Method and system for determining hydrogen ion diffusion coefficient of high-viscosity acid liquor

Abstract

The invention discloses a method and system for determining the hydrogen ion diffusion coefficient of high-viscosity acid liquor, and the method comprises the steps: building an acid liquor flow equation and an acid liquor concentration distribution equation based on the hypothesis of a parallel plate reactor, solving the two equations through the boundary conditions of the flowing process of the acid liquor in the reactor, and determining the hydrogen ion diffusion coefficient of the high-viscosity acid liquor. Forming a chart representing the mapping relation between the hydrogen ion diffusion coefficient and the acid liquor reaction speed by using the current analytical solution; the reaction speed of to-be-evaluated acid liquor is obtained by carrying out a fracture diversion trench acid liquor displacement experiment on the to-be-evaluated acid liquor, and the corresponding hydrogen ion diffusion coefficient is obtained by utilizing the chart. The method overcomes the limitation of a method for obtaining the hydrogen ion diffusion coefficient in the prior art on high-liquid-viscosity acid liquor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field development, and particularly relates to a method and system for determining a hydrogen ion diffusion coefficient of high-viscosity acid liquid. BACKGROUND

[0002] Carbonate rock oil and gas reservoirs are important types of oil and gas reservoirs worldwide. For low-permeability carbonate rock oil and gas reservoirs, acid fracturing is a widely used and relatively effective process and technical means. In order to improve the transformation effect and increase the effective action distance of acid liquid, a high-viscosity acid liquid system is often used in acid fracturing. The hydrogen ion diffusion coefficient is an important parameter of the acid liquid system and is a necessary parameter for optimizing acid fracturing design and acid liquid action distance. Common acid rock reaction kinetics parameter determination is mainly to obtain the hydrogen ion diffusion coefficient, and the determination method currently used at home and abroad is still the traditional rotating rock disc experiment method.

[0003] In the prior art, the hydrogen ion diffusion coefficient of acid liquid is mostly determined by using an acid rock reaction kinetics determination experiment device to obtain the reaction kinetics parameters of different acid liquids. Specifically, the working principle of the traditional rotating rock disc experiment instrument is to rotate the reaction rock disc to drive the acid liquid in the reaction kettle to rotate at a certain angular velocity, and to measure the acid liquid concentration at a certain time interval, and to use the measured concentration to replace the average concentration in the acid tank. Later, the technology was continuously improved on the basis of the rotating rock disc experiment instrument, and the mode was changed from the early "acid liquid not flowing rock disc rotation" to "rock surface fixed acid liquid flowing", so that the determination method is one step closer to the actual situation.

[0004] In the prior art patent technology CN102879546A (a kind of flat plate flow simulation acid rock reaction kinetics parameter test method), it relates to a kind of flat plate flow simulation acid rock reaction kinetics parameter test method.The test method is carried out on the flat high-pressure acid etching and dynamic filtration analysis device, and the specific steps are as follows: (1) coaxially put into core in core holder;(2) the high-pressure filter loss kettle is pumped through vacuum port and nitrogen injection port;(3) the high-pressure filter loss kettle and holder are heated to the set temperature according to the simulation requirements;(4) adjust the rotor speed of screw pump according to the working curve of screw pump and the flow rate requirement of test liquid;(5) inject acid;(6) open the vacuum port and nitrogen injection port to inject nitrogen into high-temperature high-pressure cavity;(7) sampling port sampling;(8) after sampling, titrate acid concentration, and analyze reaction kinetics parameters.The patent document is applicable to the flat plate flow simulation acid rock reaction kinetics parameter test method of different viscosity and flow type acid liquid system, can simulate the actual state when acid liquid and formation rock react, lays a foundation for scientific testing and analysis of reaction kinetics parameters of various acid liquid systems and rock, and simultaneously simulates the dynamic filtration parameters of different working liquids in wellbore and artificial fracture.However, this patent document has poor adaptability to high-viscosity acid liquid, the main reason is that high-viscosity acid liquid is difficult to stir uniformly, the acid concentration at the outlet is difficult to represent the average concentration of acid liquid, thereby causing measurement error, and the acid liquid flow and reaction state are different from the acid liquid flow and reaction in the fracture when using disc measurement.

[0005] Therefore, the prior art needs to provide a scheme for obtaining hydrogen ion diffusion coefficient suitable for high-viscosity acid liquid. SUMMARY

[0006] The purpose of the present application is to provide a scheme for obtaining hydrogen ion diffusion coefficient suitable for high-viscosity acid liquid.

[0007] To solve the above technical problems, the embodiment of the present application provides a method for determining hydrogen ion diffusion coefficient of high-viscosity acid liquid, comprising: based on parallel plate reactor assumption, establishing acid liquid flow equation and acid liquid concentration distribution equation, using the boundary conditions of acid liquid flow process in reactor, solving the equation, and using current analytical solution to form a chart representing the mapping relationship between hydrogen ion diffusion coefficient and acid liquid reaction speed;By carrying out fracture guide groove acid liquid displacement experiment on the acid liquid to be evaluated, the reaction speed of the acid liquid to be evaluated is obtained, and the corresponding hydrogen ion diffusion coefficient is obtained by using the chart.

[0008] Preferably, in the step of establishing the acid flow equation and the acid concentration distribution equation based on the parallel-plate reactor assumption, solving the equations by using the boundary conditions of the acid flow in the reactor, and forming a chart representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid reaction rate by using the current analytical solution, the step comprises: defining a plurality of dimensionless variable expressions for solving the acid flow equation and the acid concentration distribution equation, the plurality of dimensionless variables comprising a ratio of the surface reaction rate to the diffusion rate represented by using the hydrogen ion diffusion coefficient parameter, a rock plate length dimensionless variable represented by using the hydrogen ion diffusion coefficient parameter, and a reaction rate dimensionless variable; solving the acid flow equation and the acid concentration distribution equation by using the boundary conditions of the acid flow in the reactor and the plurality of dimensionless variable expressions to obtain the current analytical solution; and constructing a chart representing the relationship between the hydrogen ion diffusion coefficient and the acid reaction rate by taking the hydrogen ion diffusion coefficient and the reaction rate dimensionless variable as the horizontal and vertical coordinates of the chart respectively based on the analytical solution representing the correlation between the rock plate length dimensionless variable and the reaction rate dimensionless variable.

[0009] Preferably, the boundary conditions are represented by using the following expression:

[0010]

[0011]

[0012]

[0013] C(0,Y)=C0

[0014] wherein D represents the hydrogen ion diffusion coefficient, w represents the plate spacing, C represents the acid concentration, Y represents the unit vertical distance of the rock plate, y represents the distance perpendicular to the rock plate, E f represents the reaction rate constant, C A represents the concentration of the rock plate surface at the boundary, X=x / L, X represents the unit horizontal distance of the rock plate, x represents the distance in the horizontal direction of the rock plate, L represents the length of the rock plate, C0 represents the inlet acid concentration of the parallel-plate reactor, and the plurality of dimensionless variable expressions are represented by using the following expression:

[0015]

[0016]

[0017]

[0018] wherein P represents the ratio of the surface reaction rate to the diffusion rate, L * represents the rock plate length dimensionless variable, R represents the average flow rate of the injected acid liquid * R represents the dimensionless variable of reaction rate.

[0019] Preferably, the acid liquid flow equation is expressed by the following expression:

[0020]

[0021] wherein v x (y) represents the flow rate of the acid liquid along the direction of the plate, R represents the average flow rate of the injected acid liquid, x represents the distance in the horizontal direction of the rock plate, y represents the distance perpendicular to the direction of the rock plate, and w represents the distance between the plates; the acid liquid concentration distribution equation is expressed by the following expression:

[0022]

[0023] wherein D represents the diffusion coefficient of hydrogen ions, and L represents the length of the rock plate, R represents the average flow rate of the injected acid liquid, and C represents the concentration of the acid liquid, Y represents the unit vertical distance of the rock plate, X = x / L, and X represents the unit horizontal distance of the rock plate.

[0024] Preferably, the analytical solution is expressed by the following expression:

[0025]

[0026]

[0027]

[0028] wherein R * R represents the dimensionless variable of reaction rate, P represents the ratio of surface reaction rate to diffusion rate, L * L represents the dimensionless variable of the length of the rock plate, n represents the reaction order, β1, β n … β n+1 respectively represent the coefficients of the approximate boundary layer 1, n, and n+1 order, and Γ represents a function of variable n.

[0029] Preferably, in the step of carrying out a fracture flow channel acid liquid displacement experiment on the acid liquid to be evaluated to obtain the reaction rate of the acid liquid to be evaluated, and using the graph to obtain the corresponding diffusion coefficient of hydrogen ions, the method comprises: calculating the rock consumption rate by measuring the mass change of the rock plate through the experiment, so as to convert the rock consumption rate into the acid liquid reaction rate; and substituting the current acid liquid reaction rate into the graph as the dimensionless variable of reaction rate to obtain the diffusion coefficient of hydrogen ions under the current acid liquid reaction rate.

[0030] Preferably, the amount of rock dissolution at different acid-rock contact times is counted, and the average consumption rate of the rock is calculated as the consumption rate of the rock.

[0031] Preferably, the parallel-plate reactor assumption satisfies the following conditions: the rock plate surface is smooth, laminar flow, no filtration, and the flow field is not affected by the acid-rock reaction occurring on the rock plate surface.

[0032] In another aspect, the embodiments of the present application provide a computer-readable storage medium containing a series of instructions for executing the method steps as described above.

[0033] In addition, the embodiments of the present application also provide a system for determining the hydrogen ion diffusion coefficient of high-viscosity acid, comprising: a chart generation module configured to establish an acid flow equation and an acid concentration distribution equation based on a parallel-plate reactor assumption, solve the equations using the boundary conditions of the acid flow in the reactor, and form a chart representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid reaction rate using the current analytical solution; and a hydrogen ion diffusion coefficient calculation module configured to obtain the reaction rate of the acid to be evaluated by carrying out a fracture flow channel acid displacement experiment on the acid to be evaluated, and obtain the corresponding hydrogen ion diffusion coefficient using the chart.

[0034] Compared with the prior art, one or more embodiments of the above scheme can have the following advantages or beneficial effects:

[0035] The present application provides a method and system for determining the hydrogen ion diffusion coefficient of high-viscosity acid. The method and system comprise: establishing an acid flow equation and an acid concentration distribution equation based on a parallel-plate reactor, solving the equations in combination with boundary conditions, forming a chart representing the relationship between the hydrogen ion diffusion coefficient and the acid-rock dissolution rate, obtaining the acid-rock dissolution rate through an acid-etched fracture acid displacement experiment, and obtaining the hydrogen ion diffusion coefficient according to the chart. The present application forms a method for obtaining the hydrogen ion diffusion coefficient of high-viscosity acid by combining mathematical analytical models and physical experiments. In addition, the present application combines the flow and reaction state of the acid under the condition of the acid-etched fracture flow displacement experiment with the actual condition of acid fracturing, overcomes the limitations of the prior art method for obtaining the hydrogen ion diffusion coefficient for high-viscosity acid, and makes the calculation result more reliable by testing the mass change of the rock plate to obtain the hydrogen ion diffusion coefficient.

[0036] Other features and advantages of the present application will be set forth in the specification, and in part will be apparent from the specification, or can be learned by practice of the present application. The objects and other advantages of the present application will be realized and attained by the structure particularly pointed out in the specification, claims and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0037] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of the specification, illustrate embodiments of the application and are used to explain the present application, but are not intended to limit the application. In the drawings:

[0038] Figure 1 The flow chart of the method for determining the diffusion coefficient of hydrogen ion in high-viscosity acid solution according to the embodiment of the present application.

[0039] Figure 2 The flow chart of the method for determining the diffusion coefficient of hydrogen ion in high-viscosity acid solution according to the embodiment of the present application.

[0040] Figure 3 The schematic diagram of the parallel-plate reactor model in the method for determining the diffusion coefficient of hydrogen ion in high-viscosity acid solution according to the embodiment of the present application.

[0041] Figure 4 The example diagram of the chart representing the relationship between the diffusion coefficient of hydrogen ion and the reaction rate of acid solution in the method for determining the diffusion coefficient of hydrogen ion in high-viscosity acid solution according to the embodiment of the present application.

[0042] Figure 5 The module block diagram of the system for determining the diffusion coefficient of hydrogen ion in high-viscosity acid solution according to the embodiment of the present application. DETAILED DESCRIPTION

[0043] The embodiments of the present application will be described in detail hereinafter with reference to the drawings and embodiments, by which the technical means applied by the present application to solve the technical problems and achieve the technical effects can be fully understood and implemented. It should be noted that, as long as there is no conflict, each embodiment in the present application and each feature in each embodiment can be combined with each other, and the technical solutions formed thereby are all within the protection scope of the present application.

[0044] In addition, the steps shown in the flow chart of the drawings can be executed in a computer system such as a group of computer-executable instructions. Moreover, although the logical order is shown in the flow chart, in some cases, the steps shown or described herein can be executed in an order different from that shown herein.

[0045] The terms used herein are merely used to describe specific embodiments and are not intended to limit the exemplary embodiments. Unless the context clearly indicates otherwise, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well. It will be further understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0046] To solve the above technical problems in the prior art, the embodiment of the present application provides a method and system for determining a hydrogen ion diffusion coefficient of high-viscosity acid liquid.

[0047] Figure 1 A schematic diagram of steps of the method for determining the hydrogen ion diffusion coefficient of high-viscosity acid liquid according to the embodiment of the present application. Figure 2 A schematic diagram of a specific flow of the method for determining the hydrogen ion diffusion coefficient of high-viscosity acid liquid according to the embodiment of the present application. The following will be described in combination with Figure 1 and Figure 2 The method for determining the hydrogen ion diffusion coefficient of high-viscosity acid liquid (referred to as "hydrogen ion diffusion coefficient determination method") according to the embodiment of the present application.

[0048] In step S110, based on the assumption of the parallel plate reactor, an acid liquid flow equation and an acid liquid concentration distribution equation are established, the acid liquid flow equation and the acid liquid concentration distribution equation are solved by using the boundary conditions of the flow process of the acid liquid in the reactor, and thus an analytic solution representing the current result is used to form a chart representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction speed.

[0049] It should be noted that, in the embodiment of the present application, the viscosity range of the high-viscosity acid liquid is 70-120 mPa.s.

[0050] In one embodiment, the assumption of the parallel plate reactor (model) needs to meet the following combination of conditions: the surface of the rock plate is smooth, the flow state of the acid liquid is laminar flow, there is no fluid loss in the flow process, and the flow field is not affected by the acid-rock reaction occurring on the surface of the rock plate.

[0051] Figure 3 A schematic diagram of the parallel plate reactor model in the method for determining the hydrogen ion diffusion coefficient of high-viscosity acid liquid according to the embodiment of the present application. As Figure 3 shown, based on the assumption conditions of the parallel plate reactor model of the smooth surface of the rock plate (the rock plate is used to simulate the rock), the laminar flow, and the no fluid loss, an acid liquid flow reaction equation about the parallel plate reactor model is established.

[0052] The established acid liquid flow rate equation is:

[0053]

[0054] wherein, v x (y) represents the flow rate of the acid liquid along the direction of the plate, wherein, x represents a distance in a horizontal direction of the rock plate, y represents a distance in a vertical direction of the rock plate, and w represents a distance between the plates.

[0055] Assuming that the acid flow field in the parallel plate reactor model is not affected by the acid-rock reaction occurring on the surface of the rock plate, the acid concentration distribution equation of the acid under a steady state condition is as follows:

[0056]

[0057] wherein, D represents a hydrogen ion diffusion coefficient, L represents a length of the rock plate, wherein, x represents a distance in a horizontal direction of the rock plate, y represents a distance in a vertical direction of the rock plate, and w represents a distance between the plates. Y represents a unit vertical distance of the rock plate, and X = x / L, X represents a unit horizontal distance of the rock plate.

[0058] Further, the boundary condition of the steady flow of the acid in the parallel plate reactor model is as follows:

[0059]

[0060]

[0061]

[0062] C(0,Y) = C0 (6)

[0063] wherein, E f represents a reaction velocity constant, C A represents a concentration on the surface of the rock plate at the boundary, and C0 represents an inlet acid concentration of the parallel plate reactor.

[0064] After the construction of the acid flow equation, the acid concentration distribution equation, and the boundary condition of the flow of the acid in the reactor, step S110 defines a plurality of dimensionless variable expressions for solving the acid flow equation and the acid concentration distribution equation. In the embodiment of the present application, the plurality of dimensionless variables include a surface reaction velocity to diffusion velocity ratio represented by the hydrogen ion diffusion coefficient parameter, a rock plate length dimensionless variable represented by the hydrogen ion diffusion coefficient parameter, and a reaction velocity dimensionless variable.

[0065] The plurality of dimensionless variable expressions are represented by the following expressions:

[0066]

[0067]

[0068]

[0069] where P represents the ratio of surface reaction rate to diffusion rate, L * represents the dimensionless variable of rock plate length, R * represents the dimensionless variable of reaction rate.

[0070] Next, the established acid liquid flow equation and acid liquid concentration distribution equation are solved by using the boundary conditions and the multiple dimensionless variable expressions of the acid liquid flow process in the reactor, to obtain the current analytical solution.

[0071] In one embodiment, the analytical solution is expressed by the following expression:

[0072]

[0073]

[0074]

[0075] where n represents the reaction order, β1, β n … β n+1 respectively represent the coefficients of the approximate boundary layer 1, n and n+1 order, and Γ represents the function of variable n.

[0076] Finally, step S110 also constructs a chart representing the relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction rate (also referred to as the "first chart") according to the current analytical solution expression.

[0077] Specifically, based on the current analytical solution (which is used to represent the correlation between the dimensionless variable of rock plate length and the dimensionless variable of reaction rate), the hydrogen ion diffusion coefficient and the dimensionless variable of reaction rate are respectively taken as the horizontal and vertical coordinates of the (first) chart, to construct the first chart representing the relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction rate.

[0078] As can be seen from the above expression (10), R * represents the approximate solution of the high-viscosity acid liquid flowing in the parallel plate reactor model, and the unknowns in the approximate solution are only P, L * and R * , where P and L * can be replaced by expression (7) and expression (8) respectively, and after being expanded by a large amount of data of L * and R * , the first chart is drawn with the hydrogen ion diffusion coefficient as the horizontal coordinate and the dimensionless variable of reaction rate as the vertical coordinate, as shown in FIG. 1. Figure 4 . Figure 4 FIG. 1 shows the changes of the corresponding hydrogen ion diffusion coefficient under different high-viscosity acid liquid reaction rates.

[0079] Thus, after the construction of the first chart is completed, step S120 is entered.

[0080] The step S120 obtains the reaction speed of the acid liquid to be evaluated by carrying out a fracture flow channel acid liquid displacement experiment (i.e., an acid etching fracture flow capacity simulation experiment) on the acid liquid to be evaluated, and obtains the hydrogen ion diffusion coefficient of the acid liquid to be evaluated by using the first chart drawn in the step S110.

[0081] In the step S120, first, the fracture flow channel acid liquid displacement experiment is carried out on the acid liquid to be evaluated. In the embodiment of the present application, the fracture flow channel acid liquid displacement experiment is a laboratory simulation experiment in which the acid liquid to be evaluated is used to displace the formation fluid in a fracture flow channel. The fracture flow channel is simulated by using a core with a parallel plate feature of a fracture.

[0082] In the experiment, the rock consumption speed is calculated by continuously measuring the mass change of the rock plate (i.e., the core of the laboratory experiment), so as to convert the rock consumption speed into the acid liquid reaction speed.

[0083] In one embodiment, the amount of rock dissolution under different acid-rock contact times is counted, and the average consumption speed of the rock is calculated, so as to take the average consumption speed as the rock consumption speed which is to be converted into the acid liquid reaction speed.

[0084] Then, after obtaining the rock consumption speed, the current rock consumption speed is directly taken as the acid liquid reaction speed.

[0085] Finally, the step S120 takes the current acid liquid reaction speed as the reaction speed dimensionless variable into the first chart, and directly obtains the hydrogen ion diffusion coefficient under the current acid liquid reaction speed.

[0086] Example One

[0087] In Example One, a method for calculating the hydrogen ion diffusion coefficient of a cross-linked acid under the condition of 140℃ is provided.

[0088] According to the above-mentioned method for determining the hydrogen ion diffusion coefficient of the present application, the specific step process includes: step 1, based on the parallel plate reactor assumption, the acid liquid flow equation and the acid concentration distribution equation are established, and the boundary conditions are combined for solving, to form a chart of the hydrogen ion diffusion coefficient and the acid-rock dissolution speed; step 2, the acid-rock dissolution speed is obtained through the acid etching fracture acid liquid displacement experiment; step 3, the acid-rock dissolution speed is obtained through the acid etching fracture acid liquid displacement experiment, and the hydrogen ion diffusion coefficient is obtained according to the drawn chart.

[0089] Through the acid etching fracture flow capacity simulation experiment, the rock dissolution speed of the cross-linked acid under the condition of 140℃ is obtained, and the calculation process is shown in Table 1. The hydrogen ion diffusion coefficient is obtained by checking the first chart, and the result is shown in Table 1:

[0090] Table 1 karst velocity and hydrogen ion diffusion coefficient of crosslinked acid

[0091]

[0092] Example Two

[0093] In Example Two, a method for calculating the hydrogen ion diffusion coefficient of a crosslinked acid under the condition of 140 DEG C is provided.

[0094] According to the above-mentioned method for determining the hydrogen ion diffusion coefficient, the specific step flow includes: step 1, based on the parallel plate reactor assumption, the acid liquid flow equation and the acid concentration distribution equation are established, and the boundary conditions are solved to form the chart of the hydrogen ion diffusion coefficient and the acid karst corrosion rate; step 2, the acid corrosion crack acid liquid displacement experiment is used to obtain the acid karst corrosion rate; step 3, the acid corrosion crack acid liquid displacement experiment is used to obtain the acid karst corrosion rate, and the hydrogen ion diffusion coefficient is obtained according to the chart.

[0095] Through the acid corrosion crack conductivity simulation experiment, the karst velocity of the gelled acid under the condition of 140 DEG C is obtained, the calculation process is shown in Table 2, the hydrogen ion diffusion coefficient is obtained by checking the first chart, and the results are shown in Table 2:

[0096] Table 2 karst velocity and hydrogen ion diffusion coefficient of gelled acid

[0097]

[0098] Based on the above-mentioned method for determining the hydrogen ion diffusion coefficient, the embodiment of the present application also provides a computer readable storage medium. The storage medium stores a computer program, and the computer program is executed to run a method for evaluating single well production. The computer program can run computer instructions, the computer instructions include computer program codes, and the computer program codes can be in the form of source code, object code, executable file or some intermediate form.

[0099] The computer readable storage medium can include any entity or device capable of carrying computer program codes, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory (ROM), random access memory (RAM), electric carrier signal, telecommunication signal and software distribution medium.

[0100] It should be noted that the contents of computer-readable storage media may be appropriately increased or decreased according to the requirements of legislation and patent practice in the jurisdiction. For example, in some jurisdictions, the contents may be appropriately increased or decreased according to the requirements of legislation and patent practice. In other jurisdictions, computer-readable storage media may not include electrical carrier signals and telecommunication signals.

[0101] In addition, based on the above-mentioned method for determining the hydrogen ion diffusion coefficient, this embodiment of the invention also provides a system for determining the hydrogen ion diffusion coefficient of high-viscosity acid solutions (also referred to as a "hydrogen ion diffusion coefficient determination system").

[0102] Figure 5 This is a block diagram of a system for determining the hydrogen ion diffusion coefficient of a high-viscosity acid solution, according to an embodiment of this application. Figure 5 As shown, the hydrogen ion diffusion coefficient determination system described in this embodiment of the invention includes: a drawing generation module 51 and a hydrogen ion diffusion coefficient calculation module 52.

[0103] Specifically, the chart generation module 51 is implemented according to the method described in step S110, and is configured to collect multiple dynamic production data about the target well; the data processing module 62 is implemented according to the method described in step S120, and is configured to establish acid flow equations and acid concentration distribution equations based on the parallel plate reactor assumption, solve the equations using the boundary conditions of the acid flow process in the reactor, and thus use the current analytical solution to form a chart representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid reaction rate; the hydrogen ion diffusion coefficient calculation module 52 is implemented according to the method described in step S120, and is configured to obtain the reaction rate of the acid to be evaluated by conducting fracture channel acid displacement experiments on the acid to be evaluated, and obtain the corresponding hydrogen ion diffusion coefficient using the chart established by the chart generation module 51.

[0104] This invention discloses a method and system for determining the hydrogen ion diffusion coefficient of high-viscosity acid solutions. The method and system include: establishing acid flow equations and acid concentration distribution equations based on a parallel plate reactor, solving them in conjunction with boundary conditions to generate a graph relating the hydrogen ion diffusion coefficient to the acid-rock dissolution rate; obtaining the acid-rock dissolution rate through acid displacement experiments in acid-etched fractures; and obtaining the hydrogen ion diffusion coefficient based on the graph. This invention combines mathematical analytical models with physical experiments to develop a method for determining the hydrogen ion diffusion coefficient of high-viscosity acid solutions. Furthermore, under the conditions of acid-etched fracture flow displacement experiments, this invention closely matches the flow and reaction states of the acid solution to actual acid pressure conditions, overcoming the limitations of existing methods for obtaining the hydrogen ion diffusion coefficient for high-viscosity acid solutions. The method of determining the hydrogen ion diffusion coefficient by testing changes in rock mass makes the calculation results more reliable.

[0105] The above merely describes preferred specific embodiments of the present application, but the protection scope of the present application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

[0106] In the description of the present application, unless otherwise specified and limited, the meaning of "a plurality of" is two or more; the orientation or positional relationship indicated by the terms "upper", "lower", "left", "right", "inner", "outer", "front end", "rear end", "head", "tail" and the like is based on the orientation or positional relationship shown in the drawings, and is merely for the purpose of facilitating the description of the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third" and the like are only for the purpose of description and cannot be understood as indicating or implying relative importance.

[0107] In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0108] It should be understood that the embodiments disclosed herein are not limited to the specific structure, processing steps or materials disclosed herein, but extend to equivalent alternatives of these features understood by those skilled in the relevant art. It should also be understood that the terms used herein are for the purpose of describing specific embodiments only and are not meant to be limiting.

[0109] The phrase "one embodiment" or "an embodiment" appearing in the specification means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. Therefore, the phrase "one embodiment" or "an embodiment" appearing throughout the specification does not necessarily refer to the same embodiment.

[0110] Although the embodiments disclosed by the present application are as described above, the content described is only the embodiments adopted for the purpose of facilitating the understanding of the present application, and is not intended to limit the present application. Any person skilled in the art can make any modification and change in the form and details without departing from the spirit and scope of the present application, but the patent protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A method for determining the high viscosity acid liquid hydrogen ion diffusion coefficient, characterized by, The method comprises the following steps: Based on the parallel plate reactor assumption, the acid liquid flow equation and the acid liquid concentration distribution equation are established, the equations are solved by using the boundary conditions of the acid liquid flow process in the reactor, and a map representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction speed is formed by using the current analytical solution; The reaction speed of the acid liquid to be evaluated is obtained by carrying out the fracture conductive groove acid liquid displacement experiment on the acid liquid to be evaluated, and the corresponding hydrogen ion diffusion coefficient is obtained by using the map.

2. The method of claim 1, wherein, In the step of establishing the acid liquid flow equation and the acid liquid concentration distribution equation based on the parallel plate reactor assumption, solving the equations by using the boundary conditions of the acid liquid flow process in the reactor, and forming a map representing the mapping relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction speed by using the current analytical solution, the step comprises the following steps: A plurality of dimensionless variable expressions for solving the acid liquid flow equation and the acid liquid concentration distribution equation are defined, and the plurality of dimensionless variables include a surface reaction speed to diffusion speed ratio represented by a hydrogen ion diffusion coefficient parameter, a rock plate length dimensionless variable represented by a hydrogen ion diffusion coefficient parameter, and a reaction speed dimensionless variable; The acid liquid flow equation and the acid liquid concentration distribution equation are solved by using the boundary conditions of the acid liquid flow process in the reactor and the plurality of dimensionless variable expressions, and a current analytical solution is obtained; Based on the analytical solution representing the correlation between the rock plate length dimensionless variable and the reaction speed dimensionless variable, the hydrogen ion diffusion coefficient and the reaction speed dimensionless variable are taken as the horizontal and vertical coordinates of the map respectively, and a map representing the relationship between the hydrogen ion diffusion coefficient and the acid liquid reaction speed is constructed.

3. The method of claim 2, wherein, The boundary conditions are represented by the following expression: C(0,Y)=C0 where D represents a hydrogen ion diffusion coefficient, w represents a plate spacing, and C represents an acid solution concentration, Y represents a unit vertical distance of the rock plate, y represents a distance perpendicular to the rock plate direction, E f represents a reaction rate constant, C A represents a concentration of the rock plate surface on the boundary, X = x / L, X represents a unit horizontal distance of the rock plate, x represents a distance in the horizontal direction of the rock plate, L represents a length of the rock plate, and C0represents an inlet acid solution concentration of the parallel plate reactor, The plurality of dimensionless variable expressions are represented by the following expression: where P represents the ratio of the surface reaction rate to the diffusion rate, L * denotes the dimensionless variable of the rock plate length, denotes the average flow rate of the injected acid, R * denotes the dimensionless variable of the reaction rate.

4. The method according to claim 2 or 3, characterized in that, The acid liquid flow equation is represented by the following expression: where v x (y) represents the flow rate of the acid liquid in the direction of the plate, where v represents the average flow rate of the injected acid liquid, x represents the distance in the horizontal direction of the rock plate, y represents the distance perpendicular to the direction of the rock plate, and w represents the plate spacing; The acid liquid concentration distribution equation is represented by the following expression: where D represents a hydrogen ion diffusion coefficient, L represents a length of the rock plate, where V represents an average flow rate of the injected acid solution, C represents an acid solution concentration, Y represents a unit vertical distance of the rock plate, X = x / L, and X represents a unit horizontal distance of the rock plate.

5. The method according to any one of claims 2 to 4, characterized in that, The analytical solution is represented by the following expression: where R * represents the dimensionless variable of reaction rate, P represents the ratio of surface reaction rate to diffusion rate, L * represents the dimensionless variable of rock plate length, n represents the reaction order, β1, β n … β n+1 respectively represent the coefficients of the approximate boundary layer 1, n and n+1 order, and Γ represents the function of variable n.

6. The method of claim 5, wherein, In the step of carrying out the fracture conductive groove acid liquid displacement experiment on the acid liquid to be evaluated to obtain the reaction speed of the acid liquid to be evaluated, and obtaining the corresponding hydrogen ion diffusion coefficient by using the map, the step comprises the following steps: The rock consumption speed is calculated by measuring the mass change of the rock plate through the experiment, and the rock consumption speed is converted into the acid liquid reaction speed; The current acid liquid reaction speed is taken as the reaction speed dimensionless variable and substituted into the map to obtain the hydrogen ion diffusion coefficient under the current acid liquid reaction speed.

7. The method according to claim 6, wherein The average consumption speed of the rock is calculated as the rock consumption speed by counting the karst amount under different acid-rock contact times.

8. The method according to any one of claims 1 to 7, characterized in that, The parallel plate reactor assumption satisfies the following conditions: assuming that the rock plate surface is smooth, laminar, no filtration, and the flow field is not affected by the acid-rock reaction occurring on the rock plate surface.

9. A computer-readable storage medium, characterized in that, It contains a series of instructions for executing the method steps of any one of claims 1-8.

10. A system for determining the high viscosity acid liquid hydrogen ion diffusion coefficient, characterized by, The method comprises the following steps: a chart generating module configured to establish acid liquid flow equations and acid liquid concentration distribution equations based on a parallel plate reactor assumption, solve the equations by using boundary conditions of the acid liquid flow process in the reactor, and form a chart representing a mapping relationship between hydrogen ion diffusion coefficients and acid liquid reaction rates by using a current analytical solution; a hydrogen ion diffusion coefficient calculating module configured to obtain a reaction rate of the acid liquid to be evaluated by carrying out a fracture conductive channel acid liquid displacement experiment on the acid liquid to be evaluated, and obtain a corresponding hydrogen ion diffusion coefficient by using the chart.

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