MXPA00011660A - Encapsulated breakers, compositions and methods of use - Google Patents

Abstract

An encapsulated breaker is enclosed within a hydrolytically degradable polymer coating. Compositions containing this encapsulated breaker, methods of making and methods of use are also described.

Description

ENCAPSULATED FRAGMENTERS, COMPOSITIONS AND METHODS OF USE FIELD OF THE INVENTION This invention relates to encapsulated fragments. More specifically, this invention relates to fragmenters that are encapsulated with a degradable hydrolytic material and compositions and methods for using same.

BACKGROUND OF THE INVENTION Hydraulic fracturing of underground formations is a well-known technique for increasing the permeability of these formations in the recovery of materials, such as petroleum products. In this technique, a viscous fluid ("fracturing fluid" commonly an aqueous fracturing fluid, more commonly guar) is applied to the inner wall of the well, pressure is applied to induce fracture and props in the fluid (most commonly sand). ) maintain fractures in an open state. Then, the viscous fluid must be removed, and the oil is collected from the formation Ref. 125278 underground opened in this way. In order to facilitate the rapid removal of the fracturing fluid, chemicals are used to reduce or "fragment" the viscosity of the fracturing fluid; these chemicals (more commonly oxidants, and in particular persulfates) are known as "fragmenting". The chemical reaction of the fragmenter with the fracturing fluid is undesirable before the end of the fracturing operation. Therefore, it is advantageous to encapsulate or coat the particles with a polymer to delay the release of the fragmenter, and thereby delay the fragmentation of the fracturing fluid. Many materials have been used in the art to encapsulate fragments for fracturing fluids. For example, U.S. Patent No. 4,506,734 (Nolte) discloses a shredder within a ceramic or glass crushable liner that ruptures in the closure of induced fractures. U.S. Patent No. 4,741,401 (alles, et.al.) teaches that a polymer can be applied to a solid, shredder, chemical product of more preferred masonry by an air suspension coating. Polymers of alols are more typically polyolefin homopolymers and copolymers and ethylene oxides. This patent describes the release of the fragmenter by the rupture of the membrane either by the force of closure of the fractures within the underground formation or by the osmotic pressure of the water that diffuses towards the shell. In U.S. Patent No. 5,164,099 (Grupta, et al.) A polymer is applied to a solid particle of a fragmenting chemical by interfacial polymerization. Typically, this polymer is a polyamide or a crosslinked cellulosic material. This patent states that the fragmenter is released from the capsules described therein by diffusion through the membrane of the encapsulation. U.S. Patent No. 5,591,700 (Harris et al.) Refers to encapsulated fragments which refers to encapsulated fragments that are coated by surfactants that are solid to environmental surface conditions and dissolve at elevated temperatures in the underground formation. The surfactants are mixed in the dry state.

The alkyl-2-cyanoacrylate monomers are polymerized immediately in the presence of a weak base and as such have been widely used for the encapsulation and coating of particles in the pharmaceutical industry, primarily for the purpose of drug delivery. For example, Kante et al. (Int. J. Pharm., 1980, 7, 45) has described a method for preparing nanoparticles of actinomycin D using poly (butylcyanoacrylate). U.S. Patent No. 4,452,861 (to RCA Corporation) discloses a method for coating luminescent inorganic phosphorus using polymeric cyanoacrylates. The summarized procedure comprises a five-stage process which requires the complete evaporation of the non-aqueous solvent during each of the coating steps and a final step which requires the washing of the coated particles.

BRIEF DESCRIPTION OF THE INVENTION An encapsulated shredder is provided to reduce the viscosity of a fracturing fluid. The fragmenter is enclosed within a polymer coating, hydrolytically & 6 &Z - & amp; & amp;, degradable. Also described are compositions containing this encapsulated fragmenter and methods of use.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a digital image of two flasks of water-encapsulated fragmenter compositions, one flask containing the encapsulated fragmenter of the present invention and the other containing the encapsulated fragmenter coated within a polymer that it is not hydrolytically degradable. These jars have not been heated. Figure 2 is a digital image of the 15 bottles of Figure 1 after heating. Figure 3 is a graph showing the viscosity / time profile of guar compositions containing unencapsulated fragmenter and containing encapsulated fragmenter. DETAILED DESCRIPTION OF THE INVENTION The encapsulated fragmenter of the present invention is enclosed within a polymer coating, which is hydrolytically degradable. By "hydrolytically degradable" means that h * & & -, ^ 3, - ~ 42 f .fcfr * ^ *. > ^ & «? The polymer coating will react with water to chemically fragment the polymer coating to predominantly non-solid components in a suitable time and temperature range for the intended use, preferably the coating will be hydrolytically degraded in the space of four hours at 70 ° C. An encapsulated fragmenter having a coating that degrades hydrolytically is superior to the systems of the prior art, because it allows a better control of the release time and facilitates the handling previously not offered by the systems of the prior art .. Because the fragmenter is encapsulated in a material that reacts with water, dissolves in a simpler manner or dissipates in water, the release can be controlled through the reaction rate or coating with water Because the coating of the present invention is partially or completely degraded by the reaction With water, the present invention can provide complete fragmenter distribution. Preferably, the encapsulated fragmenter of the present invention is relatively stable at ambient temperatures. In this way, the encapsulated fragmenter does not reduce the viscosity by more than 50% in 5 hours at room temperature (20-25 ° C) in a normal fragmentation test. However, the fragmenter is released in a controlled manner at a final time in the fragmentation operation. In this way, preferably, the encapsulated fragmenter does not reduce the viscosity by less than 50% at 70 ° C in a predetermined first time selected between nineteen minutes and 12 hours. In this way, the period of time allows the fracturing operation to take place at the bottom of the hole. The encapsulated fragmenter reduces the viscosity by more than 50% in a second predetermined time period, selected between nineteen minutes and 12 hours at 70 ° C in a Normal Fragmentation Test, which occurs after the first predetermined time. Preferably, the first predetermined time is between about 2 and 3 hours and the second predetermined time period is between about 3 and 5 hours. Additionally, the encapsulated fragmenter reduces the viscosity by less than 50% in a Normal Fragmentation Test at least 20 minutes after the time that a similar composition takes to reduce the viscosity below 50% in a Normal Fragmentation Test where it is not encapsulated the fragmenter Preferably, the encapsulated fragmenter reduces the viscosity at least 60 minutes later with a similar composition with a non-encapsulated fragmenter. In a surprising way, the coating for the fragmenter of the present invention is substantially or completely dissipated under conditions of use in the underground system. Because no additional microcapsule shell is present or a substantially reduced amount of microcapsule shell is present, it is substantially easy to clean the well and recover the petroleum products. Preferably, no more than 50% by weight of the shell remains as a solid component after exposure of the microcapsule to water at 70 ° C for four hours, more preferably, no more than 20% of the shell remains more preferably, no more than 5% remains as a solid component after exposure of the microcapsule to water at 70 ° C for four hours.

Typically, the fracturing fluid is a hydrated polymer such as guar, hydroxyalkylguar, hydroxyalkylcellulose, carboxyalkylhydroxydant, carboxyalkylhydroxyalkyl, cellulose or other derived cellulose, xanthan and the like in an aqueous fluid to which a suitable crosslinking agent is added. Suitable crosslinking agents include compounds such as borates, zirconates, titanates, pyroantimonates, aluminates and the like. The polymeric shell material of the present invention is primarily a poly (alkyl-2-cyanoacrylate), which is present in an amount sufficient to allow the coating to hydrolytically degrade at use temperatures above room temperature. Preferably, the poly (alkyl-2-cyanoacrylate) is at least about 50% by weight of the total content of the coating, more preferably at least about 70% and more preferably at least about 90% . Other materials that can be incorporated into the coating of the present material include comonomers that are copolymerizable with alkyl-2-cyanoacrylate. In particular, the comonomers are vinyl-reactive monomers, such as those possessing α, β-unsaturated carbonyl functionalities. Preferably, the comonomers are the esters of acrylic acid and methacrylic acid. A combination of different hydrophobic monomers can be used and can include: acrylic or methacrylic esters of non-tertiary alcohols, having from 1 to 14 carbon atoms, preferably from 2 to 12 carbon atoms. It is preferred that the non-tertiary alcohol is an alkanol. Suitable alkanols for forming the ester are alkanols such as ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2-met il-1. -butanol, 1-hexanol, 2-hexanol, 2-met il-1-pent anol, 3-methyl-1-pentanol, 2-et? ll-butanol, 3, 5, 5-t rimethyl-1-hexanol, 3-heptanol, 1-octanol, 2-octanol, iso-octanol, 2-yt-1-hexanol, 1-decanol, 1-dodecanol, 1-tpdecanol and 1-tet radecanol. In addition, acrylamides such as t-butylacrylamide, t-octyl-acrylamide, and N-N-dimethylacrylamide can also be used. Finally, styrene and derivatives such as comonomers may also be used as comonomers. .t p-methoxystyrene. The preferred fragmenting material for aqueous-based fracturing fluids may comprise for example, enzymes such as hemicellulase, oxidants such as sodium or ammonium persulfate, acids or organic salts, such as citric acid or a citrate, fumaric acid, liquids adsorbed on a solid substrate, solid perbortas, solid peroxides or other oxidants, mixtures of two or more materials and the like. More preferably, the fragmenting material is potassium persulfate. For gel hydrocarbon fracturing fluids, preferred fragments include calcium oxide, calcium hydroxide, p-nit robenzoic acid, triethanolamine, sodium acetate, sodium bicarbonate, and the like. Preferably, the coated fragments 3 of the present invention are proportioned in a slurry with an organic solvent that is compatible with the underground system. The provision of the coated fragmenter in a thick composition offers significant advantages over dry shattering products. Specifically, the slurry suspensions of the encapsulated fragmenter are easier to mix and pump. Additionally, surfactants may be incorporated into the slurry to aid in preventing settling in the slurry. The particles of the coated fragmenter are preferably provided in a solvent that does not facilitate the release of the fragmenter from its coating. Preferably, the solvent is substantially free of water if the solvent is the reaction medium for preparing the coated particle. Preferred solvents are non-hygroscopic solvents that provide a pumpable slurry under conditions of use. Examples of preferred solvents include mineral oil (such as drilling mud oil), vegetable oil, canola oil, siloxanes, hydrofluoroethers, mixtures thereof and the like. The materials are preferably selected such that the material can be pumped even at freezing temperatures. Adonally, aliphatic solvents may be used, such as alkanes or aliphatic mixtures including kerosene. Preferably, the solvent is selected such that the complete slurry has a flash point of more than 93 ° C for transportation safety considerations as measured in accordance with ASTM D 93-90 (the normal test methods for the flash point by the closed tester of Pens y-Martens). In the case of solvents that have flash points that are too low, the effective flash point of the thick composition can be adjusted by mixing solvent. Optionally, the particle can be provided in a dry format that can be mixed on the site of work . Optionally, the encapsulated fragment can be provided in an oily or waxy medium to further control the fragmenter release time. Water access to the wall of the hydrolytically degradable capsule to initiate hydrolytic degradation can be delayed due to oil or wax coating. Optionally, the polymer coating the breaker material can be chemically modified by selection of pendant functionality or surface treatment of the coated fragmenter, so that the coated chipper has an improved affinity for wetting an oily or waxy solvent. This adonal affinity serves to provide adonal short-term protection of the coating from contact with water. In particular, a mixture of solvents is contemplated in this embodiment, whereby a hydrophobic solvent that will have an affinity to the coated fragmenter can be provided together with a solvent that is more hydrophilic. The presence of the more hydrophilic solvent will serve to return the slurry more easily mixable with an aqueous fracturing fluid. The thick fragmenter composition may preferably contain a surfactant. The surfactants provide improved stability of the slurry and even distribution of the suspended particles in the slurry. Preferred surfactants include oxyalkylated phenolic resin surfactants, resin ester surfactants, polyol surfactants, alkylaryl sulfonate surfactants, polymeric amine surfactants, alcohol ether sulfonates, cationic imidazoline surfactants, phosphate complex esters, amine-alkylaryl sulphonates, alkyl amidoamine surfactants, polyamide imidazoline surfactants, imidazoline surfactants, crater, dimethyl acid and trimer surfactants, polyoxyethylated rosin amines, polyoxyethylated rosin amines, surfactants of polyoxyethylene glycol, alcohol ether sulphonate surfactants, alcoholic alcohol sulfate surfactants, sulphonate surfactants, sodium alpha-olefin sulphonates, sodium alcohol ether sulphates, alkyl sulphonate sulfonates, calcium, amine-dodecylbenzene sulfonates, fatty acid amides, alkanolamides and mixtures thereof. These surfactants are generally known as petroleum surfactants, are generally commercially available from the Witco Company. Other surfactants include the fluorinated surfactants, such as the Fluorad® surfactants from 3M. Preferably, the surfactant does not adonally contain water that can adversely affect the stability of the shelf life of the suspension. to--. «« - j -. < -. "-fe i ^, a-» ", jt. . . "_" -ta &l? SBii? B¡tU? E * 4k.J > . -i ~ «, ••» - & . nm. - »?? s * thick. Clays may be used in the thick compositions of the present invention including smectite clays including modified montmorillonites, hectorites bentonites. Additionally, apuntors can be provided in the thick composition for help: to keep the fractured underground formation open after fragmentation and removal of the fracturing fluid. You can select: the proppers from any material suitable for the introduction to the bottom of the hole, including sand and sintered bauxite. Additionally thickeners can be incorporated in the thick suspension. Preferred thickeners include natural extracts such as gum arabic, ghatti coma, khaya gum, agar, pectin, carragahen and alguinatos; modified natural extract; xanthan gums; modified cellulose, such as carboxymethylcellulose, methylcellulose and hydroxyalkylcellulose and synthetic polymers such as carboxy-vinyl (carbomer) of ultra-high molecular weight and acrylic polymers.

The thick composition comprising the encapsulated fragmenter may further comprise adjuvants suitable for incorporation into fragmenter compositions, such as colorants, fragrances, preservatives, anti-settling agents, pH control buffers and viscosity modifiers. The preferred coating of the present invention is produced by dispersing the core fragmenter particles in a non-aqueous liquid containing dissolved alkyl-2-cyanoacrylate monomer. The polymerization of the alkyl-2-cyanoacrylate is carried out in the addition of a weak base, thereby depositing a coating on the surface of the particles. The present method provides both a high degree of coating efficiency as well as excellent processability and isolation of the coated particles. In this way a highly efficient coating process is achieved in a one-step process without requiring washing. In a preferred reaction of the present invention, potassium persulfate is dispersed in a stirred suspension of meth il-2-cyanoacrylate or ethyl-2-cyanoacrylate in a non-aqueous solvent. With examples of solvents, aliphatic hydrocarbons such as hexane, ethane and kerosene give excellent results, while aromatic hydrocarbons such as toluene or xylene lead to inferior results. Solvents containing a high degree of moisture can not be used since the water will induce a premature polymerization of the cyanoacrylate. After 3 rd agitation for 5 to 10 minutes to effect a complete mixed • 1, a drop of triethanolamine or a weak base is added to initiate the polymerization. Stirring is continued for an additional 30 minutes to ensure complete reaction at which time the potassium persulfate coated is collected by filtration and allowed to air dry. A coating efficiency of 93-98% is obtained, as determined by iodometric titration.

Normal Fragmentation Test An evaluation of the release conditions of a fragmenter at constant temperature was carried out, as follows. A guar gel was prepared by hydrating 25.11 < ? á¡áááááááá¿ g of guar gum (CAS number 9000-30-0, purchased from the Aldrich Chemical Company) with 2.6 L of water, in a 4 L container. "In the addition of 1.97 g of boric acid (used as received from JT Baker Chemicals) the container was sealed and placed on rollers to rotate the entire container for 12 hours at approximately 20 revolutions per minute to ensure mixing to a homogeneous fluid.Approximately 480 L of borate jointed guar fluid was added ( viscosity of approximately 1800 cps) to a 500 mL Nalgane container., 0.15 g of the encapsulated fragmenter (based on potassium persulfate) was added or as a comparison evaluation, an unencapsulated fragmenter was dispersed completely. The sample was then sealed to prevent water leakage and placed in an oven (preheater at 60 ° C). The viscosity was inspected at hourly intervals during the initial 2 hours and subsequently at 1 hour intervals in order to compare the viscosity profiles of the encapsulated versus encapsulated shredder systems. Viscosity measurements were recorded in a Brookfield Digital Viscosymetry (Model DV II), spindle # 4 at an engine speed of 20 RPM, and compared to a control sample that has not been exposed to the same temperature profile and is identical in composition except that it does not contain fragmenter. The above test does not duplicate the conditions of the drilling bottom, but rather shows the reproducible data in the laboratory for comparison of the effectiveness of the fragmented :: encapsulated with the unencapsulated fragmenter and control compositions. Current conditions at the bottom of the perforation, such as shear stress and pressure, will result in a fragmentation profile that provides a high level of distinction between the encapsulated and unencapsulated fragmenter. In this way, while the laboratory test will suggest that only a small benefit is provided to ... encapsulate the fragmenter, a much greater benefit is actually observed under the conditions of use at the bottom of the perforation. The encapsulated fragmenter of the present invention is preferably added to the fracturing fluid before the fluid is pumped to the bottom of the perforation. In a preferred aspect of the present invention, the encapsulated fragmenter is extremely stable even in the presence of water at ambient conditions below the earth, so that mixing with the fracturing fluid can be taken in due time and care without worrying of premature fragmentation of viscosity. Preferably, the encapsulated fragmenter is provided as a slurry, so that it can be easily mixed with the fracturing fluid without the need to resort to solid dosing devices. More preferably, the thick composition of the present invention is pumped simultaneously with the fracturing fluid to the bottom of the bore using liquid dosing devices. Optional liquid mixing equipment can be additionally used to ensure uniform mixing of the two liquid streams. The following examples are provided for purposes of illustrating the present invention and are not intended to be limiting of the broader concepts of the present invention. Unless otherwise indicated, all parts and percentages are in pesos. i * Ex emplos Example 1: Preparation of dry, encapsulated fragmenter 5 A polymerization flask without 500 mL baffles was charged with 350 mL of hexane, 40 g of industrial grade potassium persulfate (40-80 mesh) and 10 g of et il-2 - cyanoacrylate. The persulfate salt was dispersed by stirring at 1200 RPM with a marine style propeller with 3 blades. After stirring for about 10 minutes, 0.1 g of triethanolamine was added to the suspension. The stirring was continued at room temperature for an additional twenty minutes in which the product was collected by vacuum filtration in a Buchner funnel and dried with air under ambient conditions. The dry product is a fluid, white powder.

Example 2: Preparation of encapsulated fragmenter thick composition A 1L polymerization flask equipped with stainless steel deflectors was charged with 300 mL of drilling mud oil I PAR 3 and 80 g of industrial grade potassium persulfate -M xa »j- - ~" Af - -. • jis > , -a «fj'íp ~ '« ^ -. . & > I called & ig. j,: a »_--- (60 - 100 mesh). Over a period of about 20 minutes, 15 g of et il-2-cyanoacrylate was added to the mixture. The persulfate salt was dispersed by stirring at 1500 RPM with a 6-blade turbine agitator or blades. After stirring for about 10 minutes, 0.1 g of triethanolamine was added to the suspension. Stirring was continued at room temperature for an additional twenty minutes to ensure complete reaction of the cyanoacrylate. With continuous stirring, 17 g of silicon dioxide "Cab-O-Sil M-5" was added to the mixture in order to provide a stable thick suspension of the coated persulfate particles.

DETAILED DESCRIPTION OF THE DRAWINGS Figure 1 is a photograph of two flasks of the water-encapsulated fragmenter compositions. Bottle A contains encapsulated fragmenter of the invention (Example 1) . Bottle B contains the fragmented: encapsulation coated within a polymer that does not degrade hydrolytically. These jars have not been heated.

Figure 2 is a photograph of the bottles of Figure 1 after heating at a temperature of 80 ° C for 2.5 hours. These photographs demonstrate that the capsule shell of the present invention degrades hydrolytically on exposure to heat in the presence of water, thereby dissolving the shell wall of the capsule and reducing the amount of solid material to be recovered. of the underground formation during the oil recovery operation. Figure 3 is a graphical representation of the Normal Fragmentation Test, except that the viscosity measurements are carried out at 60 ° C. Line A represents the time / viscosity profile of a reticulated guar control sample, that is, it does not contain a fragmenter. The viscosity is reduced to an essentially stable level after about one hour. Line B represents the time / viscosity profile of a cross-linked guar control sample, comprising unencapsulated fragmenter. This sample exhibits a relatively rapid viscosity fragmentation, even under laboratory conditions where shear forces or pressure are not present in the manner S-B would experiment under real conditions of use. Line C represents the time / viscosity profile of a crosslinked guar sample, comprising the encapsulated fragmenter that has been mixed in the guar from the dry form (for example 1 above). This sample exhibits a relatively slower viscosity fragmentation compared to the encapsulating fragmenter, even under laboratory conditions. In this way, the viscosity fragmentation is delayed at 20 minutes in comparison to the non-encapsulated fragmenter. Line D represents the time / viscosity profile of a cross-linked guar sample, comprising encapsulated fragmenter that has been mixed in the guar from the slurry (for example 2 above). This sample exhibits a relatively slower viscosity fragmentation compared to the unencapsulated fragmenter. In this way, the viscosity fragmentation is delayed by at least 60 minutes compared to the non-encapsulated fragmenter.BU.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property:

Claims (27)

1. An encapsulated fragmenter, characterized in that it comprises a fragmentation: capable of reducing the viscosity of a fracturing fluid enclosed within a hydrolytically degradable coating.

2. The encapsulated fragmenter according to claim 1, characterized in that the coating is formed from a composition comprising poly (alkyl-2-cyanoacrylate).

3. The encapsulated fragmenter according to claim 2, characterized in that the coating is formed from a composition further comprising one or more comonomers which can be copolymerized with alkyl-2-cyanoacrylate.

4. The encapsulated fragmenter according to claim 3, characterized in that the comonomers are selected from the esters of acrylic acid and methacrylic acid.

5. The encapsulated fragmenter according to claim 3, characterized in that the comonomers are selected from the 5 group consisting of acrylic or methacrylic esters of non-tertiary alcohols, alcohols which are selected from the group consisting of ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol , 3-pentanol, 2 -10 methyl-1-butanol, 1-hexanol, 2-hexanol, 2-methyl-l-pentanol, 3-met il-1-pentanol, 2-et il-1-butanol, 3, 5, 5-t rimet il-1-hexanol, 3-heptanol, 1-octanol, 2-octanol, iso-octanol, 2-ethyl-1-hexanol, 1-decanol, 1-dodecanol, 1-tridecanol and 1-t et radecanol or 15 mixtures thereof.

6. The encapsulated fragmenter according to claim 3, characterized in that the comonomers are selected from the 20 group consisting of acrylamides and styrenes.

7. The encapsulated fragmenter according to claim 2, characterized in that the coating is formed from a 25 composition comprising at least about ^ -? w - Jt te; *?? A3? Aif? ~ Sítíi ?, ttM ^ -wt- ^, 50% by weight of poly (alkyl-2-cyanoacrylate) based on the total weight of the coating.

8. The encapsulated fragmenter according to claim 2, characterized in that the coating is formed from a composition comprising at least about 70% by weight of poly (alkyl-2-cyanoacrylate) based on the total weight of the coating.

9. The encapsulated fragmenter according to claim 2, characterized in that the coating is formed from a composition comprising at least about 90% by weight of poly (alkyl-2-cyanoacrylate) based on the total weight of the coating.

10. The encapsulated fragmenter according to claim 2, characterized in that the alkyl group of poly (alkyl-2-cyanoacrylate) is alkyl of 1 to 20 carbon atoms.

11. The encapsulated fragmenter according to claim 2, characterized in that the alkyl group of poly (alkyl-cyanoacrylate) is alkyl of 1 to 6 carbon atoms.

12. The encapsulated fragmenter according to claim 1, characterized in that the fragmentor comprises a persulfate salt.

13. The encapsulated fragmenter according to claim 12, characterized in that the persulfate salt is potassium persulfate.

14. A thick composition of fragment 15 characterized in that it comprises a slurry of encapsulated fragmenter of claim 1 in an organic solvent.

15. The thick composition according to claim 14, characterized in that the organic solvent is predominantly aliphatic.

16. The thick composition according to claim 14, characterized in that the organic solvent comprises kerosene.

17. The thick composition according to claim 14, characterized in that the organic solvent comprises mineral oil.

18. The thick composition according to claim 14, characterized in that the solvent comprises a mixture of one or more hydrocarbons.

19. The thick composition according to claim 14, characterized in that it comprises one or more surfactants.

20. The thick composition according to claim 19, characterized in that the surfactant is selected from the group consisting of oxyalkylated phenolic resin surfactants, resin ester surfactants, polyol surfactants, alkylarylsulfonate surfactants, polymeric amine surfactants, alcohol ether sulfonates, cationic imidazoline surfactants, complex phosphate esters, amine-alkylaryl sulfonates, alkyl amidoamine surfactants, polyamide imidazoline surfactants, fatty imidazoline surfactants, surfactants dimer and trimer acids, polyoxyethylated rosin amines, polyoxyethylated rosin amines, polyoxyethylene glycol surfactants, alcohol ether sulphonate surfactants, alcohol ether sulfate surfactants, sulfonate surfactants, sulfonate s of sodium alpha-olefins, sodium alcohol ether sulfates, calcium alkylaryl sulphonates, amine-dodecylbenzene sulfonates, fatty acid amides, alkanolamides, fluorinated surfactants and mixtures thereof.

21. An encapsulated fragmenter, characterized in that it comprises a fragmenti capable of reducing the viscosity of a fracturing fluid, the fragmenter enclosed within a hydrolytically degradable polymeric coating wherein the encapsulated fragmenter does not reduce the viscosity by more than 50% in 5 hours to 25 hours. ° C in a Normal Fragmentation Test, but the encapsulated fragmenter does not reduce the viscosity ittti »¿fel1i? fe £? ^ a? fe '- ^ afcfiftm ** ^. ** for less than 50% at 70 ° C in a predetermined first time selected between 15 minutes and 12 hours, but does not reduce the viscosity by less than 50% in a second period of the predetermined time of selected between fifteen minutes of 12 hours after the first predetermined time at 70 ° C in a normal fragmentation test and wherein the encapsulated fragmenter reduces the viscosity by: more than 50 % in a Normal Fragmentation Test at At least 20 minutes after a similar composition where the fragmenter is not encapsulated.

22. The encapsulated fragmenter according to claim 21, characterized in that the first predetermined time is between approximately 1 and 3 hours and the second predetermined time period is between approximately 3 and 5 hours.

23. A method for fragmenting a fracturing fluid, characterized in that it comprises introducing an encapsulated fragmenter of claim 1 into an underground formation which is treated with the fracturing fluid and exposing the 25 fragmenter at temperatures in excess of ' about 40 ° C, thereby releasing the fragmentifier hydrolytically.

24. The method according to claim 23, characterized in that the encapsulated fragmenter is provided as a slurry.

25. Method for manufacturing the encapsulated fragmenter, characterized in that it comprises: a) dispersing a solid fragmenter particle in a reaction solution comprising a non-aqueous solvent and an effective amount of (alkyl-2-cyanoacrylate), b) adding a weak base in "an effective amount to initiate the polymerization of (alkyl-2-cyanoacrylate).

26. The method according to claim 25, characterized in that it also comprises the step of filtering the fragmentation: encapsulation of the non-aqueous solvent.

27. The method according to claim 25, characterized in that the ^^^^^ ^^^^^^^^? ^^ * ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ reaction solution. '& & &,? ti-iiá &At? *. , - Aa-g .'fe.jj > .