Well pattern construction method for fault control oil reservoir injection-production space

Abstract

The invention belongs to the technical field of oil exploration and development, and discloses a well pattern construction method for a fault control oil reservoir injection-production space. Comprising the following steps: analyzing a fracture structure; analyzing a karst system; evaluating a static connectivity relationship; selecting a well pattern type; and determining a plane well spacing and a longitudinal depth combination mode. According to the characteristics of the fault control type carbonate rock fractured-vuggy reservoir, the spatial three-dimensional well pattern is deployed and the differentiated well pattern is constructed according to the fracture property and the communication relation, the low reserve utilization degree caused by the too large well spacing can be avoided, the problem that the well pattern is too dense and the economic benefit is poor can be solved, and therefore the maximization of reserve utilization and recovery efficiency is achieved.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and development technology, and in particular relates to a well network construction method for injection and production space in fault-controlled oil reservoirs. Background Technology

[0002] Fault-controlled carbonate fracture-cavity reservoirs are a special type of reservoir that has been newly recognized and classified in recent years. Because the reservoir development characteristics and spatial structure of these reservoirs are different from those of conventional sandstone reservoirs and weathered crust buried hill carbonate reservoirs, there are no mature methods to refer to for determining which well pattern can be used to achieve efficient reserve utilization or which injection-production well pattern can maximize inter-well displacement.

[0003] Patent CN114509809A discloses a method for constructing a structural model of ancient karst fractures and cavities in carbonate rocks. Based on a detailed depiction of the ancient karst fractures and cavities, this method constructs a fracture-cavity structural model through systematic analysis of external contour correction, cavity filling material identification, and description of structural change points between cavities. It clarifies the internal structure and interconnections (connections, separations, etc.) of each related fracture and cavity, providing a reasonable, comprehensive, and feasible identification method for analyzing the relationships between ancient karst fractures and cavities. This method has strong guiding significance for well network construction and residual oil identification in development sites. However, this method does not involve methods for constructing well networks based on fracture structure data and karst system data.

[0004] Patent CN111177871A provides a method for constructing a well network with a spatial structure for injection and production in fractured-vuggy reservoirs. The method includes: identifying and characterizing fractured-vuggy structures using geophysical methods; dividing and analyzing the connectivity of fractured-vuggy structures within fractured-vuggy units based on the identification and characterization; performing reserve classification analysis based on the results of the division and connectivity analysis of fractured-vuggy structures within fractured-vuggy units; analyzing the current completeness of the injection-production well network based on the results of the identification and characterization of fractured-vuggy structures, the division and connectivity analysis of fractured-vuggy structures within fractured-vuggy units, and the reserve classification analysis; and constructing a complete injection-production well network scheme based on the results of the completeness analysis. However, this method does not involve methods for constructing a well network based on fracture structure data or karst system data.

[0005] Patent CN113605875B provides a method, apparatus, and medium for constructing a well network in fractured-vuggy reservoirs, including the following steps: determining injection wells and production wells based on the Gini coefficient within the injection-production well group; determining the ratio of the displacement and drainage sections of the injection wells based on vertically controlled reserves and permeability; adjusting the displacement and drainage sections to meet the displacement-drainage balance conditions when the ratio does not satisfy the conditions; determining the vertical deployment position of production wells based on cumulative oil production, thus determining the optimal deployment of production and injection wells in the plane, and determining the vertical deployment position and ratio of the displacement and drainage sections of the injection wells through the displacement-drainage balance index, achieving on-demand vertical allocation of injected water. This on-demand allocation in both the horizontal and vertical directions effectively improves the utilization rate of injected water, reduces water channeling, and thereby increases water-driven recovery, significantly improving the water-driven oil recovery effect in fractured-vuggy reservoirs. This method does not involve methods for constructing a well network based on fracture structure data or karst system data.

[0006] Therefore, it is anticipated that an improved well pattern construction method for the injection-production space of fault-controlled reservoirs will be provided to improve the exploitation efficiency of fault-controlled reservoirs. Summary of the Invention

[0007] To overcome the problems existing in the prior art, this invention proposes a well pattern construction method for the injection-production space of fault-controlled reservoirs. This method constructs a differentiated well pattern based on the characteristics of fault-controlled carbonate fracture-cavity reservoirs, thereby maximizing reserve utilization and recovery rate.

[0008] To achieve the above objectives, in a first aspect, the present invention provides a well pattern construction method for the injection-production space of a fault-controlled oil reservoir, comprising:

[0009] Step S1: Fracture structure analysis;

[0010] Step S2: Karst system analysis;

[0011] Step S3: Evaluation of static connectivity;

[0012] Step S4: Well pattern type selection;

[0013] Step S5: Determine the plane well spacing and the combination of vertical depth and shallowness.

[0014] In a preferred embodiment, step S1, the fracture structure analysis specifically involves: based on the regional tectonic stress analysis, using geophysical data to systematically analyze the mechanical properties, fracture fragmentation, planar segmentation, and longitudinal continuity of the fracture.

[0015] In a preferred embodiment, in step S1, the geophysical data includes at least one of structural tensor and coherence.

[0016] In a preferred embodiment, step S2, the karst system analysis specifically involves: combining surface water systems and deep water circulation to analyze the regional karst system and clarify the relationship between reservoirs.

[0017] In a preferred embodiment, in step S2, based on the karst water circulation path and fractures and cracks, and combined with the karst genesis of the reservoir, the correlation between reservoirs is identified.

[0018] In a preferred embodiment, step S3 specifically involves evaluating the static connectivity relationship as follows: based on S1 and S2 and the regional verification results, the threshold of static connectivity attributes between wells is calibrated to form a regional connectivity pattern, and the static connectivity between fractures and caverns in the study area is classified and graded.

[0019] In a preferred embodiment, in step S3, static connectivity between fractures and cavities is classified into reservoir connectivity, fracture connectivity, fracture connectivity and combinations thereof according to static attributes, and connectivity is classified into three levels based on the potential of well network construction: connectivity containing reservoir connectivity is classified as Level 1 connectivity, connectivity containing fracture connectivity but not reservoir connectivity is classified as Level 2 connectivity, and connectivity containing only fracture connectivity is classified as Level 3 connectivity.

[0020] In a preferred embodiment, primary connectivity includes series and parallel connections between fractures and reservoirs and / or series and parallel connections between fractures and reservoirs; secondary connectivity includes series and parallel connections between fractures and / or combined connections between fractures and fractures.

[0021] In a preferred embodiment, in step S4, the selection of well network type specifically involves: based on the understanding of oil and gas charging, using the static connectivity mode between fractures and cavities to construct a single-row or multi-row well network in a plane.

[0022] In a preferred embodiment, in step S5, the determination of the plane well spacing and the vertical depth-shallow combination method is specifically as follows: based on the classification and grading results of the static connectivity of fractures and caverns, the differentiated well spacing for activation and the subsequent injection-production well spacing are determined.

[0023] Secondly, the present invention provides a storage medium storing a computer-executable program, which, when executed, is adapted to implement a well pattern construction method for controlling the injection and production space of a fault-controlled reservoir, the well pattern construction method comprising the following steps:

[0024] Step S1: Fracture structure analysis;

[0025] Step S2: Karst system analysis;

[0026] Step S3: Evaluation of static connectivity;

[0027] Step S4: Well pattern type selection;

[0028] Step S5: Determine the plane well spacing and the combination of vertical depth and shallowness.

[0029] The beneficial effects of this invention are:

[0030] 1. The well network construction method for the injection and production space of fault-controlled reservoirs of the present invention constructs a differentiated well network based on the characteristics of fault-controlled carbonate fracture-cavity reservoirs, thereby maximizing reserve utilization and recovery rate.

[0031] 2. This invention deploys a spatial three-dimensional well network based on the nature and connectivity of fractures, which can both avoid the low utilization rate of reserves due to excessive well spacing and solve the problem of poor economic benefits due to excessively dense well networks, thereby maximizing development benefits. Attached Figure Description

[0032] Figure 1 This is a flowchart of the well network construction method for the injection-production space of a fault-controlled reservoir in Example 1;

[0033] Figure 2 For fracture mechanics analysis and coherence property planar segmentation diagram;

[0034] Figure 3 To analyze the fracture plane segmentation diagram using tensor properties;

[0035] Figure 4 To analyze the fracture plane segmentation diagram using tensor properties;

[0036] Figure 5 A diagram showing the division of unit karst systems and karst elements;

[0037] Figure 6 This is a diagram of the injection-production well network for a single unit.

[0038] Figure 7 This is a diagram illustrating the effect of a unit injection-production well network. Detailed Implementation

[0039] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to specific embodiments.

[0040] Example 1

[0041] Figure 1 This is a flowchart of a well network construction method for the injection-production space of a fault-controlled reservoir according to Embodiment 1 of the present invention.

[0042] According to Figure 1 This embodiment proposes a well pattern construction method for fault-controlled carbonate fracture-vuggy reservoirs, the steps of which are as follows:

[0043] Step S1: Based on the regional tectonic stress analysis, use geophysical data such as tensor and coherence to systematically analyze the mechanical properties, fracture fragmentation, planar segmentation, and longitudinal continuity of the fracture to obtain fracture structure data.

[0044] Step S2: Combine surface water system and deep water cycle to analyze and study regional karst system, clarify the relationship between reservoirs and obtain karst system data;

[0045] Specifically, based on the karst water circulation path and fractures and cracks, and combined with the karst genesis of the reservoir, the correlation between reservoirs can be identified.

[0046] It is believed that reservoirs controlled by the same water cycle and reservoirs controlled by the same set of fault segments have good connectivity, which is conducive to establishing injection and production. However, reservoirs controlled by different karst water cycles and different faults have poor connectivity, and even if there are cross-connecting faults or fractures, the efficiency of establishing displacement is not high.

[0047] Step S3: Based on the fracture structure data, karst system data, and regional verification results, calibrate the threshold of static connectivity attributes between wells to obtain the connectivity mode of the region, as well as the classification and grading data of static connectivity between fractures and caverns in the region;

[0048] Specifically, based on static attributes, static connectivity between fractures and cavities is divided into reservoir connectivity, fracture connectivity, fracture connectivity and their combinations, and connectivity is further divided into three levels based on the potential of well network construction.

[0049] Connectivity involving reservoir connectivity is classified as Level 1 connectivity (e.g., series and parallel connections between fractures and reservoirs, series and parallel connections between fractures and reservoirs, etc.). Connectivity involving fracture connectivity but not reservoir connectivity is classified as Level 2 connectivity (including series and parallel connections between fractures, combined connections between fractures, etc.). Connectivity involving only fracture connectivity is classified as Level 3 connectivity. Level 1 connectivity is the optimal connectivity mode for constructing well networks, as it can both replenish energy and drive displacement between wells. Level 2 connectivity is secondary, primarily for replenishing energy, with relatively little effect on displacement between wells. Level 3 connectivity is the worst, essentially lacking any potential for network construction.

[0050] Step S4: Based on the understanding of oil and gas charging, construct a single-row or multi-row well network in a plane using the static connection mode between fractures and cavities.

[0051] Step S5: Based on the classification and grading data of the single or multiple row well network in the plane and the static connectivity between the fractures and cavities, determine the differentiated well spacing for operation and the subsequent injection-production well spacing.

[0052] Take the typical fault-controlled karst reservoir unit TH10303 as an example.

[0053] In steps S1-S3, the unit fracture morphology classification and connectivity evaluation are achieved through mechanical property and geophysical attribute analysis.

[0054] From a mechanical perspective, the TH10303 element fracture is a single-branch strike-slip fracture under a global tensional background. Using tensor and coherence properties, it can be divided into two large segments and three smaller segments, such as... Figure 2 , Figure 3 As shown.

[0055] In the longitudinal direction, the continuity of tensor thickness is used to identify the connectivity of fractures and to assist in determining the planar segmentation of fractures, such as... Figure 4 As shown.

[0056] In steps S4-S5, the karst system of the small well area is described in conjunction with the surface water system and fault characteristics, laying the geological foundation for well network construction. The unit karst system and karst element division map are shown below. Figure 5 .

[0057] Based on the understanding of fault segmentation and karst connectivity, a three-dimensional injection-production well network is constructed, which includes energy replenishment through water injection at deep karst water catchment points, lateral oil displacement, and surface segmented gas injection to utilize the remaining oil at the top. The unit injection-production well network is as follows: Figure 6 As shown, the effect of the unit injection-production well network is as follows: Figure 7 As shown.

[0058] By constructing a three-dimensional well network, an initial 1 injection and 5 recovery system is achieved, effectively replenishing the unit's energy. In the later stages, top gas injection significantly improves the unit's recovery rate.

[0059] It should be noted that the specific embodiments described above enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the present invention in any way. Therefore, although the present invention has been described in detail with reference to the accompanying drawings and embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the present invention. In short, all technical solutions and changes that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the present invention patent.

Claims

1. A method for constructing a well pattern for controlling an oil reservoir injection-production space, characterized by, Comprising: Step S1: fracture structure analysis; Step S2: karst system analysis; Step S3: static connectivity relationship evaluation; Step S4: well pattern type selection; Step S5: determination of planar well spacing and longitudinal depth combination mode.

2. The well pattern construction method of claim 1, wherein, In step S1, the fracture structure analysis specifically comprises: on the basis of regional tectonic stress analysis, using geophysical data to systematically analyze the mechanical properties of the fracture, fracture fragmentation, planar segmentation and longitudinal through property.

3. The pattern building method of claim 2, wherein, In step S1, the geophysical data comprises at least one of structural tensor and coherence.

4. The pattern building method of claim 1, wherein, In step S2, the karst system analysis specifically comprises: combining surface water system and deep water cycle, analyzing and researching the regional karst system, and clarifying the relationship between the reservoir bodies.

5. The pattern building method of claim 4, wherein, In step S2, on the basis of karst water circulation path and fracture, combined with the karst genesis of the reservoir body, the correlation between the reservoir bodies is identified.

6. The pattern building method of claim 1, wherein, In step S3, the static connectivity relationship evaluation specifically comprises: on the basis of S1 and S2, according to the regional verification results, the static connectivity attribute threshold between wells is calibrated, the connectivity mode of the region is formed, and the interstitial pore static connectivity classification and grading of the research area is carried out.

7. The pattern building method of claim 6, wherein, In step S3, the interstitial pore static connectivity is divided into reservoir body connectivity, fracture connectivity, crack connectivity and their combinations according to the static attribute, and the connectivity is divided into three levels combined with the potential of well pattern construction, including reservoir body connectivity, fracture connectivity and crack connectivity; the first level connectivity includes fracture and reservoir body series and parallel and / or crack and reservoir body series and parallel; the second level connectivity includes fracture connectivity series and parallel and / or fracture and crack combination connectivity.

8. The pattern building method of claim 1, wherein, In step S4, the well pattern type selection specifically comprises: on the basis of oil and gas charging understanding, using the interstitial pore static connectivity mode, constructing planar single-row or multi-row well pattern.

9. The pattern building method of claim 1, wherein, In step S5, the determination of planar well spacing and longitudinal depth combination mode specifically comprises: according to the classification and grading results of the interstitial pore static connectivity, determining the differential producing well spacing and the later injection-production well spacing.

10. A storage medium, characterized by The computer executable program is stored in the computer readable storage medium, and the program is adapted to implement the well pattern construction method of fault-controlled reservoir injection-production space when executed. Comprising: Step S1: fracture structure analysis; Step S2: karst system analysis; Step S3: static connectivity relationship evaluation; Step S4: well pattern type selection; Step S5: determination of planar well spacing and longitudinal depth combination mode.

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