CA1324753C - Method of remedial cement squeezing using phenolic-aldehyde gels - Google Patents
Method of remedial cement squeezing using phenolic-aldehyde gelsInfo
- Publication number
- CA1324753C CA1324753C CA000613255A CA613255A CA1324753C CA 1324753 C CA1324753 C CA 1324753C CA 000613255 A CA000613255 A CA 000613255A CA 613255 A CA613255 A CA 613255A CA 1324753 C CA1324753 C CA 1324753C
- Authority
- CA
- Canada
- Prior art keywords
- aldehyde
- gelling solution
- cement
- phenolic
- accordance
- 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.)
- Expired - Lifetime
Links
- 239000004568 cement Substances 0.000 title claims abstract description 73
- 238000000034 method Methods 0.000 title claims abstract description 39
- 230000000246 remedial effect Effects 0.000 title claims abstract description 27
- 239000000499 gel Substances 0.000 title description 16
- 230000008569 process Effects 0.000 claims abstract description 21
- 239000000243 solution Substances 0.000 claims description 41
- 230000015572 biosynthetic process Effects 0.000 claims description 19
- 229920001568 phenolic resin Polymers 0.000 claims description 14
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 claims description 12
- 239000000203 mixture Substances 0.000 claims description 11
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 8
- 239000005011 phenolic resin Substances 0.000 claims description 8
- 238000002347 injection Methods 0.000 claims description 7
- 239000007924 injection Substances 0.000 claims description 7
- SLGWESQGEUXWJQ-UHFFFAOYSA-N formaldehyde;phenol Chemical compound O=C.OC1=CC=CC=C1 SLGWESQGEUXWJQ-UHFFFAOYSA-N 0.000 claims description 6
- 150000002989 phenols Chemical class 0.000 claims description 6
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 claims description 5
- 229920002866 paraformaldehyde Polymers 0.000 claims description 4
- 229930040373 Paraformaldehyde Natural products 0.000 claims description 3
- 125000002485 formyl group Chemical class [H]C(*)=O 0.000 claims 14
- 230000000149 penetrating effect Effects 0.000 claims 4
- 239000002243 precursor Substances 0.000 claims 4
- 238000011065 in-situ storage Methods 0.000 claims 2
- 238000005755 formation reaction Methods 0.000 description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 13
- 238000011282 treatment Methods 0.000 description 10
- 206010017076 Fracture Diseases 0.000 description 9
- 239000003921 oil Substances 0.000 description 8
- 230000035699 permeability Effects 0.000 description 8
- 150000001299 aldehydes Chemical class 0.000 description 6
- 239000012530 fluid Substances 0.000 description 6
- 208000010392 Bone Fractures Diseases 0.000 description 5
- 239000002002 slurry Substances 0.000 description 5
- 230000007547 defect Effects 0.000 description 4
- 239000012065 filter cake Substances 0.000 description 4
- 229920005989 resin Polymers 0.000 description 4
- 239000011347 resin Substances 0.000 description 4
- 230000005251 gamma ray Effects 0.000 description 3
- 238000006116 polymerization reaction Methods 0.000 description 3
- 239000011435 rock Substances 0.000 description 3
- AZQWKYJCGOJGHM-UHFFFAOYSA-N 1,4-benzoquinone Chemical compound O=C1C=CC(=O)C=C1 AZQWKYJCGOJGHM-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- 239000003518 caustics Substances 0.000 description 2
- LEQAOMBKQFMDFZ-UHFFFAOYSA-N glyoxal Chemical compound O=CC=O LEQAOMBKQFMDFZ-UHFFFAOYSA-N 0.000 description 2
- 239000011396 hydraulic cement Substances 0.000 description 2
- 235000013824 polyphenols Nutrition 0.000 description 2
- GHMLBKRAJCXXBS-UHFFFAOYSA-N resorcinol Chemical compound OC1=CC=CC(O)=C1 GHMLBKRAJCXXBS-UHFFFAOYSA-N 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 229940005561 1,4-benzoquinone Drugs 0.000 description 1
- 239000010755 BS 2869 Class G Substances 0.000 description 1
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 description 1
- ZNZYKNKBJPZETN-WELNAUFTSA-N Dialdehyde 11678 Chemical compound N1C2=CC=CC=C2C2=C1[C@H](C[C@H](/C(=C/O)C(=O)OC)[C@@H](C=C)C=O)NCC2 ZNZYKNKBJPZETN-WELNAUFTSA-N 0.000 description 1
- 235000012571 Ficus glomerata Nutrition 0.000 description 1
- 240000000365 Ficus racemosa Species 0.000 description 1
- 208000002565 Open Fractures Diseases 0.000 description 1
- 239000011398 Portland cement Substances 0.000 description 1
- 235000015125 Sterculia urens Nutrition 0.000 description 1
- IKHGUXGNUITLKF-XPULMUKRSA-N acetaldehyde Chemical compound [14CH]([14CH3])=O IKHGUXGNUITLKF-XPULMUKRSA-N 0.000 description 1
- 238000010420 art technique Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000011575 calcium Substances 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 230000005465 channeling Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- HOOWDPSAHIOHCC-UHFFFAOYSA-N dialuminum tricalcium oxygen(2-) Chemical compound [O--].[O--].[O--].[O--].[O--].[O--].[Al+3].[Al+3].[Ca++].[Ca++].[Ca++] HOOWDPSAHIOHCC-UHFFFAOYSA-N 0.000 description 1
- 230000009969 flowable effect Effects 0.000 description 1
- 229940015043 glyoxal Drugs 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- APFVFJFRJDLVQX-AHCXROLUSA-N indium-111 Chemical compound [111In] APFVFJFRJDLVQX-AHCXROLUSA-N 0.000 description 1
- 229940055742 indium-111 Drugs 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 239000003129 oil well Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 230000002285 radioactive effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
- 235000018553 tannin Nutrition 0.000 description 1
- 229920001864 tannin Polymers 0.000 description 1
- 239000001648 tannin Substances 0.000 description 1
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B33/00—Sealing or packing boreholes or wells
- E21B33/10—Sealing or packing boreholes or wells in the borehole
- E21B33/13—Methods or devices for cementing, for plugging holes, crevices or the like
-
- 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
- C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
- C09K8/504—Compositions based on water or polar solvents
- C09K8/506—Compositions based on water or polar solvents containing organic compounds
- C09K8/508—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
- C09K8/5086—Compositions based on water or polar solvents containing organic compounds macromolecular compounds obtained otherwise than by reactions only involving carbon-to-carbon unsaturated bonds
Landscapes
- Life Sciences & Earth Sciences (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Geology (AREA)
- Physics & Mathematics (AREA)
- Fluid Mechanics (AREA)
- Geochemistry & Mineralogy (AREA)
- Environmental & Geological Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Consolidation Of Soil By Introduction Of Solidifying Substances Into Soil (AREA)
Abstract
ABSTRACT
An improved method is disclosed for remedial cementing operations. A two-stage process is provided wherein a phenolic-aldehyde gelling solution is injected into an area wherein remedial cementing is to be performed to form a gel near the wellbore and cement is sequentially squeezed into the area.
This method is useful to seal and thereby prevent loss of cement in fractured, vuggy or highly permeable zones as well as to block small channels in cement behind casing.
An improved method is disclosed for remedial cementing operations. A two-stage process is provided wherein a phenolic-aldehyde gelling solution is injected into an area wherein remedial cementing is to be performed to form a gel near the wellbore and cement is sequentially squeezed into the area.
This method is useful to seal and thereby prevent loss of cement in fractured, vuggy or highly permeable zones as well as to block small channels in cement behind casing.
Description
METHOD OF REMEDIAL CEMENT SQUEEZING
USING PHENOLIC-AlDEHYDE GELS
Field of the Invention The pre6ent invention relates generally to an improved method of remedial cement squeezing. More specifically, the pregent invention concern6 a two-stage method wherein a phenolic-aldehyde gelling solution is injected into an area wherein a remedial cement squeeze is to be performed prior to the cement squeeze operation.
Back~round of the Invention For the successful production of a fluid from a subterranean formation by way of a well, it has long been the practice to cement the casing of the well in position. This operation is termed primary cementing. It has also been the practice to use cement as a means of 6ealing defects in the primary cement sheath around the ca~ing. This treatment, termed remedial cementing, is generally carried out through perforations in the casing. Defects in the primary cement integrity lead to undesired flow of fluids or gas from undesired zones during production and to the 1066 of fluids to undesired zone6 during injection. It has traditionally been difficult to perform remedial cementing operations or to merely plug perforations when the formation accessed by the perforations contains vugs, large open fractures or is highly permeable.
f~
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~ :
.
.':
The cement employed in cementing operations concerned with control of fluid production fxom subterranean formations usually consists principally of a hydraulic cement and sufficient water to provide a readily pumpable and flowable composition which becomes, upon setting, a strong monolithic solid. The term, hydraulic cement, as used herein~ refers to portland cement, including aluminuous cements which contain a relatively high proportion of tricalcium aluminate, cements which contain a relatively high proportion of calcium sulfoaluminate, and pozzolana cements which contain a relatively high proportion of light weight mineral sources such a6 fly a6h and volcanic rock.
Remedial fcfqueeze cementing is an operation wherein a cement slurry i6 forced under pressure into a specific point in a well for remedial purposes. The objective is to fill all the perforations or defects in the primary cement sheath (channels) behind casing with cement to obtain a 6eal be~ween the ca6ing ¦ and formation. However, because cement slurry is a suspension 1 20 having a high viscosity, the cement can only fill the larger ¦ channels, leaving the small channels near the wellbore ¦ unfilled. As a result, many conventional cement squeeze ¦ operations are not succe6sful in completely shutting off flow of gas or fluids through the cement defects or channels.
¦ Formations containing natural fracture6, induced ¦ fractures or vugs present additional difficulty in cement ~quee~iDg. Io theDe ca~e~ the matris per=eability i~ Iov aod ,1 the high effective permeability is due to the interconnected voidfi or fracture systems. In these formations, the cement / slurry may move into the large voids or fracture system under S low pressure differentials. Consequently, cement filtercake i6 5 not formed on the vug or fracture faces to immobilize the cement i~ in the near wellbore area. The problem then becomes one of confining the remedial cement slurry to the near area of the ~ wellbore so that squeeze pressure can be developed. ~igher ;~ fluid 108s cements which form filtercake more easily or slurries 9 lO which set faster may be used in these cases, but they are limited because they still require differential pressure to form a cake. This differential pressure is difficult to develop in the highly conductive channels, and as a result, all the cement flows away from the near wellbore region resulting in an 15 unsuccessful cement squeeze.
It is known to inject solutions into highly permeable formations, which at least partially plug the high permeability zones. Phenol-aldehyde resins and gels have heretofore been 20 employed in permeability reducing and ~and consolidating g operations. Solutions of pre-cstalyzed polyphenol-paraformaldehyde resin have also been employed to permanently plug ruptures or perforations in oil well ca6ings. However, these prior art techniques are used as 6ub6titutes for cement 2~ 6queeze operations and do not offer a solution to the above mentioned problems in cement 6queeze operations. Prior art ~ethodfi w ing resin6 or gels alone are ineffective to provide depeDdoble, Bt~bl~, laDg-ter= pluggiDg of l~rg6 ch~DD~I8 or ~1 "
~ 1 324753 perforations. Prior art methods using cement alone are ineffective to provide plugging or sealing of ~mall channels or high permeability zones. Consequently, there exists a need in the art for a method to make the frequently used remedial cement squeeze technique effective in plugging channels and perforations in vuggy, fractured and highly permeable formations.
In the practice of the present invention, an improved method of remedial cement squeezing is provided to overcome the difficulties of cement squeezing in the formations discussed above. This improvement comprises a two-stage method of remedial cementing.
SUMMARY OF T~E INVENTION
The present invention i A directed to a two-stage method for remedial cementing of an area in a wellbore. The method comprises the steps of: a) injecting a phenolic-aldehyde gelling solution into an area wherein remedial cementing i~ to be 20 performed such that a gel form~ near the wellbore, and b) sequentially squeezing cement into the area. This method is useful to effectively seal perforation~ or areas in fractured, vuggy or highly permeable zones having large pore sizes as well as to block small channels in cement behind the casing resulting 25 in an effective remedial cement squeezing operation.
In a preferred embodiment, the cement is squeezed into the area a6 the gel forms.
-DESCRIPTION OF T~E PREFERRED EMBODIMENTS
The present invention provides a method for remedial or ~queeze cementing of a specific point in a well 80 that all perforations or channels behind the casing are filled to obtain a ~eal between the casing and the formation. This method overcomes the difficulty of cement squeez~ng in fractured, vuggy or highly permeable rock wherein the cement flows into the voids or highly permeable regions under low pressure differentials.
In such formations, cement filtercake i6 prevented from being built up on the vug or fracture faces to seal the vug or fracture and the cement is therefore not confined to the near wellbore area. This method al60 provides an effective means for ¦ blocking small, hairline channels in cement behind the casing that cannot be reached with a conventional cement squeeze.
¦~ According to the present invention, a two-stage process -~
l~ is provided wherein a phenolic-aldehyde gelling solution is first injected into the area to be shut off in a wellbore. The 20 gelling solution is prepared as is known in the art by adding l; any commercially available mixture of a phenolic resin and an ¦ aldehyte to water to which caustic has been added. The caustic ' acts as the catalist for the polymerization reaction which forms i a stiff, i.e. highly viscous, impermeable gel. Rate of ! 25 polymerization is controlled, as i8 ~nown in the art, ~o that the co1ution vill not ~tiffen in the wellbor-.
The phenolic component may be one or more of any phenolic compounds such as phenol, resorcinol, catachol, and the like, as well as selected oxidized phenolic compound6 ~uch as 1, 4-benzoquinone and natural or modified tannins. The aldehyde may be either a monoaldehyde, such as formaldehyde and acetaldehyde, or a dialdehyde, such as glyoxal. Formaldehyde is the most preferred aldehyde. The aldehyde may algo be generated in-6itu by an aldehyde precusor, guch as paraformaldehyde. The phenolic compound to aldehyde ratio may be any ratio suitable to form a ~tiff gel upon polymerization.
For purposes of this invention, the concentration of the phenolic resin and aldehyde mixture is from about 1 to about 50 weight percent of the gelling solution. Preferably, the concentration is from about 5 to about 30 weight percent, and most preferably from about 10 to about 20 weight percent.
The amount of gelling solution injected depends on the application and may be determined based on previous plugging treatments, formation permeability, and desired extent of plugging.
The gelling golution as injected preferably has a low ViAC06ity (2-3 Cp) and will invade gmall channels in the 25 formation rock. The ~olution forms a time-controlled stiff gell thae hat a low deo~ity aDd teDds to stay where it i~ placed.
i : 1 324753 The re~in ~cts to seal the small channel6, w gs, fractures or high permeability zones in the near wellbore region. The resin also forms a cushion for the second stage conventional cement squeeze. The phenolic-aldehyde gel is superior to other known resins because of its tolerance of high temperature and pH
variations.
After a predetermined amount of gelling solution is injected, a conventional cement squeeze operation is performet.
The variou~ methods of remedial cementing are old and known by those skilled in the art. Although the gel may be allowed to stiffen before cement is injected, a water or other suitable 6pacer must be injected to displace the gelling 601ution from the perforations or other treated area prior to cement injection. It i6 therefore preferred that the cement squeeze take place as the gel 6tiffen6 60 that the cement di6place6 the ~- gelling 601ution. The gel forms a cushion ~o that pre6sure may - be applied to the cement 61urry for cement filtercake buildup and consequent sealing of the w gs, f ractures and high 20 permeability zone~ without 1068 of cement Erom the near wellbore ~-region.
In another embodiment, a second treatment of the gelling solution may be injected prior to cement injection.
~,; :, ' ~"-.
~ ' ",: .
In order to illustrate the benefits of this invention, a field test was conducted to shut off water which was 5 channeling through suspected fractures or channels behind the casing to the perforated interval in a well. The well was completed in a carbonate reef which is dolomitized and w gular in nature. The poro6ity is le6s than 9~ and the permeability is in the Darcy range due to fractures and w gs. The oil 10 production mechanism is bottom water drive. The well when , initially completed at a first set of perforations produced i 40-50 m3 oil per day, but gradually started to produce large amounts of water.
Initially, the first set of perforations were cement squeezed and the well was completed 4 meters higher up with a second set of perforations. The production of oil went up to 35 m3 per day and water production dropped to about 5 m3 per day temporarily for a period of about two months. However, the 20 oil protuction started to decline again and the well started to produce water at about 15 m3 per day. At this time it was suspected that the water was coming to perforations either through vertical channel6 near the wellbore or through very fine channels in cement behind the casing.
g The well was then treated in accordance with the present invention. The treatment consi6ted of pumping 10 m of a 10% phenolformaldehyde gelling solution tagged with radioactive Indium 111, followed by 0.7 m3 of class G cement through the retainer in the second set of perforation6. Three days after the treatment, the cement was drilled out and the cemented interval held the pressure well. A gamma-ray log was run to trace the phenolformaldehyde gel di~tribution behind the ca6ing. The gamma-ray log suggested that the gelling solution traveled 15m vertically. It is interesting to note that while the injected gelling solution only went 2n above the injected perforation6, a sub6tantial portion of it went into the formation at the treatment perforation depth as well as downward from the treatment perforations, past the lower previously cemented perforations, evidently through channels or voids in the near wellbore area.
The well was completed 2m higher at the ga6 oil contact at a third set of perforations. The well started production 20 with a hi8her ga6 cut a6 expected, but five months after the treatment it produced largely oil and no water. The initial result6 suggest that gel blocked the water channels not blocked by the cement. Therefore, a two-stage treatment involving phenolformaldehyde gel followed by cement ha6 been shown to work 25 better than a cement squeeze alone.
Example II
A well completed near the top of a carbonate reef in a vugular, low pressure and fractured formation was treated in accordance with the present invention. The well was producing 22m3 oil and 295m3 water per day. To shut off the excessive water production, the existing perforations were treated with 24m3 of radioactively tagged phenolformaldehyde gelling solution, followed by 2.4m3 cement. Three days after the treatment, the cement was drilled out and pressure tested to 7MPa. The test indicated that the treated perforations were successfully shut off. The gamma ray log indicated 9m of gel placement vertically behind the casing. The well was then perforated just above the plugged perforations. Initial data indicates production of 55m3 oil and 27m3 water per day.
This corresponds to a reduction of the water-oil-ratio from 14 to 0.5.
The preferred embodiments of the present invention have 20 been described above. It should be understood that the foregoing description is intended only to illustrate certain l~ preferred embodiments of the invention and is not intended to ¦ define the invention in any way. Other embodiments of the invention can be employed without departing from the full scope 25 of the lnveotloo as ~et forth io the appeoded cl~
~' .
i 1 .
USING PHENOLIC-AlDEHYDE GELS
Field of the Invention The pre6ent invention relates generally to an improved method of remedial cement squeezing. More specifically, the pregent invention concern6 a two-stage method wherein a phenolic-aldehyde gelling solution is injected into an area wherein a remedial cement squeeze is to be performed prior to the cement squeeze operation.
Back~round of the Invention For the successful production of a fluid from a subterranean formation by way of a well, it has long been the practice to cement the casing of the well in position. This operation is termed primary cementing. It has also been the practice to use cement as a means of 6ealing defects in the primary cement sheath around the ca~ing. This treatment, termed remedial cementing, is generally carried out through perforations in the casing. Defects in the primary cement integrity lead to undesired flow of fluids or gas from undesired zones during production and to the 1066 of fluids to undesired zone6 during injection. It has traditionally been difficult to perform remedial cementing operations or to merely plug perforations when the formation accessed by the perforations contains vugs, large open fractures or is highly permeable.
f~
f ~ :~
~ :
.
.':
The cement employed in cementing operations concerned with control of fluid production fxom subterranean formations usually consists principally of a hydraulic cement and sufficient water to provide a readily pumpable and flowable composition which becomes, upon setting, a strong monolithic solid. The term, hydraulic cement, as used herein~ refers to portland cement, including aluminuous cements which contain a relatively high proportion of tricalcium aluminate, cements which contain a relatively high proportion of calcium sulfoaluminate, and pozzolana cements which contain a relatively high proportion of light weight mineral sources such a6 fly a6h and volcanic rock.
Remedial fcfqueeze cementing is an operation wherein a cement slurry i6 forced under pressure into a specific point in a well for remedial purposes. The objective is to fill all the perforations or defects in the primary cement sheath (channels) behind casing with cement to obtain a 6eal be~ween the ca6ing ¦ and formation. However, because cement slurry is a suspension 1 20 having a high viscosity, the cement can only fill the larger ¦ channels, leaving the small channels near the wellbore ¦ unfilled. As a result, many conventional cement squeeze ¦ operations are not succe6sful in completely shutting off flow of gas or fluids through the cement defects or channels.
¦ Formations containing natural fracture6, induced ¦ fractures or vugs present additional difficulty in cement ~quee~iDg. Io theDe ca~e~ the matris per=eability i~ Iov aod ,1 the high effective permeability is due to the interconnected voidfi or fracture systems. In these formations, the cement / slurry may move into the large voids or fracture system under S low pressure differentials. Consequently, cement filtercake i6 5 not formed on the vug or fracture faces to immobilize the cement i~ in the near wellbore area. The problem then becomes one of confining the remedial cement slurry to the near area of the ~ wellbore so that squeeze pressure can be developed. ~igher ;~ fluid 108s cements which form filtercake more easily or slurries 9 lO which set faster may be used in these cases, but they are limited because they still require differential pressure to form a cake. This differential pressure is difficult to develop in the highly conductive channels, and as a result, all the cement flows away from the near wellbore region resulting in an 15 unsuccessful cement squeeze.
It is known to inject solutions into highly permeable formations, which at least partially plug the high permeability zones. Phenol-aldehyde resins and gels have heretofore been 20 employed in permeability reducing and ~and consolidating g operations. Solutions of pre-cstalyzed polyphenol-paraformaldehyde resin have also been employed to permanently plug ruptures or perforations in oil well ca6ings. However, these prior art techniques are used as 6ub6titutes for cement 2~ 6queeze operations and do not offer a solution to the above mentioned problems in cement 6queeze operations. Prior art ~ethodfi w ing resin6 or gels alone are ineffective to provide depeDdoble, Bt~bl~, laDg-ter= pluggiDg of l~rg6 ch~DD~I8 or ~1 "
~ 1 324753 perforations. Prior art methods using cement alone are ineffective to provide plugging or sealing of ~mall channels or high permeability zones. Consequently, there exists a need in the art for a method to make the frequently used remedial cement squeeze technique effective in plugging channels and perforations in vuggy, fractured and highly permeable formations.
In the practice of the present invention, an improved method of remedial cement squeezing is provided to overcome the difficulties of cement squeezing in the formations discussed above. This improvement comprises a two-stage method of remedial cementing.
SUMMARY OF T~E INVENTION
The present invention i A directed to a two-stage method for remedial cementing of an area in a wellbore. The method comprises the steps of: a) injecting a phenolic-aldehyde gelling solution into an area wherein remedial cementing i~ to be 20 performed such that a gel form~ near the wellbore, and b) sequentially squeezing cement into the area. This method is useful to effectively seal perforation~ or areas in fractured, vuggy or highly permeable zones having large pore sizes as well as to block small channels in cement behind the casing resulting 25 in an effective remedial cement squeezing operation.
In a preferred embodiment, the cement is squeezed into the area a6 the gel forms.
-DESCRIPTION OF T~E PREFERRED EMBODIMENTS
The present invention provides a method for remedial or ~queeze cementing of a specific point in a well 80 that all perforations or channels behind the casing are filled to obtain a ~eal between the casing and the formation. This method overcomes the difficulty of cement squeez~ng in fractured, vuggy or highly permeable rock wherein the cement flows into the voids or highly permeable regions under low pressure differentials.
In such formations, cement filtercake i6 prevented from being built up on the vug or fracture faces to seal the vug or fracture and the cement is therefore not confined to the near wellbore area. This method al60 provides an effective means for ¦ blocking small, hairline channels in cement behind the casing that cannot be reached with a conventional cement squeeze.
¦~ According to the present invention, a two-stage process -~
l~ is provided wherein a phenolic-aldehyde gelling solution is first injected into the area to be shut off in a wellbore. The 20 gelling solution is prepared as is known in the art by adding l; any commercially available mixture of a phenolic resin and an ¦ aldehyte to water to which caustic has been added. The caustic ' acts as the catalist for the polymerization reaction which forms i a stiff, i.e. highly viscous, impermeable gel. Rate of ! 25 polymerization is controlled, as i8 ~nown in the art, ~o that the co1ution vill not ~tiffen in the wellbor-.
The phenolic component may be one or more of any phenolic compounds such as phenol, resorcinol, catachol, and the like, as well as selected oxidized phenolic compound6 ~uch as 1, 4-benzoquinone and natural or modified tannins. The aldehyde may be either a monoaldehyde, such as formaldehyde and acetaldehyde, or a dialdehyde, such as glyoxal. Formaldehyde is the most preferred aldehyde. The aldehyde may algo be generated in-6itu by an aldehyde precusor, guch as paraformaldehyde. The phenolic compound to aldehyde ratio may be any ratio suitable to form a ~tiff gel upon polymerization.
For purposes of this invention, the concentration of the phenolic resin and aldehyde mixture is from about 1 to about 50 weight percent of the gelling solution. Preferably, the concentration is from about 5 to about 30 weight percent, and most preferably from about 10 to about 20 weight percent.
The amount of gelling solution injected depends on the application and may be determined based on previous plugging treatments, formation permeability, and desired extent of plugging.
The gelling golution as injected preferably has a low ViAC06ity (2-3 Cp) and will invade gmall channels in the 25 formation rock. The ~olution forms a time-controlled stiff gell thae hat a low deo~ity aDd teDds to stay where it i~ placed.
i : 1 324753 The re~in ~cts to seal the small channel6, w gs, fractures or high permeability zones in the near wellbore region. The resin also forms a cushion for the second stage conventional cement squeeze. The phenolic-aldehyde gel is superior to other known resins because of its tolerance of high temperature and pH
variations.
After a predetermined amount of gelling solution is injected, a conventional cement squeeze operation is performet.
The variou~ methods of remedial cementing are old and known by those skilled in the art. Although the gel may be allowed to stiffen before cement is injected, a water or other suitable 6pacer must be injected to displace the gelling 601ution from the perforations or other treated area prior to cement injection. It i6 therefore preferred that the cement squeeze take place as the gel 6tiffen6 60 that the cement di6place6 the ~- gelling 601ution. The gel forms a cushion ~o that pre6sure may - be applied to the cement 61urry for cement filtercake buildup and consequent sealing of the w gs, f ractures and high 20 permeability zone~ without 1068 of cement Erom the near wellbore ~-region.
In another embodiment, a second treatment of the gelling solution may be injected prior to cement injection.
~,; :, ' ~"-.
~ ' ",: .
In order to illustrate the benefits of this invention, a field test was conducted to shut off water which was 5 channeling through suspected fractures or channels behind the casing to the perforated interval in a well. The well was completed in a carbonate reef which is dolomitized and w gular in nature. The poro6ity is le6s than 9~ and the permeability is in the Darcy range due to fractures and w gs. The oil 10 production mechanism is bottom water drive. The well when , initially completed at a first set of perforations produced i 40-50 m3 oil per day, but gradually started to produce large amounts of water.
Initially, the first set of perforations were cement squeezed and the well was completed 4 meters higher up with a second set of perforations. The production of oil went up to 35 m3 per day and water production dropped to about 5 m3 per day temporarily for a period of about two months. However, the 20 oil protuction started to decline again and the well started to produce water at about 15 m3 per day. At this time it was suspected that the water was coming to perforations either through vertical channel6 near the wellbore or through very fine channels in cement behind the casing.
g The well was then treated in accordance with the present invention. The treatment consi6ted of pumping 10 m of a 10% phenolformaldehyde gelling solution tagged with radioactive Indium 111, followed by 0.7 m3 of class G cement through the retainer in the second set of perforation6. Three days after the treatment, the cement was drilled out and the cemented interval held the pressure well. A gamma-ray log was run to trace the phenolformaldehyde gel di~tribution behind the ca6ing. The gamma-ray log suggested that the gelling solution traveled 15m vertically. It is interesting to note that while the injected gelling solution only went 2n above the injected perforation6, a sub6tantial portion of it went into the formation at the treatment perforation depth as well as downward from the treatment perforations, past the lower previously cemented perforations, evidently through channels or voids in the near wellbore area.
The well was completed 2m higher at the ga6 oil contact at a third set of perforations. The well started production 20 with a hi8her ga6 cut a6 expected, but five months after the treatment it produced largely oil and no water. The initial result6 suggest that gel blocked the water channels not blocked by the cement. Therefore, a two-stage treatment involving phenolformaldehyde gel followed by cement ha6 been shown to work 25 better than a cement squeeze alone.
Example II
A well completed near the top of a carbonate reef in a vugular, low pressure and fractured formation was treated in accordance with the present invention. The well was producing 22m3 oil and 295m3 water per day. To shut off the excessive water production, the existing perforations were treated with 24m3 of radioactively tagged phenolformaldehyde gelling solution, followed by 2.4m3 cement. Three days after the treatment, the cement was drilled out and pressure tested to 7MPa. The test indicated that the treated perforations were successfully shut off. The gamma ray log indicated 9m of gel placement vertically behind the casing. The well was then perforated just above the plugged perforations. Initial data indicates production of 55m3 oil and 27m3 water per day.
This corresponds to a reduction of the water-oil-ratio from 14 to 0.5.
The preferred embodiments of the present invention have 20 been described above. It should be understood that the foregoing description is intended only to illustrate certain l~ preferred embodiments of the invention and is not intended to ¦ define the invention in any way. Other embodiments of the invention can be employed without departing from the full scope 25 of the lnveotloo as ~et forth io the appeoded cl~
~' .
i 1 .
Claims (19)
1. A process for remedial cementing of channels behind a well casing in a wellbore penetrating a subterranean formation comprising:
(a) injecting a phenolic-aldehyde gelling solution into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area.
(a) injecting a phenolic-aldehyde gelling solution into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area.
2. A process in accordance with claim 1 wherein said gelling solution comprises phenol and formaldehyde.
3. A process in accordance with claim 1 wherein said gelling solution comprises a phenolic compound and an aldehyde precursor such that aldehyde is formed in-situ.
4. A process in accordance with claim 3 wherein said aldehyde precursor is paraformaldehyde.
5. A process in accordance with claim 1 wherein said injection of gelling solution is followed by a second injection of gelling solution prior to said squeezing of cement.
6. A process in accordance with claim 1 wherein said cement squeeze is performed as said gel forms.
7. A process in accordance with claim 1 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 1 to about 50 weight percent of said gelling solution.
8. A process in accordance with claim 1 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 5 to about 30 weight percent of said gelling solution.
9. A process in accordance with claim 1 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 10 to about 20 weight percent of said gelling solution.
10. A process for remedial cementing of channels behind a well casing in a wellbore penetrating a subterranean formation comprising:
(a) injecting a phenolformaldehyde gelling solution, comprising a mixture of phenolic compound and aldehyde from about 10 to about 20 weight percent of said gelling solution, into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area as said gel forms.
(a) injecting a phenolformaldehyde gelling solution, comprising a mixture of phenolic compound and aldehyde from about 10 to about 20 weight percent of said gelling solution, into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area as said gel forms.
11. A process for remedial cementing of perforations in a wellbore penetrating a subterranean formation comprising:
(a) injecting a phenolic-aldehyde gelling solution into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area.
(a) injecting a phenolic-aldehyde gelling solution into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area.
12. A process in accordance with claim 11 wherein said gelling solution comprises phenol and formaldehyde.
13. A process in accordance with claim 11 wherein said gelling solution comprises a phenolic compound and an aldehyde precursor such that aldehyde is formed in-situ.
14. A process in accordance with claim 13 wherein said aldehyde precursor is paraformaldehyde.
15. A process in accordance with claim 11 wherein said injection of gelling solution is followed by a second injection of gelling solution prior to said squeezing of cement.
16. A process in accordance with claim 11 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 1 to about 50 weight percent of said gelling solution.
17. A process in accordance with claim 1 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 5 to about 30 weight percent of said gelling solution.
18. A process in accordance with claim 1 wherein said phenolic-aldehyde gelling solution comprises a mixture of a phenolic resin and an aldehyde from about 10 to about 20 weight percent of said gelling solution.
19. A process for remedial cementing of perforations in a wellbore penetrating a subterranean formation comprising:
(a) injecting a phenolformaldehyde gelling solution, comprising a mixture of phenolic compound and aldehyde from about 10 to about 20 weight percent of said gelling solution, into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area as said gel forms.
(a) injecting a phenolformaldehyde gelling solution, comprising a mixture of phenolic compound and aldehyde from about 10 to about 20 weight percent of said gelling solution, into an area wherein said remedial cementing is to be performed such that a gel forms near said wellbore; and (b) sequentially squeezing cement into said area as said gel forms.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000613255A CA1324753C (en) | 1989-09-26 | 1989-09-26 | Method of remedial cement squeezing using phenolic-aldehyde gels |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000613255A CA1324753C (en) | 1989-09-26 | 1989-09-26 | Method of remedial cement squeezing using phenolic-aldehyde gels |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1324753C true CA1324753C (en) | 1993-11-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000613255A Expired - Lifetime CA1324753C (en) | 1989-09-26 | 1989-09-26 | Method of remedial cement squeezing using phenolic-aldehyde gels |
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| Country | Link |
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| CA (1) | CA1324753C (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114961638A (en) * | 2022-07-07 | 2022-08-30 | 大庆市佰昂石油科技有限公司 | Supermolecule gel-low-temperature high-strength gel casing damage sand consolidation leakage stopping method |
-
1989
- 1989-09-26 CA CA000613255A patent/CA1324753C/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114961638A (en) * | 2022-07-07 | 2022-08-30 | 大庆市佰昂石油科技有限公司 | Supermolecule gel-low-temperature high-strength gel casing damage sand consolidation leakage stopping method |
| CN114961638B (en) * | 2022-07-07 | 2023-06-20 | 大庆市佰昂石油科技有限公司 | Supermolecule gel-low-temperature high-strength gel casing damage sand-fixing plugging method |
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