A method for improving the precision of a shale gas reservoir structure model

Abstract

A method for improving the accuracy of shale gas reservoir structural models, belonging to the field of unconventional and new energy, includes: conducting detailed interpretation of seismic data to predict small-scale fault development; establishing a fault model through well-seismic integration; identifying feature points on the horizontal sections of completed horizontal wells and converting them into virtual wells; compiling planar maps of different sub-layer thicknesses based on regional geological research results, extracting sub-layer thickness data at virtual wells and converting it into variable-thickness virtual well stratification point data; interpreting structural information of structural surfaces, appraisal wells, and pilot wells using seismic data, and establishing a bedding model under the control of variable-thickness virtual wells at feature points of horizontal wells; inserting small bedding planes into the fault model and bedding model using variable-thickness virtual well stratification point data and sub-layer thickness planar maps to form a shale gas reservoir structural model. The shale gas reservoir structural model established by this invention is more refined and can accurately describe the structural changes and sub-layer thickness variations of underground reservoirs, significantly improving the accuracy of faults and sub-layer bedding planes.

Description

Technical Field

[0001] This invention belongs to the field of unconventional and new energy technologies, specifically relating to a method for improving the accuracy of shale gas reservoir structural models. Background Technology

[0002] In the development of shale gas reservoirs, to quantitatively characterize features such as burial depth, fault displacement, fault extension length, and sub-layer thickness variations, and to guide horizontal well drilling and fracturing operations, a three-dimensional structural model needs to be established. Two methods are typically used: ① Establishing a structural model based on seismic interpretation of fault and structural bedding data, combined with appraisal well implementation data. However, the established structural model is affected by the resolution of the seismic data and cannot accurately describe the local small-scale fault development characteristics and formation thickness variations. ② Establishing a structural model using horizontal well data and virtual well control in the horizontal section, based on seismic interpretation of fault and structural bedding data. Because the horizontal section length is generally 1500-2300 meters, which is relatively long, using a uniform thickness virtual well constraint for the entire horizontal section can cause structural distortion.

[0003] In conclusion, regardless of which structural modeling method is used, it is impossible to accurately describe the structural characteristics and layer thickness variation characteristics of underground gas reservoirs. Summary of the Invention

[0004] To address the problem that existing methods for establishing shale gas reservoir structural models cannot accurately describe the structural characteristics and subsurface thickness variations of underground gas reservoirs, this invention provides a method to improve the accuracy of shale gas reservoir structural models. This invention starts with the study of fault development characteristics and subsurface thickness variation patterns to identify the main factors that may affect the accuracy of shale gas reservoir structural models. Through detailed structural interpretation, research on the development characteristics of small faults and microstructures, and analysis of subsurface thickness variation patterns, the fault model is constrained to form a variable-thickness virtual well structural constraint model, achieving quantitative and detailed characterization of shale gas reservoir structural features.

[0005] The technical solution adopted by this invention to solve the technical problem is as follows:

[0006] This invention provides a method for improving the accuracy of shale gas reservoir structural models, which specifically includes the following steps:

[0007] Step 1: Conduct detailed interpretation of seismic data and predict the development of small-scale faults by combining seismic data and actual drilling data from horizontal wells;

[0008] Step 2: Under the constraints of the detailed interpretation results of seismic data, and combined with the prediction results of small-scale fault development, establish a fault model by combining well and seismic data.

[0009] Step 3: Identify feature points on the horizontal section of the completed horizontal well and convert the identified feature points into virtual wells; compile planar maps of different layer thicknesses based on regional geological research results, extract layer thickness data at the virtual wells, and convert them into layer point data of the variable thickness virtual wells;

[0010] Step 4: Use seismic data to interpret the structural information of structural surfaces, appraisal wells, and pilot wells, and establish a layer model under the control of a virtual well with varying thickness at the characteristic points of the horizontal well;

[0011] Step 5: Insert small-layer planes into the fault model and bedding plane model using variable-thickness virtual well layer point data and small-layer thickness planar maps to form a shale gas reservoir structural model.

[0012] Furthermore, in step one, high-resolution three-dimensional seismic data is used to perform fine interpretation of the fault system. Seismic attribute volumes are used to identify small-scale faults in the work area. The fault development characteristics of small-scale faults interpreted from seismic data are analyzed, and small-scale faults are grouped according to specific fault development characteristics.

[0013] Furthermore, the earthquake attribute volume is a coherent volume, an ant volume, a maximum likelihood volume, and a curvature volume.

[0014] Furthermore, the fracture development characteristics information includes the strike, displacement, and extension length of small-scale faults.

[0015] Furthermore, in step two, a fault prediction map is generated based on the prediction results of the development of large-scale and small-scale faults according to the earthquake interpretation; the fault prediction map is converted into fault lines, and faults are generated based on the fault development characteristics of faults in different regions to establish a fault model.

[0016] Furthermore, in step three, gamma data and elemental logging data are used to determine the characteristic points of the horizontal well.

[0017] Furthermore, in step three, the thickness of the small layer at the feature point is picked up and transferred to the virtual well to realize the variable thickness constraint of the formation thickness correction point in the shale gas reservoir structural model.

[0018] The beneficial effects of this invention are:

[0019] This invention comprehensively applies seismic data and horizontal well geological steering knowledge to predict small-scale fault development, establishing a more refined and reliable fault model. Based on regional geological research, it predicts the thickness of subsurface layers and employs a variable-thickness virtual well control method to improve the accuracy of the bedding plane model. By inserting subsurface layers into the fault and bedding plane models using variable-thickness virtual well layer point data and subsurface thickness planar maps, a final shale gas reservoir structural model is formed. The shale gas reservoir structural model established using this method to improve the accuracy of shale gas reservoir structural models is more refined and can accurately describe the changes in underground reservoir structure and subsurface layer thickness. The accuracy of faults and subsurface layers is significantly improved, making it highly operable and with broad application prospects. Attached Figure Description

[0020] Figure 1 This invention provides a technical roadmap for improving the accuracy of shale gas reservoir structural models.

[0021] Figure 2 Fault maps for earthquake attribute identification. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings.

[0023] See Figure 1 The present invention provides a method for improving the accuracy of shale gas reservoir structural models, the specific implementation process of which is as follows:

[0024] Step 1: Conduct detailed interpretation of seismic data and predict the development of small-scale faults by combining seismic data with actual drilling data from horizontal wells.

[0025] The specific operating procedure is as follows:

[0026] High-resolution 3D seismic data is used for detailed interpretation of the fault system. Seismic attribute volumes such as coherence volume, ant volume, maximum likelihood volume, and curvature volume are employed to identify small-scale faults within the work area. The strike, displacement, and extension length of these small-scale faults, interpreted from the seismic data, are analyzed to identify their developmental characteristics. Small-scale faults are then grouped according to their specific developmental features. For example, based on their strike, small-scale faults within the work area can be divided into two groups: those with a north-northeast strike and those with a north-west strike, laying the foundation for predicting small-scale fault development. Then, faults passing through completed horizontal wells are identified. These faults are used to analyze and summarize the strike, displacement, and extension length of small-scale faults. Based on the strike, displacement, and fault properties, these faults are grouped in planar combinations to form a table of small-scale fault analysis results for different regions and scales. Based on the geological steering of the horizontal wells, and under the constraints of 3D seismic attributes, the strike, displacement, and extension length of small-scale faults are predicted for different regions, thus completing the prediction of small-scale fault development.

[0027] Table 1 shows the data of faults identified in completed horizontal wells.

[0028] Table 1. Statistical Table of Faults Passing Through Horizontal Wells

[0029]

[0030] Step 2: Under the constraints of detailed interpretation of seismic data, establish a fault model by combining well-seismic analysis with predictions of small-scale fault development.

[0031] The specific operating procedure is as follows:

[0032] Based on the prediction results of the development of large-scale and small-scale faults in the seismic interpretation and the understanding of geological steering faults during drilling, a fault prediction map is generated. The fault prediction map is converted into fault lines, and faults are generated based on the fault development characteristics such as the strike, grouping, and displacement of faults in different regions, and a fault model is established.

[0033] Among them, the method for generating fault prediction result maps based on seismic attributes and drilling geological steering fault identification is as follows: Figure 2 As shown, using the geological guidance fault identification method during drilling, potential fault ant bodies are manually screened on the seismic ant body attribute map to generate fault development prediction results. These results are then converted into fault lines and input into the fault model.

[0034] Step 3: Identify feature points on the horizontal section of the completed horizontal well and convert the identified feature points into virtual wells; compile planar maps of different sub-layer thicknesses based on regional geological research results, extract sub-layer thickness data at the virtual wells, and convert them into layer point data of the variable thickness virtual wells.

[0035] Among them, the sub-layer thickness data in the actual drilling data of horizontal wells is hard data for geological modeling and plays a key role in constraining the model. The horizontal section length of shale gas horizontal wells is usually 1500m-2000m, and the thickness of each sub-layer may vary in the horizontal section. Based on the results of regional geological research, different sub-layer thickness plans are compiled. At the same time, the feature points of the horizontal well trajectory determined by gamma data and elemental logging data are identified, and the sub-layer thickness at the feature points is picked up and transferred to the virtual well. This realizes the variable thickness constraint of the formation thickness correction points in the shale gas reservoir structural model, thereby improving the accuracy of the shale gas reservoir structural model.

[0036] Step 4: Use seismic data to interpret the structural information of structural surfaces, appraisal wells, and pilot wells, and establish a layer model under the control of a virtual well with varying thickness at the characteristic points of the horizontal well.

[0037] Seismic data serves as a soft constraint in geological modeling, as its resolution limits the identification of only key layers with reflective interfaces. The geological modeling process requires using seismic data to interpret structural information from structural surfaces, appraisal wells, and pilot wells, and combining this with virtual wells of varying thickness at characteristic points of horizontal wells to establish key stratigraphic models.

[0038] Step 5: Insert small-layer planes into the fault model and bedding plane model using variable-thickness virtual well layer point data and small-layer thickness planar maps to form the final shale gas reservoir structural model.

[0039] The present invention provides a method for improving the accuracy of shale gas reservoir structural models. It makes full use of geological knowledge and actual production data, has sufficient theoretical support, conforms to reality, is highly operable, and has broad application prospects. It is beneficial to improve the accuracy of shale gas reservoir structural models and has important practical application significance for guiding horizontal well geological engineering integrated drilling and fracturing operations.

[0040] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for improving the accuracy of shale gas reservoir structural models, characterized in that, Includes the following steps: Step 1: Conduct detailed interpretation of seismic data and predict the development of small-scale faults by combining seismic data and actual drilling data from horizontal wells; Step 2: Under the constraints of the detailed interpretation results of seismic data, and combined with the prediction results of small-scale fault development, establish a fault model by combining well and seismic data. Step 3: Identify feature points on the horizontal section of the completed horizontal well and convert the identified feature points into virtual wells; compile planar maps of different layer thicknesses based on regional geological research results, extract layer thickness data at the virtual wells, and convert them into layer point data of the variable thickness virtual wells; Step 4: Use seismic data to interpret the structural information of structural surfaces, appraisal wells, and pilot wells, and establish a layer model under the control of a virtual well with varying thickness at the characteristic points of the horizontal well; Step 5: Insert small-layer planes into the fault model and bedding plane model using variable-thickness virtual well layer point data and small-layer thickness planar maps to form a shale gas reservoir structural model.

2. The method for improving the accuracy of shale gas reservoir structural models according to claim 1, characterized in that, In step one, high-resolution three-dimensional seismic data is used to perform fine interpretation of the fault system. Seismic attribute volumes are used to identify small-scale faults in the work area. The fault development characteristics of small-scale faults interpreted from seismic data are analyzed, and small-scale faults are grouped according to specific fault development characteristics.

3. The method for improving the accuracy of shale gas reservoir structural models according to claim 2, characterized in that, The earthquake attribute volumes are coherence volumes, ant volumes, maximum likelihood volumes, and curvature volumes.

4. The method for improving the accuracy of shale gas reservoir structural models according to claim 2, characterized in that, The fault development characteristics information includes the strike, displacement, and extension length of small-scale faults.

5. The method for improving the accuracy of shale gas reservoir structural models according to claim 1, characterized in that, In step two, a fault prediction map is generated based on the prediction results of the development of large-scale and small-scale faults according to the earthquake interpretation; the fault prediction map is converted into fault lines, and faults are generated according to the fault development characteristics of different regions to establish a fault model.

6. The method for improving the accuracy of shale gas reservoir structural models according to claim 1, characterized in that, In step three, gamma data and elemental logging data are used to determine the characteristic points of the horizontal well.

7. The method for improving the accuracy of shale gas reservoir structural models according to claim 1, characterized in that, In step three, the thickness of the small layer at the feature point is picked up and transferred to the virtual well to realize the variable thickness constraint of the formation thickness correction point in the shale gas reservoir structural model.

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