CN-116978475-B - Method for acquiring electrochemical property in oil and gas exploitation process

CN116978475BCN 116978475 BCN116978475 BCN 116978475BCN-116978475-B

Abstract

The invention relates to the field of oil and gas exploitation, in particular to a method for acquiring electrochemical properties in the oil and gas exploitation process, which comprises the steps of constructing a chemical reaction network between shale and external fluid; the method comprises the steps of constructing a surface complexing model, constructing a diffusion double-layer model, setting a thermodynamic equilibrium constant initial value and a shale charge density initial value, acquiring a Zeta potential theoretical value through the surface complexing model and the diffusion double-layer model, and acquiring electrochemical properties of shale after the shale is contacted with external fluid when convergence conditions are met between the Zeta potential theoretical value and the Zeta potential actual value, wherein the Zeta potential actual value is measured through an indoor experiment. The Zeta potential theoretical value obtained by the method is accurate, electrochemical properties of the shale and the external fluid after contact can be obtained efficiently and conveniently based on the Zeta potential theoretical value, and analysis data and scientific guidance are provided for efficient development of subsequent shale oil reservoirs.

Inventors

DING HONGNA
PAN ZHEJUN
YANG ERLONG
ZHANG JIHONG
GUO ZHENGHUAI
WANG YUANYUAN

Assignees

东北石油大学

Dates

Publication Date: 20260508
Application Date: 20230803

Claims (9)

1. The method for acquiring the electrochemical property in the oil and gas exploitation process is characterized by comprising the following steps of: Constructing a chemical reaction network between shale and external fluid, wherein the chemical reaction network comprises at least one of a dissolution reaction of shale minerals, a precipitation reaction of shale minerals, an adsorption reaction of various ions in the external fluid on the surfaces of the minerals, a lattice ion exchange reaction and a reaction between the external fluid and various ions of stratum fluid; Constructing a surface complexation model, and setting chemical reactions occurring in a diffusion double layer and initial values of thermodynamic equilibrium constants of the reactions, wherein the chemical reaction network comprises the chemical reactions; constructing a diffusion double electric layer model, and setting an initial value of the charge density of shale; Acquiring a Zeta potential theoretical value of the shale surface through the surface complexation model and the diffusion double electric layer model based on the initial thermodynamic equilibrium constant value and the initial charge density value; when the convergence condition is met between the Zeta potential theoretical value and the Zeta potential actual value, the electrochemical property of the shale contacted with the external fluid is obtained, wherein the Zeta potential actual value is measured through an indoor experiment; The electrochemical properties include at least one of a theoretical composition of formation fluid, a theoretical pH, a theoretical surface potential of a shale surface, a theoretical charge density, a theoretical electrostatic force between shale and crude oil, a theoretical composition of an external fluid, and a theoretical concentration of each composition; Based on the initial thermodynamic equilibrium constant value and the initial charge density value, acquiring a Zeta potential theoretical value of the shale surface through the surface complexation model and the diffusion double electric layer model, wherein the Zeta potential theoretical value comprises the following steps: Acquiring the initial concentration of reactants and products in a first chemical reaction based on the shale surface charge density, the composition and the concentration of the external fluid ions according to a surface complexing model, wherein the chemical reaction network comprises the first chemical reaction; Obtaining a surface potential of the first chemical reaction from a value based on the initial value of the thermodynamic equilibrium constant and the preliminary concentration; and acquiring the Zeta potential theoretical value based on the surface potential according to a diffusion double layer model.
2. The method of claim 1, wherein the convergence condition is satisfied when the deviation between the theoretical value of Zeta potential and the actual value of Zeta potential is less than a first threshold value.
3. The method of claim 2, wherein the first threshold is in the range of 5-10%.
4. The method of claim 1, wherein the surface complexation reaction model is selected from a 1pK or 2pK state model.
5. The method of claim 4, wherein the diffusion double layer model is selected from the group consisting of a helmholtz model, a gully-Chapman model, and a gully-Chapman-Stoken model.
6. The method of claim 1, wherein when the diffusion electric double layer model is a helmholtz model, the step of obtaining the Zeta potential theoretical value based on the surface potential comprises: Acquiring a diffusion potential based on the surface potential; Acquiring the Zeta potential theoretical value based on a relation between the Zeta potential theoretical value and the diffusion potential; The relation is as follows: Zeta m is the theoretical value of Zeta potential, the unit is V, x is the position of the slip plane in the diffusion layer, the unit is m, kappa -1 is the Debye length, and the unit is m.
7. The method of deriving electrochemical properties during hydrocarbon production according to claim 1, wherein deriving the theoretical charge density comprises: acquiring the theoretical surface potential based on the Zeta potential theoretical value; Acquiring the theoretical charge density based on the theoretical surface potential; wherein the theoretical charge density comprises a diffusion layer theoretical charge density and a ston layer theoretical charge density.
8. Use of the method of obtaining electrochemical properties in hydrocarbon production as claimed in claim 1 in a process of chemical contact of shale with formation fluids.
9. Use of the method for obtaining electrochemical properties in an oil and gas extraction process according to claim 1 in a process of dissolution of shale minerals by a gas.

Description

Method for acquiring electrochemical property in oil and gas exploitation process Technical Field The invention belongs to the field of oil and gas exploitation, and particularly relates to a method for acquiring electrochemical properties in an oil and gas exploitation process. Background In the petroleum industry, the exploration and development of shale oil and gas resources is particularly important, shale oil refers to petroleum resources contained in shale layers mainly comprising shale, including petroleum in shale pores and cracks, and also including petroleum resources in sandstone or carbonate adjacent layers in the shale layers. Because shale reservoirs are mostly land-phase sediments, mineral components are complex, usually contain more clay minerals, and have higher organic matter content, so that the porosity and the permeability are extremely low, the crude oil exploitation is extremely difficult, and the shale reservoirs can be effectively developed by means of a large-scale hydraulic fracturing technology. The specific principle is that a large amount of fracturing fluid (such as slickwater, carbon dioxide, low-salt water, nano emulsion and the like, which can also be called as external fluid) enters a shale reservoir in the hydraulic fracturing process, a series of chemical reactions are induced, such as hydration and expansion of clay minerals, dissolution/precipitation of soluble minerals such as rock salt, calcite and the like, ion adsorption in aqueous solution and the like, and the chemical reactions can change physical parameters such as porosity, permeability, pore throat connectivity and the like of the shale reservoir, and can also change the electrical properties of the shale surface (such as increasing the negative charge density of the shale surface), change the wettability of the shale reservoir, further improve the seepage capability of the shale reservoir to crude oil and promote the seepage rate and efficiency of the crude oil. However, variations in the porosity of shale reservoirs, variations in permeability, and variations in the electrochemical properties between shale and fracturing fluid are unknown during contact of the different exogenous fluids with the shale. The effect between the shale reservoir and the external fluid is very difficult to study by an experimental method, taking the shale reservoir carbon dioxide fracturing as an example, the experiment needs to be carried out under the conditions of high temperature and high pressure, and the carbon dioxide has corrosiveness and has strict requirements on experimental equipment and operation safety; in addition, because shale samples are very dense, it is difficult to saturate formation water or crude oil, and the experiment takes up to several months. Therefore, the effect between the shale reservoir and the external fluid is obtained efficiently and conveniently, and the electrochemical property of the shale reservoir and the external fluid after contact is obtained, so that the method has important significance for shale oil exploitation. Up to the present, no research on electrochemical reaction between shale reservoirs and external fluids has been developed at home and abroad, and no quantification and acquisition method for electrochemical property change after the shale reservoirs are contacted with the external fluids has been provided. Disclosure of Invention In view of the above-mentioned drawbacks and problems of the prior art, the present invention has developed a method for obtaining electrochemical properties during oil and gas recovery. The first aspect of the invention provides a method for obtaining electrochemical properties in an oil and gas exploitation process, comprising the following steps: Constructing a chemical reaction network between shale and external fluid, wherein the chemical reaction network comprises at least one of a dissolution reaction of shale minerals, a precipitation reaction of shale minerals, an adsorption reaction of various ions in the external fluid on the surfaces of the minerals, a lattice ion exchange reaction and a reaction between the external fluid and various ions of stratum fluid; Constructing a surface complexation model, and setting chemical reactions occurring in a diffusion double layer and initial values of thermodynamic equilibrium constants of the reactions, wherein the chemical reaction network comprises the chemical reactions; constructing a diffusion double electric layer model, and setting an initial value of the charge density of shale; Acquiring a Zeta potential theoretical value of the shale surface through the surface complexation model and the diffusion double electric layer model based on the initial thermodynamic equilibrium constant value and the initial charge density value; when the convergence condition is met between the Zeta potential theoretical value and the Zeta potential actual value, the electrochemical property of the shale contac