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

Definitions

• 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.
• 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.
• 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.
• Filter cakes are desirable, at least temporarily, in subterranean operations for several reasons.
• a filter cake may be used in a fluid-loss control 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.
• 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).
• 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.
• 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 andor sodium chloride).
• Starch is a polysaccharide that comprises monosaccharide units linked by glycosidic bonds, e.g., ⁇ -1,4 glucosidic bonds and ⁇ -1,6 glucosidic bonds.
• filter cakes commonly include drilled solids, weighting agents, and viscosifying polymers that have been used to viscosity 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the methods of the present invention also may comprise degradation of bridging agents from a filter cake in a subterranean formation.
• 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.
• 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.
• glycosidase enzymes (E.C. 3.2.1) may be used.
• the precipitation resistant enzymes include ⁇ -amylase enzymes (E.C. 3.2.1.1), ⁇ -amylase enzymes (E.C. 3.2.1.2), glucan 1,4- ⁇ -glucosidase enzymes (E.C. 3.2.1.3), or combinations thereof.
• suitable precipitation resistant enzymes 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.
• 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.
• salt refers to salts of monovalent cations and anions.
• 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.
• the precipitation resistant enzymes may be present in an amount in the range of from about 10 kilo novo units (KNU) to about 150 KNU.
• KNU kilo novo units
• One KNU is defined as the quantity of enzyme which degrades 4.87 grams of starch (Merck, soluble amylum, Erg.
• 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.
• 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.
• the precipitation resistant enzymes in the filter cake degradation compositions may be spray- dried, freeze-dried, or the like.
• cells capable of producing the precipitation resistant enzymes that have been lyophilized may provide the precipitation resistant enzymes.
• the precipitation resistant enzymes of the present invention may be provided, mter alia, in a purified form, in a partially purified form, as whole cells, as whole cell lysates, or any combination thereof.
• 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.
• the filter cake degradation compositions of the present invention may comprise agents designed to remove or dissolve bridging agents in a filter cake.
• 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).
• complexing agents e.g., salts of ethylenediaminetetraacetic acid, a salt thereof, or other chelating agents
• organic acids 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.
• 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.
• a strong acid such as hydrochloric acid or hydrofluoric acid
• 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.
• 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.
• the filter cake degradation compositions may be incorporated in a clean-up fluid.
• clean-up fluid refers to any fluid introduced into a subterranean formation for the purposes of facilitating the degradation of a filter cake.
• 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.
• servicing fluid refers to any fluid suitable for use in subterranean operations.
• servicing fluids include, but are not limited to, drill-in fluids, fracturing fluids, and gravel packing fluids.
• the precipitation resistant enzyme may be incorporated internally in the fluid or onto a paniculate used in the process.
• 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.
• 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.
• 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.
• 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.
• a precipitation resistant enzyme component that will at least partially degrade a portion of a filter cake.
• 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.
• 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.
• a stock salt solution was made as follows. 9.36 grams NaCl, 69 grams KH 2 P0 4 and 4.8 grams Na 2 HPO 4 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.
• 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.
• Berea sandstone core plugs were cut, dried, and vacuum saturated in 1.2 specific gravity NaCl 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% v/v enzyme in a NaCl 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.
• 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
• 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 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 demonstrate that the comparative test samples tend to precipitate when heated.
• 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.
• Table 3 demonstrates that the concentration of sodium chloride in the carrier brine has a marked impact on the precipitation tendency.
• 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.

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)

Priority Applications (3)

Applications Claiming Priority (2)

Publications (2)

Family

ID=34968220

Family Applications (1)

Country Status (5)

Cited By (1)

Families Citing this family (16)

Citations (3)

Family Cites Families (8)

• 2004
  • 2004-05-19 US US10/850,422 patent/US20050257932A1/en not_active Abandoned
• 2005
  • 2005-05-17 CA CA002566367A patent/CA2566367A1/en not_active Abandoned
  • 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
• 2006
  • 2006-11-16 NO NO20065277A patent/NO20065277L/no unknown

Patent Citations (3)

Also Published As

Similar Documents

Legal Events