CN113505472A - Numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme - Google Patents

Numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme Download PDF

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CN113505472A
CN113505472A CN202110670730.2A CN202110670730A CN113505472A CN 113505472 A CN113505472 A CN 113505472A CN 202110670730 A CN202110670730 A CN 202110670730A CN 113505472 A CN113505472 A CN 113505472A
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姚传进
曲晓欢
达祺安
孟祥祥
孟凡怡
李蕾
王晓璞
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China University of Petroleum East China
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Abstract

The invention provides a numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme, which relates to the technical field of microbial oil recovery and comprises the following specific steps of S1, determining components of enzymatic reaction kinetics, S2, establishing an enzymatic reaction kinetics equation, S3, determining parameters of enzymatic reaction kinetics, S4, establishing an enzymatic reaction kinetics model, S5, establishing a geological concept model based on CMG oil reservoir numerical simulation software, and verifying the accuracy of the enzymatic reaction kinetics model.

Description

Numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme
Technical Field
The invention relates to the technical field of microbial oil recovery, in particular to a numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme.
Background
Hydraulic fracturing has been rapidly developed and widely used as an important measure for increasing the production and injection of oil and water wells. The level of fracturing has a great influence on the development effect of the oil field. At present, a water-based guanidine gum fracturing fluid system is one of the most commonly used systems for reservoir fracturing, but the fracturing fluid can cause damage to the reservoir in the fracturing process, and the development effect of an oil-gas well can be influenced when the fracturing fluid is serious. The traditional gel breaking method is a chemical method, and the chemical gel breaker is generally an oxidizing agent, such as potassium persulfate, ammonium persulfate and the like. However, oxidative breakers suffer from a number of disadvantages, such as randomness, inability to completely degrade guanidine gum chains; the synthetic method belongs to a non-specific reactant, can react with any encountered reactant, such as a pipe, a stratum matrix, hydrocarbon and the like, and the generated substance is incompatible with the stratum to cause damage to the stratum; short gel breaking duration, incomplete gel breaking and the like. Compared with the traditional gel breaker, the biological enzyme provides an effective way for solving the damage of the reservoir fracturing fluid. The biological enzyme gel breaker is environment-friendly and only reacts with a specific polymer, so that additional formation damage cannot be caused; has the advantages of rapid and uniform viscosity reduction capability, small residue and no additional damage to pipelines and strata.
In recent years, the technology for repairing the damage of the reservoir guanidine gum fracturing fluid by using the biological enzyme is generally regarded at home and abroad by the advantages of wide sources, high efficiency, environmental friendliness and the like, and the biological enzyme gel breaker serving as an environment-friendly gel breaker has a unique point in reducing the gel breaking residue of the fracturing fluid compared with the traditional gel breaker. The biological enzyme repairing reservoir guanidine gum fracturing fluid damage technology is mainly characterized in that biological enzyme liquid is injected into an underground oil layer, and the molecular size of the fracturing fluid is reduced by utilizing the gel breaking effect of the biological enzyme, so that gel breaking liquid is easier to discharge from a stratum, and the damage to the reservoir is reduced.
The oil reservoir numerical simulation technology becomes an important means for carrying out optimization design and development effect prediction on an oil field development scheme in the later stage of oil field development. In order to simulate the effect of biological enzyme on repairing the damage of the reservoir guanidine gum fracturing fluid and reduce the risk of field application, a numerical simulation technology for repairing the damage of the reservoir guanidine gum fracturing fluid by the biological enzyme must be developed on the basis of mastering the principle that the biological enzyme degrades the guanidine gum. The simulation research of the biological enzyme repairing reservoir guanidine gum fracturing fluid damage numerical value has important guiding significance for the application of the biological enzyme repairing reservoir guanidine gum fracturing fluid damage technology in mines.
The existing biological enzyme gel breaking technology is mainly based on indoor experimental research and is further applied to field operation. However, the experimental method has the disadvantages of complicated process, excessive limited factors, limited feasible scheme, large difference from field effect and the like. Aiming at the defects, a numerical simulation technology can be used for obtaining more feasible schemes in a short time, and the simulation result is more consistent with the field operation effect, so that the risk of field application is reduced.
Disclosure of Invention
The embodiment of the invention provides a numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme, which is characterized in that an enzymatic reaction kinetic equation is established by determining enzymatic reaction kinetic components, enzymatic reaction kinetic parameters are determined, an enzymatic reaction kinetic model is established, a geological concept model is established by combining CMG oil reservoir numerical simulation software, and the accuracy of the enzymatic reaction kinetic model is verified.
In view of the above problems, the technical solution proposed by the present invention is:
a numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme comprises the following steps:
s1, determining enzymatic reaction kinetic components, wherein the enzymatic reaction kinetic components comprise biological enzyme, guar gum, degraded guar gum and water;
s2, establishing an enzymatic reaction kinetic equation;
s3, determining an enzymatic reaction kinetic parameter comprising the half-life t1/2Residual coefficient of resistance FrThe number of reaction stages n and the reaction frequency factor k0；
S4, establishing an enzymatic reaction kinetic model;
and S5, establishing a geological concept model based on CMG oil reservoir numerical simulation software, and verifying the accuracy of the enzymatic reaction kinetic model.
Further, in the above-mentioned case,
the molecular weight range of the biological enzyme is 10000-1000000 g/mol;
the molecular weight range of the guar gum is 100000-300000 g/mol;
the molecular weight range of the degraded guar gum is 10000-100000 g/mol;
and the water is proper.
Further, in the above-mentioned case,
the kinetic equation of the degradation reaction of the guanidine gum is as follows:
aG1→ bW; formula (1)
In the formula: g1Is guanidine gum; w is water; a. b isA coefficient is to be calculated;
② the reaction kinetic equation of degrading guanidine gum by biological enzyme is:
cG1+dE→eG2+ fE; formula (2)
In the formula: g2Degraded guanidine gum; e is a biological enzyme; c. d, e and f are coefficients to be solved.
Further, in the above-mentioned case,
firstly, determining kinetic parameters of the guanidine gum degradation reaction:
aG1formula (3) of → bW
The half-life t of the degradation of the guar gum can be determined according to the existing experimental data1/21000 days, residual drag coefficient Fr＝12；
Determining reaction kinetic parameters of the guanidine gum degradation by the biological enzyme:
cG1+dE→eG2+ fE formula (4)
According to the Mie's equation, when the concentration of the substrate is very small, the product generation rate and the concentration of the substrate are in a linear relation and are expressed as first-order reaction characteristics, so that the reaction order number n is 1;
third reaction frequency factor k0The arrhenius equation was used to determine:
Figure BDA0003119130140000041
Figure BDA0003119130140000042
in the formula: k is a reaction rate constant; k is a radical of0Is a reaction frequency factor; eaTo activate energy, EaHas the unit of kJ. mol-1(ii) a R is a molar gas constant, R is 8.314J mol-1·K-1(ii) a T is the absolute temperature, the unit K of the absolute temperature T; t is t1/2For substrate concentration half-life, substrate concentration half-life t1/2The unit of (d);
wherein, during the enzymatic reaction, the temperature change is not considered for the reactionInfluence of the rate, so activation energy Ea＝0。
Further, the enzymatic reaction kinetics model establishes a geological concept model through a Builder module in CMG reservoir numerical simulation software, and utilizes a STARS thermal recovery and chemical flooding simulator, wherein the specific formula is as follows:
the biological enzyme migration equation is as follows:
Figure BDA0003119130140000043
in the formula, DE' is the diffusion convection coefficient of the biological enzyme (experimentally determined); e is the concentration of the biological enzyme, g/L (one/L); gamma-shaped∞Change of biological enzyme concentration (determined by experiments) caused by the fact that the surface of a unit rock volume is filled with a monolayer of biological enzyme, g/L; a. b is a constant and is determined by experiments; vwThe water phase seepage velocity is cm/h; swThe water saturation; Φ is porosity.
Metabolite transport equation:
Figure BDA0003119130140000051
wherein i is the ith component in the nutrient substrate; ciIs the concentration of the product i component, g/L; dci' is the convective diffusion coefficient of the nutrient substrate i (determined experimentally); y isi/EThe yield of the component metabolite is expressed as the concentration variation of the component i, g/g, along with the variation rate of the biological enzyme; n isiIs the rate of metabolism of the biological enzyme, h-1；
Figure BDA0003119130140000052
The amount of the component i which is a product generated when the biological enzyme is metabolized; Γ 'of'∞Is the maximum concentration of the i component of the unit rock adsorption product (determined by experiments), g/L;
Figure BDA0003119130140000053
the amount of the i component which is a rock adsorption product; a 'and b' are respectively the adsorption constants of the products, and the experiment determines。
Further, a Builder module of CMG oil reservoir numerical simulation software is utilized to establish a geological concept model of a one-injection one-extraction five-point method in a Cartesian coordinate system, and a 10 multiplied by 9 grid system is adopted to optimize a damage scheme of the biological enzyme repaired rock core guanidine gum fracturing fluid;
introducing a guar gum-biological enzyme system through a Process Wizard Process guide of CMG oil reservoir numerical simulation software;
introducing a Reaction kinetic equation of natural degradation of the guar gum and degradation of the guar gum by biological enzyme through a Reaction module of CMG oil reservoir numerical simulation software;
setting injection parameters, and calculating the damage rate and the repair rate of the rock core;
the implantation parameters include: guanidine gum injection concentration, biological enzyme injection concentration and biological enzyme-guanidine gum reaction frequency factor;
analyzing parameter sensitivity;
and sixthly, optimizing parameters.
Compared with the prior art, the invention has the beneficial effects that: the method has the advantages that the enzymatic reaction kinetic equation is utilized, the natural degradation process of the guanidine gum and the process of degrading the guanidine gum by the biological enzyme are quantitatively described, the CMG oil reservoir numerical simulation software is combined, the functional development is carried out on the numerical simulation of the injury of the guanidine gum fracturing fluid of the biological enzyme repairing reservoir, a set of practical numerical simulation method for repairing the injury of the guanidine gum fracturing fluid of the reservoir by the biological enzyme is formed, and an important reference basis is provided for the technology of repairing the injury of the guanidine gum fracturing fluid of the reservoir by the biological enzyme applied to the oil field.
The foregoing description is only an overview of the technical solutions of the present invention, and the embodiments of the present invention are described below in order to make the technical means of the present invention more clearly understood and to make the above and other objects, features, and advantages of the present invention more clearly understandable.
Drawings
FIG. 1 is a flow chart of a numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzymes;
FIG. 2 is a graph of substrate concentration versus enzyme reaction rate for an enzymatic reaction;
FIG. 3 is a three-dimensional view of a geological conceptual model;
FIG. 4 is a graph showing the viscosity-concentration relationship of guar gum;
FIG. 5 is a graph of the relationship between the core damage rate and the guar gum injection concentration;
FIG. 6 is a graph showing the relationship between the damage rate and the repair rate of a rock core and the injection concentration of guar gum;
FIG. 7 is a graph showing the relationship between the damage rate and the repair rate of a rock core and the injection concentration of a biological enzyme;
FIG. 8 is a graph showing the relationship between the core damage rate and the repair rate and the bio-enzyme-guanidine gum reaction frequency factor.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
Referring to the attached figure 1, a numerical simulation method for repairing damages of reservoir guanidine gum fracturing fluid by biological enzyme comprises the following steps:
and step S1, determining enzymatic reaction kinetic components, wherein the enzymatic reaction components mainly comprise biological enzyme, guar gum, degraded guar gum and water. According to the indoor experimental data, the molecular weight of the guar gum before degradation is 139034.5g/mol, and the molecular weight of the guar gum after degradation is 27806.9 g/mol. However, since in the STARS module of the CMG, a default value of 10E is used-7Rather than algebraically, the flow equation is formed by the numerical differentiation of the concentration excursion of (a). Thus, when defining a high molecular weight polymer (e.g. 10 e)+6) The numerical stability of the simulator may be reduced. Since the concentration of the polymer is very low in the mole fraction based model, if the value varies more than the injected mole fraction, inaccurate differentiation may occur, which affects the convergence of the calculation. Also, when water is injected at the end of the simulation to displace the polymer out of the reservoir, the numerical stability may be reduced, and further reduction in polymer concentration may result in poorer differential calculations. To solve this problem, we need to define a comparisonThe "pseudo-polymer" of small molecular weight has the same viscosity and adsorption effect as the polymer of high molecular weight. This "polymer-mimetic" mole fraction approach will retain the mass fraction used for the true polymer mole fraction model. Therefore, the molecular weight of the guar gum before degradation is 8000g/mol, the molecular weight of the guar gum after degradation is 1600g/mol, the molecular weight of water is 18g/mol, and the molecular weight of the biological enzyme is 120 g/mol.
In step S2, according to the enzymatic reaction kinetics component determined in step S1, the following enzymatic reaction kinetics equation is established:
equation of kinetics of degradation reaction of guanidine gum:
1G1→444.44W
in the formula: g1Is guanidine gum; w is water.
② the reaction kinetic equation of degrading guanidine gum by biological enzyme:
200G1+1E→1000G2+1E
in the formula: g2Degraded guanidine gum; e is a biological enzyme.
According to the mass conservation equilibrium reaction equation, the biological enzyme can be regarded as a catalyst in the reaction process, so that the biological enzyme does not change before and after the degradation of the guar gum.
Step S3, determining the kinetic parameters of the enzymatic reaction,
kinetic parameters of the enzymatic reaction include the half-life t1/2Residual coefficient of resistance FrThe number of reaction stages n and the reaction frequency factor k0。
Firstly, determining kinetic parameters of the guanidine gum degradation reaction:
1G1→444.44W
the half-life t of the degradation of the guar gum can be determined according to the existing experimental data1/21000 days, residual drag coefficient Fr＝12。
Determining reaction kinetic parameters of the guanidine gum degradation by the biological enzyme:
200G1+1E→1000G2+1E
from the michaelis equation, when the substrate concentration is very small, the product formation rate is linear with the substrate concentration, showing the first order reaction characteristic, so the reaction order number n is 1, see fig. 2.
Reaction frequency factor k0The arrhenius equation was used to determine:
Figure BDA0003119130140000081
Figure BDA0003119130140000082
in the formula: k is a reaction rate constant; k is a radical of0Is a reaction frequency factor; eaTo activation energy, activation energy EaHas the unit of kJ. mol-1(ii) a R is a molar gas constant, R is 8.314J mol-1·K-1(ii) a T is the absolute temperature, the unit K of the absolute temperature T; t is t1/2For substrate concentration half-life, substrate concentration half-life t1/2The unit of (d);
due to the activation energy E a0, so there is:
Figure BDA0003119130140000091
in this example model, the bio-enzyme-guar reaction frequency factor k0＝5。
Step S4, establishing a reaction kinetic model,
in CMG reservoir numerical simulation software, the biological enzyme and the metabolite thereof obtained by an enzymatic reaction equation are respectively defined as components dissolved in water, and the migration, diffusion, adsorption and other characteristics are considered (the CMG reservoir numerical simulation software default value or the experimental measurement value is adopted in a model), so that the simulation calculation of the migration of the biological enzyme and the metabolite thereof can be realized.
Biological enzyme transport equation:
Figure BDA0003119130140000092
in the formula, DE' is the diffusion convection coefficient of the biological enzyme (experimentally determined); e is the concentration of the biological enzyme, g/L (one/L); gamma-shaped∞Change of biological enzyme concentration (determined by experiments) caused by the fact that the surface of a unit rock volume is filled with a monolayer of biological enzyme, g/L; a. b is a constant and is determined by experiments; vwThe water phase seepage velocity is cm/h; swThe water saturation; Φ is porosity.
Metabolite transport equation:
Figure BDA0003119130140000093
wherein i is the ith component in the nutrient substrate; ciIs the concentration of the product i component, g/L; dci' is the convective diffusion coefficient of the nutrient substrate i (determined experimentally); y isi/EThe yield of the component metabolite is expressed as the concentration variation of the component i, g/g, along with the variation rate of the biological enzyme; n isiIs the rate of metabolism of the biological enzyme, h-1；
Figure BDA0003119130140000094
The amount of the component i which is a product generated when the biological enzyme is metabolized; Γ 'of'∞Is the maximum concentration of the i component of the unit rock adsorption product (determined by experiments), g/L;
Figure BDA0003119130140000101
the amount of the i component which is a rock adsorption product; a 'and b' are the adsorption constants of the products, respectively, and are determined experimentally.
In step S5, a conceptual model is established based on CMG oil reservoir numerical simulation software, and the damage scheme of the biological enzyme repaired core guanidine gum fracturing fluid is optimally designed.
Firstly, a Builder module of CMG oil reservoir numerical simulation software is utilized to establish a geological conceptual model of a one-injection-one-sampling five-point method in a Cartesian coordinate system, a 10 multiplied by 9 grid system is adopted, the geological conceptual model is shown in a figure 3, relevant reservoir and fluid parameters are input, and the parameters in the model are shown in a table 1.
TABLE 1 reservoir and fluid parameters table
Parameter name Numerical value
Reservoir size (m) 10×9×9
Reservoir temperature (. degree.C.) 50
Initial atmospheric pressure (kPa) 101
Formation porosity (%) 22.96
Initial oil saturation (%) 20
Permeability (10)-3μm2) 1000
Guiding in a guar gum-biological enzyme system through a Process Wizard Process guide of CMG oil reservoir numerical simulation software, and referring to the graph in figure 4 by using a guar gum viscosity-concentration relation curve.
And thirdly, introducing a Reaction kinetic equation of natural degradation of the guanidine gum and degradation of the guanidine gum by biological enzyme through a Reaction module of CMG oil reservoir numerical simulation software.
Setting injection parameters, calculating the damage rate and the repair rate of the rock core:
in this example model, the injection parameters include: guar gum injection concentration, biological enzyme injection concentration and biological enzyme-guar gum reaction frequency factor.
In the preset injury model, water is injected for 65min, then guanidine gum is injected for 4min, and finally water is injected all the time. Recording the pressure value after 65min of water injection as P0The pressure value after injecting the guanidine gum fracturing fluid for 4min is P1. In the preset restoration model, water is injected for 65min, then guar gum is injected for 4min, then biological enzyme is injected for 10min, and finally water is injected all the time. Recording the pressure value after 65min of water injection as P0The pressure value after injecting the guanidine gum fracturing fluid for 4min is P1The pressure value after injecting the biological enzyme for 10min and then injecting water for 65min is P2. And respectively calculating the damage rate and the repair rate of the rock core according to the formulas (9) and (10).
Figure BDA0003119130140000111
In the formula: rdThe damage rate of the core fracturing fluid is percent; Δ p0For initial injection pressure p of core0The difference from the pressure (atmospheric pressure) at the extraction port of the core model, kPa; Δ p1For injecting pressure p after core fracturing fluid damage1The difference from the pressure (atmospheric pressure) at the extraction port of the core model, kPa.
Figure BDA0003119130140000112
In the formula: rrThe core biological enzyme repair rate is percent; Δ p2Injecting pressure p after core biological enzyme repair2The difference from the pressure (atmospheric pressure) at the extraction port of the core model, kPa.
Sequentially changing the guar gum injection concentration, the biological enzyme injection concentration and the biological enzyme-guar gum reaction frequency factor, and respectively calculating the damage rate of the rock core under different guar gum injection concentrations (shown in table 2) and the repair rate of the rock core under different guar gum injection concentrations, biological enzyme injection concentrations and biological enzyme-guar gum reaction frequency factors (shown in tables 3-5) by using formulas (9) and (10).
TABLE 2 core damage Rate for different guar injection concentrations
Figure BDA0003119130140000113
Figure BDA0003119130140000121
TABLE 3 core repair Rate for different guar gum injection concentrations
Guar gum injection concentration/%) p0 p1 p2 Repair rate/%)
0.06 121.4 130.76 124.44 87.03
0.08 121.4 371.48 125.88 81.99
0.10 121.4 968.62 134.73 60.48
0.12 121.4 1047.52 147.95 43.45
TABLE 4 core repair Rate at different bio-enzyme injection concentrations
Bio-enzyme injection concentration/%) p0 p1 p2 Repair rate/%)
1.60 121.4 968.62 137.23 56.31
1.80 121.4 968.62 136.54 57.40
2.00 121.4 968.62 134.73 60.48
2.20 121.4 968.62 134.11 61.61
2.40 121.4 968.62 134.47 60.95
2.80 121.4 968.62 136.44 57.56
TABLE 5 core repair Rate for different bio-enzyme-guar reaction frequency factors
Figure BDA0003119130140000122
Figure BDA0003119130140000131
Analyzing parameter sensitivity:
as can be seen from fig. 5, when the guar gum injection concentration increases from 0.06% to 0.08%, the core damage rate increases rapidly; when the injection concentration of the guanidine gum is increased from 0.08% to 0.10%, the injury rate is slowly increased; when the injection concentration of the guanidine gum is increased from 0.10% to 0.12%, the damage rate is only increased by 0.19%, which shows that when the concentration of the guanidine gum is increased to 0.10%, the damage rate of the core is close to the maximum value, so that the change range of the damage rate of the core is not large.
As can be seen from fig. 6, the core restoration rate gradually decreases with the increase of the injection concentration of guar gum, and the larger the injection concentration of guar gum is, the higher the core damage rate is, and the worse the bio-enzyme restoration effect is.
As can be seen from fig. 7, when the bio-enzyme injection concentration is less than 2.2%, the core repair rate increases slowly with the increase of the bio-enzyme injection concentration; when the injection concentration of the biological enzyme is more than 2.2%, the core repair rate is slowly reduced along with the increase of the injection concentration of the biological enzyme; when the concentration of the biological enzyme is about 2.2%, the core restoration rate reaches the maximum value. In the range of 1.6-2.8%, the core restoration rate is 56-62%. The result shows that the concentration of the biological enzyme has an optimal value, and if the concentration is too high or too low, the repairing effect of the biological enzyme on the rock core is poor.
As shown in FIG. 8, when the bio-enzyme-guar reaction frequency factor is less than 0.05h-1When the reaction frequency factor is increased, the core repairing rate gradually increases; when the frequency factor of the biological enzyme-guanidine gum reaction is more than 0.05h-1After that, the core restoration rate gradually decreases with the increase of the reaction frequency factor. The result shows that the reaction frequency factor of the biological enzyme-guanidine gum has an optimal value, and when the reaction frequency factor is smaller than the optimal value, the increase of the reaction frequency factor can accelerate the reaction rate of the biological enzyme for degrading the guanidine gum, so that the core repair rate is increased; however, when the value is larger than the above value, the speed of degrading guar gum by the biological enzyme is too high, so that products after guar gum reaction cannot be timely discharged from the core, and the core restoration rate is reduced.
Sixthly, optimizing parameters:
and analyzing main factors influencing the damage effect of the biological enzyme repaired rock core guanidine gum fracturing fluid by an orthogonal design method, and optimally designing the damage scheme of the biological enzyme repaired rock core guanidine gum fracturing fluid. The orthogonal design parameters adopted in the example are shown in table 6, three parameters of guanidine gum injection concentration, biological enzyme injection concentration and biological enzyme-guanidine gum reaction frequency factor are selected to be orthogonally combined on 4 levels, parameters of the biological enzyme repair core guanidine gum fracturing fluid damage scheme and orthogonal test results are shown in table 7, and the optimal scheme is selected according to the repair rate index.
Table 6 orthogonal design table for repairing damage of rock core guanidine gum fracturing fluid by biological enzyme
Figure BDA0003119130140000141
TABLE 7 tables of bio-enzyme-repaired rock core guanidine gum fracturing fluid damage parameters and orthogonal test results
Figure BDA0003119130140000151
As can be seen from table 7, the scheme 4 parameters are most effective in combination with the levels, which are the design parameter levels: the injection concentration of the guanidine gum is 0.06 percent, the injection concentration of the biological enzyme is 2.40 percent, and the biological enzyme-guanidine gum reaction frequency factor is 5h-1And the final core restoration rate is 87.41%.
The present invention is not limited to the above embodiments, and various other equivalent modifications, substitutions and alterations can be made without departing from the basic technical concept of the invention according to the common technical knowledge and conventional means in the field.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (1)

1. A numerical simulation method for repairing reservoir guanidine gum fracturing fluid damage by biological enzyme is characterized by comprising the following steps:
s1, determining enzymatic reaction kinetic components, wherein the enzymatic reaction kinetic components comprise biological enzyme, guar gum, degraded guar gum and water;
s2, establishing an enzymatic reaction kinetic equation;
s3, determining an enzymatic reaction kinetic parameter comprising the half-life t1/2Residual coefficient of resistance FrThe number of reaction stages n and the reaction frequency factor k0；
S4, establishing an enzymatic reaction kinetic model;
s5, establishing a geological concept model based on CMG oil reservoir numerical simulation software, and verifying the accuracy of an enzymatic reaction kinetic model;
the molecular weight range of the biological enzyme is 10000-1000000 g/mol;
the molecular weight range of the guar gum is 100000-300000 g/mol;
the molecular weight range of the degraded guar gum is 10000-100000 g/mol;
the water is proper;
the kinetic equation of the degradation reaction of the guanidine gum is as follows:
aG1→ bW; formula (1)
In the formula: g1Is guanidine gum; w is water; a. b is a coefficient to be solved;
② the reaction kinetic equation of degrading guanidine gum by biological enzyme is:
cG1+dE→eG2+ fE; formula (2)
In the formula: g2Degraded guanidine gum; e is a biological enzyme; c. d, e and f are coefficients to be solved;
firstly, determining kinetic parameters of the guanidine gum degradation reaction:
aG1formula (3) of → bW
The half-life t of the degradation of the guar gum can be determined according to the existing experimental data1/21000 days, residual drag coefficient Fr＝12；
Determining reaction kinetic parameters of the guanidine gum degradation by the biological enzyme:
cG1+dE→eG2+ fE formula (4)
According to the Mie's equation, when the concentration of the substrate is very small, the product generation rate and the concentration of the substrate are in a linear relation and are expressed as first-order reaction characteristics, so that the reaction order number n is 1;
third reaction frequency factor k0The arrhenius equation was used to determine:
Figure RE-FDA0003257670640000021
Figure RE-FDA0003257670640000022
in the formula: k is a reaction rate constant; k is a radical of0Is a reaction frequency factor; eaTo activate energy, EaHas the unit of kJ. mol-1(ii) a R is a molar gas constant, R is 8.314J mol-1·K-1(ii) a T is the absolute temperature, the unit K of the absolute temperature T; t is t1/2For substrate concentration half-life, substrate concentration half-life t1/2The unit of (d);
wherein, during the enzymatic reaction, the influence of the temperature change on the reaction rate is not considered, so that the activation energy Ea0; the enzymatic reaction kinetics model establishes a geological concept model through a Builder module in CMG oil reservoir numerical simulation software, and utilizes a STARS thermal recovery and chemical flooding simulator, wherein the specific formula is as follows:
the biological enzyme migration equation is as follows:
Figure RE-FDA0003257670640000023
in the formula, DE' is the diffusion convection coefficient of the biological enzyme (experimentally determined); e is the concentration of the biological enzyme, g/L (one/L); gamma-shaped∞The surface of the unit rock volume is full of biological enzyme caused by a monolayer of biological enzymeChange in concentration (determined by experiment), g/L; a. b is a constant and is determined by experiments; vwThe water phase seepage velocity is cm/h; swThe water saturation; phi is porosity;
metabolite transport equation:
Figure RE-FDA0003257670640000031
wherein i is the ith component in the nutrient substrate; ciIs the concentration of the product i component, g/L; dci' is the convective diffusion coefficient of the nutrient substrate i (determined experimentally); y isi/EThe yield of the component metabolite is expressed as the concentration variation of the component i, g/g, along with the variation rate of the biological enzyme; n isiIs the rate of metabolism of the biological enzyme, h-1；
Figure RE-FDA0003257670640000032
The amount of the component i which is a product generated when the biological enzyme is metabolized; Γ 'of'∞Is the maximum concentration of the i component of the unit rock adsorption product (determined by experiments), g/L;
Figure RE-FDA0003257670640000033
the amount of the i component which is a rock adsorption product; a 'and b' are respectively the adsorption constants of the product, and are determined by experiments;
firstly, establishing a geological concept model of a one-injection one-sampling five-point method in a Cartesian coordinate system by using a Builder module of CMG oil reservoir numerical simulation software, and optimizing a damage scheme of the biological enzyme repairing core guanidine gum fracturing fluid by using a 10 multiplied by 9 grid system;
introducing a guar gum-biological enzyme system through a Process Wizard Process guide of CMG oil reservoir numerical simulation software;
introducing a Reaction kinetic equation of natural degradation of the guar gum and degradation of the guar gum by biological enzyme through a Reaction module of CMG oil reservoir numerical simulation software;
setting injection parameters, and calculating the damage rate and the repair rate of the rock core;
the implantation parameters include: guanidine gum injection concentration, biological enzyme injection concentration and biological enzyme-guanidine gum reaction frequency factor;
analyzing parameter sensitivity;
and sixthly, optimizing parameters.
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