelating agents, foaming agents, and the like. With the benefit of this disclosure, one of ordinary skill in the art will recognize when such additives may be useful in a given application.
In certain embodiments, the filter cake degradation compositions of the present invention may comprise agents designed to remove or dissolve bridging agents in a filter cake. Examples of such agents include, but are not limited to, complexing agents (e.g., salts of ethylenediaminetetraacetic acid, a salt thereof, or other chelating agents), organic acids, or acid precursors (e.g., diethylene glycol diformate, glycerol diacetate, and glycerol triacetate).
Some organic acids of this type may react with the bridging agents (e.g., acid-soluble bridging agents like calcium carbonate) and, in the presence of a conjugate base, may form a buffered system with a pH of about 4 or greater. Similarly, in the case of the acid precursors, which can produce organic acids in situ, since the acid is produced very slowly, the pH may stay in a range where precipitation resistant enzymes are active (e.g., in the range of from about 4 to about S.5).
In certain embodiments, the filter cake degradation compositions of the present invention may be used in conjunction with agents designed at least to partially remove a bridging agent component of the filter cake. For example, a strong acid, such as hydrochloric acid or hydrofluoric acid, may be used in a two-stage, sequential process.
Such a process may involve treatment of the filter cake with a filter cake degradation composition of the present invention and then treatment of the filter cake with the strong acid.
Thus, inactivation of the precipitation resistant enzyme at the resultant low pHs created by a strong acid may be avoided. In embodiments where the bridging agent is water soluble, e.g., a salt, the bridging agent may be removed with fresh water or water undersaturated with respect to the water-soluble bridging agent.
The filter cake degradation compositions of the present invention may be contacted with a filter cake to degrade at least a portion of the filter cake using any method. For instance, the filter cake degradation compositions may be incorporated in a clean-up fluid.
The term "clean-up fluid" refers to any fluid introduced into a subterranean formation for the purposes of facilitating the degradation of a filter cake. In certain embodiments, the filter cake degradation compositions of the present invention are internally incorporated in a servicing fluid, externally applied to a servicing fluid, or any combination thereof. The term "servicing fluid" refers to any fluid suitable for use in subterranean operations. Examples of servicing fluids, include, but are not limited to, drill-in fluids, fracturing fluids, and gravel packing fluids. For applications such as, e.g., fracturing and gravel packing, the precipitation resistant enzyme may be incorporated internally in the fluid or onto a particulate used in the process. In one embodiment, the filter cake degradation compositions of the present invention may be pumped to the location of the treatment zone at a rate sufficient to introduce sufficient precipitation resistant enzymes to at least partially degrade the fluid-loss additive component in a portion of a filter cake. To achieve certain beneficial effects of the present invention, the filter cake degradation compositions of the present invention may be shut in the formation for a time sufficient to at least partially degrade the fluid-loss additive component of a filter cake. This shut-in-time may be affected by the activity and/or concentration of the precipitation resistant enzyme and/or by the environmental conditions of the well bore, such as temperature, pH, and the like. If necessary, the pH of the treatment fluid may be adjusted through the use of acids, bases, or buffers. One of ordinary skill in the art with the benefit of this disclosure will recognize the conditions that might affect the requisite shut-in time needed to achieve a desired result.
An example of a method of the present invention is a method of degrading a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising:
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component; and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
An example of a composition of the present invention is a filter cake degradation composition comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
To facilitate a better understanding of the present invention, the following examples of specific embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.
EXAMPLES
Methods and Procedures In general, the test method for assessing enzyme activity generally involved addition of a known amount of an enzyme concentrate to a solution containing a standard amount of a standard starch in solution. The course of the resulting reaction is then followed by testing for the presence of starch with an iodine test solution. The starch was judged to have been consumed when coloration due to a complex formed between starch and iodine was no longer observed as compared to a colored glass standard. Reaction conditions were controlled to a pH of 5, a temperature of 37°C, and included a trace concentration of calcium (0.0003 molar).
The enzyme assay was performed as follows. 5 milliliters iodine solution B was pipetted into at least 5 test tubes per sample, which were placed in a water bath at 40°C. 20 milliliters starch solution was pipetted into a large test tube. The pH was checked to ensure a pH of 5. 5 milliliters of calcium chloride solution was then added to the test tube. The test tube was warmed to 40°C before adding an enzyme solution. An amount of enzyme solution was gradually added to the mixture and mixed. The reaction was allowed to proceed at 40°C.
At suitable intervals, 1 milliliter of the reaction mixture was removed and added to the test tubes containing 5 milliliters iodine solution B. Each tube was shaken briefly and color checked to determine the presence of starch.
Iodine solution A was made as follows. 22 grams of potassium iodine were dissolved in approximately 60 milliliters of demineralised water in a 500 milliliter volumetric flask. 11 grams of iodine were dissolved in the flask, which was then filled to the mark with demineralised water.
Iodine solution B was made as follows. 80 grams of potassium iodine was weighed out and added to a 2,000 milliliter volumetric flask. Then 8 milliliters of iodine solution A
was added and the flask was filled to the mark with demineralised water.
A stock salt solution was made as follows. 9.36 grams NaCI, 69 grams KH2P04 and 4.8 grams Na2HPOa. were weighed out and poured into a 1,000 milliliter volumetric flask, which was then filled to the mark with demineralized water. The pH of the solution was checked, and when necessary, adjusted using HCl or NaOH as appropriate to reach a pH of 5.2.
A starch solution was made as follows. An equivalent amount of 6.95 grams of dry matter content starch was added to demineralized water to a volume of 1,000 milliliters. The percentage dry matter content (DM %) of the starch was analyzed at 105°C (water determination at 105°C). The starch was suspended in 100 milliliters of demineralised water.
The starch solution was then transferred quantitatively while stirring to a beaker containing 200 milliliters boiling demineralised water. The solution was boiled for approximately 30 seconds. The solution was transferred quantitatively to a 1,000 milliliter volumetric flask and cooled to room temperature. The pH was adjusted to 5 with HCl or NaOH as appropriate.
The solution was then made up to the mark with demineralised water.
A calcium chloride solution was prepared as follows. 0.82 grams of CaCl2 in milliliter solution of demineralised water. The pH was then adjusted to 5 with HCl or NaOH
as appropriate.
An enzyme solution was prepared as followed. Enzyme concentrates were dissolved in 100 milliliters deionised water and diluted to the degree necessary to yield a measurable rate (e.g., 5 to 20 minutes) in the test procedures described. The pH was then adjusted to 5 with HCl or NaOH as appropriate.
A test method for precipitation of enzymes based on salinity was conducted as follows. Three test brine solutions were made up by combining fresh water, saturated sodium chloride brine (density 1.2 kilograms per liter) and sodium chloride brine at SO% saturation (density 1.2 kilograms per liter). An enzyme sample at a moderately high concentration and at a low concentration were added to the brine and then heated to 90°C.
The appearance of the solutions was monitored for formation of a precipitate.
Simulation of the tendency of a precipitated enzyme to block porous media was tested by noting the rate of flow through fine filter paper and core flow studies using sandstone of low permeability.
A pore blockage test using fllterpaper was conducted as follows. A steel cell of diameter 5 centimeters and length 150 centimeters was fitted with filter paper having a pore dimension of 2.7 microns. The cell was then filled with 100 milliliters of water, sealed and pressurized to 100 pounds per square inch. The rate of water discharge through the filterpaper was timed in seconds to measure the initial inj ectivity of water through the filterpaper. Enzyme solutions of known concentrations were prepared in brine solutions and either heated and allowed to cool before being tested or tested without prior heating. The cell was then filled with 100 milliliters of the enzyme solutions, sealed, and pressurized to 100 pounds per square inch and the rate of discharge was timed. Next, water was injected through the filter paper as described above to check whether any precipitated enzyme creates a lasting permeability reduction in the filterpaper.
A pore blockage test using a test core was conducted as follows. An enzyme solution was injected into a test core at ambient temperature. The temperature was then raised to 93°C to induce precipitation. The direction of flow into the core was reversed to assess whether any precipitation occurring inside the core affected the permeability of the core.
Specifically, Berea sandstone core plugs were cut, dried, and vacuum saturated in 1.2 specific gravity NaCI brine. A core plug was then mounted in the permeameter and sealed with 500 pounds per square confining pressure. The temperature was increased to 200°F while maintaining the confining pressure. Soltrol~ 170, an isoparaffin solvent commercially available from Chevron Phillips Chemical Company, The Woodlands, Texas, was flowed through the core in the production direction until a stable permeability was measured (Ki).
Ten pore volumes of the 0.5% vlv enzyme in a NaCI brine solution having a specific gravity of 1.2 was flowed through the core in the injection direction. The core was shut in and held for 24 hours at 200°F. Flow of Soltrol~ 170 was resumed in the production direction and continued until the permeability reached a stable value (Kf).
One example of a precipitation resistant enzyme suitable for use in the methods of the present invention, Liquizyme X (commercially available from Novozymes A/S, Bagsaerd, Denmark), was compared to comparative test samples of other enzymes. The comparative test samples were: Termamyl~ 120L (commercially available from Novozymes A/S, Bagsaerd, Denmark); Ban~ (commercially available from Novozymes A/S, Bagsaerd, Denmark); and Nervanase~ BT2 (commercially available from Rhodia Food Ltd, Cheshire, United Kingdom).
The activities per gram of the various enzyme samples tested as quoted by suppliers and estimated according to the method outlined above are summarized in Table 1.
Table 1 Enzyme Activity (KNU/g enzyme concentrate Li uiz a X 200 a rox Termam 1 120L 120 a rox Ban 240L 240 a rox Nervanase BT2 120 a rox The exemplary precipitation resistant enzyme, Liquizyme X, and comparative test samples were tested using the method to determine enzyme precipitation described above.
The precipitation tendencies of the comparative enzyme samples were determined at 20°C
and 95°C and in different concentrations of sodium chloride in the brine carrier. Table 2 shows the thermal precipitation potential of the Liquizyme~ X and comparative test samples.
Table 2 Enzyme Activity Precipitation Precipitation KNU/100 mL observed observed at at 95C
NaCI Molari 5.27M 2.63M 5.27M 2.63M
Li ui a X 40 no no no no Li uiz a X 100 no no no no Termam 1 120L 24 no no es no Termam 1 120L 60 no no es es Ban 240L 48 no no es es Ban 240L 120 no no es es Nervanase BT2 24 no no es es Nervanase BT2 65 no no es es The data in Table 2 exemplify the stability of precipitation resistant enzymes in sodium chloride brine. The comparative samples all produced precipitates.
The exemplary precipitation resistant enzyme, Liquizyme~ X, and comparative test samples were tested using the methods to determine pore blockage using the filter paper method as described above. Table 3 shows the effect of temperature on enzyme precipitation based on injection through filterpaper.
Table 3 Test mixture Observation Injectivity sec./100 mL
At 23C At 90C Initial Final Liquizyme'~ X No effect No effect 8 8 100 KNU/100 mL in water Liquizyme~' X No effect No effect 8 8 100 KNU/100 mL NaCI brine 2.63 Liquizyme~' X No effect No effect 8 9 100 KNU/100 mL NaCI brine (5.27 Nervanase~' BT 2 No effect Cloudy 8 30 60 KNU/100 mL in water Nervanase'e' BT 2 No effect Precipitate9 90 60 I~NU/100 mL in NaCI brine formed 2.63M
Nervanase~' BT 2 No effect Precipitate8 236 60 KNU/100 mL in NaCI brine formed 5.27M
Termamyl~' 120L No effect cloudy 10 50 60 KNU/100 mL in water Termamyl"5' 120L No effect Very cloudy8 74 60 KNU/100 mL in NaCI brine 2.63M
The results in the Table 3 demonstrate that the comparative test samples tend to precipitate when heated. In the case of the Termamyl~ 120L and the Nervanase~
BT2 there is evidence that a precipitate capable of reducing the permeability of filterpaper is produced even when the solvent is fresh water. Additionally, Table 3 demonstrates that the concentration of sodium chloride in the carrier brine has a marked impact on the precipitation tendency. In the case of the Nervanase~ BT2, the precipitation in saturated sodium chloride was severe. Table 3 also shows that the exemplary precipitation resistant enzyme, Liquizyme~ X, is resistant to precipitation over the entire sodium chloride concentration range tested.
The effect of precipitation on return permeability was determined using the pore blockage method using a test core as described above. The Termamyl~ 120L (60 mL) comparative test sample was compared to the exemplary precipitation resistant enzyme Liquizyme~ X (100 KNU/100 mL) in 5.27M sodium chloride brine. Upon heating to 90°C
the Termamyl~ 120L solution developed an obvious precipitate whereas the solution of Liquizyme~ X did not. Termamyl~ 120L demonstrated the potential to be more damaging to permeability than a precipitation resistant enzyme. Figure 2 illustrate the return of permeability when Liquizyme~ ~ is used in an exemplary composition and method of the present invention. Following the injection of 10 pore volumes of the Liquizyme X sample and a static aging period of 24 hours at 90°C only a mean volume of 20 pore volumes of oil produced through the core was required to restore permeability to 100% of the original when flow was recommenced in the production direction. In the case of the Termamyl~
comparative test sample, over the same time span return permeability was only 33% of the original after a flow of more than 400 pore volumes through the core as shown in Figure 3.
Thus, the tests carned out with the sandstone core demonstrate that the precipitation resistant enzymes are less damaging to the core's permeability.
[0001] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. While numerous changes may be made by those skilled in the art, such changes are encompassed within the spirit of this invention as defined by the appended claims.
BACKGROiTND
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In general, filter cakes are residues deposited on the walls of subterranean well bores as a result of various subterranean operations such as drilling, completion, and work-over operations. Such filter cakes are often tough, dense, substantially water insoluble, and usually capable of reducing the permeability of a surface on which they have formed. In general, filter cakes may prevent a fluid used in subterranean operations from being lost into the formation. Filter cakes also may prevent solids from entering the pores of the formation, thus preventing damage to the conductivity of the formation. Eventually, for a subterranean formation or portion of a subterranean formation to produce, the filter cake is often removed from the walls of the well bore.
Filter cakes are desirable, at least temporarily, in subterranean operations for several reasons. For instance, a filter cake may be used in a fluid-loss control operation. In such an operation, a filter cake may act to localize the flow of a servicing fluid and minimize undesirable fluid loss into the formation matrix. This is an important function of a filter cake because if too much fluid is lost the conductivity or permeability of the formation may be damaged. A filter cake also may add strength and stability to the formation surfaces on which the filter cake forms. For example, one type of drilling fluid, commonly referred to as a "drill-in fluid," may be used to drill a well bore while minimizing the damage to the permeability of the producing zone. Drill-in fluids may include a fluid-loss additive (e.g., starch) and a bridging agent to block fluid entry into formation pores (e.g., calcium carbonate). Typically, a drill-in fluid forms a filter cake on the walls of the well bore that prevents or reduces fluid loss during drilling, and upon completion of the drilling operation, stabilizes the well bore during subsequent completion operations. The filter cake may be beneficial to other well bore operations, for example, hydraulic fracturing, and gravel packing.
In general, filter cakes include bridging agents that block formation pores and fluid-loss additives that, inter alia, bind the bridging agents to the well bore and further inhibit fluids from entering the formation. The fluid-loss additive component of a filter cake generally should form a coherent membrane so that the filter cake maintains its integrity.
Although useful, the coherent membrane oftentimes can make it difficult to remove the filter cake from the face of the formation when it is desirable to do so. Typical fluid-loss additives include starches (e.g., xanthan, amylose, and/or amylopectin) and typical bridging agents include salts (e.g., calcium carbonate andlor sodium chloride). Starch is a polysaccharide that comprises monosaccharide units linked by glycosidic bonds, e.g., a-1,4 glucosidic bonds and a-1,6 glucosidic bonds. In addition, filter cakes commonly include drilled solids, weighting agents, and viscosifying polymers that have been used to viscosify fluids used in some subterranean operations. Although some fluids used in well bore operations do not form filter cakes, these fluids may create conditions analogous to those found within filter cakes, e.g., by plugging formation pores. Therefore, the term "filter cake" when used herein also refers to these conditions.
Although desirable for a certain amount of time or during a certain operation, to produce the desirable fluids from the formation, at some point the filter cake generally may need to be removed. Accordingly, some subterranean fluids may comprise an additional component that is capable of degrading the fluid-loss additive of the filter cake. Such components include acids, enzymes, and oxidizers.
Although enzymes may be useful for degrading the fluid-loss additive component of a filter cake, enzymes may be unstable at certain elevated temperatures like those frequently encountered in some subterranean operations. At sufficiently high temperatures, enzymes can undergo irreversible denaturation (i. e., conformational alteration entailing a loss of biological activity). Enzymes also may be intolerant to the salt concentrations commonly found in well bores. In addition, the combination of salt concentration and temperature may cause enzymes to coagulate and precipitate as shown in Figure 1. Typical enzymes often produce this damaging precipitate at the enzyme concentrations, salinity, and temperatures needed to effectively remove the filter cake. This sort of precipitation is particularly problematic with filter cakes because the gelatinous precipitate may clog formation pore throats, which can decrease the permeability of the formation and ultimately reduce production from the formation.
SUMMARY
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In one embodiment, the present invention provides a method of degrading a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising:
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component; and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
In one embodiment, the present invention provides a filter cake degradation composition comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
The features and advantages of the present invention will be readily apparent to those skilled in the art upon a reading of the description of the embodiments that follows.
BRIEF DESCRIPTION OF THE FIGURES
A more complete understanding of the present disclosure and advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying drawings. The patent or application file contains at least one figure executed in color. Copies of this patent or patent application publication with color figures) will be provided by the Office upon request and payment of the necessary fee.
FIGURE 1 illustrates an embodiment of a precipitated enzyme.
FIGURE 2 illustrates a graph of the change in permeability possible if using certain methods of the present invention.
FIGURE 3 illustrates a graph of the change in permeability with a comparative test sample.
While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown in the figures and are herein described. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
The present invention relates to at least the partial degradation of filter cakes in subterranean formations. More particularly the present invention provides filter cake degradation compositions and methods of degrading filter cakes.
In general, the present invention provides filter cake degradation compositions and methods of degrading the fluid-loss additive components of filter cakes. In certain embodiments, the methods of the present invention degrade at least a portion of the fluid-loss additive component of a filter cake in a subterranean formation. The term "degrade," as used herein, refers to at least a partial degradation of the fluid-loss additive component of the filter cake, e.g., by hydrolysis. In certain embodiments, the methods of the present invention also may comprise degradation of bridging agents from a filter cake in a subterranean formation.
In certain exemplary embodiments, the methods of the present invention compromise the integrity of the filter cake to a degree at least sufficient to allow any pressure differential between formation fluids and the well bore to induce flow from the formation.
The filter cake degradation compositions of the present invention comprise precipitation resistant enzymes. Suitable precipitation resistant enzymes should be capable of hydrolyzing starch and should be resistant to precipitation under conditions sometimes found in subterranean well bores, e.g., elevated temperatures. Precipitation resistant enzymes suitable for use in the methods of the present invention generally catalyze the hydrolysis of the fluid-loss additive component of a filter cake, e.g., by chemically removing any of the linkages between the monomers of a starch molecule. In certain embodiments, the precipitation resistant enzymes include hydrolase enzymes of enzyme classification (E.C.) number 3.2, according to the Recommendations of the Nomenclature Committee of the International Union of Biochemistry on the Nomenclature and Classification of Enzymes. In certain embodiments of the present invention, glycosidase enzymes (E.C. 3.2.1) may be used.
In certain exemplary embodiments, the precipitation resistant enzymes include a-amylase enzymes (E.C. 3.2.1.1), J3-amylase enzymes (E.C. 3.2.1.2), glucan 1,4-a-glucosidase enzymes (E.C. 3.2.1.3), or combinations thereof. Examples of suitable precipitation resistant enzymes that are commercially available, include, but are not limited to, Liquezyme~ X
(Novozymes A/S of Bagsaerd, Denmark) and Optisize HT (Genencor International, Palo Alto, California). The precipitation resistant enzymes of the present invention should resist precipitation in temperatures ranging from about 10°C (50°F) to about 150°C (327°F) and pHs ranging from about 2 to about 11. In addition, the precipitation resistant enzymes should resist precipitation at salt concentrations of up to at least about 2.5 molar;
and may resist precipitation at salt concentrations up to at least 5 molar. The term "salt"
refers to salts of monovalent cations and anions. A person of ordinary skill in the art, with the benefit of this disclosure, will recognize how the valency of the salt will affect molarity and ionic strength.
In certain exemplary embodiments, the precipitation resistant enzymes of the filter cake degradation compositions of the present invention are capable of degrading starch without precipitation in saturated brines (e.g., sodium chloride) at a temperature up to about at least 90°C.
The precipitation resistant enzymes may be present in the compositions of the present invention in an amount sufficient to degrade at least a desired portion of a filter cake. In some exemplary embodiments, the precipitation resistant enzymes may be present in an amount in the range of from about 10 kilo novo units (~ to about 150 KNU. One KNU
is defined as the quantity of enzyme which degrades 4.87 grams of starch (Merck, soluble amylum, Erg. B6, Batch No.: 6380528), at pH 5.6, and at a temperature of 37°C.
The filter cake degradation compositions of the present invention may be used in any form including a solid, a liquid, an emulsion, or a combination thereof. The precipitation resistant enzymes in the compositions of the present invention also may be used as, or with, encapsulated particles, particles that are impregnated on a carrier, solids, liquids, emulsions, or mixtures thereof. The filter cake degradation compositions may be designed to have a delayed effect on a portion of a filter cake, for instance, when the process will involve a long pump time and consequently it is necessary to delay the enzymatic action of the precipitation resistant enzymes. Examples of delayed forms include encapsulated embodiments and solid embodiments. If immediate enzymatic action is desired, a liquid form may be preferable, e.g., in an aqueous solution. In certain embodiments of the present invention, the precipitation resistant enzymes in the filter cake degradation compositions may be spray-dried, freeze-dried, or the like. In certain embodiments, cells capable of producing the precipitation resistant enzymes that have been lyophilized may provide the precipitation resistant enzymes. In certain embodiments, the precipitation resistant enzymes of the present invention may be provided, inter alia, in a purified form, in a partially purified form, as whole cells, as whole cell lysates, or any combination thereof. One of ordinary skill in the art with the benefit of this disclosure will be able to determine the appropriate form for a given application.
In certain embodiments of the present invention, the filter cake degradation compositions of the present invention may comprise other additives, including, but not limited to, glycerol, bactericides, microbiocides, surfactants, chelating agents, foaming agents, and the like. With the benefit of this disclosure, one of ordinary skill in the art will recognize when such additives may be useful in a given application.
In certain embodiments, the filter cake degradation compositions of the present invention may comprise agents designed to remove or dissolve bridging agents in a filter cake. Examples of such agents include, but are not limited to, complexing agents (e.g., salts of ethylenediaminetetraacetic acid, a salt thereof, or other chelating agents), organic acids, or acid precursors (e.g., diethylene glycol diformate, glycerol diacetate, and glycerol triacetate).
Some organic acids of this type may react with the bridging agents (e.g., acid-soluble bridging agents like calcium carbonate) and, in the presence of a conjugate base, may form a buffered system with a pH of about 4 or greater. Similarly, in the case of the acid precursors, which can produce organic acids in situ, since the acid is produced very slowly, the pH may stay in a range where precipitation resistant enzymes are active (e.g., in the range of from about 4 to about S.5).
In certain embodiments, the filter cake degradation compositions of the present invention may be used in conjunction with agents designed at least to partially remove a bridging agent component of the filter cake. For example, a strong acid, such as hydrochloric acid or hydrofluoric acid, may be used in a two-stage, sequential process.
Such a process may involve treatment of the filter cake with a filter cake degradation composition of the present invention and then treatment of the filter cake with the strong acid.
Thus, inactivation of the precipitation resistant enzyme at the resultant low pHs created by a strong acid may be avoided. In embodiments where the bridging agent is water soluble, e.g., a salt, the bridging agent may be removed with fresh water or water undersaturated with respect to the water-soluble bridging agent.
The filter cake degradation compositions of the present invention may be contacted with a filter cake to degrade at least a portion of the filter cake using any method. For instance, the filter cake degradation compositions may be incorporated in a clean-up fluid.
The term "clean-up fluid" refers to any fluid introduced into a subterranean formation for the purposes of facilitating the degradation of a filter cake. In certain embodiments, the filter cake degradation compositions of the present invention are internally incorporated in a servicing fluid, externally applied to a servicing fluid, or any combination thereof. The term "servicing fluid" refers to any fluid suitable for use in subterranean operations. Examples of servicing fluids, include, but are not limited to, drill-in fluids, fracturing fluids, and gravel packing fluids. For applications such as, e.g., fracturing and gravel packing, the precipitation resistant enzyme may be incorporated internally in the fluid or onto a particulate used in the process. In one embodiment, the filter cake degradation compositions of the present invention may be pumped to the location of the treatment zone at a rate sufficient to introduce sufficient precipitation resistant enzymes to at least partially degrade the fluid-loss additive component in a portion of a filter cake. To achieve certain beneficial effects of the present invention, the filter cake degradation compositions of the present invention may be shut in the formation for a time sufficient to at least partially degrade the fluid-loss additive component of a filter cake. This shut-in-time may be affected by the activity and/or concentration of the precipitation resistant enzyme and/or by the environmental conditions of the well bore, such as temperature, pH, and the like. If necessary, the pH of the treatment fluid may be adjusted through the use of acids, bases, or buffers. One of ordinary skill in the art with the benefit of this disclosure will recognize the conditions that might affect the requisite shut-in time needed to achieve a desired result.
An example of a method of the present invention is a method of degrading a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising:
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component; and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
An example of a composition of the present invention is a filter cake degradation composition comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
To facilitate a better understanding of the present invention, the following examples of specific embodiments are given. In no way should the following examples be read to limit, or to define, the scope of the invention.
EXAMPLES
Methods and Procedures In general, the test method for assessing enzyme activity generally involved addition of a known amount of an enzyme concentrate to a solution containing a standard amount of a standard starch in solution. The course of the resulting reaction is then followed by testing for the presence of starch with an iodine test solution. The starch was judged to have been consumed when coloration due to a complex formed between starch and iodine was no longer observed as compared to a colored glass standard. Reaction conditions were controlled to a pH of 5, a temperature of 37°C, and included a trace concentration of calcium (0.0003 molar).
The enzyme assay was performed as follows. 5 milliliters iodine solution B was pipetted into at least 5 test tubes per sample, which were placed in a water bath at 40°C. 20 milliliters starch solution was pipetted into a large test tube. The pH was checked to ensure a pH of 5. 5 milliliters of calcium chloride solution was then added to the test tube. The test tube was warmed to 40°C before adding an enzyme solution. An amount of enzyme solution was gradually added to the mixture and mixed. The reaction was allowed to proceed at 40°C.
At suitable intervals, 1 milliliter of the reaction mixture was removed and added to the test tubes containing 5 milliliters iodine solution B. Each tube was shaken briefly and color checked to determine the presence of starch.
Iodine solution A was made as follows. 22 grams of potassium iodine were dissolved in approximately 60 milliliters of demineralised water in a 500 milliliter volumetric flask. 11 grams of iodine were dissolved in the flask, which was then filled to the mark with demineralised water.
Iodine solution B was made as follows. 80 grams of potassium iodine was weighed out and added to a 2,000 milliliter volumetric flask. Then 8 milliliters of iodine solution A
was added and the flask was filled to the mark with demineralised water.
A stock salt solution was made as follows. 9.36 grams NaCI, 69 grams KH2P04 and 4.8 grams Na2HPOa. were weighed out and poured into a 1,000 milliliter volumetric flask, which was then filled to the mark with demineralized water. The pH of the solution was checked, and when necessary, adjusted using HCl or NaOH as appropriate to reach a pH of 5.2.
A starch solution was made as follows. An equivalent amount of 6.95 grams of dry matter content starch was added to demineralized water to a volume of 1,000 milliliters. The percentage dry matter content (DM %) of the starch was analyzed at 105°C (water determination at 105°C). The starch was suspended in 100 milliliters of demineralised water.
The starch solution was then transferred quantitatively while stirring to a beaker containing 200 milliliters boiling demineralised water. The solution was boiled for approximately 30 seconds. The solution was transferred quantitatively to a 1,000 milliliter volumetric flask and cooled to room temperature. The pH was adjusted to 5 with HCl or NaOH as appropriate.
The solution was then made up to the mark with demineralised water.
A calcium chloride solution was prepared as follows. 0.82 grams of CaCl2 in milliliter solution of demineralised water. The pH was then adjusted to 5 with HCl or NaOH
as appropriate.
An enzyme solution was prepared as followed. Enzyme concentrates were dissolved in 100 milliliters deionised water and diluted to the degree necessary to yield a measurable rate (e.g., 5 to 20 minutes) in the test procedures described. The pH was then adjusted to 5 with HCl or NaOH as appropriate.
A test method for precipitation of enzymes based on salinity was conducted as follows. Three test brine solutions were made up by combining fresh water, saturated sodium chloride brine (density 1.2 kilograms per liter) and sodium chloride brine at SO% saturation (density 1.2 kilograms per liter). An enzyme sample at a moderately high concentration and at a low concentration were added to the brine and then heated to 90°C.
The appearance of the solutions was monitored for formation of a precipitate.
Simulation of the tendency of a precipitated enzyme to block porous media was tested by noting the rate of flow through fine filter paper and core flow studies using sandstone of low permeability.
A pore blockage test using fllterpaper was conducted as follows. A steel cell of diameter 5 centimeters and length 150 centimeters was fitted with filter paper having a pore dimension of 2.7 microns. The cell was then filled with 100 milliliters of water, sealed and pressurized to 100 pounds per square inch. The rate of water discharge through the filterpaper was timed in seconds to measure the initial inj ectivity of water through the filterpaper. Enzyme solutions of known concentrations were prepared in brine solutions and either heated and allowed to cool before being tested or tested without prior heating. The cell was then filled with 100 milliliters of the enzyme solutions, sealed, and pressurized to 100 pounds per square inch and the rate of discharge was timed. Next, water was injected through the filter paper as described above to check whether any precipitated enzyme creates a lasting permeability reduction in the filterpaper.
A pore blockage test using a test core was conducted as follows. An enzyme solution was injected into a test core at ambient temperature. The temperature was then raised to 93°C to induce precipitation. The direction of flow into the core was reversed to assess whether any precipitation occurring inside the core affected the permeability of the core.
Specifically, Berea sandstone core plugs were cut, dried, and vacuum saturated in 1.2 specific gravity NaCI brine. A core plug was then mounted in the permeameter and sealed with 500 pounds per square confining pressure. The temperature was increased to 200°F while maintaining the confining pressure. Soltrol~ 170, an isoparaffin solvent commercially available from Chevron Phillips Chemical Company, The Woodlands, Texas, was flowed through the core in the production direction until a stable permeability was measured (Ki).
Ten pore volumes of the 0.5% vlv enzyme in a NaCI brine solution having a specific gravity of 1.2 was flowed through the core in the injection direction. The core was shut in and held for 24 hours at 200°F. Flow of Soltrol~ 170 was resumed in the production direction and continued until the permeability reached a stable value (Kf).
One example of a precipitation resistant enzyme suitable for use in the methods of the present invention, Liquizyme X (commercially available from Novozymes A/S, Bagsaerd, Denmark), was compared to comparative test samples of other enzymes. The comparative test samples were: Termamyl~ 120L (commercially available from Novozymes A/S, Bagsaerd, Denmark); Ban~ (commercially available from Novozymes A/S, Bagsaerd, Denmark); and Nervanase~ BT2 (commercially available from Rhodia Food Ltd, Cheshire, United Kingdom).
The activities per gram of the various enzyme samples tested as quoted by suppliers and estimated according to the method outlined above are summarized in Table 1.
Table 1 Enzyme Activity (KNU/g enzyme concentrate Li uiz a X 200 a rox Termam 1 120L 120 a rox Ban 240L 240 a rox Nervanase BT2 120 a rox The exemplary precipitation resistant enzyme, Liquizyme X, and comparative test samples were tested using the method to determine enzyme precipitation described above.
The precipitation tendencies of the comparative enzyme samples were determined at 20°C
and 95°C and in different concentrations of sodium chloride in the brine carrier. Table 2 shows the thermal precipitation potential of the Liquizyme~ X and comparative test samples.
Table 2 Enzyme Activity Precipitation Precipitation KNU/100 mL observed observed at at 95C
NaCI Molari 5.27M 2.63M 5.27M 2.63M
Li ui a X 40 no no no no Li uiz a X 100 no no no no Termam 1 120L 24 no no es no Termam 1 120L 60 no no es es Ban 240L 48 no no es es Ban 240L 120 no no es es Nervanase BT2 24 no no es es Nervanase BT2 65 no no es es The data in Table 2 exemplify the stability of precipitation resistant enzymes in sodium chloride brine. The comparative samples all produced precipitates.
The exemplary precipitation resistant enzyme, Liquizyme~ X, and comparative test samples were tested using the methods to determine pore blockage using the filter paper method as described above. Table 3 shows the effect of temperature on enzyme precipitation based on injection through filterpaper.
Table 3 Test mixture Observation Injectivity sec./100 mL
At 23C At 90C Initial Final Liquizyme'~ X No effect No effect 8 8 100 KNU/100 mL in water Liquizyme~' X No effect No effect 8 8 100 KNU/100 mL NaCI brine 2.63 Liquizyme~' X No effect No effect 8 9 100 KNU/100 mL NaCI brine (5.27 Nervanase~' BT 2 No effect Cloudy 8 30 60 KNU/100 mL in water Nervanase'e' BT 2 No effect Precipitate9 90 60 I~NU/100 mL in NaCI brine formed 2.63M
Nervanase~' BT 2 No effect Precipitate8 236 60 KNU/100 mL in NaCI brine formed 5.27M
Termamyl~' 120L No effect cloudy 10 50 60 KNU/100 mL in water Termamyl"5' 120L No effect Very cloudy8 74 60 KNU/100 mL in NaCI brine 2.63M
The results in the Table 3 demonstrate that the comparative test samples tend to precipitate when heated. In the case of the Termamyl~ 120L and the Nervanase~
BT2 there is evidence that a precipitate capable of reducing the permeability of filterpaper is produced even when the solvent is fresh water. Additionally, Table 3 demonstrates that the concentration of sodium chloride in the carrier brine has a marked impact on the precipitation tendency. In the case of the Nervanase~ BT2, the precipitation in saturated sodium chloride was severe. Table 3 also shows that the exemplary precipitation resistant enzyme, Liquizyme~ X, is resistant to precipitation over the entire sodium chloride concentration range tested.
The effect of precipitation on return permeability was determined using the pore blockage method using a test core as described above. The Termamyl~ 120L (60 mL) comparative test sample was compared to the exemplary precipitation resistant enzyme Liquizyme~ X (100 KNU/100 mL) in 5.27M sodium chloride brine. Upon heating to 90°C
the Termamyl~ 120L solution developed an obvious precipitate whereas the solution of Liquizyme~ X did not. Termamyl~ 120L demonstrated the potential to be more damaging to permeability than a precipitation resistant enzyme. Figure 2 illustrate the return of permeability when Liquizyme~ ~ is used in an exemplary composition and method of the present invention. Following the injection of 10 pore volumes of the Liquizyme X sample and a static aging period of 24 hours at 90°C only a mean volume of 20 pore volumes of oil produced through the core was required to restore permeability to 100% of the original when flow was recommenced in the production direction. In the case of the Termamyl~
comparative test sample, over the same time span return permeability was only 33% of the original after a flow of more than 400 pore volumes through the core as shown in Figure 3.
Thus, the tests carned out with the sandstone core demonstrate that the precipitation resistant enzymes are less damaging to the core's permeability.
[0001] Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. While numerous changes may be made by those skilled in the art, such changes are encompassed within the spirit of this invention as defined by the appended claims.
Claims (38)
1. A method of degrading a fluid-loss additive component in a portion of a filter cake in a subterranean formation comprising:
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component;
and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
contacting the fluid-loss additive component with a filter cake degradation composition that comprises a precipitation resistant enzyme, wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive component;
and allowing the filter cake degradation composition to at least partially degrade the fluid-loss additive component in a portion of the filter cake.
2. The method of claim 1 wherein the precipitation resistant enzyme comprises a hydrolase enzyme.
3. The method of claim 1 wherein the precipitation resistant enzyme comprises a glycosidase enzyme.
4. The method of claim 1 wherein the precipitation resistant enzyme comprises an .alpha.-amylase enzyme.
5. The method of claim 1 wherein the precipitation resistant enzyme comprises a .beta.-amylase enzyme.
6. The method of claim 1 wherein the precipitation resistant enzyme comprises a glucan 1,4-.alpha.-glucosidase enzyme.
7. The method of claim 1 wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive without precipitation in a saturated brine and at a temperature up to at least about 90°C.
8. The method of claim 1 wherein the precipitation resistant enzyme is present in the filter cake degradation composition in an amount sufficient to degrade a fluid-loss additive component of the filter cake.
9. The method of claim 1 wherein the precipitation resistant enzyme is present in the filter cake degradation composition in an amount in the range of from about 10 KNU to about 150 KNU.
10. The method of claim 1 wherein the filter cake degradation composition further comprises glycerol, bactericides, microbiocides, surfactants, chelating agents, foaming agents, or combinations thereof.
11. The method of claim 1 wherein the filter cake degradation composition further comprises one or more agents capable of at least partially degrading a bridging agent component of the filter cake.
12. The method of claim 11 wherein the agent comprises a complexing agent, organic acid, an acid precursor, or a combination thereof.
13. The method of claim 11 wherein the agent comprises ethylenediaminetetraacetic acid, a salt of ethylenediaminetetraacetic acid, diethyelene glycol diformate, glycerol diacetate, glycerol triacetate, or a combination thereof.
14. The composition of claim 1 wherein the filter cake degradation composition is provided in a clean-up fluid.
15. The composition of claim 1 wherein the filter cake degradation composition is provided in a servicing fluid.
16. The composition of claim 15 wherein the servicing fluid is a drilling fluid.
17. The composition of claim 15 wherein the servicing fluid is a fracturing fluid or a gravel packing fluid.
18. The method of claim 1 wherein the filter cake degradation composition is present in an amount sufficient to at least partially degrade a fluid-loss additive component of the filter cake.
19. The method of claim 1 wherein the filter cake degradation composition is present in an amount sufficient to at least partially degrade a bridging agent component of the filter cake.
20. A filter cake degradation composition comprising a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
21. The composition of claim 20 wherein the precipitation resistant enzyme comprises a hydrolase enzyme.
22. The composition of claim 20 wherein the precipitation resistant enzyme comprises a glycosidase enzyme.
23. The composition of claim 20 wherein the precipitation resistant enzyme comprises an .alpha.-amylase enzyme.
24. The composition of claim 20 wherein the precipitation resistant enzyme comprises a .beta.-amylase enzyme.
25. The composition of claim 20 wherein the precipitation resistant enzyme comprises a glucan 1,4-.alpha.-glucosidase enzyme.
26. The composition of claim 20 wherein the precipitation resistant enzyme is capable of degrading the fluid-loss additive without precipitation in a saturated brine and at a temperature up to at least about 90°C.
27. The composition of claim 20 wherein the precipitation resistant enzyme is present in the filter cake degradation composition in an amount sufficient to degrade a fluid-loss additive component of the filter cake.
28. The composition of claim 20 wherein the precipitation resistant enzyme is present in the filter cake degradation composition in an amount in the range of from about 10 KNU to about 150 KNU.
29. The composition of claim 20 wherein the filter cake degradation composition further comprises glycerol, bactericides, microbiocides, surfactants, chelating agents, foaming agents, or combinations thereof.
30. The composition of claim 20 wherein the filter cake degradation composition further comprises one or more agents capable of at least partially degrading a bridging agent.
31. The composition of claim 30 wherein the agent comprises a complexing agent, organic acid, an acid precursor, or a combination thereof.
32. The composition of claim 30 wherein the agent comprises ethylenediaminetetraacetic acid, a salt of ethylenediaminetetraacetic acid, diethyelene glycol diformate, glycerol diacetate, glycerol triacetate, or a combination thereof.
33. The composition of claim 20 wherein the filter cake degradation composition is provided in a clean-up fluid.
34. The composition of claim 20 wherein the filter cake degradation composition is provided in a servicing fluid.
35. The composition of claim 34 wherein the servicing fluid is a drilling fluid.
36. The composition of claim 34 wherein the servicing fluid is a fracturing fluid or a gravel packing fluid.
37. The composition of claim 20 wherein the filter cake degradation composition is present in an amount sufficient to at least partially degrade a fluid-loss additive component of the filter cake.
38. The method of claim 20 wherein the filter cake degradation composition is present in an amount sufficient to at least partially degrade a bridging agent component of the filter cake.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US10/850,422 | 2004-05-19 | ||
US10/850,422 US20050257932A1 (en) | 2004-05-19 | 2004-05-19 | Filter cake degradation compositions and associated methods |
PCT/GB2005/001908 WO2005113933A2 (en) | 2004-05-19 | 2005-05-17 | Filter cake degradation compositions and associated methods |
Publications (1)
Publication Number | Publication Date |
---|---|
CA2566367A1 true CA2566367A1 (en) | 2005-12-01 |
Family
ID=34968220
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CA002566367A Abandoned CA2566367A1 (en) | 2004-05-19 | 2005-05-17 | Filter cake degradation compositions and associated methods |
Country Status (5)
Country | Link |
---|---|
US (1) | US20050257932A1 (en) |
EP (1) | EP1749142A2 (en) |
CA (1) | CA2566367A1 (en) |
NO (1) | NO20065277L (en) |
WO (1) | WO2005113933A2 (en) |
Families Citing this family (17)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7635028B2 (en) | 2006-09-18 | 2009-12-22 | Schlumberger Technology Corporation | Acidic internal breaker for viscoelastic surfactant fluids in brine |
US7779915B2 (en) * | 2006-09-18 | 2010-08-24 | Schlumberger Technology Corporation | Methods of limiting leak off and damage in hydraulic fractures |
US8481462B2 (en) | 2006-09-18 | 2013-07-09 | Schlumberger Technology Corporation | Oxidative internal breaker system with breaking activators for viscoelastic surfactant fluids |
US7398829B2 (en) * | 2006-09-18 | 2008-07-15 | Schlumberger Technology Corporation | Methods of limiting leak off and damage in hydraulic fractures |
US9040468B2 (en) | 2007-07-25 | 2015-05-26 | Schlumberger Technology Corporation | Hydrolyzable particle compositions, treatment fluids and methods |
US10011763B2 (en) | 2007-07-25 | 2018-07-03 | Schlumberger Technology Corporation | Methods to deliver fluids on a well site with variable solids concentration from solid slurries |
US7906464B2 (en) | 2008-05-13 | 2011-03-15 | Halliburton Energy Services, Inc. | Compositions and methods for the removal of oil-based filtercakes |
US7833943B2 (en) | 2008-09-26 | 2010-11-16 | Halliburton Energy Services Inc. | Microemulsifiers and methods of making and using same |
US9139759B2 (en) * | 2009-04-02 | 2015-09-22 | Schlumberger Technology Corporation | Method of treating a subterranean formation with combined breaker and fluid loss additive |
JP5683850B2 (en) * | 2010-01-28 | 2015-03-11 | 富士フイルム株式会社 | Radiation detection element and radiographic imaging device |
US10208239B2 (en) | 2010-06-28 | 2019-02-19 | M-I Drilling Fluids Uk Ltd | Method of removing water-based filter cake |
CA2848002A1 (en) * | 2011-09-29 | 2013-04-04 | Saudi Arabian Oil Company | In-situ generated buffer system |
US20130146289A1 (en) | 2011-12-07 | 2013-06-13 | Saudi Arabian Oil Company | Two-stage filter cake removal composition for drilling fluids and method of use thereof |
US10563113B2 (en) * | 2016-01-05 | 2020-02-18 | Saudi Arabian Oil Company | Removal of barite weighted mud |
CN110819317B (en) * | 2018-08-08 | 2022-03-29 | 中国石油大学(华东) | Drilling fluid and application thereof in tight sandstone reservoir or fractured tight sandstone reservoir |
US10934474B2 (en) * | 2018-09-13 | 2021-03-02 | Baker Hughes Holdings Llc | Method to generate acidic species in wellbore fluids |
CN110067533B (en) * | 2019-04-28 | 2021-03-16 | 西南石油大学 | Biological enzyme composite acid deep blockage removal process |
Family Cites Families (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5165477A (en) * | 1990-12-21 | 1992-11-24 | Phillips Petroleum Company | Enzymatic decomposition of drilling mud |
US5247995A (en) * | 1992-02-26 | 1993-09-28 | Bj Services Company | Method of dissolving organic filter cake obtained from polysaccharide based fluids used in production operations and completions of oil and gas wells |
US5881813A (en) * | 1996-11-06 | 1999-03-16 | Bj Services Company | Method for improved stimulation treatment |
GB2338254B (en) * | 1998-06-12 | 2002-10-16 | Sofitech Nv | Well completion clean-up fluids and method for cleaning up drilling and completion filtercakes |
US6138760A (en) * | 1998-12-07 | 2000-10-31 | Bj Services Company | Pre-treatment methods for polymer-containing fluids |
US6140277A (en) * | 1998-12-31 | 2000-10-31 | Schlumberger Technology Corporation | Fluids and techniques for hydrocarbon well completion |
US6494263B2 (en) * | 2000-08-01 | 2002-12-17 | Halliburton Energy Services, Inc. | Well drilling and servicing fluids and methods of removing filter cake deposited thereby |
US6422314B1 (en) * | 2000-08-01 | 2002-07-23 | Halliburton Energy Services, Inc. | Well drilling and servicing fluids and methods of removing filter cake deposited thereby |
CN100577809C (en) * | 2001-02-21 | 2010-01-06 | 维莱尼姆公司 | Enzymes having alpha amylase activity and method of use thereof |
US6978838B2 (en) * | 2002-07-19 | 2005-12-27 | Schlumberger Technology Corporation | Method for removing filter cake from injection wells |
US7066260B2 (en) * | 2002-08-26 | 2006-06-27 | Schlumberger Technology Corporation | Dissolving filter cake |
-
2004
- 2004-05-19 US US10/850,422 patent/US20050257932A1/en not_active Abandoned
-
2005
- 2005-05-17 EP EP05744933A patent/EP1749142A2/en not_active Withdrawn
- 2005-05-17 WO PCT/GB2005/001908 patent/WO2005113933A2/en not_active Application Discontinuation
- 2005-05-17 CA CA002566367A patent/CA2566367A1/en not_active Abandoned
-
2006
- 2006-11-16 NO NO20065277A patent/NO20065277L/en unknown
Also Published As
Publication number | Publication date |
---|---|
WO2005113933A3 (en) | 2006-04-27 |
WO2005113933A2 (en) | 2005-12-01 |
US20050257932A1 (en) | 2005-11-24 |
EP1749142A2 (en) | 2007-02-07 |
NO20065277L (en) | 2007-02-19 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CA2566367A1 (en) | Filter cake degradation compositions and associated methods | |
CA2833522C (en) | Environmentally friendly low temperature breaker systems and related methods | |
CA2140845C (en) | Well drilling and servicing fluids which deposit an easily removable filter cake | |
US5247995A (en) | Method of dissolving organic filter cake obtained from polysaccharide based fluids used in production operations and completions of oil and gas wells | |
US7727936B2 (en) | Acidic treatment fluids comprising xanthan and associated methods | |
US6035936A (en) | Viscoelastic surfactant fracturing fluids and a method for fracturing subterranean formations | |
US6488091B1 (en) | Subterranean formation treating fluid concentrates, treating fluids and methods | |
CA2676296C (en) | Methods for reducing the viscosity of treatment fluids comprising diutan | |
US7727937B2 (en) | Acidic treatment fluids comprising xanthan and associated methods | |
US7497278B2 (en) | Methods of degrading filter cakes in a subterranean formation | |
US4502969A (en) | Workover and completion fluids | |
US20080139415A1 (en) | Acid-generating fluid loss control additives and associated methods | |
US20050061504A1 (en) | Methods and compositions for treating subterranean zones | |
CA2461297C (en) | Viscous well treating fluids and methods | |
Harris | Fracturing-fluid additives | |
WO2009098668A1 (en) | Use of relative permeability modifiers in treating subterranean formations | |
US5055209A (en) | Reduction of the viscosity of solutions viscosified with Xanthan gum polymers | |
Battistel et al. | Enzymes breakers for viscosity enhancing polymers | |
CA2667005A1 (en) | Process for the enzymatic removal of filter-cakes produced by water-based drilling and completion fluids | |
US20020193343A1 (en) | Controlled enzymatic degradation of guar galactomannan solutions using enzymatic inhibition | |
EP1104798A1 (en) | Non-damaging drilling fluids | |
US7195071B2 (en) | Enzyme compositions and methods of using these compositions to degrade succinoglycan | |
CA2449083A1 (en) | Thermal extenders for well fluid applications | |
CN115322763B (en) | Biological acidolysis blocking agent, preparation method thereof and application thereof in low-permeability reservoir | |
US4798245A (en) | Method of treating heterogeneous formation with potassium hydroxide |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
EEER | Examination request | ||
FZDE | Discontinued |