A calculation method for avoiding faults in oil reservoir well pattern streamlines

Abstract

The present invention belongs to the field of streamline calculation in oil reservoir development, and specifically relates to a method for calculating streamline fault avoidance in oil reservoir well network. The method comprises the following steps: (1) using seismic and geological exploration data to establish a three-dimensional oil reservoir geological model, and using Delaunay triangulation technology to obtain a gridded oil reservoir model; (2) performing streamline simulation based on the seepage equation of underground fluid, and generating streamline distribution of the oil reservoir well network in the gridded oil reservoir model; (3) determining the contact risk between streamlines and faults, and calculating the avoidance path of streamlines; (4) using simulated annealing algorithm to optimize well locations to ensure that streamlines and faults do not intersect; (5) performing streamline verification, and if the verification is passed, outputting streamline results; if the streamline verification fails, returning to step (4). The method provided by the present invention simulates and optimizes streamlines in the oil reservoir, avoids fault areas in the well network layout, and realizes efficient development of the oil reservoir.

Description

Technical Field

[0001] The invention belongs to the field of streamline calculation in oil reservoir development, and in particular relates to a method for calculating streamline fault avoidance in oil reservoir well network. Background Art

[0002] Reasonable layout of well patterns in reservoir development is a key factor in improving recovery and optimizing resource allocation. However, under complex geological conditions with faults, well pattern design faces great challenges, mainly because well flow lines easily cross fault areas, resulting in reduced fluid recovery efficiency and even oil and gas leakage or inter-well interference. Traditional well pattern design relies heavily on experience or rule-based layout, lacks a systematic fault avoidance calculation method, and cannot fully consider the spatial impact of faults. Based on this, it is crucial to develop an efficient and accurate fault avoidance calculation method to achieve reasonable well layout and avoid faults in reservoir well pattern design. Summary of the invention

[0003] In view of the above technical problems, the present invention provides a method for calculating the fault avoidance of oil reservoir well network streamlines. By simulating and optimizing the streamlines in the oil reservoir, the fault area is avoided in the well network layout, thereby achieving efficient development of the oil reservoir.

[0004] The present invention is achieved through the following technical solutions:

[0005] A method for calculating fault avoidance of oil reservoir well pattern streamlines, the method comprising the following steps:

[0006] (1) Use seismic and geological exploration data to establish a three-dimensional reservoir geological model, and use Delaunay triangulation technology to obtain a gridded reservoir model;

[0007] (2) performing streamline simulation based on the seepage equation of underground fluid, and generating streamline distribution of the reservoir well network in the gridded reservoir model;

[0008] (3) Determine the contact risk between the streamline and the fault, and calculate the avoidance path of the streamline;

[0009] (4) Use simulated annealing algorithm to optimize well location to ensure that streamlines and faults do not intersect;

[0010] (5) Perform streamline verification. If the verification passes, output the streamline result; if the streamline verification fails, return to step (4).

[0011] Furthermore, step (1) is specifically as follows:

[0012] Using seismic data and geological exploration data, a three-dimensional reservoir geological model of the reservoir area is established; the fault structure in the three-dimensional reservoir geological model is represented by polygonal boundaries;

[0013] The Delaunay triangulation technique is used to divide the reservoir in the three-dimensional reservoir geological model into regular grid unit blocks to obtain a gridded reservoir model;

[0014] The locations of faults are marked in the gridded reservoir model.

[0015] Furthermore, in step (2), streamline simulation is performed based on the seepage equation of underground fluid driven by the inter-well pressure difference, and the streamline distribution of the reservoir well network is generated in the gridded reservoir model. The specific steps include:

[0016] (2.1) Use the seepage control equation to establish the pressure field distribution:

[0017] ;

[0018] in, is the divergence operator, k is the permeability tensor, p is the pressure, is the pressure gradient, q is the source and sink term;

[0019] Depending on the location of the oil well, When the corresponding well is set as an injection well, When setting the corresponding well as a production well, the permeability value is set at the fault;

[0020] (2.2) Calculate the flow trajectory of fluid particles using the velocity field , the streamline distribution from each well position is calculated, and the streamline equation is:

[0021] ;

[0022] Where V is the Darcy velocity, , k is the permeability tensor, is the fluid viscosity, is the pressure gradient;

[0023] (2.3) In the fault area, the flow direction of the streamline is adjusted by locally adjusting the permeability.

[0024] Furthermore, step (3) includes the following steps:

[0025] (3.1) For any two well positions, four three-dimensional coordinate points perpendicular to the plane are obtained according to the effective perforation depth, and then the plane equation corresponding to the streamline between the two wells is obtained:

[0026] ;

[0027] in, is the normal vector of the plane corresponding to the streamline between the two wells , D1 is a constant;

[0028] x, y, z represent the x-axis, y-axis, and z-axis in the three-dimensional coordinate axis respectively;

[0029] (3.2) The fault plane is represented by the following plane equation:

[0030] ;

[0031] in, is the normal vector of the plane corresponding to the fault plane, ; D2 is a constant;

[0032] (3.3) Using the intersection point judgment method, first solve the intersection line equation by solving two plane equations, and then determine whether the intersection line intersects with the sides of the two quadrilaterals. If so, it is determined that there is a risk of contact between the corresponding streamline and the fault.

[0033] (3.4) For streamlines that are at risk of contacting faults, the angle deflection method is used to adjust the streamline direction so that the streamline is away from the fault area;

[0034] Calculate the streamline deflection angle The formula is:

[0035] ;

[0036] in, , n is the fault normal vector;

[0037] (3.5) The path smoothing algorithm Bezier curve is used to smooth the path after streamline adjustment.

[0038] Furthermore, step (4) includes:

[0039] (4.1) Define the objective function F of well location optimization to minimize the contact distance between the well and the fault and maximize the recovery efficiency:

[0040] ;

[0041] in: is the distance penalty term between the well flow line and the fault; is the well-to-well interference degree; is the recovery efficiency correlation coefficient; , , is the weight coefficient; i represents a group of wells or a well;

[0042] (4.2) Execute the simulated annealing algorithm, set the initial temperature, randomly perturb the well positions, accept the best solutions, gradually reduce the temperature, and finally obtain the optimal well positions;

[0043] (4.1) Make adjustments based on the optimization results; and calculate the streamline distribution of the adjusted well locations to ensure that the streamlines and faults do not intersect.

[0044] Furthermore, in step (5), the streamline verification is performed by analyzing the streamline distribution of the well network optimized in step (4) through fluid simulation. If the two three-dimensional planes formed by the streamline and the fault do not intersect, the avoidance is judged to be successful and the verification is passed; if the two three-dimensional planes formed by the streamline and the fault intersect, the avoidance is judged to be unsuccessful, the streamline verification fails, and the process returns to step (4).

[0045] Furthermore, step (5) also includes updating the three-dimensional reservoir geological model through verification.

[0046] Beneficial technical effects of the present invention:

[0047] The present invention provides a systematic fault avoidance calculation method based on numerical simulation. The method provided by the present invention uses polygonal boundaries to accurately characterize the fault structure, and constructs a gridded reservoir model through Delaunay triangulation technology, which can present the various spatial characteristics of the fault in detail. At the same time, the permeability and porosity of the fault area are differentiated in the gridded reservoir model, which more realistically simulates the characteristics of the fault as a fluid barrier or diversion channel, providing a solid foundation for subsequent accurate streamline simulation and fault avoidance calculation.

[0048] The method provided by the present invention adopts streamline simulation, which is based on the fluid flow equation driven by the inter-well pressure difference. In the calculation process, the influence of the permeability change at the fault on the velocity field is fully considered. The method can accurately simulate the velocity field mutation occurring during the streamline simulation process in the fault area, and reasonably adjust the flow direction of the streamline by locally adjusting the permeability, thereby generating a streamline distribution that is more in line with the actual reservoir conditions.

[0049] The present invention accurately calculates the closest contact distance between the streamline and the fault, uses the intersection judgment method to determine whether the streamline and the fault intersect, and combines the angle deflection method and the path smoothing algorithm to optimize the streamline path, effectively avoiding the contact between the high-risk streamline and the fault, and improving the rationality and stability of the well network layout.

[0050] The present invention uses a simulated annealing algorithm to achieve path optimization and well location adjustment. By defining an objective function that includes multiple factors such as the contact distance between the well and the fault, the interference between wells, and the recovery efficiency, the scientific optimization of the well location is achieved, ensuring that the well location distribution maximizes the recovery efficiency while meeting the fault avoidance requirements, which is difficult to achieve with existing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is the intersection diagram of the streamline and the fault plane in the embodiment of the present invention;

[0052] Figure 2 It is a flow chart of the calculation method for avoiding faults in oil reservoir well network streamlines in an embodiment of the present invention. DETAILED DESCRIPTION

[0053] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0054] On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims. Further, in order to make the public have a better understanding of the present invention, some specific details are described in detail in the detailed description of the present invention below. Those skilled in the art can fully understand the present invention without the description of these details.

[0055] An embodiment of a method for calculating a fault avoidance of a well pattern streamline in an oil reservoir, such as Figure 2 As shown, the method comprises the following steps:

[0056] (1) Use seismic and geological exploration data to establish a three-dimensional reservoir geological model, and use Delaunay triangulation technology to obtain a gridded reservoir model;

[0057] (2) performing streamline simulation based on the seepage equation of underground fluid, and generating streamline distribution of the reservoir well network in the gridded reservoir model;

[0058] (3) Determine the contact risk between the streamline and the fault, and calculate the avoidance path of the streamline;

[0059] (4) Use simulated annealing algorithm to optimize well location to ensure that streamlines and faults do not intersect;

[0060] (5) Perform streamline verification. If the verification passes, output the streamline result; if the streamline verification fails, return to step (4).

[0061] In this embodiment, step (1) is specifically as follows:

[0062] Using seismic interpretation and geological exploration data, a three-dimensional reservoir geological model of the reservoir area is established; the fault structure in the three-dimensional reservoir geological model is represented by polygonal boundaries, and the fault parameters include the dip, strike, location, and extension depth of the fault;

[0063] The Delaunay triangulation technique is used to divide the reservoir in the three-dimensional reservoir geological model into regular grid unit blocks (for example, tetrahedral units or hexahedral units) to obtain a gridded reservoir model Ω(x, y, z); the grid unit blocks have uniform physical property parameters;

[0064] The location of the fault is marked in the three-dimensional reservoir geological model to enable identification and avoidance in subsequent streamline calculations.

[0065] Among them, Delaunay triangulation is a common method for irregular meshing on a two-dimensional plane. It divides a set of points on the plane into a series of triangles so that the triangular mesh has good geometric properties. The formula is as follows:

[0066] For any triangle , there is no fourth point D that falls on Inside the circumcircle, that is:

[0067] ;

[0068] in, It is a triangle The circumcircle radius of .

[0069] In step (2) of this embodiment, streamline simulation is performed based on the seepage equation of underground fluid driven by the inter-well pressure difference, and the streamline distribution of the reservoir well pattern is generated in the gridded reservoir model. The specific steps include:

[0070] (2.1) Use the seepage control equation to establish the pressure field distribution:

[0071] ;

[0072] in, is the divergence operator, k is the permeability tensor, p is the pressure, is the pressure gradient, q is the source and sink term;

[0073] in, is the divergence operator, which is used to describe the divergence or convergence of the vector field. k is the permeability tensor, which describes the resistance of the medium to the flow of fluid. The permeability tensor can be anisotropic, that is, it has different permeabilities in different directions. is the pressure gradient, which represents the spatial rate of change of the pressure field. q is the source-sink term, which represents the source (positive value) or sink (negative value) of the fluid in a unit volume.

[0074] Depending on the location of the oil well, When the corresponding well is set as an injection well, Set the corresponding well as a production well and set the permeability value at the fault; set the permeability value to a smaller value (the default setting is less than 50×10^(-3)μm²) or zero;

[0075] (2.2) Calculate the flow trajectory of fluid particles using the velocity field , the streamline distribution from each well position is calculated, and the streamline equation is:

[0076] ;

[0077] Where V is the Darcy velocity, , k is the permeability tensor, is the fluid viscosity, is the pressure gradient; where V is the Darcy velocity (the average velocity of the fluid in the porous medium); k is the permeability tensor, which describes the resistance of the porous medium to the flow of the fluid. It is a second-order tensor that can represent the permeability characteristics of anisotropic media.

[0078] (2.3) In the fault area, the flow direction of the streamline is adjusted by locally adjusting the permeability. The permeability of some fault areas is set to an extremely low value to simulate the characteristics of the fault as a fluid barrier; in some fault zones, a higher permeability can be set to simulate the fault diversion channel. That is, the permeability and porosity values ​​of the fault area can be selected and set as needed to achieve differentiated settings of the permeability and porosity of the fault area in the gridded reservoir model under construction.

[0079] In step (3) of this embodiment, after the streamline simulation, the contact risk between the streamline and the fault is determined, and the avoidance path of the streamline is calculated, including the following steps:

[0080] (3.1) For any two well positions, four three-dimensional coordinate points perpendicular to the plane are obtained according to the effective perforation depth, and then the plane equation corresponding to the streamline between the two wells is obtained:

[0081] ;

[0082] in, is the normal vector of the plane corresponding to the streamline between the two wells , D1 is a constant;

[0083] x, y, z represent the x-axis, y-axis, and z-axis in the three-dimensional coordinate axis respectively;

[0084] (3.2) The fault plane is represented by the following plane equation:

[0085] ;

[0086] in, is the normal vector of the plane corresponding to the fault plane, ; D2 is a constant;

[0087] (3.3) Whether the streamline and the fault intersect can be expressed as whether two finite planes (quadrilateral planes) intersect in three-dimensional space. The present invention uses the intersection point judgment method to first solve the intersection line equation by combining two plane equations, and then judge whether the intersection line intersects with the sides of the two quadrilaterals. If they intersect, it is determined that there is a contact risk between the corresponding streamline and the fault.

[0088] Specifically, the judgment methods include:

[0089] Find the intersection line equation: Let the direction vector of the intersection line be for ;in, , .

[0090] Determine whether the intersection line intersects with the sides of the two quadrilaterals: the sides of the two quadrilaterals are all line segments, and each line segment is judged separately, for any line segment and the straight line where the intersection line is located. , represents a known point on the line, which is the equation of the line is used to determine the position of the line. Here t is a parameter. When t takes different values, Will follow a straight line Move. This equation describes a straight line where is the direction vector of the line.

[0091] The intersection is determined by substituting the endpoints of the line segment into the solution of the straight line equation and judging whether it is within the threshold range; if it intersects, it is determined that there is a risk of contact between the corresponding streamline and the fault.

[0092] like Figure 1 As shown, a, b, c, d are planes formed by faults, e, f, g, h are planes formed by effective perforation sections of any two wells, where e and f are from the same well, and g and h are from another well and are perpendicular to the ground plane.

[0093] (3.4) For streamlines that are at risk of contacting faults, the angle deflection method is used to adjust the streamline direction so that the streamline is away from the fault area;

[0094] Calculate the streamline deflection angle The formula is:

[0095] ;

[0096] in, , n is the fault normal vector;

[0097] (3.5) Use the path smoothing algorithm Bezier curve to smooth the path after streamline adjustment. The smoothing algorithm used in this step is a conventional smoothing algorithm.

[0098] Step (4) of this embodiment includes:

[0099] (4.1) Define the objective function F of well location optimization to minimize the contact distance between the well and the fault and maximize the recovery efficiency:

[0100] ;

[0101] in: is the distance penalty term between the well flow line and the fault; is the well-to-well interference degree; is the recovery efficiency correlation coefficient; , , is the weight coefficient; i represents a group of wells or a well; iterate each well; each well has a corresponding , and value.

[0102] (4.2) Execute the simulated annealing algorithm, set the initial temperature, randomly perturb the well position, accept the excellent solution, gradually reduce the temperature, and finally obtain the optimal well position; the simulated annealing algorithm used in the present invention is a conventional algorithm;

[0103] (4.1) Make adjustments based on the optimization results to ensure that the well location distribution meets the fault avoidance requirements; and calculate the streamline distribution of the adjusted well location to ensure that the streamline and fault do not intersect.

[0104] In step (5) of this embodiment, the streamline verification is performed by analyzing the streamline distribution of the well network optimized in step (4) through fluid simulation. If the two three-dimensional planes formed by the streamline and the fault do not intersect, the avoidance is judged to be successful and the verification is passed; if the two three-dimensional planes formed by the streamline and the fault intersect, the avoidance is judged to be unsuccessful, the streamline verification fails, and the process returns to step (4).

[0105] In this embodiment, step (5) also includes updating the three-dimensional reservoir geological model through verification.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating the fault avoidance of oil reservoir well pattern streamlines, characterized in that: The method comprises the following steps: (1) Use seismic and geological exploration data to establish a three-dimensional reservoir geological model, and use Delaunay triangulation technology to obtain a gridded reservoir model; (2) performing streamline simulation based on the seepage equation of underground fluid, and generating streamline distribution of the reservoir well pattern in the gridded reservoir model; (3) Determine the contact risk between the streamline and the fault, and calculate the avoidance path of the streamline; (4) Use simulated annealing algorithm to optimize well location to ensure that streamlines and faults do not intersect; (5) Perform streamline verification. If the verification passes, output the streamline result; if the streamline verification fails, return to step (4); In step (2), streamline simulation is performed based on the seepage equation of underground fluid driven by the inter-well pressure difference, and the streamline distribution of the reservoir well network is generated in the gridded reservoir model. The specific steps include: (2.1) Use the seepage control equation to establish the pressure field distribution: in, is the divergence operator, k is the permeability tensor, p is the pressure, is the pressure gradient, q is the source and sink term; According to the location of the oil well, when q>0, the corresponding well is set as an injection well, and when q<0, the corresponding well is set as a production well, and the permeability value is set at the fault; (2.2) The velocity field is used to calculate the flow trajectory X(t) of the fluid particle, and the streamline distribution from each well position is calculated. The streamline equation is: Where V is the Darcy velocity, k is the permeability tensor, μ is the fluid viscosity, is the pressure gradient; (2.3) In the fault area, the flow direction of the streamline is adjusted by locally adjusting the permeability; Step (3) comprises the following steps: (3.1) For any two well positions, four three-dimensional coordinate points perpendicular to the plane are obtained according to the effective perforation depth, and then the plane equation corresponding to the streamline between the two wells is obtained: A1x+B1y+C1z+D1=0; in, is the normal vector of the plane corresponding to the streamline between the two wells D1 is a constant; x, y, z represent the x-axis, y-axis, and z-axis in the three-dimensional coordinate axis respectively; (3.2) The fault plane is represented by the following plane equation: A2x+B2y+C2z+D2=0; is the normal vector of the plane corresponding to the fault plane D2 is a constant; (3.3) Using the intersection point judgment method, first solve the intersection line equation by solving two plane equations simultaneously, and then determine whether the intersection line intersects with the sides of the two quadrilaterals. If so, it is determined that there is a risk of contact between the corresponding streamline and the fault. (3.4) For streamlines that are at risk of contacting faults, the angle deflection method is used to adjust the streamline direction so that the streamline is away from the fault area; The formula for calculating the streamline deflection angle θ is: in, n is the fault normal vector; (3.5) Use the path smoothing algorithm Bezier curve to smooth the path after streamline adjustment; Step (4) comprises: (4.1) Define the objective function F of well location optimization to minimize the contact distance between the well and the fault and maximize the recovery efficiency: Where: d i is the distance penalty term between the well flow line and the fault; R i is the well-to-well interference degree; C i is the recovery efficiency correlation coefficient; α, β, γ are weight coefficients; i represents a group of wells or a well; (4.2) Execute the simulated annealing algorithm, set the initial temperature, randomly perturb the well location, accept the best solution, gradually reduce the temperature, and finally obtain the optimal well location; (4.1) Make adjustments based on the optimization results; and calculate the streamline distribution of the adjusted well positions to ensure that the streamlines and faults do not intersect; In step (5), the streamline verification is performed by analyzing the streamline distribution of the well network optimized in step (4) through fluid simulation. If the two three-dimensional planes formed by the streamline and the fault do not intersect, the avoidance is judged to be successful and the verification is passed; if the two three-dimensional planes formed by the streamline and the fault intersect, the avoidance is judged to be unsuccessful, the streamline verification fails, and the process returns to step (4).

2. The method for calculating the fault avoidance of oil reservoir well pattern streamlines according to claim 1, characterized in that: Step (1) is specifically as follows: Using seismic data and geological exploration data, a three-dimensional reservoir geological model of the reservoir area is established; the fault structure in the three-dimensional reservoir geological model is represented by polygonal boundaries; The Delaunay triangulation technique is used to divide the reservoir in the three-dimensional reservoir geological model into regular grid unit blocks to obtain a gridded reservoir model; The locations of faults are marked in the gridded reservoir model.

3. The method for calculating the fault avoidance of oil reservoir well pattern streamlines according to claim 1, characterized in that: Step (5) also includes updating the three-dimensional reservoir geological model through verification.

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