Well pattern test simulation and interpretation method based on connection unit topology maintenance

Abstract

The application discloses a well pattern test simulation and interpretation method based on connection unit topology maintenance, and belongs to the technical field of reservoir engineering test analysis. In view of the problems that the topology structure of a traditional Cartesian grid is prone to be averaged when processing a connection unit model, the source of a late boundary response is difficult to trace, and the model conversion and test interpretation process are poor in connection, connection edge is converted into an equivalent conductive structure recognizable by a numerical simulator and a mapping relationship is constructed by reading and checking the connection unit model data, so that the topology identification and conductive properties of the connection unit are retained; a test scheme is designed, in which a target well is shut in and adjacent wells maintain original working systems, a logarithmic time step is adopted to control a simulation process, a pressure sequence is extracted and a pressure derivative is calculated, and finally, the connection source of the late boundary response is traced in combination with the topology mapping relationship. The connection topology can be traced in the whole process, the accuracy of test interpretation under well pattern conditions is improved, and the test simulation and interwell connectivity evaluation are suitable for various injection-production well patterns.

Description

Technical Field

[0001] This invention relates to the field of reservoir engineering well test analysis technology, and in particular to a well network well test simulation and interpretation method based on topology preservation of connection units. Background Technology

[0002] Reservoir well test interpretation has developed a mature numerical simulation and curve diagnosis process. Typically, a geological model or equivalent model is first established, followed by setting production and shut-in operating regimes. Finally, the characteristics of wellbore storage, radial flow, boundary response, and inter-well disturbances are determined based on pressure response and pressure derivative curves. Existing technologies are mainly divided into three categories: The first category is the regular grid numerical simulation method, which divides the reservoir into regular grids or locally refined grids, describes the reservoir heterogeneity through grid properties, and then uses a reservoir numerical simulator to calculate the bottom hole pressure change. It has good versatility but is prone to weakening the directional transmission characteristics of the connecting edges.

[0003] The second category is the equivalent radial or homogeneous partitioning model method, which simplifies the influence range of the well perimeter or well network into a radial flow model, a partitioned homogeneous model, or an equivalent boundary model. It has higher computational efficiency but is only applicable to working conditions with clear boundaries and simple connectivity.

[0004] The third category is the interpretation method of well network interference and replenishment boundary. It combines the production, injection volume and pressure changes of adjacent wells to analyze the target well curve, but it is mostly interpreted from the perspective of well control or equivalent boundary, and does not retain the local connected topology of the connecting unit as an independent object.

[0005] Existing technologies have significant shortcomings when dealing with heterogeneous reservoirs, obliquely dominant channels, and irregular well networks. The grid orientation effect easily distorts pressure propagation paths. Even when using a connected element model for modeling, the original connectivity topology information is easily lost after gridding, making it difficult to trace abnormal responses in well test curves back to specific well channels, thus limiting the reliability of multi-well test interpretation results. Existing technologies suffer from the following drawbacks: First, the connection relationship is easily averaged out. The regular grid model will incorporate the direction, endpoints and conduction capacity of the original connection edge into the grid attribute, and there is no clear correspondence between non-adjacent connectivity and dominant channels. Second, the interpretation of late boundary is easily confused. When the target well is shut in and adjacent wells continue to produce, the late pressure derivative may come from the outer boundary or from well network leakage and inter-well interference. A single interpretation logic is easy to cause misjudgment. Third, the outer ring well curves cannot directly replace the target well curves; they can only be used as auxiliary references. Fourth, there is a lack of continuity between model conversion and well test interpretation. The corresponding relationship of the connecting edges is not saved by the system, making it impossible to trace the changes of the derivative curve back to the specific connecting unit. Summary of the Invention

[0006] The purpose of this invention is to propose a well network test simulation and interpretation method based on topology preservation of connection units. This method preserves the topological correspondence of connection edges throughout the entire process of model conversion, system design, simulation operation and curve interpretation, enabling traceability of late boundary responses and improving the accuracy and process coherence of well test interpretation under well network conditions.

[0007] To achieve the above objectives, this invention provides a well network testing simulation and interpretation method based on topology preservation of connection units, comprising the following steps: Step S1: Read and verify the connection unit model data, and establish the correspondence between the target well, adjacent wells and surrounding connection edges; Step S2: Convert the connection edges of the connection unit into an equivalent conduction structure that can be recognized by the numerical simulator, and establish a mapping relationship between the original connection edges and the equivalent conduction structure; Step S3: Perform topological identification on well locations, nodes, and connecting edges, and retain the connectivity topology and conduction attribute information of the connecting units; Step S4: Design the well network testing operation system so that the target well is switched to the shut-in operation state, while the adjacent wells maintain the original production or injection operation system; Step S5: Perform numerical simulation calculations, extract the shut-in pressure time series of the target well and calculate the pressure derivative; Step S6: Identify the flow stage based on the double logarithmic curve and trace the connectivity source of the late boundary response by combining the topological mapping relationship.

[0008] Preferably, in step S1, the read connection unit model data includes node coordinates, connection edge start and end nodes, layer number, well location, porosity, permeability, and connection conduction capacity; a data index is established according to the layer segment and connection edge number, duplicate connections, breakpoint connections, and cross-layer mismatch anomalies are checked, and then a mapping base table between wells and corresponding connection edges is established based on the well location.

[0009] Preferably, in step S2, the equivalent conduction structure is selected from one or more of special grid bands, non-adjacent connections, and equivalent conduction terms; local grid densification is set for the well perimeter area and high conduction connection locations to avoid near-well pressure propagation being weakened by the grid scale.

[0010] Preferably, in step S3, independent identifiers are set for the target well, adjacent wells, multiple connection nodes, and dominant channels respectively; the convergence relationship of multiple connection nodes is preserved and they are not homogenized into grid attributes; the number, endpoints, layer segments, and connection conduction capacity information of the connection edges that affect the late boundary response are retained for subsequent interpretation and tracing.

[0011] Preferably, in step S4, a production stage is first set up so that the target well and adjacent wells operate according to the actual development system to establish a stable well network pressure field; then, the well testing stage is entered, where only the working system of the target well is adjusted to the shut-in state, while the adjacent wells maintain their original working systems.

[0012] Preferably, during the shut-in phase, logarithmic time steps are used for simulation output to control the initial shut-in time and the maximum time interval, while retaining a high density of bottom hole pressure output sampling points.

[0013] Preferably, in step S5, the converted equivalent model is input into the reservoir numerical simulator for operation, and the pressure field at the end of the production period, the bottom hole pressure data of the target well during the shut-in period, and the working system records of adjacent wells are saved; the pressure data of the target well is used as the main body of analysis, and the data of adjacent wells are used as the auxiliary basis for boundary interpretation.

[0014] Preferably, in step S5, the pressure derivative is calculated using the adjacent point difference method or the Bourdet derivative method on a logarithmic time scale, and duplicate time points are eliminated to ensure the smoothness of the curve.

[0015] Preferably, in step S6, the wellbore reservoir section is identified in the early stage on the double logarithmic curve, the radial flow platform section is identified in the middle stage, and the specific source of the boundary response is analyzed in the late stage by combining the spatial location of the connecting edge, the working system of adjacent wells, and the topological mapping relationship; the calculation results are compared with the results of the traditional regular grid model to determine the consistency of the main flow section and locate the cause of the late-stage derivative difference.

[0016] Preferably, the well network is an injection-production well network that includes one target well and multiple adjacent wells. The target well is an injection well, a production well, or an observation well, and the adjacent wells are production wells or injection wells.

[0017] Therefore, the present invention employs the above-described well network testing simulation and interpretation method based on connection unit topology preservation, which has the following advantages: (1) It has a wide range of applications and does not limit the type of well network or the number of wells. As long as the model contains the target well, adjacent wells, nodes and connecting edge relationships, it can be implemented. The well type and simulator type can be adjusted as needed. (2) Topology is traceable. After model conversion, the connection edge number, endpoint node, layer segment and conduction capacity are completely preserved. When the pressure derivative changes in the later stage, the specific connection unit can be directly checked back to avoid the loss of connectivity information caused by mesh averaging. (3) The working conditions are close to reality. During the well test stage, only the target well is shut in, while the adjacent wells maintain their original production, injection or pressure control system. The late response of the curve can truly reflect the characteristics of well network leakage and interference with adjacent wells. (4) The results are reliable and comparable. The curve of the main flow section is in the same flow stage as the traditional equivalent regular grid model. The pressure response and derivative piecewise error are controllable, taking into account both the consistency of results and the topological identification. (5) The process is coherent and efficient. Model reading, transformation, system design, time step control, result extraction and curve interpretation form a complete closed loop, reducing the amount of manual data processing work between multiple software programs.

[0018] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall process of a well network testing simulation and interpretation method based on connection unit topology preservation in an embodiment of the present invention; Figure 2 This is a schematic diagram of the connection unit nodes and connection relationships of a four-well network in one injection and four-well production according to an embodiment of the present invention. Figure 3 This is a comparison chart of the double logarithmic curves of well test pressure and pressure derivative between the connected element method and the traditional regular grid model in this embodiment of the invention. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] Example like Figures 1-3 As shown, this embodiment proposes a well network testing simulation and interpretation method based on topology preservation of connection units, combined with... Figure 1 The implementation process shown in this embodiment uses a one-injection-four-production well network as the object for well test simulation and interpretation. The connection unit structure of the well network is as follows: Figure 2As shown in the figure. The model in this embodiment has a planar area of ​​600m × 600m, with one injection well at the center as the target well and four production wells at the four corners as adjacent wells. A total of 45 connecting unit nodes are set in the plane, divided into three layers longitudinally, with a single layer thickness of 15m and a total effective thickness of 45m. The average permeability of the model plane ranges from 10.33 to 197.67 mD, with an average of 61.87 mD; the porosity ranges from 0.100 to 0.298, with an average of 0.200; the connectivity conductivity ranges from 0.329 to 3.218, with an average of 0.959, and the conductivity coefficient of variation is 0.54, exhibiting significant heterogeneity.

[0023] The specific steps in this embodiment are as follows: Step S1: Connecting unit model reading and verification: Read the node coordinates, start and end nodes of the connection edge, layer number, well location, porosity, permeability and connection conduction capacity data from the CGS format connection unit model; establish a data index according to the layer segment and connection edge number, and check for duplicate connections, broken connections and cross-layer mismatch anomalies one by one; establish the correspondence between the central injection well and the four corner production wells and their surrounding connection edges according to the well location, and form the basic data table for subsequent conversion.

[0024] In this embodiment, the basic parameters of each well are as follows: the central injection well is located at coordinates (300, 300), with a perforation thickness of 45m, an average permeability of 59.45mD, and an average porosity of 0.221; the four production wells are located at the four corners of the model, with differences in permeability and porosity, which are used to simulate heterogeneous connectivity conditions.

[0025] Step S2: Connection relationship transformation and equivalent model establishment: Based on the length, direction, endpoint nodes, and conduction capacity of each connecting edge, the connecting elements are converted into equivalent conduction structures that can be handled by the numerical simulator. This embodiment adopts a combination of non-adjacent connections and locally refined meshes. Locally refined meshes are set at the well perimeter and high conduction connections to prevent near-well pressure propagation from being weakened by excessively coarse meshes. After the conversion, a one-to-one mapping table is established between the original connecting edges, the simulator mesh, and non-adjacent connections, recording the equivalent structure number and spatial location corresponding to each connecting edge.

[0026] Step S3: Maintain topology of connection units: Unique identifiers are set for the central target well, four adjacent production wells, multiple connecting nodes, and high-conduction advantage channels. For a single node connecting multiple connecting edges, the convergence relationship of the node is fully preserved, and it is not simplified to a homogeneous grid attribute. Connecting edges that may affect the late boundary response on the periphery of the model are screened out, and their numbers, endpoint coordinates, layer segments, and conduction capacity information are retained for retrospective use in the subsequent curve interpretation stage.

[0027] Step S4: Well pattern testing system design: First, a production period is set up, with the central injection well and four production wells operating according to the established development regime until the well network pressure field reaches a stable state. After entering the well testing period, only the central target well is switched to a shut-in state, while the four adjacent production wells maintain their original production regimes.

[0028] During the shut-in phase, logarithmic time steps are used to output pressure data. The initial shut-in time is set to 0.00001h, and the maximum time interval does not exceed 1d to ensure that the bottom hole pressure sampling points are output with sufficient density, so as to meet the accuracy requirements of early derivative calculation and late boundary identification.

[0029] Step S5: Simulation, Result Extraction, and Derivative Calculation: Input the converted equivalent model into the CMG / GEM numerical simulator for calculation; after the simulation is completed, save the full model pressure field at the end of the production period, the bottom hole pressure time series of the target well during the shut-in phase, and the working regime records of adjacent wells.

[0030] Using the shut-in pressure data of the target well as the main analysis data, shut-in time and pressure change are extracted. The pressure derivative is calculated using a logarithmic time scale and employing pressure derivative calculation methods (including but not limited to the adjacent point difference method and the Bourdet derivative method; in this embodiment, the Bourdet derivative method is used). During the calculation, duplicate time points are removed to ensure a smooth derivative curve. Pressure data from adjacent wells are used only as auxiliary references for boundary interpretation and do not directly replace the well test curve of the target well.

[0031] Step S6: Curve Comparison and Boundary Interpretation: Based on pressure and pressure derivative data, double logarithmic curves are plotted. The early curve segment is used to determine the wellbore reservoir effect, the mid-term curve plateau is used to determine the radial flow stage, and the late curve segment, combined with the retained connection edge information, the working system of adjacent wells, and the topology mapping table, analyzes the specific source of the boundary response and distinguishes whether the response comes from the outer boundary of the reservoir or from inter-well connectivity interference.

[0032] Simultaneously, the calculation results of this method are compared with those of the traditional regular grid model to verify the consistency of the main flow section curve. In this embodiment, the segmentation error of the pressure response and derivative in the main flow section is controlled within the range of 5% to 10%, and the two are well matched in the main flow stage, reflecting the close characteristics of the main flow section; there are significant differences in the late derivatives, and the corresponding inter-well dominant connectivity channels can be located through the topology mapping table to achieve traceability of late differences and quantitative identification of inter-well connectivity.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A well network testing simulation and interpretation method based on topology preservation of connection units, characterized in that, Includes the following steps: Step S1: Read and verify the connection unit model data, and establish the correspondence between the target well, adjacent wells and surrounding connection edges; Step S2: Convert the connection edges of the connection unit into an equivalent conduction structure that can be recognized by the numerical simulator, and establish a mapping relationship between the original connection edges and the equivalent conduction structure; Step S3: Perform topological identification on well locations, nodes, and connecting edges, and retain the connectivity topology and conduction attribute information of the connecting units; Step S4: Design the well network testing operation system so that the target well is switched to the shut-in operation state, while the adjacent wells maintain the original production or injection operation system; Step S5: Perform numerical simulation calculations, extract the shut-in pressure time series of the target well and calculate the pressure derivative; Step S6: Identify the flow stage based on the double logarithmic curve and trace the connectivity source of the late boundary response by combining the topological mapping relationship.

2. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S1, the read connection unit model data includes node coordinates, connection edge start and end nodes, layer number, well location, porosity, permeability, and connection conduction capacity; a data index is established according to the layer segment and connection edge number, duplicate connections, breakpoint connections, and cross-layer mismatch anomalies are checked, and then a mapping base table between wells and corresponding connection edges is established based on the well location.

3. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S2, the equivalent conduction structure is selected from one or more of special grid bands, non-adjacent connections, and equivalent conduction terms; local grid densification is set for the well perimeter area and high conduction connection locations to avoid near-well pressure propagation being weakened by the grid scale.

4. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S3, independent identifiers are set for the target well, adjacent wells, multiple connection nodes, and dominant channels respectively; the convergence relationship of multiple connection nodes is preserved and they are not homogenized into grid attributes; the number, endpoints, layer segments, and connection conduction capacity information of the connection edges that affect the late boundary response are retained for subsequent interpretation and tracing.

5. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S4, the production stage is first set up so that the target well and adjacent wells operate according to the actual development system to establish a stable well network pressure field; then the well testing stage is entered, where only the working system of the target well is adjusted to the shut-in state, while the working system of adjacent wells remains unchanged.

6. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 5, characterized in that: During the shut-in phase, logarithmic time steps are used for simulation output to control the initial shut-in time and the maximum time interval, while retaining a high density of bottom hole pressure output sampling points.

7. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S5, the converted equivalent model is input into the reservoir numerical simulator for operation, and the pressure field at the end of the production period, the bottom hole pressure data of the target well during the shut-in period, and the working system records of adjacent wells are saved; the pressure data of the target well is used as the main body of analysis, and the data of adjacent wells are used as the auxiliary basis for boundary interpretation.

8. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S5, the pressure derivative is calculated using the adjacent point difference method or the Bourdet derivative method on a logarithmic time scale, and repeated time points are eliminated to ensure the smoothness of the curve.

9. The well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: In step S6, the wellbore reservoir section is identified in the early stage on the double logarithmic curve, the radial flow platform section is identified in the middle stage, and the specific source of the boundary response is analyzed in the late stage by combining the spatial location of the connecting edge, the working system of adjacent wells, and the topological mapping relationship. The calculation results are compared with the results of the traditional regular grid model to determine the consistency of the main flow section and locate the cause of the late-stage derivative difference.

10. A well network testing simulation and interpretation method based on topology preservation of connection units according to claim 1, characterized in that: A well network is an injection-production well network consisting of a target well and multiple adjacent wells. The target well is an injection well, a production well, or an observation well, and the adjacent wells are production wells or injection wells.

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