Method for predicting acid-rock reaction rates based on mass transfer control

Abstract

In the field of petroleum process testing technology, we aim to improve the accuracy of calculating acid-rock reaction rates. [Solution] The following steps are included: Reactant H in solution + When mass transfer occurs on a rock wall via diffusion, the mass transfer flux between the wall and the acid solution is calculated based on Newton's law of cooling and Fick's first law, respectively. The mass transfer coefficient equation from the center of the fracture to the fracture wall is obtained and then non-dimensionalized to obtain a dimensionless mass transfer coefficient equation. The convective mass transfer coefficient and the mass transfer of the acid solution within the slit are derived, and a simultaneous solution is obtained to obtain a correlation equation for the convective mass transfer coefficient of laminar flow in a rock fracture. By analyzing the acid-rock reaction in the rock fracture, a mathematical model of the effective mass transfer coefficient of the reactants of the acid solution in the rock fracture is established. A derivation is performed for the acid-rock reaction under mass transfer control, and a model of the acid-rock reaction rate under mass transfer control is established, which is used to predict the rock erosion rate of pure dolomite and pure tuff.

Description

Technical Field

[0001] The present invention relates to the technical field of petroleum engineering tests, and specifically relates to a method for predicting the acid-rock reaction rate based on mass transfer control.

Background Art

[0002] At present, the development of carbonate rock oil and gas resources in China is gradually moving towards deeper layers, and deep carbonate rock oil and gas has already become an essential part of China's energy supply. Deep carbonate rock has strong heterogeneity, high formation temperature, and high confining pressure. Therefore, after acid fracturing, it faces the problems of weak conductivity and short production increase duration. Here, the acid-rock reaction rate is a crucial parameter for calculating the effective action distance of acid etching, and the accuracy of acid-rock reaction rate calculation is directly related to the accuracy of acid fracturing effect evaluation. Moreover, due to the high temperature of deep carbonate rock formations, the acid-rock reaction is mainly controlled by H + mass transfer. Therefore, the research on the method for calculating the acid-rock reaction rate based on mass transfer control has very important significance for the evaluation of acid fracturing effects.

[0003] In the process of mass transfer, much of the actual mass transfer is the interphase transfer of substances. Due to the phase change, the substance concentration at the interface between phases is necessarily discontinuous. Moreover, the phase interface is very thin and impossible to measure directly. Therefore, up to now, the description of the phase interface is still not clear. Based on some assumptions, certain progress has also been made in the quantitative calculation of convective mass transfer, such as the double-film model, solute penetration model, and surface renewal model. However, all of the above mass transfer models simply and clearly set the physical concepts during mass transfer and simplify the establishment of mass transfer coefficients. For example, the film thickness in the double-film model, the exposure time in the solute penetration model, and the surface renewal rate in the surface renewal model are all difficult to measure. Therefore, it is difficult to quantitatively evaluate the solute mass transfer process, and a complete mass transfer model with universal laws has not been established so far.

Summary of the Invention

[0004] In response to the aforementioned shortcomings of the conventional technology, the present invention provides a method for predicting the acid-rock reaction rate based on mass transfer control, solving the problem of not being able to quantitatively measure solute mass transfer and simultaneously improving the accuracy of the calculated acid-rock reaction rate.

[0005] To achieve the objective of the above invention, the technical solution adopted by the present invention is as follows. A method for predicting the reaction rate of acid rock based on mass transfer control, comprising the following steps: S1, reactant H in solution + When mass transfer occurs on a rock wall via diffusion, the mass transfer flux between the wall and the acid solution is calculated based on Newton's law of cooling and Fick's first law, respectively. The mass transfer coefficient equation from the center of the fracture to the fracture wall is then obtained and non-dimensionalized to obtain a dimensionless mass transfer coefficient equation. S2, based on the dimensionless mass transfer coefficient equation, the convective mass transfer coefficient and the acid liquid mass transfer within the slit are derived separately, and a simultaneous solution is obtained to obtain a correlation equation for the convective mass transfer coefficient of laminar flow in a geological fracture. S3. Based on the correlation equation for the convective mass transfer coefficient of laminar flow in stratigraphic fractures, we will analyze acid-rock reactions in stratigraphic fractures to establish a mathematical model for the effective mass transfer coefficient of acid reactants in stratigraphic fractures. In S4, based on the established mathematical model of the effective mass transfer coefficient of acid reactants in strata fractures, a derivation was performed for mass transfer-controlled acid-rock reactions, establishing a mass transfer-controlled acid-rock reaction rate model, which is used to predict the rock erosion rates of pure dolomite and pure sludge.

[0006] Furthermore, step S1 specifically includes the following:

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[0007] Furthermore, step S2 specifically includes the following: In S21, the convective mass transfer coefficient is derived, and the specific process is as follows.

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[0008] Furthermore, step S3 specifically includes the following:

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[0009] Furthermore, step S4 specifically includes the following:

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[0010] The present invention has the following beneficial effects. The present invention provides a method for predicting the acid-rock reaction rate based on mass transfer control, establishing an acid-rock reaction rate model that considers mass transfer control in acid solution viscosity, acid solution concentration, acid solution flow rate, and slit width, and predicting the reactant H in the acid solution. + This method quantitatively characterizes the acid-rock reaction rate in mass transfer modes, takes into account the acid-liquid parameter state under geological conditions, and has the advantage of predicting the acid-rock reaction rate under true geological conditions, being easier to calculate, and highly accurate. [Brief explanation of the drawing]

[0011] [Figure 1] This is a flowchart illustrating the method for predicting the reaction rate of acid rocks based on mass transfer control as proposed in the present invention. [Modes for carrying out the invention]

[0012] In order to help those skilled in the art understand the present invention, specific embodiments of the present invention will be described below. However, the present invention is not limited to the scope of these specific embodiments, and it should be made clear that any variations that fall within the spirit and scope of the present invention as defined and limited by the appended claims will be obvious to an ordinary person skilled in the art, and that any inventive creation utilizing the concept of the present invention is subject to protection.

[0013] As shown in FIG. 1, a method for predicting the acid-rock reaction rate based on mass transfer control, comprising the following steps S1 to S4:

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[0014] S2. Based on the dimensionless mass transfer coefficient equation, the convective mass transfer coefficient and the acid solution mass transfer in the slit are respectively derived, and they are solved simultaneously to obtain the correlation equation of the convective mass transfer coefficient of the laminar flow in the formation fracture. Specifically, step S2 specifically includes S21 - S23. S21. Derive the convective mass transfer coefficient, and the specific process is as follows.

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[0015] S3. Based on the correlation equation of the convective mass transfer coefficient of the laminar flow in the formation fracture, analyze the acid-rock reaction in the formation fracture to establish a mathematical model of the effective mass transfer coefficient of the reactants of the acid solution in the formation fracture. Specifically, step S3 specifically includes S31 - S37.

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[0016] S4. Based on the established mathematical model of the effective mass transfer coefficient of the reactants of the acid solution in the formation fracture, perform derivation on the acid-rock reaction under mass transfer control to establish an acid-rock reaction rate model under mass transfer control, which is used for predicting the formation rock erosion rate of pure dolomite and the formation rock erosion rate of pure limestone. Specifically, process S4 specifically includes S41 - S48:

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[0017]

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[0018] This invention will describe the principles and embodiments of the present invention using specific examples, and the above description of examples is merely intended to aid in understanding the method and core concept of the present invention. Furthermore, those skilled in the art will be able to modify the specific embodiments and scope of application based on the concept of the present invention, and therefore, the contents of this specification should not be understood as limiting the present invention.

[0019] Those skilled in the art will understand that the examples described herein are intended to help readers understand the principles of the present invention, and that the scope of protection of the present invention is not limited to such specific descriptions and examples. Those skilled in the art will understand that, based on these technical suggestions disclosed herein, a variety of other specific modifications and combinations can be made that do not depart from the essence of the present invention, and these modifications and combinations remain within the scope of protection of the present invention.

Claims

1. A method for predicting the reaction rate of acid rock based on mass transfer control, comprising the following steps: S1, Reactant H in solution ＋ When mass transfer occurs on a rock wall by diffusion, the mass transfer flux between the wall and the acid solution is calculated based on Newton's law of cooling and Fick's first law, respectively. The mass transfer coefficient equation from the center of the fracture to the fracture wall is then obtained and non-dimensionalized to obtain a dimensionless mass transfer coefficient equation. S2, based on the dimensionless mass transfer coefficient equation, the convective mass transfer coefficient and the acid liquid mass transfer within the slit are derived, and a simultaneous solution is obtained to obtain a correlation equation for the convective mass transfer coefficient of laminar flow in a geological fracture. S3. Based on the correlation equation for the convective mass transfer coefficient of laminar flow in stratigraphic fractures, we will analyze acid-rock reactions in stratigraphic fractures to establish a mathematical model for the effective mass transfer coefficient of acid reactants in stratigraphic fractures. S4. A method for predicting acid rock reaction rates based on mass transfer control, characterized in that a mathematical model of the effective mass transfer coefficient of acid reactants in a strata fracture is derived for mass transfer controlled acid rock reactions, a mass transfer controlled acid rock reaction rate model is established, and this model is used to predict the rock erosion rate of pure dolomite and pure sludge.

2. Step S1 specifically includes the following: [Math 1]

3. Step S2 specifically includes the following: In S21, the convective mass transfer coefficient was derived, and the specific process is as follows: [Math 2]

4. Step S3 specifically includes the following: [Math 3]

5. Step S4 specifically includes the following: [Math 4]

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