A simulation method for pressure wave conduction in unsteady seepage of heterogeneous oil and gas reservoirs

Abstract

The present invention relates to a method for simulating the pressure wave conduction of unsteady seepage in heterogeneous oil and gas reservoirs, belonging to the field of oil and gas seepage. This method establishes a 100×100 grid model on the C# platform to simulate the situation in the formation. First, according to the heterogeneity characteristics of the formation, the permeability of the grid, as well as the formation porosity, fluid viscosity, and fluid compressibility coefficient are imported. Then, the conduction time formula is derived through the pressure conductivity coefficient equation and the detection radius equation, and the weighted average permeability is used to solve the conduction time error problem caused by the permeability difference in different directions. Starting from the wellhead, the time for the pressure wave to conduct to each grid is calculated and the results are stored in an array. Finally, by inputting the production time, the pressure wave conduction range at this time point is output and visualized. The present invention can accurately simulate the conduction path and time of the pressure wave in heterogeneous formations, improve the prediction accuracy and resource exploitation efficiency in the process of oil and gas reservoir development, and has broad application prospects.

Description

Technical Field

[0001] The invention relates to a pressure wave conduction simulation method for unstable seepage in a heterogeneous oil and gas reservoir, and belongs to the field of oil and gas reservoir engineering. Background Art

[0002] During the development of oil and gas reservoirs, seepage characteristics have a significant impact on the effectiveness of oil and gas resource extraction. This is especially true in highly heterogeneous formations, where traditional stable seepage models struggle to accurately reflect actual seepage conditions. Formation heterogeneity often leads to unstable transmission of fluid pressure waves within the reservoir, resulting in complex pressure wave transmission phenomena. Existing research methods, most of which rely on the homogeneous assumption, are unable to effectively simulate the pressure wave transmission process caused by permeability variations within the formation. In heterogeneous formations, significant permeability differences between regions lead to inconsistent pressure wave transmission velocities in different directions, thus impacting oil and gas extraction efficiency and the accuracy of resource prediction.

[0003] To address these issues, the present invention proposes a method for simulating the propagation of unstable seepage pressure waves based on grid division and weighted average permeability calculation. By finely meshing the actual formation and combining it with computer simulation technology, this method can accurately simulate and predict the propagation range and duration of pressure waves under unstable seepage conditions, effectively improving the accuracy and reliability of oil and gas reservoir development. Summary of the Invention

[0004] The purpose of this invention is to provide a method for simulating pressure wave propagation in unstable seepage in heterogeneous oil and gas reservoirs, addressing the existing technical challenge of accurately simulating the pressure wave propagation process in heterogeneous formations. Traditional seepage simulation methods are typically based on the assumption of homogeneous formations, which makes it difficult to reflect the complexity of actual formations. In particular, when formations have significant heterogeneity, the propagation range and duration of pressure waves cannot be effectively predicted, resulting in low oil and gas reservoir recovery efficiency and large prediction errors.

[0005] To achieve the above object, the present invention provides a method for simulating pressure wave conduction of unstable seepage in heterogeneous oil and gas reservoirs, the method comprising the following steps:

[0006] S100, using the C# platform to create a 100×100 grid, simulate the actual formation, and determine the well location coordinates;

[0007] S101, determining the wellhead position at the center of the grid;

[0008] S102. The actual formation is heterogeneous. The heterogeneity of the formation is due to the permeability K at different locations. i Different, the permeability K i Import the grid, the length of each grid is 10m;

[0009] S103. Obtain and import formation porosity φ, fluid viscosity μ, and fluid compressibility coefficient C t ;

[0010] S200, calculating the time required for transmission to each grid, and saving the time required for transmission;

[0011] S201. Derive the pressure wave conduction formula and transform the pressure conduction coefficient equation into Substitute into the detection radius equation The conduction time equation is derived as:

[0012]

[0013] where r j is the straight-line distance between the wellhead and the center of a grid, in meters; j is the index variable, traversing from the first grid to the last grid, in units of 1; is the weighted average permeability, in μm 2 ; φ is the formation porosity, in decimal units; μ is the fluid viscosity, in mPa·s; C t is the fluid compressibility coefficient, in MPa -1 ; t is the conduction time, in hours; η is the pressure conduction coefficient, in m 2 / s;

[0014] S202. Split the straight line connecting the grid and the wellhead into individual small line segments. Each small line segment corresponds to the length of the grid. The weighted average permeability of the entire line is obtained by weighting the average permeability of the length. The equation for the weighted average permeability is:

[0015]

[0016] in, is the weighted average permeability; the unit is μm 2 ;L i is the length of the small line segment in the grid that is transmitted from the wellhead to a certain grid, in meters; r j is the transmission radius of the pressure wave, in m; j is the index variable, traversing from the first grid to the last grid, in 1; K i is the permeability of the grid, in μm 2 ; i is the index variable, traversing the grids that the line passes through, the unit is 1; n is the total number of grids that the line passes through, the unit is 1;

[0017] S203, combining the equations obtained in S201 and S202, calculating the time required for transmission from the wellhead position to each grid, and storing the transmission time to any grid in a two-dimensional array established in C#;

[0018] S300. Represent the propagation range of the pressure wave;

[0019] S301. Input the production time t, output the grid positions reached by the pressure wave at this time and previous times, and mark the propagation range on the grid map.

[0020] Through the method of the present invention, the propagation time and range of the pressure wave in heterogeneous formations can be calculated, and the propagation of the pressure wave at different time points can be simulated. This simulation method can effectively improve the prediction accuracy of the pressure wave propagation during the development of oil and gas reservoirs and optimize the exploitation plan of oil and gas resources. Brief Description of the Drawings

[0021] Figure 1 is the technical roadmap of this method;

[0022] Figure 2 is the program interface diagram established in C#;

[0023] Figure 3 is the simulation diagram of the pressure wave propagation in a certain gas reservoir at a production time of 10 h;

[0024] Figure 4 is the simulation diagram of the pressure wave propagation in a certain gas reservoir at a production time of 50 h. Detailed Embodiment

[0025] The present invention provides a method for simulating the pressure wave propagation in the unstable seepage of heterogeneous oil and gas reservoirs. Figure 1 For the technical roadmap of this method, for a certain gas reservoir in China, the following steps are implemented:

[0026] First step: Prepare the relevant parameters of the gas reservoir and the gas well, including the average porosity of the gas reservoir, gas viscosity, fluid compressibility, gas well coordinates, and boundary coordinates;

[0027] Second step: Use the C# platform to establish a 100×100 grid model, where each grid represents a formation area of 100 m 2 Import the permeability K value of each grid, and the established interface is as Figure 2 shown. Establish a pressure wave propagation simulation system on the C# platform, embed S100 to S300 into the code, and import the formation porosity φ, fluid viscosity μ, and fluid compressibility C t and select the wellhead position as the starting point of the pressure wave propagation;

[0028] Third step: Substitute the pressure diffusion coefficient equation into the detection radius equation to derive the propagation time equation Because the straight line connecting the grid and the wellhead position passes through many grids with different permeabilities, the straight line is split into small segments. Each small segment corresponds to the length of the grid. The permeabilities on all small segments are weighted averaged to obtain the weighted average permeability of the entire straight line. It can be regarded as the pressure wave being transmitted on this line at this permeability. The equation of the weighted average permeability is:

[0029]

[0030] in, is the weighted average permeability; the unit is μm 2 ;L i is the length of the small line segment in the grid that is transmitted from the wellhead to a certain grid, in meters; r j is the transmission radius of the pressure wave, in m; j is the index variable, traversing from the first grid to the last grid, in 1; K i is the permeability of the grid, in μm 2 ; i is the index variable, traversing the grids that the line passes through, the unit is 1; n is the total number of grids that the line passes through, the unit is 1;

[0031] Step 4: Combine the equations in step 3 to calculate the time required for transmission from the wellhead to each grid;

[0032] Step 5: Store the transmission time from the wellhead to each grid, and create an array to store the transmission time of each grid;

[0033] Step 6: Input the production time t, output the grid positions to which the pressure wave is transmitted at that time and before, and mark the transmission range in the grid diagram.

[0034] Using the compiled pressure wave conduction simulation software, taking a gas reservoir as an example, the pressure wave conduction area of a single well is predicted.

[0035] According to the single well logging data, the average porosity of a gas reservoir is 0.295, the fluid viscosity is 0.0126 mPa·s, and the fluid compressibility is 1.8×10 -4 MPa -1 ;

[0036] According to the obtained permeability, the grid established by the software is imported to simulate the pressure wave and the pressure wave transmission area of the gas well after 10 hours of production is drawn, as shown in the figure. Figure 3 As shown in Figure 2, the pressure wave conduction area of the gas well after 50 hours of production is as follows: Figure 4 shown.

[0037] Compared with the prior art, the present invention has the following beneficial effects: (1) A formation model is established and regions are divided, and the permeabilities in different regions are imported to reflect the heterogeneity of the formation; (2) Programming is implemented to perform weighted averaging of the permeabilities in the pressure wave propagation direction, saving a large amount of calculation time; (3) It directly reflects the conduction range of the pressure wave after a certain production time.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate rather than limit the technical solutions of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the present invention or make equivalent replacements without departing from the spirit and scope of the present invention. Any modification or partial replacement shall be covered by the scope of the claims of the present invention.

Claims

1. A simulation method for pressure wave conduction of unsteady seepage in heterogeneous oil and gas reservoirs, characterized in that, The method comprises the following steps: S100, using the C# platform to create a 100×100 grid, simulate the actual formation, and determine the well location coordinates; S101, determining the wellhead position at the center of the grid; S102. The actual formation has heterogeneity, and the heterogeneity of the formation is due to different permeabilities K at different positions i being different. Import the obtained permeability K i into the grid, and the length of each grid is 10 m; S103. Obtain and import the formation porosity φ, fluid viscosity μ, and fluid compressibility C t ; S200, calculating the time required for transmission to each grid, and saving the time required for transmission; S201. Derive the conduction formula of the pressure wave and substitute the coefficient of pressure conduction equation into the detection radius equation to derive the conduction time equation: where r j is the straight-line distance from the wellhead to the center of a certain grid, with the unit of m; j is an index variable that traverses from the first grid to the last grid, with the unit of 1; is the weighted average permeability, with the unit of μm 2 ; φ is the formation porosity, in decimal; μ is the fluid viscosity, in mPa·s; C t is the fluid compressibility, in MPa -1 ; t is the conduction time, in hours; η is the pressure conductivity coefficient, in m 2 / s; S202. Split the straight line connecting the grid and the wellhead into individual small line segments. Each small line segment corresponds to the length of the grid. The weighted average permeability of the entire line is obtained by weighting the average permeability of the length. The equation for the weighted average permeability is: Among them, is the weighted average permeability; the unit is μm 2 ; L i is the length of the small line segment in the grid passed from the wellhead to a certain grid, the unit is m; r j is the conduction radius of the pressure wave, the unit is m; j is the index variable, traversing from the first grid to the last grid, the unit is 1; K i is the permeability of the grid, the unit is μm 2 ; i is the index variable, traversing the grids passed by the straight line, the unit is 1; n is the total number of grids passed by the straight line, the unit is 1; S203, combining the equations obtained in S201 and S202, calculating the time required for transmission from the wellhead position to each grid, and storing the transmission time to any grid in a two-dimensional array established in C#; S300, completing the display of the conduction range of the pressure wave; S301. Input the production time t, output the grid positions to which the pressure wave is transmitted at that time and before, and mark the transmission range in the grid diagram.

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