Determination method for oil and gas filling points related to strike-slip fracture of sedimentary basin

Abstract

The invention relates to the technical field of geological exploration, and provides a sedimentary basin strike-slip fracture related oil and gas filling point judgment method, which comprises the following steps: collecting geological information of a target area, obtaining strike-slip fracture segment characteristics, fault properties and strike-slip fracture grids of a hydrocarbon source rock overlying compact layer (such as a gypsum-salt layer) in the target area by adopting qualitative analysis, and determining the strike-slip fracture segment characteristics and fault properties of the target area according to the strike-slip fracture segment characteristics, the fault properties and the strike-slip fracture grids. Determining a rough range of a charging point; calculating the key layer thickness of the hydrocarbon source rock stratum and the compact layer and the conduction coefficient of the top of the compact layer, carrying out normalization processing, and carrying out filling point correction according to quantitative data obtained through calculation and in combination with strike-slip fracture segmentation characteristics; and verifying the corrected charging point according to the fluctuation point of the segmented change of the oil-gas migration index and the crude oil physical property parameter index. According to the method provided by the invention, the accuracy and reliability of the method for judging the strike-slip fracture related oil and gas filling points can be remarkably improved, guiding significance is provided for oil and gas exploration, and exploration benefits are greatly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geological exploration, in particular to a method for determining a hydrocarbon charging point related to a strike-slip fault in a sedimentary basin. BACKGROUND

[0002] Strike-slip fault is an important structure type in a sedimentary basin, which not only affects the tectonic framework and the distribution of the sedimentary system of the basin, but also plays a crucial role in the generation, migration, accumulation and preservation of oil and gas. Unlike pure extensional or compressional structures, strike-slip faults have unique structural characteristics, including flower structures in vertical fault zones, pull-apart basins, and compressional uplift zones. In recent years, strike-slip fault-related oil and gas reservoirs have been found in the Tarim and Sichuan cratonic basins. In the Tarim Basin, strike-slip faults can not only serve as pathways for oil and gas migration, but also form fractured reservoirs to store oil and gas.

[0003] A hydrocarbon charging point refers to a key position for vertical or lateral charging of oil and gas from deep source rocks or carrier beds to shallow traps. Accurate identification of these charging points is of decisive significance for predicting oil and gas enrichment areas, reducing exploration risks, and improving drilling success rates. In the strike-slip fault system, the hydrocarbon charging point is usually closely related to specific structural positions. At the inflection points or curved parts of the main fault, such as stress release areas, the rock is broken and the porosity is high, making it easy for fluids to pass through. At the intersection of secondary faults and main faults, a "crossroads" for fluid migration is formed, connecting multiple carrier beds. The extensional section of the strike-slip fault zone is a weak structural zone and an advantageous vertical migration pathway for fluids. The roots or tops of flower structures are conversion zones of stress concentration and release, with highly developed fracture systems.

[0004] However, despite its importance, the existing technology still faces great challenges in accurately identifying the hydrocarbon charging points in the strike-slip fault zone. Traditional seismic interpretation is difficult to effectively distinguish between active carrier pathways and closed ancient pathways. Strike-slip faults have multiple activity characteristics, with heterogeneous and dynamic evolution characteristics in space and time. The existing static structural interpretation cannot effectively depict the opening and closing of faults in different geological history periods, and cannot accurately determine the effective carrier pathway during the main hydrocarbon charging period.

[0005] Therefore, there is an urgent need in the field for an innovative technical method that can overcome the above technical bottlenecks and efficiently, accurately and quantitatively identify the hydrocarbon charging points in the strike-slip fault zone of a sedimentary basin, in order to guide the target area optimization of oil and gas exploration and significantly improve the exploration efficiency. SUMMARY

[0006] In view of this, the present application provides a sedimentary basin strike-slip fault related oil and gas charging point determination method, which aims at the technical problem that the identification of oil and gas charging points in the strike-slip fault zone is not accurate and the effective transport channel during the main charging period of oil and gas cannot be accurately determined because the source rock is covered by a dense layer (such as a gypsum layer) and oil and gas needs to be transported upward by the strike-slip fault. The method initially determines the charging point by using the segmentation characteristics, fault properties and fault fracture grid of the strike-slip fault on the top of the dense layer, quantitatively evaluates the transport property of the fault at the top of the dense layer by using the thickness of the key layer and the weighting of the drainage coefficient, and determines the final charging point by combining the oil and gas migration index and the crude oil physical property parameters.

[0007] To achieve the above-mentioned purpose, the present application provides a sedimentary basin strike-slip fault related oil and gas charging point determination method, characterized in that it comprises the following steps: Collect the geological information of the target area, obtain the segmentation characteristics of the strike-slip fault on the top of the dense layer, the fault properties and the strike-slip fault fracture grid of the source rock in the target area by qualitative analysis, and determine the rough range of the charging point; Calculate the thickness of the key layer of the source rock layer and the dense layer, the transport coefficient at the top of the dense layer, and perform normalization processing, correct the charging point according to the quantitative data obtained by calculation and the segmentation characteristics of the strike-slip fault; Verify the corrected charging point according to the fluctuation points of the segmentation changes of the oil and gas migration index and the crude oil physical property parameter index.

[0008] Further, the segmentation characteristics of the strike-slip fault are completed by coherence or other fault attributes combined with artificial interpretation; The fault properties are determined by seismic profile interpretation, which are divided into tension-torsion, compression-torsion and translation, wherein the tension-torsion refers to the deformation of the formation caused by the fault, the compression-torsion refers to the deformation of the formation, and the translation refers to the horizontal formation without deformation; The analysis process of the strike-slip fault fracture grid includes: using a topological method or other fault density prediction method to obtain the fracture density of different positions in the fault zone.

[0009] Further, the thickness of the key layer of the source rock layer is specifically the thickness of the top and bottom surfaces of the source rock layer, which is calculated according to the seismic profile; The thickness of the key layer of the dense layer is specifically the thickness of the top and bottom surfaces of the dense layer, which is calculated according to the seismic profile; The transport coefficient at the top of the dense layer is specifically the strike-slip fault transport coefficient of the top interface of the dense layer, and the calculation method is to multiply the vertical height difference of the top interface of the dense layer and the fault fracture zone width, and then normalize the product.

[0010] Further, the vertical height difference of the top interface of the compact layer is calculated by the absolute value of the difference between the uplift or subsidence height of the strike-slip fault site and the horizontal plane of the layer, and the product is normalized by the Min-Max normalization method.

[0011] Further, the calculation method of the top transport coefficient of the compact layer is as follows: The top transport coefficient of the compact layer = the height difference of the fracture zone * the width of the fracture zone * the thickness of the source rock / the maximum thickness of the source rock * the maximum thickness of the compact layer / the thickness of the compact layer.

[0012] Further, according to the quantitative data calculated, the process of correcting the charging point combined with the segmentation characteristics of the strike-slip fault includes: Based on the key layer thickness of the source rock layer and the compact layer, the vertical transport capacity of the strike-slip fault breaking through the compact layer is calculated according to the top transport coefficient of the compact layer, and the vertical charging capacity of the strike-slip fault is calculated comprehensively, which is taken as the quantitative basis for selecting the charging point of the strike-slip fault.

[0013] Further, the calculation method of the vertical charging capacity of the strike-slip fault is: the vertical charging capacity of the strike-slip fault = the transport coefficient of the compact layer * the thickness of the source rock / the thickness of the compact layer.

[0014] Further, taking the vertical charging capacity of the strike-slip fault as the quantitative basis for selecting the charging point of the strike-slip fault includes: On the basis of determining the rough range of the charging point, the charging point is corrected by superimposing the position with the maximum charging capacity.

[0015] Further, the oil and gas migration index and the crude oil physical parameter are obtained by collecting parameters along the strike-slip fault and mapping, the oil and gas migration index is 4-1-MDBT, and the crude oil physical parameter includes oil column height, oil and gas ratio, crude oil density, wax content and natural gas dry coefficient.

[0016] Compared with the prior art, the beneficial effects of the present application are: The sedimentary basin strike-slip fault related oil and gas charging point determination method provided by the present application uses the segmentation characteristics of the top of the compact layer, the properties of the fracture and the fracture grid to preliminarily determine the charging point, uses the key layer thickness (positive effect of source rock thickness and negative effect of compact layer thickness) and transport coefficient (quantitative fault transport capacity) to quantitatively evaluate the transport property of the fault on the top of the compact layer, and combines the oil and gas migration index and the crude oil physical parameter to redetermine the charging point. The accuracy and reliability of the strike-slip fault related oil and gas charging point determination method can be significantly improved, which provides guidance for oil and gas exploration and greatly improves the exploration benefit. BRIEF DESCRIPTION OF DRAWINGS

[0017] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments with reference made to the accompanying drawings. The drawings are for purposes of illustration only and are not intended to limit the present application thereto. In the drawings: Figure 1 The overall flowchart of the method of the present application is shown in the figure; Figure 2 The segmentation feature diagram of strike-slip fault in the embodiment of the present application is shown in the figure; Figure 3 The crack density statistical diagram in the embodiment of the present application is shown in the figure; Figure 4 The key layer thickness coefficient division diagram of source rock layer and tight layer in the embodiment of the present application is shown in the figure; Figure 5 The vertical filling capacity division diagram of strike-slip fault in the embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0018] Exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided so that the present disclosure can be more thoroughly understood and the scope of the present disclosure can be accurately conveyed to those skilled in the art. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments.

[0019] Embodiment one The present embodiment provides a specific implementation of a method for determining strike-slip fault related hydrocarbon filling points in a sedimentary basin, as shown in Figure 1 The method comprises the following steps: Step S1: Collect geological information of the target area, and determine the strike-slip fault segmentation features, fault properties and strike-slip fault fracture grid of the overlying tight layer of the source rock in the target area, and preliminarily determine the filling points; The target area is Halahatang Sag in the northern Tarim Basin, the source rock is Cambrian Yurtus Formation, the overlying tight layer is tight and seals the source rock, and the reservoir is Ordovician limestone; the strike-slip fault cuts through the Cambrian source rock and its overlying tight layer and migrates to the overlying reservoir. Among them, the strike-slip fault segmentation features are completed by coherence or other fault attributes combined with artificial interpretation, as shown in Figure 2The property of strike-slip fault is determined by seismic profile interpretation, which is divided into tensional shear, compressional shear and translation. The tensional shear refers to the deformation of stratum caused by the concave deformation of fault. The compressional shear refers to the deformation of stratum caused by the convex deformation of fault. The translation refers to the stratum being basically horizontal without up and down deformation. The fracture grid of the overlying dense layer of source rock is determined, i.e. the fracture density of different positions of the fracture zone is obtained by using the topological method. Other fracture density prediction methods can also be used to realize the fracture density of the fracture zone, as shown in the following figure. Figure 3 Step S2: quantitative parameters such as the key layer thickness of the source rock layer and the dense layer and the transport coefficient of the top of the dense layer are obtained, and normalized processing is performed, as shown in the following figure. Figure 4 According to the quantitative data, the original filling point is corrected, reduced or removed in combination with the fracture structure characteristics in the previous section.

[0020] The thickness of the source rock refers to the thickness of the top and bottom surface of the source rock layer, which can be obtained according to the seismic profile. The thickness of the dense layer refers to the thickness of the top and bottom surface of the dense layer, which can be obtained according to the seismic profile. The strike-slip fault transport coefficient of the top interface of the dense layer refers to the strike-slip fault transport coefficient of the top interface of the dense layer. The calculation method is to multiply the vertical height difference of the top interface of the dense layer by the width of the fault fracture zone, and to normalize the product.

[0021] The vertical height difference of the top interface of the dense layer is the absolute value of the difference between the uplift or subsidence height of the strike-slip fault part and the horizontal plane of the layer. The product normalization method is Min-Max normalization.

[0022] Based on the transport coefficient of the strike-slip fault in the dense layer and the thickness of the key layer, the vertical transport capacity of the strike-slip fault penetrating the dense layer is calculated, and the vertical filling capacity of the strike-slip fault is obtained. The vertical filling capacity of the strike-slip fault is taken as the quantitative basis for selecting the strike-slip fault filling point.

[0023] The calculation method of the vertical filling capacity of the strike-slip fault is: vertical filling capacity of strike-slip fault = transport coefficient of dense layer x thickness of source rock / thickness of dense layer, as shown in the following figure. Figure 5

[0024] On the basis of determining the filling point in the previous step, the filling point is corrected by superimposing the position with the maximum filling capacity, realizing the double evaluation of qualitative and quantitative.

[0025] Step S3: the oil and gas migration index and the crude oil property parameters are used to verify and modify the oil and gas filling point in combination with the fluctuation points of the segmented changes of these indexes. The oil and gas migration index and other parameters such as the crude oil property are collected along the strike-slip fault and plotted, as shown in the following figure. Figure 5

[0026] ​​​Through the calculation of the source conductivity of strike-slip fractures, such as Figure 4 As shown, the vertical charging of the strike-slip fractures illustrated in the examples can be divided into four levels, with Class I representing the optimal oil and gas charging location and Class IV representing the worst oil and gas charging point location. The accuracy of the charging point can be verified by superimposing fluctuation points of oil and gas migration indicators and crude oil physical properties with the optimal oil and gas charging location. The coincidence rate between high-yield wells and Class I charging points is over 70%.

[0027] Example 2 This embodiment proposes a method for determining hydrocarbon injection points associated with strike-slip faults in sedimentary basins, including the following steps: Step S1: Collect geological information of the target area and determine the approximate range of the injection point through qualitative analysis; Step S2: Correct, reduce, or eliminate existing filling points using other parameters (quantitative analysis); Step S3: Verify the oil and gas injection point by analyzing the fluctuation points of segmented changes in oil and gas migration indicators and crude oil physical properties.

[0028] As a preferred embodiment, the qualitative analysis in step S1 refers to clarifying the fracture segmentation characteristics, fracture properties, and fracture crack grid of the top surface of the dense layer at the top of the source rock, wherein the preferred location is the fault tension and torsion part and the part with the highest degree of fracture development as the initial filling location.

[0029] Among them, the segmentation characteristics and fracture properties of the top surface of the dense layer at the top of the source rock are interpreted by the seismic profile and plan view of the target area. The fracture grid is constructed by topological analysis of the strike-slip fracture at the top surface of the dense layer at the top of the source rock, combined with the fracture density and the degree of connection.

[0030] As a preferred embodiment, the step S2, which involves correcting, reducing, or eliminating the original injection points through other parameters (quantitative analysis), refers to the quantitative evaluation of the conductivity of the fault at the top surface of the tight layer of the source rock by using the thickness of the key stratigraphic layer and the conductivity coefficient.

[0031] The critical layer thickness refers to the thickness of the source rock and the thickness of the compact layer. The source rock thickness refers to the depth of the top surface, with priority given to injection points that are thicker and deeper at the top surface, while the compact layer preferentially selects injection points that are thinner.

[0032] The conductivity coefficient refers to the product of the height difference of the fracture zone and the width of the fracture zone, and the filling point with a large conductivity coefficient is preferred.

[0033] The calculation method for quantitatively evaluating the conductivity of the top surface of the compact layer is shown in the following formula: The conductivity of the top surface of the compact layer = the height difference of the fracture zone * the width of the fracture zone * the thickness of the source rock / the maximum thickness of the source rock * the maximum thickness of the compact layer / the thickness of the compact layer. As a preferred embodiment, the oil and gas charging points are mapped by fluctuation points of the oil and gas migration index and the segmented change of the crude oil physical parameter in step S3, and specifically include: Combined with the oil and gas migration index and the crude oil physical parameter, the segmented change of the fluctuation point is used to verify the charging points determined by the qualitative and quantitative comprehensive judgment.

[0034] The oil and gas migration index refers to 4-1-MDBT. The crude oil physical parameter refers to the oil column height, the oil and gas ratio, the crude oil density, the wax content, the natural gas dry coefficient, etc. The calculation method of the normalization processing is shown in the following formula: β = crude oil physical parameter / maximum crude oil physical parameter.

[0035] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it. Although the present application has been described in detail with reference to the above examples, those skilled in the art should understand that the specific embodiments of the present application can be modified or replaced by the equivalent, without departing from the spirit and scope of the present application. Any modification or equivalent replacement without departing from the spirit and scope of the present application should be covered within the protection scope of the claims of the present application.

Claims

1. A method for determining hydrocarbon injection points associated with strike-slip faults in sedimentary basins, characterized in that, Includes the following steps: Geological information of the target area was collected, and qualitative analysis was used to obtain the segment characteristics of strike-slip faults, fault properties and strike-slip fault fracture grids of the dense layer overlying the source rock in the target area, and to determine the approximate range of the injection point. The thickness of the key layers of the source rock strata and the tight layer, and the transport coefficient of the top of the tight layer are calculated and normalized. Based on the calculated quantitative data, the filling point is corrected in combination with the segmentation characteristics of the strike-slip fault. The corrected injection point is verified based on the fluctuation points of the segmented changes in oil and gas migration indicators and crude oil physical property parameters.

2. The method according to claim 1, characterized in that, The segmentation characteristics of the strike-slip fracture are determined by combining coherence or other fracture properties with manual interpretation. The nature of the fault is determined by the interpretation of seismic profiles and is divided into extensional-torsional, compressional-torsional, and translational faults. Extensional-torsional faults refer to the subsidence deformation caused by the fault, compressional-torsional faults refer to the convex deformation caused by the fault, and translational faults refer to the basic horizontality of the strata with no vertical deformation. The analysis process of the strike-slip fracture crack mesh includes: using topological methods or other fracture density prediction methods to obtain the crack density at different locations of the fracture zone.

3. The method according to claim 1, characterized in that, The key layer thickness of the source rock layer is specifically the thickness of the top and bottom surfaces of the source rock layer, which is calculated based on the seismic profile. The critical layer thickness of the dense layer is specifically the thickness of the top and bottom surfaces of the dense layer, which is calculated based on the seismic profile. The conductivity coefficient at the top of the compact layer is specifically the strike-slip fracture conductivity coefficient at the top interface of the compact layer. The calculation method is as follows: multiply the vertical height difference at the top interface of the compact layer by the width of the fault fracture zone, and then normalize the product.

4. The method according to claim 3, characterized in that, The vertical height difference at the top interface of the dense layer is calculated by the absolute value of the difference between the uplift or subsidence height of the strike-slip fault and the horizontal plane of the layer. The product normalization method is Min-Max normalization.

5. The method according to claim 1, characterized in that, The conductivity coefficient at the top of the dense layer is calculated using the following formula: The conductivity coefficient of the top surface of the compact layer = height difference of the fracture zone * width of the fracture zone * thickness of the source rock / maximum thickness of the source rock * maximum thickness of the compact layer / thickness of the compact layer.

6. The method according to claim 1, characterized in that, The process of correcting the injection point based on the calculated quantitative data and the segmented characteristics of the strike-slip fracture includes: Based on the key layer thickness of the source rock layer and the tight layer, and the conductivity coefficient at the top of the tight layer, the vertical transport capacity of the strike-slip fault penetrating the tight layer is calculated. The vertical charging capacity of the strike-slip fault is then calculated and used as a quantitative basis for selecting the charging point of the strike-slip fault.

7. The method according to claim 6, characterized in that, The calculation method for the vertical charging capacity of the strike-slip fault is as follows: Vertical charging capacity of strike-slip fault = conductivity coefficient of the tight layer × source rock thickness / thickness of the tight layer.

8. The method according to claim 6, characterized in that, Using the vertical injection capacity of strike-slip fractures as a quantitative basis for selecting injection points includes: Based on the rough range of the filling point, the filling point is corrected by overlapping it with the position with the greatest filling capacity.

9. The method according to claim 1, characterized in that, The oil and gas migration index and crude oil physical property parameters are obtained by collecting parameters along strike-slip fractures and plotting them. The oil and gas migration index is specifically 4-1-MDBT, and the crude oil physical property parameters include oil column height, oil-gas ratio, crude oil density, wax content, and natural gas drying coefficient.

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