Pressure wave conduction simulation method for unstable seepage of heterogeneous oil and gas reservoir

Abstract

The invention relates to a pressure wave conduction simulation method for unstable seepage of a heterogeneous oil and gas reservoir, and belongs to the field of oil and gas seepage, the method simulates the condition in a stratum by establishing a 100 * 100 grid model on a C # platform, and comprises the following steps: firstly, according to the heterogeneity characteristic of the stratum, introducing the permeability of a grid, the method comprises the following steps of: firstly, calculating the permeability, the formation porosity, the fluid viscosity and the fluid compression coefficient, then deducing a conduction time formula through a pressure conduction coefficient equation and a detection radius equation, and weighting the average permeability to solve the problem of conduction time error caused by permeability difference in different directions; and calculating the conduction time of the pressure wave to each grid and storing the result in an array, and finally, outputting and visualizing the conduction range of the pressure wave at the time point by inputting the production time. The method can accurately simulate the conduction path and time of the pressure wave in the heterogeneous formation, improves the prediction precision and resource exploitation efficiency in the oil and gas reservoir development process, and has a wide application prospect.

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] In the process of oil and gas reservoir development, the seepage characteristics have an important impact on the recovery effect of oil and gas resources, especially in formations with strong heterogeneity. The traditional stable seepage model is difficult to accurately reflect the actual seepage situation. The heterogeneity of the formation usually leads to the unstable transmission of fluid pressure waves inside the oil and gas reservoir, forming a complex pressure wave transmission phenomenon. Most of the existing research methods rely on the homogeneous assumption and cannot effectively simulate the pressure wave transmission process caused by permeability changes in the formation. In heterogeneous formations, due to the significant differences in permeability in different regions, the transmission speed of pressure waves in different directions is inconsistent, which affects the recovery efficiency of oil and gas and the accuracy of resource prediction.

[0003] In order to solve the above problems, the present invention proposes a method for simulating the conduction of unstable seepage pressure waves based on grid division and weighted average permeability calculation. This method can accurately simulate and predict the conduction range and time of pressure waves under unstable seepage conditions by finely gridding the actual formation and combining computer simulation technology, effectively improving the accuracy and reliability of oil and gas reservoir exploitation. Summary of the invention

[0004] The purpose of the present invention is to provide a method for simulating the conduction of pressure waves in unstable seepage in heterogeneous oil and gas reservoirs, so as to solve the problem that the prior art cannot accurately simulate the conduction process of pressure waves in heterogeneous formations. Traditional seepage simulation methods are usually based on the assumption of homogeneous formations, which is difficult to reflect the complexity of actual formations, especially when the formation has significant heterogeneity, and it is impossible to effectively predict the conduction range and time of pressure waves, resulting in low efficiency of oil and gas reservoir exploitation 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 build a 100×100 grid, simulate the actual stratum, and determine the well location coordinates;

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

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

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

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

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

[0012]

[0013] where r j is the straight-line distance between the wellhead and the center of a grid, in meters; j is an 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 decimals; 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 position into individual small line segments, each of which corresponds to the length passing through the grid, and obtain the weighted average permeability of the entire straight line by weighted average permeability of the length. The equation of 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 m; 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 straight line passes through, the unit is 1; n is the total number of grids that the straight 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 time for transmission to any grid in a two-dimensional array established in C#;

[0018] S300, completing the transmission range of the pressure wave;

[0019] S301. Input the production time t, output the grid positions to which the pressure wave is transmitted at this time and before, and mark the transmission range in the grid diagram.

[0020] Through the method of the present invention, the conduction time and range of pressure waves in heterogeneous formations can be calculated, and the pressure wave conduction conditions at different time points can be simulated. This simulation method can effectively improve the prediction accuracy of pressure wave conduction during oil and gas reservoir development and optimize the exploitation plan of oil and gas resources. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0023] Figure 3 This is a simulation diagram of pressure wave transmission in a gas reservoir with a production time of 10 hours;

[0024] Figure 4 This is a simulation diagram of pressure wave transmission in a gas reservoir with a production time of 50 hours. DETAILED DESCRIPTION

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

[0026] Step 1: Prepare relevant parameters of gas reservoirs and gas wells, including average porosity of gas reservoirs, gas viscosity, fluid compressibility, gas well coordinates, and boundary coordinates;

[0027] Step 2: Use C# to build a 100×100 grid model, where each grid represents 100m 2 The permeability K value of each grid is imported into the formation area, and the interface established is as follows Figure 2 As shown in the figure, a pressure wave conduction simulation system is established on the C# platform, S100 to S300 are embedded into the code, and the formation porosity φ, fluid viscosity μ and fluid compressibility coefficient C are imported. t And select the wellhead position as the starting point of pressure wave transmission;

[0028] Step 3: Convert the pressure conductivity equation Substitute into the detection radius equation The conduction time equation was derived Because the straight line connecting the grid and the wellhead position passes through many grids with different permeabilities, the straight line is divided 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 straight line at this permeability. The equation of 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 m; 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 straight line passes through, the unit is 1; n is the total number of grids that the straight 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 this 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 draw the pressure wave transmission area of ​​the gas well after 10 hours of production, such as Figure 3 As shown in Figure 2, the pressure wave conduction area of ​​the gas well after 50 hours of production is Figure 4 shown.

[0037] Compared with the prior art, the present invention has the following beneficial effects: (1) a formation model is established and divided into regions, and the permeabilities in different regions are imported to reflect the heterogeneity of the formation; (2) programming is used to realize the weighted average of the permeabilities in the propagation direction of the pressure wave, saving a lot of calculation time; (3) the conduction range of the pressure wave after a certain production time is directly reflected.

[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 skilled in the art should understand that the present invention can still be modified or replaced by equivalents. Any modification or partial replacement that does not depart from the spirit and scope of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for simulating pressure wave conduction of unstable seepage in heterogeneous oil and gas reservoirs, characterized in that: The method comprises the following steps: S100, using the C# platform to build a 100×100 grid, simulate the actual stratum, and determine the well location coordinates; S101, determining the wellhead position at the center of the grid; S102. The actual stratum is heterogeneous. The heterogeneity of the stratum is due to the permeability K at different locations. i Different, the permeability K i Import the grid, each grid is 10m long; S103. Obtain and import formation porosity φ, fluid viscosity μ and fluid compressibility coefficient C t ; S200, calculating the time for transmission to each grid, and saving the time required for transmission; S201. Derive the conduction formula of pressure wave and transform the pressure conduction coefficient equation into Substitute into the detection radius equation The conduction time equation is derived as: where r j is the straight-line distance between the wellhead and the center of a grid, in meters; j is an 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; S202, split the straight line connecting the grid and the wellhead position into individual small line segments, each of which corresponds to the length passing through the grid, and obtain the weighted average permeability of the entire straight line by weighted average permeability of the length. The equation of the weighted average permeability is: 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 m; 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 straight line passes through, the unit is 1; n is the total number of grids that the straight line passes through, 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 time for transmission to any grid in a two-dimensional array established in C#; S300, completing the transmission range of the pressure wave; S301. Input the production time t, output the grid positions to which the pressure wave is transmitted at this time and before, and mark the transmission range in the grid diagram.

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