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Invention relates to a method for sucrose based thermal stabilization of enzymes for breaking of biopolymer damage in gas and oil wells. The said enzyme includes Amylase and/or a Biopolymer Hydrolase Enzyme mix of Cellulase and/or Hemicellulase-Mannanase enzymes. The method comprises step of preparing Thermostable Enzyme Treatment Fluid by combining the Amylase and Hydrolase enzymes with Sucrose and brine and a surfactant, extending into an oil or gas or water producing reservoir via a well bore with high down hole temperatures, using a drill string or deployed using a coiled tube or bullheaded into the fractures, while injecting the treatment fluid below or above the fracture pressure and shut off the contents for a period of time, allowing to react and disintegrate the Biopolymer based formation damage or filter cake completely and subsequently removed by normal flushing techniques known manner.
The Field of invention
The invention relates to method for sucrose based thermal stabilization of enzymes for breaking of biopolymer damage in gas and oil wells. More particularly the method of the present invention is applicable to the production of oil, gas or water from wells drilled into underground reservoirs where a Biopolymer based formation damage needs to be efficiently disintegrated by Hydrolase enzymes, by virtue of Thermally Stabilizing it, despite the high downhole temperatures, which would otherwise completely or partially deactivate the enzyme rendering it's kinetics unpredictable and inefficient.
Description of the Prior Art:
Since the formation damage can be in such area which is close to the oil producing openhole, the same could largely effect production. Therefore, such Biopolymer Filter cake based damage needs to be effectively removed to significantly increase production of Hydrocarbon or water in water producing wells and injectivity of such wells.
Though, such Biopolymer based formation damage needs to be removed to increase the flow of production fluids from the formation, it cannot be easily flushed out of the formation being nearly insoluble in aqueous fluids,
As a result, removal of such filter cake warrants either treatment by strong oxidants, like persulfates or strong acids, both of which are extremely hazardous for operation and environment.
In the past, with a view to stimulate an under-producing well, often a harsh Inorganic Acids (e.g. HCL) has been used to dislodge and liquefy the damage and remove rapidly. However, it has been observed that such practices have many disadvantages, which includes and not limited to, forming of worm holes leaking off treatment fluid, corroding tubes and plugging screens, triggering localized breakage, etc. Especially for deviated and horizontal wells, the treatment fluid would leak off through worm holes containing strong acids or oxidants, and contaminate gas or water layers. Such leaking off also reduce the zone of treatment of formation damage and compromise productivity.
Strong acids are not only hazardous to handle, they are also corrosive to tubing and equipments, resulting in Sludging and contaminating crude and clogging screens, which is an expensive affair to clean. Corrosion inhibitors are usually toxic in nature.
Since Calcium Carbonates are often used as a weighting agent in the drilling mud formulation, the Filtercake would practically consist of a combination of Carbonate and the Biopolymer matrix. Carbonate fines generated during drilling of carbonate rocks may also be present in the filter cakes.
Filter cakes form as the gel fluids are pumped into the subterranean formation and some part of the fluid leaks into the small rock pores of the formation, leaving behind the macromolecules of biopolymer gel on the rock surface, forming a relatively impermeable layer. Those Biopolymers which does not form cakes, still increases viscosity on localization, which acts similar to a filtercake, blocking off production fluid. Since the Filtercake is a concentrated retentate buildup of the fracturing liquid, it often contains high densities of polysaccharide, U.S.Pat. No. 5,247,995 cites SPE Paper 21497 indicating that they can contain up to about 48% polysaccharide versus about 4% in fracturing fluids, which no doubt, is substantial.
U.S. Pat. No. 5,165,477, to Shell, et. al., and assigned to Phillips Petroleum Co. which describes a method of removing used drilling mud of the type comprising solid materials including at least one polymeric organic viscosifier from a well bore and portions of formations adjacent thereto comprising: injecting a well treatment fluid comprising an enzyme capable of rapidly enzymatically degrading polymeric organic viscosifier into well; and allowing enzyme to degrade polymeric organic viscosifier and well treatment fluid to disperse used drilling mud. In this invention, Shell adds the enzyme to a viscosifier.
U.S. Pat. No. 5,881,813, to Brannon, et. al., and assigned to Phillips Petroleum Co. describes a method for improving the effectiveness of a well treatment in subterranean formations comprising the steps of: injecting a clean-up fluid into the well wherein the clean-up fluid contains one or more enzymes in an amount sufficient to degrade polymeric viscosifiers; contacting the well bore and formation with the clean-up fluid for a period of time sufficient to degrade polymeric viscosifiers therein; performing a treatment to remove non-polymer solids that may be present; and removing the non-polymer solids in the well to improve productivity or injectivity of the subterranean formation.
U.S. Pat. No. 5,247,995, to Tjon-Joe-Pin, et. al., and assigned to BJ Services, which describes a method of increasing the flow of production fluids from a subterranean formation by removing a polysaccharide-containing filter cake formed during production operations and found within the subterranean formation which surrounds a completed well bore comprising the steps of allowing production fluids to flow from the well bore, reducing the flow of production fluids from the formation below expected flow rates and formulating an enzyme treatment by blending together an aqueous fluid and enzymes. The enzyme treatment is pumped to a desired location within the well bore and the enzyme treatment is allowed to degrade the polysaccharide-containing filter cake, whereby the filter cake can be removed from the subterranean formation to the well surface.
U.S. Pat. No. 6,110,875, to Tjon-Joe-Pin, et. al., and assigned to BJ Services, describes a method for degrading xanthan molecules comprising the step of contacting the molecules with xanthanase enzyme complex produced by a soil bacterium bearing the ATCC No. 55941 under conditions such that at least a portion of the molecules are degraded.
U.S. Pat. No. 6,936,454, to Kelly, et. al., and assigned to North Carolina State University, which describes a composition comprising an isolated mannanase enzyme that hydrolyzes (3-1,4 hemicellulolytic linkages in galactomannans at a temperature above 180Â° F. and that is essentially incapable of degrading the linkages at a temperature of 100Â° F. or less.
US Pat. No 4,617,662, to Curtis J, et. al., and assigned to Miles Laboratories, Inc. disclosed is a method for enhancing the thermal stability of microbial alpha-amylase. The method involves adding a stabilizing amount of an amphiphile to the enzyme in its aqueous solution. Also included within the scope of the invention is the stabilized alpha-amylase formulation and its use in the liquefaction of starch.
U.S. Pat. No. 4,284,722, to Masaki Tamuri, et.al., and assigned to CPC International Inc.claims a heat and acid stable alpha-amylase derived from an organism of the species Bacillus stearothermophilus.
U.S. Pat. No. 4,497,897 to Jens H. Eilertsen, et. al., and assigned to Novo Industri A/S, disclosed a method for enhancing the shelf life during storage of protease from Subtilisin Carlsberg which involves the addition of calcium ion and a water soluble carboxylate selected from the group of formate, acetate, propionate and mixtures thereof to a solution of the enzyme.
U.S. Pat. No. 4,451,569, to Setsuo Kobayashi, et.al., and assigned to Toyo Boseki Kabushiki Kaisha, describes a stable enzyme composition comprising glutathione peroxidase and at least one stabilizer compound selected from the group consisting of pentoses, hexoses, penthahydric sugar alcohols, hexahydric sugar alcohols and disaccharides.
K.Samborska et al., Journal of Food Process Engineering 29 (2006) 287-303. report that among all stabilizing compounds investigated, sucrose exhibited the largest protective effect on tested Amylase enzyme. The decimal reduction time of a-amylase activity increased by 33.9 times when 420 mg/mL of sucrose was added to the environment. When the same concentration of trehalose was used, the D-value increased by 6.4 times compared to the value in the buffer system. The nOH provided in the enzyme
solution could not be related to the D-values for the enzyme thermal inactivation, meaning that the enzyme heat stability was not dependent on the nOH.
JC Lee and SN Timasheff et al., J. Biol. Chem., Vol. 256, Issue 14, 7193-7201, Jul, 1981, reports that the results from the protein-solvent interaction study indicate that sucrose is preferentially excluded from the protein domain, increasing the free energy of the system.They report that Thermodynamically this leads to protein stabilization since the unfolded state of the protein becomes thermodynamically even less favorable in the presence of sucrose.
Once subjected to High Temperatures that could otherwise deactivate enzymes in downhole conditions, effectiveness of a Filtercake breaking Hydrolase enzyme system can be established in the laboratory. This can be done, either by checking the increase of filtration rate through a Biopolymer based filter-bed of similar composition prepared and cured in the lab or simply by estimating the reducing sugar produced as a hydrolysis product of the Biopolymer in the bed.
It has been reported that although enzymes potentially offer a number of advantages over conventional chemical catalysts, they are generally unstable in extreme conditions and they get deactivated rapidly by heat and other environmental modifications such as changes in pH and ionic disÂ¬balance. Since the active site of the enzyme consists of amino acids brought together only in the native three-dimensional structure, an unfolded enzyme loses its catalytic activity.
Therefore, thermally fortifying and protecting the Hydrolase enzymes to deliver an efficient Enzyme Hydrolysis at extremely high downhole temperatures not only bears commercial value of Enzyme dosage in treatment fluid formulation, it also provides higher predictability of the Enzyme kinetic rate in downhole conditions, bringing about ease in operation, planning and calculation.
It is an object of the present invention to provide a simple and effective method for Thermal Fortification of the Hydrolase enzymes by stabilizing it even at extremely high downhole temperatures of an underground reservoir, for an efficient and predictable Enzymatic hydrolysis of the Biopolymers.
It is a particular object of the present invention to provide simple and effective methods for the efficient removal of filter cakes from downhole conditions with relatively high temperatures, above 100 Deg C, which could potentially deactivate most enzymes with incubation.
Another object of the present invention is to provide a thermal fortification for the enzyme proteins for a more predictable functioning of the enzymes in hydrolyzing the Biopolymers even at not so high temperatures e.g. below 100 Deg C, but more than 60 Deg C, so that Biopolymer based damage can be
easily removed and matrix permeability can be increased for a better production.
It is a further object of the present invention to provide methods which are not harmful for the environment and easy to handle by the operators without any amount of hazards.
Summary of the Invention:
The present invention provides a method of Thermally Stabilizing Hydrolase enzymes for pumping into a subterranean formation bearing high downhole temperatures, along with other ingredients of the Treatment Fluid, for effective removal of Biopolymer based filter cake, without the Enzyme getting De-activated. Efficient removal of filter cake increases the permeability of the formation or the fracture, stimulating the well to produce at a higher rate.
The method relates to Hydrolase enzyme chosen based on the nature of the Biopolymer substrate, e.g. Amylase for Starch substrate, Cellulase for a CMC substrate or Mannanase for Guar derivative based damage substrate, to Thermally Stabilize the enzyme and ensure that it works at an efficient kinetic rate, even when subjected to high downhole temperatures. The scope of this invention particularly addresses oil, gas or water producing wells with high downhole temperatures ranging between 80 to 130 Deg C, that is 176 to 266 Deg F.
Accordingly the invention provides a method for sucrose based thermal stabilization of enzymes for breaking of biopolymer damage in gas and oil wells, said enzyme includes Amylase and/or a Biopolymer Hydrolase Enzyme mix of Cellulase and/or Hemicellulase-Mannanase enzymes, the said method comprises step of preparing Thermostable Enzyme Treatment Fluid by combining the Amylase and Hydrolase enzymes with Sucrose and brine and a surfactant, extending into an oil or gas or water producing reservoir via a wellbore with high downhole temperatures, using a drill string or deployed using a coiled tube or bullhead into the fractures, while injecting the treatment fluid below or above the fracture pressure and shut off the contents for a period of time, allowing to react and disintegrate the Biopolymer based formation damage or filter cake completely and subsequently removed by normal flushing techniques known manner.
Detailed Description of Invention:
The present invention provides a method for treating an underground reservoir, which method comprises introducing into the reservoir a treatment
fluid comprising, dissolved or dispersed in water, a Hydrolase enzyme or a combination of Hydrolase Enzymes aimed at a complex Biopolymer substrate, and a Sugar to protect the Hydrolase enzyme from Thermal Deactivation in high downhole temperatures.
The method of the invention fortifies and thermally Stabilizes Hydrolase Enzymes, enabling these to stay active at high downhole temperatures and partially or completely disintegrate Biopolymer Matrix of filter cake formed due to using polysaccharide-containing drilling fluids, in subterranean formations. Without suitable stabilization or fortification, the Hydrolase enzymes would be completely or partially deactivated in the Treatment fluid, and not perform as predicted, in an efficient manner.
When a Biopolymeric Viscosifier based drilling mud is used in a subterranean reservoir, a filter cake forms on the rock matrix by filtering the aqueous fluid from the polymer suspension, through the small rock pores. This filtercake contributes to decreased permeability of the formation and slows down production substantially. This Filtercake of Biopolymeric deposits consists primarily the Long chain Polysaccharide Biopolymers embedding the carbonate weighting agents, often used in water based mud. These Polysaccharides can be Starch or Amylum, Xanthan Gum and derivatives, Cellulose and derivatives like Carboxymethyle Cellulose or Guar Derivatives like Hydroxymethylguar or Hydroxypropylguar.
Starch based Biopolymeric Viscosifiers in formation damage are nothing but glucose polymers linked together by the alpha-1,4 and alpha-1,6 glucosidic bonds. Because of the existence of two types of linkages, the alpha-1,4 and the alpha-1,6, different conformational existence are possible for starch molecules. An un-branched, single chain polymer of 500 to 2000 glucose subunits with only the alpha-1,4 glucosidic bonds is called amylose, while the presence of alpha-1,6 glucosidic linkages results in a branched glucose polymer called amylopectin. The degree of branching in amylopectin is approximately one per twenty-five glucose units in the unbranched segments.
Another Biopolymer used as mud viscosifier is Cellulose, the most abundant biopolymer on earth. Cellulose consists of D-glucopyranose monomer units bound by p (1->4) glycosidic linkages. The cellulose molecule forms a linear, almost fully extended chain with a two-fold screw axis on which successive glucose residues are rotated 180Â° relative to each other and the glycosidic oxygens point alternatively up and down.
Another Biopolymer based gelling agent Guar gum-Galactomannan is a high molecular weight carbohydrate polymer derived from the natural seed of guar plant (Cyampopis tetragonolobus). Part of the seed is Hull (14-17%), Endosperm (35-42%), and germ (43-47%). Guar gum is a polysaccharide consisting of a mannose backbone with a galactose side chain. The
galactose is randomly placed on the mannose backbone with the average ratio 1:2 of galactose to mannose.
Though enzymes offer a number of advantages over conventional chemical catalysts, they are generally unstable in extreme conditions and are inactivated rapidly by heat and other environmental modifications such as changes in pH and ionic disbalance. Since the active site of the enzyme consists of amino acids brought together only in the native three-dimensional structure, an unfolded enzyme loses its catalytic activity.
Therefore, an efficient Enzyme Hydrolysis not only bears commercial value in terms of Enzyme dosage in treatment fluid formulation, it also provides higher predictability of the Enzyme's Kinetic rate in downhole conditions.
The method in this invention includes an addition of sugars to aqueous solutions of the Hydrolase enzymes in the Treatment fluid formulation, thus strengthening the hydrophobic interactions among nonpolar amino acid residues. These interactions, together with hydrogen bonds and ionic and van der Waals interactions, are essential to maintain the native, catalytically active structure of the enzyme. Thus, the strengthened hydrophobic interactions make protein macromolecules more rigid, and therefore more resistant to thermal unfolding, which would otherwise render the Hydrolase enzymes inactive in downhole conditions, when the treatment fluid is pumped and shut in for hours at extremely high temperatures.
This method of enzyme stabilization in the Treatment Fluid formulation in the presence of sugars in aqueous media do not change the protein conformation, but influence the physicochemical properties of the system such as the solvent structure, resulting in protein stabilization. The solvent composition in the immediate domain of the protein is different from that of the bulk solvent and the difference is a function of the concentration of co-solvent. This co-solvent added to the enzyme aqueous solution is excluded from the protein domain and increases the Free Energy shifting the Thermodynamic Equilibrium towards the native state.
In the particular method, the Sugar is Sucrose, a disaccharide of glucose and fructose with an a (alpha) 1,2 Glycosidic linkage and with molecular formula C12H22O11 The concentration of Sucrose in the Treatment fluid should be sufficient to attain Thermal Stability of the 3-D structure of the Enzyme Protein in high downhole temperatures. The concentration of sugar incorporated into the treatment fluid of the present invention will be from 0.1% w/v but may be up to 5% w/v (1 to 50 kgs per m3). In general it has been found that 0.2% to 4% w/v (2 to 40 kgs per m3) sugar when used in combination with the Hydrolase enzymes and 2% brine or sea water, substantially fortifies the enzymes against harsh downhole conditions.
When the Hydrolytic activity of a starch degrading Enzyme is fortified against high downhole temperatures as per this method, Gelatinized and polymerized starch of the formation damage would be actively attacked by the Enzyme components of the treatment fluid in contact. Depending on the relative location of the bond under attack as counted from the end of the chain, the water soluble products could be dextrin, maltotriose, maltose, and glucose, etc. The specificity of the bond attacked by alpha-amylases depends on the sources of the enzymes e.g. bacterial or, fungal. Usually a Bacterial alpha-amylase randomly attacks only the alpha-1,4 bonds, and liquefies gelatinized starch of the Filtercake of the damage, first reducing its viscosity by cutting down chain length and finally rendering it soluble in water.
Amongst the major types of Amylase enzymes, this method of Thermal Stabilization of Treatment Fluid Enzymes relates to Alpha or Endo Amylases, which are 1,4-a-D-glucan glucanohydrolase. The Thermally Stabilized Endo-Amylase, by acting at random locations along the starch chain of the formation damage in contact, will break down long-chain carbohydrates, ultimately yielding maltotriose and maltose from amylose, or maltose, glucose and "limit dextrin" from amylopectin. Because it can act anywhere on the substrate, a-amylase tends to be faster-acting than 3-amylase or Glucoamylases, and hence preferred for this method.
Depending on the type of starch used in the formation damage, Beta or Exo Amylases, 1,4-a-D-glucan maltohydrolase would work from the non-reducing end and catalyze the hydrolysis of the second a-1,4 glycosidic bond, cleaving off two glucose units (maltose) at a time. Finally, the Amyloglucosidase or Glucoamylases component of the treatment fluid would cleave a(1-6) glycosidic linkages and the last a(1-4)glycosidic linkages at the non-reducing end of amylose and amylopectin, yielding glucose.
When thermally protected as per this method against temperature shock at downhole conditions, Cellulolytic Hydrolase enzymes or, cellulases, would hydrolyse -1, 4- glycosidic linkages in cellulose Biopolymer of the formation damage. Three different cellulolytic activities can be used in the process, e.g. Exoglucanases (1, 4- -D-glucan cellobiohydrolase) hydrolyse cellulose from the free chain ends, producing mainly cellobiose and are called Exo cellulase or cellobiohydrolases. Endoglucanases (1,4- D-glucan-4-glucanohydrolase) on the other hand attack randomly internal linkages within the cellulose chain, p -Glucosidases finally hydrolyse small oligomers, mainly trimers and dimers, to water soluble monomers.
When thermally protected as per this method against temperature shock at downhole conditions, the Guar derivative biopolymer Hydrolase enzymes are Galactomannanase or Mannanase type of Hemicellulase that will attack the galactomannosidic and mannosidic linkages in the guar residue, breaking the molecules into monosaccharide and disaccharide fragments, which are soluble in water and renders the mud damage to be easily removable.
These Hydrolase enymes specifically hydrolyze the (1,6)-.alpha.-D-galactomannosidic and the (1,4)-.beta.-D-mannosidic linkages between the monosaccharide units in the guar-containing filter cake respectively.
In the particular method, sufficient amount of Hydrolase enzyme should be present in the Treatment fluid formulation, to be able to efficiently disintegrate and slacken the rigid filter Biopolymer matrix of the formation damage. Depending on the type of Biopolymer used in mud formulation, an Amylase, a Cellulase or a Hemicellulase enzyme should be chosen to work independently or in a combination, whereas the combination of enzymes should be in the same ratio of the biopolymer substrate used in mud formulation. Typically a single enzyme or multiple enzymes together of total 0.1 to 5 % w/v or, 1 to 50 kg/m3 of the Treatment fluid formulation has been found to be suitable for an effective dissolution of the Biopolymer Matrix when Thermally fortified as per this method.
As per the method, the treatment fluid is prepared by dissolving the Thermal Stabilizer Sucrose in suitable water, like city water or produced brine water or sea water and finally the Enzymes are added to the mixing tank. Since no harsh chemicals are used in this method, tank material can be mild steel or a polymer like HDPE. Subsequently other chemical additives like surfactants, chelating agents, antifoam or biocides can be added as are commonly used in the oil industry. A suitable biocide will control growth of unwanted microbes in the treatment fluid during pumping and shut in hours.
The mixed fluid is introduced into the underground formation via injection or production wells and for newly drilled wells the fluid may introduced through the drill string using the mud pumps or spotted by using Coiled tubing or Bullheading to contact the zone of formation damage or filter cakes. Depending on formation and reservoir properties, the treatment fluid would be introduced at pressure below or above fracture pressure.
Depending on the openhole or near wellbore treatments, volume of treatment fluid will typically be at 120% to 200% of the openhole volume or well bore volume, accounting for the leak-offs and dead volumes.
Enzyme kinetics being directly influenced by pH and Temperature conditions at downhole, the enzyme treatment is shut in the formation for a time sufficient to efficiently degrade the damage and as per this method will vary between 45 minutes to a week, preferably 3 to 36 hours for an efficient damage removal.
The present invention has the following particular advantages over the prior art:
The method provides a simple way to Thermally Fortify and maximize the benefits of Hydrolase enzymes for effective removal of Biopolymer based damage from a subterranean formation, where downhole temperatures can be very high and may otherwise deactivate large parts of these enzymes.
Though enzymatic mud breaking offers a number of advantages over conventional chemical catalysts, there is every possibility of enzymes to abruptly retard or even stop working at high downhole temperatures. This makes it difficult for the operator to judge the effectiveness of enzyme in dissociating Biopolymer based formation damage, in a predictable Kinetic rate, and plan his operations accordingly. However, this method of sugar addition to the treatment fluid will strengthen the hydrophobic interactions among non-polar amino acid residues and these interactions, together with hydrogen bonds and ionic and van der Waals interactions, would maintain the native, catalytically active structure of the enzyme and not let it be deactivated at relatively higher temperatures.
An efficient Enzyme Hydrolysis would mean reduction of enzyme doses to attain same level of catalysis rate or cake breakage, directly effecting economics of such process.
Since the non reactive nature of this fluid formulation, it can be easily deployed for deep well stimulation as well as fracture face damage near the surface.
Sugar, being a food grade commodity produced from natural sources, is completely environment friendly and at this level, readily biodegrades when mixed in water or, land
The following example illustrates the invention.
The Thermal stabilizing effect as per current invention was tested by dual method of Filtration rate increase and Reducing Sugar production for a range of Treatment fluids with different concentrations of Thermally Stabilizing Sugar.
Blank filtration rate through perforated disc with Whatman No 1 Filter-paper was checked at 2 Atmosphere Vacuum using 2% brine solution. The Disc was then damaged by passing mud containing Biopolymers like Starch, Xanthan gum, Calcium Carbonate weighting agents and Sodium Hydroxide under 2 Atmosphere vacuum. The filter cake was allowed to settle further by incubating at 90 Deg C for 4 hours. The filtercake was then incubated with different treatment fluids at 105 Deg C for 12 hours. After incubation, the
filtercakes were subjected to 2% brine flow at 2 atmosphere and Filtration rate tested and presented in Table 1.
The Residual filter cake and Filtration Permeates of each sample was collected separately & mixed well. Reducing sugar production due to Enzymatic Hydrolysis was estimated by following method. The aliquoted samples (1.5ml) were centrifuged for 15min at 10,000rpm. The supernatant was collected and centrifuged for 15min at 10,000rpm. The pellets were discarded and 700ul_ supernatant was taken from all the tubes in Boiling Tubes. To this, 50mL Sodium acetate buffer (pH 4.8) and 1.2ml_ DNS ( Dinitrosalicylic Acid Solution) were added and tubes were incubated for 30 min at room temperature. Subsequently, the tubes were put in Boiling water Bath and incubated at 95Â°C for 15mins. The tubes were then transferred to a water bath at Room Temperature for 10min and then incubated at Room Temp for 10min. The coagulated samples were then crushed well in their own contents and fully collected in Eppendorf tubes and centrifuged at 10,000rpm for 10min. Supernatant was collected and diluted with DM water (as per below table 2) to get sufficient volume for Cuvette used in Spectrophotometer. Absorbance was measured at 540nm and calculated back using the formula: Final O.D of sample = [(Vol of Supernatant + Vol of diluting water)/Vol of Supernatant]* Measured O.D. The Reducing sugar production was observed as per Table 2.
Treatment Fluid Compositions
Alpha Amylase Enzyme
Mixed Carbohydrase Enzyme
Alpha Amylase Enzyme
Mixed Carbohydrase Enzyme
Alpha Amylase Enzyme
Mixed Carbohydrase Enzyme
4% 2% 1% 2% Remaining
4% 2% 3% 2% Remaining
4% 2% 5% 2% Remaining
Sample Brine Flow
Damage Brine Flow as % of
Blank after Enzyme
Treatment Crushability of Filter-cake
A-Mud Control 0 4% Hard cake
B- Mud + TFA1 0 62% Crushable cake
C-Mud + TFA2 0 75% Easily crushable and largely soluble cake
D-Mud + TFA3 0 93% Easily crushable and Largely soluble cake
Sample Measured OD Dilution Final OD Blanked OD
Supernat ant (MO Water (Ml)
A-Mud Control I .052 650 350 .079 0
B-Mud+TFA1 .280 650 350 .430 0.351
C-Mud + TFA2 .376 900 600 .626 0.547
D-Mud+TFA3 .529 800 700 .991 0.912
1. A method for sucrose based thermal stabilization of enzymes for breaking of biopolymer damage in gas and oil wells, said enzyme includes Amylase and/or a Biopolymer Hydrolase Enzyme mix of Cellulase and/or Hemicellulase-Mannanase enzymes, the said method comprises step of preparing Thermostable Enzyme Treatment Fluid by combining the Amylase and Hydrolase enzymes with Sucrose and brine and a surfactant, extending into an oil or gas or water producing reservoir via a wellbore with high downhole temperatures, using a drill string or deployed using a coiled tube or bullheaded into the fractures, while injecting the treatment fluid below or above the fracture pressure and shut off the contents for a period of time, allowing to react and disintegrate the Biopolymer based formation damage or filter cake completely and subsequently removed by normal flushing techniques known manner.
2. A method according to claim 1 wherein the underground reservoir is a hydrocarbon reservoir.
3. A method according to claim 2 wherein the hydrocarbon is oil.
4. A method according to claim 2 wherein the hydrocarbon is a gas.
5. A method according to claim 1 wherein the said Hydrolase Enzyme mix is a combination of an Amylase, Cellulase, Hemicellulase, Mannanase & Galactomannanase.
6. A method according to claim 5 wherein all the said enzymes are mixed together or only two of the said enzymes are chosen based on the nature of Biopolymer used in mud formulation.
7. A method according to claim 6 where the said enzymes are mixed in the same ratio of the Biopolymer substrates used in the mud formulation, on basis of declared Enzyme activity units.
8. A method according to claim 1 wherein the said Amylase is an Alpha Amylase enzyme that catalyses the endo-hydrolysis of 1,4-alpha-glycosidic linkages in starch, glycogen, and related polysaccharides and oligosaccharides containing 3 or more 1,4-alpha-linked d-glucose units.
9. A method according to claim 1 wherein the Sucrose is a table sugar or saccharose and/or a disaccharide of glucose and fructose with an a (alpha) 1,2 Glycosidic linkage and with molecular formula C12H22O11.
10. A method according to claim 1 wherein the Sucrose concentration is at least about 0.1% w/v in the treatment fluid.
11. A method according to claim 1 wherein the said Amylase and Hydrolase Enzyme mix are liquid enzyme formulations.
12. A method according to claim 1 wherein the Biopolymer is Starch, Xanthan, Cellulose or Guar Derivatives.
13. A method according to claim 1 wherein the temperature of the formation bearing the Biopolymer based filtercake or mud damage of the reservoir is at least 60Â° C. or higher.
14. A method according to claim 1 wherein the treatment fluid is shut off in the reservoir for at least 45 minutes.
15. A method according to claim 1 wherein the wellbore is vertical, deviated, inclined or horizontal.