Method for evaluating source-conduit property of strike-slip fault in sedimentary basin

Abstract

A method for evaluating the source-conducting property of strike-slip faults in a sedimentary basin relates to the technical field of geological exploration and mainly comprises the following steps: collecting geological information of a target area, calculating the conductive coefficient of the top interface of source rocks in the target area, calculating the conductive coefficient of the bottom interface of reservoirs in the target area, respectively calculating the conductive coefficient of each interface between the source rocks and the reservoirs, calculating the vertical conductive coefficient of the strike-slip faults, calculating the comprehensive conductive coefficient of the strike-slip faults based on the vertical conductive coefficient of the strike-slip faults, obtaining the vertical conductive capacity of the strike-slip faults, and taking the vertical conductive capacity of the strike-slip faults as the quantitative basis for evaluating the source-conducting property of the strike-slip faults. The method for evaluating the source-conducting property of strike-slip faults in a sedimentary basin combines the vertical conductive coefficient, the thickness of source rocks and the distance from the hydrocarbon-generating center to quantitatively calculate the source-conducting property of the strike-slip faults, and can significantly improve the accuracy and reliability of the source-conducting property evaluation of the strike-slip faults.

Description

Technical Field

[0001] This invention relates to the field of geological exploration technology, specifically a method for evaluating the source-transportation properties of strike-slip faults in sedimentary basins. Background Technology

[0002] Strike-slip fault systems are widely developed in the Earth's lithosphere, distributed along plate margins, mid-ocean ridges, or the periphery of intraplate sedimentary basins. In recent years, they have also been discovered within stable cratonic plates, such as the large strike-slip fault systems in the Tarim, Sichuan, and Ordos basins of China. Strike-slip faults within sedimentary basins are steep and vertical, with complex formation mechanisms and multi-phase activity. They are correlated with basin sedimentary infilling, hydrocarbon accumulation conditions (such as hydrocarbon migration channels and trap formation), geothermal resource distribution, and seismic activity.

[0003] In recent years, with the expansion of oil and gas exploration into ultra-deep and complex structural areas, especially the discovery of large oil and gas fields (such as Fuman Oilfield and Shunbei Oilfield) associated with strike-slip faults in sedimentary basins, the "source-transport capacity" of strike-slip faults (i.e., whether the fault possesses connectivity across the deep (basement) to shallow (caprock) layers and can serve as a key channel for oil and gas migration) has become a critical scientific issue for oil and gas exploration and development in these basins. Outcrop well data and other evidence confirm that a complex three-dimensional fractured body, or fault fracture zone, is formed during fault deformation. This three-dimensional deformed fractured body exhibits heterogeneity in both the horizontal and vertical directions, but the fractures and related dissolution within it can serve as channels for oil and gas migration. Traditional geological studies often rely on outcrop observations or single geophysical methods (such as seismic reflection profiles), making it difficult to accurately identify the spatial distribution, activity phases, and closure characteristics of faults in the deep-shallow region. Conventional seismic exploration offers high resolution for shallow faults, but its ability to track the continuity of deep (>3km) faults is susceptible to errors in velocity models. Furthermore, strike-slip faults are steep, vertical, and have small longitudinal displacements, making them difficult to image on seismic profiles. Limited drilling data also hinders direct verification of the existence, imaging, and activity of deep strike-slip faults. Within relatively stable sedimentary basins, deep source rocks migrate to shallow reservoirs via strike-slip faults. The fracture zones are controlled by host lithology, stress variations, multiple phases of activity, and diagenesis, resulting in heterogeneity in their internal structure. Previously, the source-transporting capacity of strike-slip faults relied primarily on qualitative descriptions using traditional methods, lacking quantitative evaluation models. Summary of the Invention

[0004] Therefore, the main objective of this invention is to provide a method for evaluating the source-transport capacity of strike-slip faults in sedimentary basins. Addressing the problems of unclear source-transport capacity laws of strike-slip faults and the lack of quantitative characterization parameters and methods, this invention combines quantitative parameters of strike-slip fault deformation (deformation parameters of strike-slip faults such as source rock layers and reservoirs) with relevant parameters of source rocks (thickness and distance from hydrocarbon generation centers) to conduct a comprehensive evaluation of the vertical transport capacity of the faults.

[0005] The technical solution of this invention is a method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins, comprising the following steps: Step S1: Collect geological information of the target area and calculate the transport coefficient of the top interface of the source rock in the target area; Step S2: Calculate the conductivity coefficient of the bottom interface of the reservoir in the target area; Step S3: Calculate the transport coefficients of each interface between the source rock and the reservoir; Step S4: Calculate the vertical conduction coefficient of the strike-slip fracture; Step S5: Calculate the comprehensive conductivity coefficient of the strike-slip fracture based on the vertical conductivity coefficient of the strike-slip fracture, and obtain the vertical conductivity capacity of the strike-slip fracture. Use the vertical conductivity capacity of the strike-slip fracture as a quantitative basis for evaluating the source conductivity of the strike-slip fracture.

[0006] The technical effects of this invention are: The method for evaluating the source and transport properties of strike-slip faults in sedimentary basins provided in this invention combines the vertical transport coefficient, source rock thickness, and distance from the hydrocarbon generation center to quantitatively calculate the source and transport properties of strike-slip faults. This method can significantly improve the accuracy and reliability of strike-slip fault source assessment and provide key technical support for the study of fault-controlled reservoir development, geothermal resource development, and earthquake hazard assessment in oil and gas exploration. Attached Figure Description

[0007] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below.

[0008] Figure 1 This is an overall flowchart of the present invention; Figure 2 This is a schematic diagram of the distribution of transport coefficients at the top interface of the source rock in the target area in an embodiment of the present invention; Figure 3 This is a schematic diagram of the transport coefficient distribution at the bottom interface of the reservoir in the target area in an embodiment of the present invention; Figure 4 This is a schematic diagram of the vertical transport capacity distribution in the target area in an embodiment of the present invention. Detailed Implementation

[0009] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0010] 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. The described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0011] Example

[0012] like Figure 1 As shown, a method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins includes the following steps: Step S1: Collect geological information of the target area and calculate the transport coefficient of the top interface of the source rock in the target area; The target area is the strike-slip fault in the Halahatang Depression in the northern Tarim Basin, with the fault base cutting into the Cambrian source rocks. The distribution of the transport coefficient at the top interface of the source rocks is as follows: Figure 2 As shown, the transport coefficient of the top interface of the source rock refers to the strike-slip fracture transport coefficient of the top interface of the source rock. The calculation method is as follows: multiply the vertical height difference of the top interface of the source rock by the width of the fault fracture zone, and then normalize the product.

[0013] The vertical height difference at the top interface of the source rock is the absolute value of the difference between the uplift or subsidence height of the strike-slip fault and the horizontal plane of that layer. The product normalization method is obtained by Min-Max normalization.

[0014] Step S2: Calculate the conductivity coefficient of the bottom interface of the reservoir in the target area; The reservoir in the target area consists of the Middle Ordovician Jianfang Formation carbonate rocks, such as... Figure 3 As shown, the conductivity coefficient of the reservoir bottom interface refers to the strike-slip fracture conductivity coefficient of the reservoir bottom interface. It is calculated by multiplying the vertical height difference of the reservoir bottom interface by the width of the fault fracture zone and then performing Min-Max normalization on the product.

[0015] The vertical height difference at the bottom interface of the reservoir is the absolute value of the difference between the uplift or subsidence height of the strike-slip fault and the horizontal plane of that layer.

[0016] Step S3: Calculate the transport coefficients of each interface between the source rock and the reservoir; The method for calculating the transport coefficients of each interface between the source rock and the reservoir is as follows: multiply the vertical height difference of each interface by the width of the fault fracture zone, and then normalize the product using the Min-Max method.

[0017] Step S4: Calculate the vertical conduction coefficient of the strike-slip fracture; The calculation method for the vertical conductivity coefficient of strike-slip fracture is shown in equation (1): (1) In equation (1), β ( v () represents the vertical conductance coefficient of the strike-slip fracture; β n It represents the conductivity coefficient of the bottom interface of the nth stratum above the source rock, that is, the conductivity coefficient of each stratum above the source rock. β 1 represents the transport coefficient at the top interface of the source rock; min( β 0, β 1) Represents variables β 0 and β The smallest of 1.

[0018] As can be seen from equation (1), the vertical transport coefficient of the strike-slip fault can be calculated by combining the source rock, the reservoir, and the transport coefficients of each interface between the source rock and the reservoir.

[0019] Step S5: Calculate the comprehensive conductivity coefficient of the strike-slip fracture based on the vertical conductivity coefficient of the strike-slip fracture, and obtain the vertical conductivity capacity of the strike-slip fracture. Use the vertical conductivity capacity of the strike-slip fracture as a quantitative basis for evaluating the source conductivity of the strike-slip fracture.

[0020] The calculation method for the comprehensive transport coefficient of strike-slip faults is as follows: Comprehensive transport coefficient of strike-slip faults = Vertical transport coefficient of strike-slip faults × Thickness of source rock × Distance from hydrocarbon generation center.

[0021] The thickness of the source rock is the thickness of the source rock strata inhabited by the strike-slip fault.

[0022] The distance from the hydrocarbon generation center is the Min-Max normalized distance extending from the starting point of the strike-slip fault to the hydrocarbon generation center of the source rock.

[0023] Then, by performing Min-Max normalization on the comprehensive conduction coefficient of the strike-slip fracture, the quantified vertical conduction capacity of the strike-slip fracture can be obtained.

[0024] Through the calculation of the source conductivity of strike-slip fractures, such as Figure 4 As shown, the vertical transport of the strike-slip faults illustrated in the examples can be divided into four levels. Level one represents the optimal oil and gas transport location and is also the main strike-slip fault development segment forming high-yield wells. Level four represents the worst oil and gas transport location. The coincidence rate between high-yield wells and Level one transport fault segments is over 80%.

[0025] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins, characterized in that, Includes the following steps: Step S1: Collect geological information of the target area and calculate the transport coefficient of the top interface of the source rock in the target area; Step S2: Calculate the conductivity coefficient of the bottom interface of the reservoir in the target area; Step S3: Calculate the transport coefficients of each interface between the source rock and the reservoir; Step S4: Calculate the vertical conduction coefficient of the strike-slip fracture; Step S5: Calculate the comprehensive conductivity coefficient of the strike-slip fracture based on the vertical conductivity coefficient of the strike-slip fracture, obtain the vertical conductivity of the strike-slip fracture, and use the vertical conductivity of the strike-slip fracture as a quantitative basis for evaluating the source conductivity of the strike-slip fracture. The calculation method for the vertical conduction coefficient of the strike-slip fracture in step S4 is shown in equation (1): （1） In equation (1), β ( v () represents the vertical conductance coefficient of the strike-slip fracture; β n This represents the conductivity coefficient of the bottom interface of the nth layer above the source rock; β 1 represents the transport coefficient at the top interface of the source rock; min( β 0, β 1) Represents variables β 0 and β The smallest of 1; The calculation method for the strike-slip fault comprehensive transport coefficient in step S5 is as follows: strike-slip fault comprehensive transport coefficient = strike-slip fault vertical transport coefficient × source rock thickness × distance from hydrocarbon generation center; The vertical transport capacity of strike-slip faults is obtained by normalizing the comprehensive transport coefficient of strike-slip faults.

2. The method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins according to claim 1, characterized in that: The method for calculating the transport coefficient of the top interface of the source rock in step S1 is as follows: multiply the vertical height difference of the top interface of the source rock by the width of the fault fracture zone, and normalize the product.

3. The method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins according to claim 1, characterized in that: The method for calculating the conductivity coefficient of the reservoir bottom interface in step S2 is as follows: multiply the vertical height difference of the reservoir bottom interface by the width of the fault fracture zone, and then normalize the product.

4. The method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins according to claim 1, characterized in that: The method for calculating the transport coefficient of each interface between the source rock and the reservoir in step S3 is as follows: multiply the vertical height difference of each interface by the width of the fault fracture zone, and then normalize the product.

5. The method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins according to claim 1, characterized in that: The thickness of the source rock is the thickness of the source rock strata inhabited by the strike-slip fault.

6. The method for evaluating the source-source conductivity of strike-slip faults in sedimentary basins according to claim 1, characterized in that: The distance from the hydrocarbon generation center is the normalized distance from the starting point of the strike-slip fault to the hydrocarbon generation center of the source rock.

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