CN113416531B - Microbial-based viscosity-reducing oil-displacing fracturing fluid composition and application thereof - Google Patents
Microbial-based viscosity-reducing oil-displacing fracturing fluid composition and application thereof Download PDFInfo
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Abstract
The invention provides a microorganism-based viscosity-reducing oil-displacing fracturing fluid composition and application thereof. The microbial-based viscosity-reducing oil-displacing fracturing fluid composition comprises: thickening agent, microorganism, cross-linking agent, gel breaker and water, wherein the microorganism is Bacillus subtilis, the Latin chemical name is Bacillus subtilis, and the preservation number is CGMCC No.19809. The thickening agent and the cross-linking agent can form a high molecular structure with a specific structure and strength through a cross-linking effect, and can support formation cracks in the process of thick oil exploitation. The gel breaker can break the gel of the high-molecular structure, so that the gel breaker returns, the flow resistance of the thick oil is reduced, and the effect of improving the recovery rate of the thick oil is achieved. The specific bacillus subtilis strain can be propagated by using thickened oil, a thickening agent and the like as carbon sources, secrete viscosity-reducing biosurfactant and micromolecular organic matters, greatly reduce the viscosity of the thickened oil and improve the recovery ratio of the thickened oil.
Description
Technical Field
The invention relates to the field of thickened oil recovery, in particular to a microorganism-based viscosity-reducing oil-displacing fracturing fluid composition and application thereof.
Background
The thickened oil is a multi-hydrocarbon mixture, and has the characteristics of complex composition, high content of colloid and asphaltene, high viscosity, high density, poor fluidity and the like. At present, the main mature technologies of heavy oil production are steam injection thermal production, in-situ combustion, combination of hot water and chemical huff and puff, sand carrying cold production and the like, but the problems of complex process, high cost and the like exist.
The application range of the hydraulic fracturing as an important yield increasing measure for improving the recovery efficiency is continuously increased in the development of the thickened oil, and the fracturing fluid carrying the propping agent is pumped into a reservoir stratum to form a high-flow-guide channel, so that the recovery efficiency of the thickened oil can be effectively improved. The viscous oil has high viscosity and poor fluidity, and the fracturing fluid is required to reduce the viscosity of the viscous oil, increase the fluidity of crude oil and improve the recovery ratio of the viscous oil while forming a high-flow-guide channel by fracturing. An effective method for reducing the viscosity of the thick oil by the fracturing fluid is to add the thick oil viscosity reducer, but the amount of the fracturing fluid injected into an oil reservoir is small, the reachable volume is small, and the duration of the thick oil viscosity reduction effect is short along with the flowback of the fracturing fluid.
The microbial thickened oil viscosity reduction method is characterized in that microbes utilize a carbon source to carry out growth, reproduction and metabolism, and generate a biosurfactant with excellent thickened oil viscosity reduction and oil displacement functions, so that the thickened oil is quickly emulsified and reduced in viscosity, and petroleum is promoted to flow to the bottom of a well in a sandstone matrix, so that the purpose of improving the yield of an oil well is achieved. The microorganism can utilize the carbon source contained in the thick oil to grow and reproduce and metabolize the biosurfactant for a long time, so the sustained effect of the microorganism on viscosity reduction and oil displacement is longer.
The existing literature provides a novel water-based fracturing enzyme-microorganism coupling fracturing fluid system for oil and natural gas exploitation, wherein a chemical auxiliary agent in a water-based fracturing fluid is replaced by a biological auxiliary agent with the same action, and exogenous microorganisms are added to degrade residues and residual gum, so that the gel breaking efficiency is improved, and the formation damage is reduced. The action principle of the pressure liquid system is as follows: biological enzyme gel breaking is adopted, chemical additives in the water-based fracturing fluid are replaced by biological additives with the same effect, and exogenous microorganisms are added to degrade residues and residual gel, so that the gel breaking efficiency is improved.
Another prior document provides a method for reducing the residue of a guanidine gum fracturing fluid, comprising adding a biological enzyme gel breaker to the guanidine gum fracturing fluid, wherein the biological enzyme gel breaker breaks gel at a pH of 7-14 and a temperature of 40-70 ℃, and degrades cross-linked guanidine gum into a gel breaker solution containing polysaccharides, monosaccharides, and residues; adding microorganism gram-negative bacilli into the gel breaking liquid, fermenting the microorganism gram-negative bacilli for 24-48 h at 40-70 ℃ by taking the biological enzyme gel breaking liquid as a nutrient source, converting the gel breaking liquid and residues into small molecular substances, and further degrading the residues which are not degraded by the biological enzyme. The action principle of the pressure liquid system is as follows: adopting biological enzyme to break the gel, and degrading the cross-linked guar gum into gel breaking liquid containing polysaccharide, monosaccharide and residue; adding microorganism gram-negative bacilli into the gel breaking liquid, wherein the microorganism gram-negative bacilli take the biological enzyme gel breaking liquid as a nutrient source, convert the gel breaking liquid and residues into small molecular substances, and further degrade the residues which are not degraded by the biological enzyme.
However, effective propagation of microorganisms cannot be realized in the two methods, so that the two guanidine gum fracturing fluids cannot realize long-acting viscosity reduction and oil displacement. Therefore, in view of the above problems, there is an urgent need in the art to develop a microbial-based viscosity-reducing, oil-displacing and fracturing fluid system to solve the problems of short duration and limited effect of viscosity-reducing effect of the conventional post-fracturing chemical viscosity reducer.
Disclosure of Invention
The invention mainly aims to provide a microorganism-based viscosity-reducing oil-displacing fracturing fluid composition and application thereof, and aims to solve the problems in the prior art.
In order to achieve the above object, the present invention provides a microbial-based viscosity-reducing oil-displacing fracturing fluid composition, which comprises: thickening agent, microorganism, cross-linking agent, gel breaker and water, wherein the microorganism is Bacillus subtilis strain, the Latin chemical name is Bacillus subtilis, and the preservation number is CGMCC No.19809.
Further, the microorganism is present in the formation of a microbial liquid, preferably, the content of the Bacillus subtilis strain in the microbial liquid is 1.0X 10 7 ～1.0×10 11 CFU。
Further, the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition comprises the following components in parts by weight: 0.10 to 0.30 portion of thickening agent, 5 to 15 portions of microbial solution, 0.10 to 0.20 portion of cross-linking agent, 0.01 to 0.03 portion of gel breaker and the balance of water.
Further, the microorganism-based viscosity-reducing, oil-displacing and fracturing fluid composition also comprises a clay stabilizer and/or a cleanup additive.
Further, the microorganism-based viscosity-reducing, oil-displacing and fracturing fluid composition comprises 0-0.3 part of clay stabilizer and 0-0.3 part of cleanup additive in parts by weight.
Further, the gel breaker is a biological gel breaker.
Further, the thickening agent is selected from one or more of the group consisting of natural galactomannan-based compounds (guar gum, hydroxypropyl guar gum, carboxymethyl hydroxypropyl bis-derivative guar gum, hydroxypropyl carboxymethyl guar gum), polyacrylamide organic compounds, cellulose-based thickening agents (carboxymethyl cellulose, carboxyethyl cellulose, carboxymethyl pathogenic cellulose).
The application also provides an application of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition in a thick oil viscosity-reducing system.
Furthermore, the addition amount of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition is 20-30 wt%.
By applying the technical scheme of the invention, the thickening agent and the cross-linking agent can form a high molecular structure with specific structure and strength through cross-linking, and can support formation cracks in the process of thick oil exploitation. The gel breaker can break the gel of the high-molecular structure, so that the gel breaker returns, the flow resistance of the thick oil is reduced, and the effect of improving the recovery rate of the thick oil is achieved. The specific bacillus subtilis strain belongs to a novel strain obtained by the applicant, and can be propagated by using thickened oil, a thickening agent and the like as carbon sources and secrete viscosity-reducing biosurfactant and small molecular organic matters. The biosurfactant can greatly reduce the viscosity of the thick oil (for example, the viscosity of the thick oil is 4400mPa & s to 185mPa & s, and the viscosity reduction rate reaches 95.8%), and the biosurfactant can solve the problems of low yield, difficult pipeline transportation and treatment of the thick oil on the ground and the like after fracturing modification of an underground thick oil reservoir which is difficult to flow. Because the microorganism can be effectively propagated in the thick oil and continuously secretes the viscosity-reducing biosurfactant, the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition provided by the application can be applied to the field of thick oil exploitation for a long time and has an obvious viscosity-reducing effect, so that the development of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition provided by the application has a very good promoting effect on the field of thick oil exploitation and has a higher economic value.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the invention and, together with the description, serve to explain the invention and not to limit the invention. In the drawings:
FIG. 1 is an electron micrograph obtained by subjecting the microorganism obtained in the example to a scanning electron micrograph test;
fig. 2 is an electron microscope image obtained by performing a scanning electron microscope test on a core before displacing a microorganism-based viscosity-reducing flooding fracturing fluid gel breaking liquid in example 1.
Fig. 3 is an electron microscope image obtained by performing a scanning electron microscope test on a core after the displacement of the microbial-based viscosity-reducing flooding fracturing fluid gel breaking liquid in example 1.
Preservation information of the strains of the invention
A Bacillus subtilis strain is characterized in that the Bacillus subtilis strain is Latin, namely Bacillus subtilis, and is preserved in the China general microbiological culture Collection center (CGMCC), the preservation address is No. 3 of No.1 Hospital, no. 3 of Beijing, chaoyang, the preservation date is 2020, 5 and 12 days, and the preservation number is CGMCC No.19809.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the existing post-fracturing chemical viscosity reducers have the problems of short duration of viscosity reduction action and limited action effect. In order to solve the technical problem, the application provides a microbial-based viscosity-reducing oil-displacing fracturing fluid composition, which comprises: thickening agent, microorganism, cross-linking agent, gel breaker and water, wherein the microorganism is Bacillus subtilis with Latin chemical name of Bacillus subtilis strain and the preservation number of CGMCC No.19809.
The thickening agent and the cross-linking agent can form a high molecular structure with a specific structure and strength through a cross-linking effect, and can support formation cracks in the process of thick oil exploitation. The gel breaker can break the gel of the high-molecular structure, so that the gel breaker returns, the flow resistance of the thick oil is reduced, and the effect of improving the recovery rate of the thick oil is achieved. The specific bacillus subtilis strain belongs to a novel strain obtained by the applicant, and can be propagated by using thickened oil, a thickening agent and the like as carbon sources and secrete viscosity-reducing biosurfactant and small molecular organic matters. The biosurfactant can greatly reduce the viscosity of the thick oil (for example, the viscosity of the thick oil is 4400mPa & s to 185mPa & s, and the viscosity reduction rate reaches 95.8%), and the biosurfactant can solve the problems of low yield, difficult pipeline transportation and treatment of the thick oil on the ground and the like after fracturing modification of an underground thick oil reservoir which is difficult to flow. Because the microorganism can be effectively propagated in the thick oil and continuously secretes the viscosity-reducing biosurfactant, the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition provided by the application can be applied to the field of thick oil exploitation for a long time and has an obvious viscosity-reducing effect, so that the development of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition provided by the application has a very good promoting effect on the field of thick oil exploitation and has a higher economic value.
During the application process, the microorganisms (bacillus subtilis strains) exist in the form of bacterial liquid. For example, in a preferred embodiment, the seed solution is added to the culture medium at an inoculum size of 5wt%, and cultured at 35 ℃ for 36 hours at 170rpm to obtain the microbial broth.
The medium employed may be of a composition commonly used in the art. In a preferred embodiment, the culture medium comprises sucrose (12 g/L), NH 4 Cl 1.5g/L，K 2 HPO 4 ·12H 2 O 3.0g/L，KH 2 PO 4 0.5g/L，NaCl 10g/L，FeSO 4 ·7H 2 O0.015g/L，MnSO 4 0.005g/L，CuSO 4 ·5H2O 0.005g/L，pH 6.5。
More preferably, the content of the microorganism (Bacillus subtilis strain) in the microbial solution is 1.0X 10 7 ～1.0×10 11 CFU。
The specific microorganism is added into the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition, so that the fracturing fluid composition has a continuous and efficient viscosity-reducing effect. In order to better improve the viscosity reducing effect, the dosage of each component in the fracturing composition needs to be optimized. In a preferred embodiment, the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition comprises the following components in parts by weight: 0.10-0.30 part of thickening agent, 5-15 parts of microbial liquid, 0.10-0.20 part of cross-linking agent, 0.01-0.03 part of gel breaker and the balance of water. The dosage of the components comprises but is not limited to the range, and the dosage can be limited in the range, so that the cross-linking effect of the thickening agent and the cross-linking agent can realize better synergistic effect with the viscosity reduction effect of microorganisms, and the effects of viscosity reduction and thickened oil yield increase and efficiency improvement can be further improved.
In order to further improve the practical effect of the microbial-based viscosity-reducing, oil-displacing and fracturing fluid composition provided by the application in the process of heavy oil production, because different production strata have different stratum structures and compositions, in a preferred embodiment, the microbial-based viscosity-reducing, oil-displacing and fracturing fluid composition further comprises a clay stabilizer and/or a cleanup additive.
The addition of clay stabilizers can inhibit formation clay swelling and clay particle migration. The addition of the discharge assistant is beneficial to improving the discharge of working residual liquid from the stratum in the fracturing action process. More preferably, the microorganism-based viscosity-reducing, oil-displacing and fracturing fluid composition comprises, by weight, 0-0.3 part of a clay stabilizer, 0-0.3 part of a cleanup additive and 0.01-0.03 part of a biological enzyme gel breaker.
In the microorganism-based viscosity-reducing, oil-displacing and fracturing fluid composition, a thickening agent, a cross-linking agent, a clay stabilizer, a cleanup additive and a gel breaker can be of the types commonly used in the field.
Alternatively, the thickening agent includes, but is not limited to, one or more of the group consisting of natural galactomannan-based compounds (guar gum, hydroxypropyl guar gum, carboxymethyl hydroxypropyl bis-derivatized guar gum, hydroxypropyl carboxymethyl guar gum), polyacrylamide based organics, cellulosic thickening agents (carboxymethyl cellulose, carboxyethyl cellulose, carboxymethyl pathogenic cellulose).
The cross-linking agent comprises one or more of a polyepoxy compound pEPC, a modified organoboron and methylene bisacrylamide. Such breakers include, but are not limited to, biological enzyme breakers (e.g., beta-mannanase, and the like). Compared with a chemical gel breaker, the biological enzyme gel breaker has more excellent gel breaking effect and less damage to the stratum.
Another aspect of the present application also provides a method for preparing a preferred fracturing fluid: adding thickener (such as guar gum) into water under stirring, and stirring for 30min; adding the microbial liquid, uniformly stirring, selectively adding the clay stabilizer, the cleanup additive, the gel breaker and the cross-linking agent, and uniformly stirring and mixing to form the required guanidine gum fracturing fluid.
The application further provides an application of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition in a thick oil viscosity-reducing system.
The microbial-based viscosity-reducing, oil-displacing and fracturing fluid composition has a long-term and stable viscosity-reducing effect in the process of thick oil exploitation, so that the composition has a very good promoting effect on the development of the industry when being applied to the field of thick oil exploitation, and has a high economic value.
Preferably, the addition amount of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition is 20-30 wt%.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
Culture process of microbial species in examples:
adding the seed solution into the culture medium according to the inoculation amount of 5wt%, and culturing at 35 deg.C and 170rpm for 36h to obtain microorganism solution. The culture medium comprises sucrose 12g/L and NH 4 Cl 1.5g/L，K 2 HPO 4 ·12H 2 O 3.0g/L，KH 2 PO 4 0.5g/L，NaCl 10g/L，FeSO 4 ·7H 2 O 0.015g/L，MnSO 4 0.005g/L，CuSO 4 ·5H2O 0.005g/L，pH 6.5。
The morphological appearance of the strain is observed by a scanning electron microscope, as shown in figure 1, the strain is bacillus, the size is (0.5-0.6) Mumx (2-3) Mum, no capsule exists, the flagellum is generated in the cycle, the strain can move, and the strain is preliminarily identified as the bacillus. The identification was carried out using the gram stain-identifying bacteria method, and as shown in FIG. 2, the result showed that the strain XJ-21 was a gram-positive bacterium.
16S rRNA gene sequence analysis is carried out on the strain, and phylogenetic analysis is carried out according to the 16S rRNA gene sequencing result, and a phylogenetic tree is shown in figure 3. The analysis result shows that the strain XJ-021 has the highest homology with Bacillus subtilis NBRC 101239. Therefore, the bacillus subtilis is identified as bacillus by combining the morphological observation and the physiological and biochemical characteristics of the thallus.
The preparation process of the fracturing fluid system comprises the following steps: adding a thickening agent (such as guar gum) into water under stirring, and stirring for 30min; adding the microbial liquid, uniformly stirring, selectively adding the clay stabilizer, the cleanup additive, the gel breaker and the cross-linking agent, and uniformly stirring and mixing to form the required guanidine gum fracturing fluid.
Example 1
The microbial-based viscosity-reducing, oil-displacing and fracturing fluid system provided by the embodiment comprises microbial fluid, guar gum and a fracturing fluid additive, and comprises the following components in parts by weight: 0.10 part of thickening agent (hydroxypropyl guanidine gum), 15 parts of microbial fluid, 0.10 part of cross-linking agent (modified organic boron, new Polymer industry and trade Limited liability company of Clarity City, XJ-03), 0.3 part of clay stabilizer (organic quaternary ammonium salt polymer, clarity Correct Chenopodium Limited liability company of Clarity City, JN-1), 0.3 part of cleanup additive (rhamnolipid), 0.01 part of biological enzyme gel breaker (beta-mannase), and the balance of water for 100 parts.
The fracturing fluid gel breaking solution is obtained after gel breaking of the prepared fracturing fluid, and tests are carried out on the viscosity reduction performance and the oil displacement performance of the thick oil of the gel breaking solution.
(1) Viscosity reduction performance test of gel breaking liquid
And (3) adding 30g of the gel breaking solution into 70g of dehydrated thick oil (the source of the thick oil is Xinjiang oil field Ji 7 well region), uniformly shaking, placing in a 60 ℃ oven, and measuring the viscosity change of the crude oil before and after.
After 2 days, the viscosity of the thick oil is reduced from 4400 mPas to 620 mPas, and the viscosity reduction rate is 85.9%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 188 mPas, and the viscosity reduction rate is 95.8%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: and (3) placing the standard natural rock core in a drying oven at 105 ℃ for drying, establishing saturated oil by using crude oil with the viscosity of 1.5mPa & s, and then respectively carrying out displacement experiments. Filling the prepared simulated formation water into an intermediate container, displacing a core of saturated oil until no oil is produced, reading the scale of an oil-water separator, and calculating the crude oil production degree; filling the gel breaking liquid into an intermediate container, displacing the water-driven rock core (10 PV), and recording the 1 st oil production; closing valves at the front end and the rear end of the rock core, keeping the confining pressure at 2MPa, and incubating for 2d in a holder; using simulated formation water to drive until oil is not produced, and recording the second oil production; and the sum of the secondary oil recovery is the total oil recovery, and the final oil recovery degree is calculated according to the total oil recovery. The final recovery ratio of the core displacement experiment is 64.41%, wherein the oil displacement rate of water is 49.3%, and the oil displacement rate of the gel breaking liquid is 15.11%.
(3) And (3) carrying out scanning electron microscope test on the rock core before and after displacement of the gel breaking liquid of the microbial-based viscosity-reducing oil-displacing fracturing fluid.
And observing the state change of the rock core before and after displacement. Fig. 2 shows an electron micrograph before displacement, and fig. 3 shows an electron micrograph after displacement. The rectangular area in fig. 3 clearly shows that rod-shaped thalli exist in the pores of the rock core, and microorganisms have growth and reproduction phenomena in the displaced rock core, which indicates that the microorganisms in the fracturing fluid can enter the rock core to grow and metabolize to generate active substances.
Example 2
The microbial-based viscosity-reducing, oil-displacing and fracturing fluid system provided by the embodiment comprises microbial fluid, guar gum, a fracturing fluid auxiliary agent and a cross-linking agent, and comprises the following components in parts by weight:
0.20 part of thickening agent (hydroxypropyl guanidine gum), 10 parts of microbial liquid (XJ-21 fermentation liquid), 0.10 part of cross-linking agent (modified organic boron, new Polymer industry and trade company, limited liability company, clarity, inc.), 0.3 part of clay stabilizing agent (organic quaternary ammonium salt polymer, correct Chenopodium company, clarity, inc., manufacturer, JN-1), 0.3 part of cleanup additive (rhamnolipid), 0.01 part of biological enzyme gel breaker (beta-mannase), and the balance of water to make up 100 parts.
The fracturing fluid gel breaking solution is obtained after gel breaking of the prepared fracturing fluid, and tests are carried out on the viscosity reduction performance and the oil displacement performance of the thick oil of the gel breaking solution.
(1) Viscosity reduction performance test of gel breaking liquid
The procedure was as in example 1.
After 2 days, the viscosity of the thick oil is reduced from 4400 mPas to 612 mPas, and the viscosity reduction rate is 86.1%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 183 mPas, and the viscosity reduction rate is 95.8%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: the procedure is as in example 1.
The final recovery ratio of the core displacement experiment is 62.76%, wherein the oil displacement rate of water is 47.59%, and the oil displacement rate of the gel breaking liquid is 15.17%.
Example 3
The microbial-based viscosity-reducing, oil-displacing and fracturing fluid system provided by the embodiment comprises microbial fluid, guar gum, a fracturing fluid auxiliary agent and a cross-linking agent, and comprises the following components in parts by weight:
0.30 part of thickening agent (hydroxypropyl guanidine gum), 5 parts of microbial solution (XJ-21 fermentation liquor), 0.20 part of cross-linking agent (modified organic boron, new Polymer industry and trade company, inc. of Clarity City, XJ-03), 0.3 part of clay stabilizer (organic quaternary ammonium salt polymer, correct Chenopodium company, clarity City, JN-1), 0.3 part of cleanup additive (rhamnolipid), 0.01 part of biological enzyme gel breaker (beta-mannase), and the balance of water to make up 100 parts.
The fracturing fluid gel breaking solution is obtained after gel breaking of the prepared fracturing fluid, and tests are carried out on the viscosity reduction performance and the oil displacement performance of the thick oil of the gel breaking solution.
(1) Viscosity reduction performance test of gel breaking liquid
The procedure was as in example 1.
After 2 days, the viscosity of the thick oil is reduced from 4400 mPas to 723 mPas, and the viscosity reduction rate is 83.6%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 199 mPas, and the viscosity reduction rate is 95.5%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: the procedure is as in example 1.
The final recovery ratio of the core displacement experiment is 64.55%, wherein the oil displacement rate of water is 48.25%, and the oil displacement rate of the gel breaking liquid is 16.3%.
Example 4
The microbial-based viscosity-reducing, oil-displacing and fracturing fluid system provided by the embodiment comprises microbial fluid, guar gum, a fracturing fluid auxiliary agent and a cross-linking agent, and comprises the following components in parts by weight:
0.20 part of thickening agent (hydroxypropyl guanidine gum), 2 parts of microbial solution (XJ-21 fermentation liquor), 0.10 part of cross-linking agent (modified organic boron, new Polymer industry and trade Limited liability company in Clarity City, XJ-03), 0.3 part of clay stabilizer (organic quaternary ammonium salt polymer, correct Chenopodium Limited liability company in Clarity City, JN-1), 0.3 part of cleanup additive (rhamnolipid), 0.01 part of biological enzyme gel breaker (beta-mannase), and the balance of water to make up 100 parts.
The fracturing fluid gel breaking solution is obtained after gel breaking of the prepared fracturing fluid, and tests are carried out on the viscosity reduction performance and the oil displacement performance of the thick oil of the gel breaking solution.
(1) Viscosity reduction performance test of gel breaking liquid
The procedure was as in example 1.
After 2 days, the viscosity of the thick oil is reduced from 4400 mPas to 2300 mPas, and the viscosity reduction rate is 47.73%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 430 mPas, and the viscosity reduction rate is 90.23%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: the procedure is as in example 1.
The final recovery ratio of the core displacement experiment is 58.75 percent, wherein the oil displacement rate of water is 48.25 percent, and the oil displacement rate of the gel breaking liquid is 10.5 percent.
Example 5
The differences from example 2 are: the clay stabilizer, the cleanup additive and the bio-enzyme breaker are not added.
(1) Viscosity reduction performance test of gel breaking liquid
The procedure was as in example 1.
After 2 days, the viscosity of the thick oil is reduced from 4400 mPas to 2750 mPas, and the viscosity reduction rate is 37.5%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 740 mPas, and the viscosity reduction rate is 83.18%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: the procedure is as in example 1.
The final recovery ratio of the core displacement experiment is 58.15%, wherein the oil displacement rate of water is 47.92%, and the oil displacement rate of the gel breaking liquid is 10.23%.
Comparative example 1
The differences from example 2 are: the above microbial solution was not added.
(1) Viscosity reduction performance test of gel breaking liquid
The procedure was as in example 1.
After 2 days, the viscosity of the thick oil is reduced from 4400mPa & s to 3150mPa & s, and the viscosity reduction rate is 28.41%; after 6 days, the viscosity of the thick oil is reduced from 4400 mPas to 2670 mPas, and the viscosity reduction rate is 39.32%.
(2) Testing of oil displacement performance of gel breaking liquid
Core displacement experiment: the procedure is as in example 1.
The final recovery ratio of the core displacement experiment is 52.04%, wherein the oil displacement rate of water is 48.13%, and the oil displacement rate of the gel breaking liquid is 3.91%.
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects: compared with the existing oil displacement composition, the microbial-based viscosity-reducing oil displacement fracturing fluid composition provided by the application is applied to the field of heavy oil exploitation, has a relatively obvious viscosity-reducing effect, and is beneficial to greatly improving the recovery ratio of heavy oil.
It is noted that the terms first, second and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described or illustrated herein.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (3)
1. The microbial-based viscosity-reducing oil-displacing fracturing fluid composition is characterized by comprising the following components in parts by weight: 0.10-0.30 part of thickening agent, 5-15 parts of microorganism, 0.10-0.20 part of cross-linking agent, 0.01-0.03 part of gel breaker, 0-0.3 part of clay stabilizer, 0-0.3 part of cleanup additive and the balance of water, wherein the dosage of the clay stabilizer and the dosage of the cleanup additive are not 0, the microorganism is Bacillus subtilis strain, the Latin is Bacillus subtilis, and the preservation number is CGMCC No.19809; the microorganism exists in the form of microorganism liquid, and the content of bacillus subtilis strain in the microorganism liquid is 1.0 multiplied by 10 7 ～1.0×10 11 A CFU; the thickening agent is selected from hydroxypropyl guar gum; the gel breaker is selected from beta-mannanase.
2. The application of the microorganism-based viscosity-reducing oil-displacing fracturing fluid composition of claim 1 in a viscous oil viscosity-reducing system.
3. The application of the microbial-based viscosity-reducing, oil-displacing and fracturing fluid composition in a thick oil viscosity-reducing system according to claim 2, wherein the addition amount of the microbial-based viscosity-reducing, oil-displacing and fracturing fluid composition is 20-30 wt%.
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