A method for finely classifying shale gas reservoir development strata based on multi-factor analysis

Abstract

A method for finely delineating shale gas reservoir development layers based on multi-factor analysis is disclosed, relating to the field of shale gas development. This method includes the following steps: dividing the gas-bearing shale intervals in pilot wells into smaller layers and interpreting key parameters through well logging; calculating the original geological reserve abundance of each layer; establishing a map of the economically recoverable reserves corresponding to the total investment in a single well; calculating the reserve abundance corresponding to different recovery rates; quantitatively describing the minimum horizontal principal stress and delineating vertical stress barriers; predicting the upper and lower fracture heights of fractures when traversing different strata; compiling a comprehensive columnar section of a single well based on the above analysis results; and comprehensively delineating the development layers based on factors such as thickness, reserve abundance, and differences in vertical stress. The method for finely delineating shale gas reservoir development layers based on multi-factor analysis provided in this application can clearly define reasonable development layers to solve the problem of insufficient utilization of shale gas reserves and achieve efficient shale gas development.

Description

Technical Field

[0001] This application relates to the field of shale gas development, and more specifically, to a method for finely classifying shale gas reservoir development strata based on multi-factor analysis. Background Technology

[0002] Shale gas, as a typical clean and green energy source, is an effective supplement to conventional oil and coal energy. my country has abundant shale gas resources, with recoverable resources estimated at approximately 25 trillion cubic meters. Its development potential is enormous, and initial exploration and development have yielded positive results, making China the third country, after the United States and Canada, to achieve commercial shale gas development.

[0003] my country's shale gas development methods are still relatively extensive, and production from gas wells in some blocks is entering a period of decline, making it difficult to maintain stable production. Against this backdrop, shale gas development methods need to shift towards a more refined approach. Accurately delineating shale gas development strata is fundamental to shale gas development, involving the overall deployment of shale gas development blocks and affecting the degree of underground resource utilization and recovery rate. Mistakes in this area could lead to significant resource waste. Summary of the Invention

[0004] The purpose of this application is to provide a method for finely dividing the development strata of shale gas reservoirs based on multi-factor analysis, which can identify reasonable development strata to solve the problem of insufficient utilization of shale gas reserves and achieve efficient development of shale gas.

[0005] The embodiments of this application are implemented as follows:

[0006] This application provides a method for finely classifying the development strata of shale gas reservoirs based on multi-factor analysis, which includes the following steps:

[0007] S1. Analyze the sedimentary characteristics, lithological assemblage, and electrical properties of the gas-bearing shale section in the pilot well, perform stratigraphic division, and conduct well logging interpretation of key parameters;

[0008] S2. Calculate the original geological reserve abundance of each sub-layer according to the shale gas reserve calculation standard;

[0009] S3. Using the shale gas economic evaluation method, combined with the investment cost of a single well in the block and the tax rate, calculate the economic limit recoverable reserves corresponding to different investments when calculating the predetermined after-tax internal rate of return, and establish the economic limit recoverable reserves corresponding to the investment of a single well.

[0010] S4. Using the economically recoverable reserves, calculate the reserve abundance corresponding to different recovery rates.

[0011] S5. Use geophysical logging technology to quantitatively describe the rock mechanical parameters of the target layer, and statistically analyze the minimum horizontal principal stress to identify stress-isolated layers with a stress difference greater than 1 MPa from the overlying and underlying layers.

[0012] S6. Based on the fracturing data, dynamic monitoring data and production dynamic analysis of the fracturing wells in the work area, use the fracturing network simulation technology to predict the upper and lower fracture heights of the fracturing fractures when traversing different strata.

[0013] S7. Compile a single-well composite column chart based on the data obtained from steps S1-S6. The single-well composite column chart includes conventional logging curves, lithology, depth, sub-layer name and thickness, reserve abundance of each sub-layer, minimum horizontal principal stress curve, minimum horizontal principal stress value of stress-isolated sections, mean minimum horizontal principal stress of each sub-layer, and stress segmentation.

[0014] S8. Development layers are comprehensively divided based on the thickness of each sublayer, the abundance of reserves in each sublayer, and the differences in longitudinal stress.

[0015] In some alternative implementations, in step S1, the logging interpretation of key parameters includes effective thickness, organic carbon abundance, rock mineral composition, porosity, gas content, and gas saturation.

[0016] In some alternative implementations, in step S4, when calculating the reserve abundance corresponding to different recovery rates, the lower limit of the reserve abundance is determined by taking a value based on a shale gas recovery rate of 50%.

[0017] In some alternative implementations, in step S5, the geophysical logging technique includes the dipole acoustic logging method.

[0018] In some optional implementations, in step S6, the fracturing data includes cluster number, proppant type, sand addition intensity, fluid addition intensity, fracturing process, dynamic monitoring data includes microseismic monitoring, tracer, pressure excitation response of adjacent wells during fracturing, well test analysis, and production dynamic analysis includes production pressure, daily gas production, and daily water production of adjacent wells before and after this well is put into production.

[0019] In some alternative implementations, in step S7, the conventional logging curves include gamma, resistivity, compensated sonic logging, lithological density, and compensated neutron logging.

[0020] In some alternative implementations, in step S8, when dividing the development layer system, the thickness of the development layer system is not less than the sum of the predicted upper seam height and lower seam height.

[0021] In some optional implementations, in step S8, when dividing the development strata, the abundance of reserves in the development strata is not less than the abundance of reserves corresponding to the economically recoverable reserves.

[0022] In some alternative implementations, in step S8, when dividing the development layer system, the stress barrier layer serves as the top and bottom interface of a development layer system.

[0023] The beneficial effects of this application are as follows: The method for finely dividing the development strata of shale gas reservoirs based on multi-factor analysis provided in this application includes the following steps: analyzing the sedimentary characteristics, lithological assemblage, and electrical characteristics of the gas-bearing shale intervals in the pilot well, performing stratigraphic division, and interpreting key parameters through well logging; calculating the original geological reserve abundance of each sub-layer according to the shale gas reserve calculation specification; calculating the economically recoverable reserves corresponding to different investments when using shale gas economic evaluation methods combined with the block's single-well investment cost and tax rate values, and establishing the economically recoverable reserves corresponding to single-well investment; calculating the reserve abundance corresponding to different recovery rates using the economically recoverable reserves; and using geophysical logging technology to analyze the rock mechanics of the target layer. The parameters are quantitatively described and the minimum horizontal principal stress is statistically analyzed to delineate stress barriers with a stress difference greater than 1 MPa from the overlying and underlying stresses. Based on the fracturing data, dynamic monitoring data, and production dynamic analysis of the fracturing wells in the work area, the upper and lower fracture heights of the fracturing fractures when traversing different strata are predicted using fracturing network simulation technology. A comprehensive single-well columnar section is compiled based on the data obtained in steps S1-S6. The comprehensive single-well columnar section includes conventional logging curves, lithology, depth, sub-layer name and thickness, reserve abundance of each sub-layer, minimum horizontal principal stress curve, minimum horizontal principal stress value of the stress barrier segment, mean minimum horizontal principal stress of each sub-layer, and stress segmentation. The development strata are comprehensively delineated based on sub-layer thickness, reserve abundance of each sub-layer, and vertical stress differences. The method for finely delineating shale gas reservoir development strata based on multi-factor analysis provided in this application can clearly define reasonable development strata to solve the problem of insufficient utilization of shale gas reserves and achieve efficient shale gas development. Attached Figure Description

[0024] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The method for finely dividing shale gas reservoir development strata based on multi-factor analysis provided in this application provides a map of economically recoverable reserves corresponding to different single-well investments.

[0026] Figure 2 Reserve abundance charts corresponding to different economically recoverable reserves in the method for finely dividing shale gas reservoir development strata based on multi-factor analysis provided in the embodiments of this application;

[0027] Figure 3 The single-well composite columnar section is provided in the method for finely dividing the development strata of shale gas reservoirs based on multi-factor analysis, which is provided in the embodiments of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] The following detailed description of the features and performance of the method for finely classifying shale gas reservoir development strata based on multi-factor analysis, in conjunction with embodiments, further illustrates these features.

[0031] like Figure 1 , Figure 2 and Figure 3 As shown in the embodiments of this application, a method for finely dividing the development strata of shale gas reservoirs based on multi-factor analysis is provided, which includes the following steps:

[0032] S1. Analyze the sedimentary characteristics, lithological assemblage, and electrical properties of the gas-bearing shale interval in the pilot well, perform stratigraphic division, and conduct well logging interpretation of key parameters; optionally, the well logging interpretation of key parameters includes effective thickness, organic carbon abundance, rock mineral composition, porosity, gas content, and gas saturation.

[0033] S2. Calculate the original geological reserve abundance of each sub-layer according to the shale gas reserve calculation standard;

[0034] S3. Using shale gas economic evaluation methods, and combining the investment cost of a single well in the block with the tax rate, calculate the economically recoverable reserves corresponding to different investments when calculating the predetermined after-tax internal rate of return, and establish the economically recoverable reserves corresponding to single-well investment, such as... Figure 1 As shown;

[0035] S4. Using the economically recoverable reserves, calculate the reserve abundance corresponding to different recovery rates, such as... Figure 2 As shown; optionally, when calculating the reserve abundance corresponding to different recovery rates, the lower limit of the reserve abundance is determined by taking a value of 50% of the shale gas recovery rate.

[0036] S5. Quantitatively describe the rock mechanical parameters of the target layer using geophysical logging technology, and statistically analyze the minimum horizontal principal stress to identify stress-isolated layers with a stress difference greater than 1 MPa from the overlying and underlying layers; optionally, geophysical logging technology includes dipole sonic logging method.

[0037] S6. Based on the fracturing data, dynamic monitoring data, and production dynamic analysis of the fracturing wells in the work area, use fracturing network simulation technology to predict the upper and lower fracture heights of the fracturing fractures when traversing different strata; optionally, the fracturing data includes cluster number, proppant type, sand addition intensity, fluid addition intensity, and fracturing process; the dynamic monitoring data includes microseismic monitoring, tracer, pressure excitation response of adjacent wells during fracturing, and well test analysis; the production dynamic analysis includes the production pressure, daily gas production, and daily water production of adjacent wells before and after the well is put into production.

[0038] S7. Compile a comprehensive columnar section of the data obtained from steps S1-S6, such as... Figure 3 As shown; the single-well integrated columnar section includes conventional logging curves, lithology, depth, sub-layer name and thickness, reserve abundance of each sub-layer, minimum horizontal principal stress curve, minimum horizontal principal stress value of stress-isolated sections, mean minimum horizontal principal stress of each sub-layer and stress segmentation; optionally, conventional logging curves include gamma, resistivity, compensated sonic logging, lithology density, and compensated neutron logging.

[0039] S8. Development layers are comprehensively divided based on the thickness of each sublayer, the abundance of reserves in each sublayer, and the difference in vertical stress. When dividing development layers, the thickness of the development layer is not less than the sum of the predicted upper and lower fracture heights, and the abundance of reserves in the development layer is not less than the abundance of reserves corresponding to the economically recoverable limit. The stress barrier layer serves as the top and bottom interface of a development layer system.

[0040] The method for finely classifying shale gas reservoir development layers based on multi-factor analysis provided in this application involves dividing the gas-bearing shale strata in pilot wells into smaller layers and interpreting key parameters through logging. This includes calculating the original geological reserve abundance of each layer, establishing a map of the economically recoverable reserves corresponding to the total investment in a single well, calculating the reserve abundance corresponding to different recovery rates, quantitatively describing the minimum horizontal principal stress, classifying longitudinal stress barriers, predicting the upper and lower fracture heights of the fractures when traversing different strata, and compiling a comprehensive single-well columnar section based on the above analysis results. Finally, the development layers are comprehensively classified according to factors such as thickness, reserve abundance, and differences in longitudinal stress. This determines the economically limit reserve abundance, predicts the extension scale of the fracture network and longitudinal stress barriers, clarifies the economically effective development layers for shale gas horizontal wells, and guides shale gas development deployment. It can fully utilize underground resources, save investment caused by redundant construction, significantly improve the utilization of reserves in the block and the development efficiency of the gas field, and provide a reference for the classification of development layers in other shale gas reservoirs.

[0041] The embodiments described above are some, but not all, of the embodiments of this application. The detailed description of the embodiments of this application is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

Claims

1. A method for fine division of development layer series of shale gas reservoirs based on multi-factor analysis, characterized in that, It comprises the following steps: S1, analyzing the sedimentary characteristics, lithologic combination and electrical characteristics of the gas-bearing shale section of the pilot well, carrying out stratigraphic division, and developing well logging interpretation of key parameters; the well logging interpretation of key parameters includes effective thickness, organic carbon abundance, rock mineral composition, porosity, gas content, gas saturation; S2, calculating the original geological reserve abundance of each small layer according to the shale gas reserve calculation specification; S3, using the shale gas economic evaluation method, combining the single well investment cost and tax rate value of the block to calculate the economic limit recoverable reserves corresponding to different investments when the predetermined after-tax internal rate of return, and establishing the single well investment corresponding to the economic limit recoverable reserves; S4, using the economic limit recoverable reserves to calculate the reserve abundance corresponding to different recovery efficiencies; S5, using geophysical logging technology to quantitatively describe the rock mechanics parameters of the target layer, and counting the minimum horizontal principal stress to divide the stress barrier layer with a stress difference greater than 1 megapascal from the overlying and underlying stress; S6, according to the fracturing data, dynamic monitoring data and production dynamic analysis of the fracturing well in the work area, using the fracturing fracture network simulation technology to predict the upper fracture height and lower fracture height when passing through different layers; S7, preparing a single well comprehensive columnar graph by comprehensively using the data obtained in steps S1-S6; the single well comprehensive columnar graph includes conventional logging curves, lithology, depth, small layer name and thickness, reserve abundance of each small layer, minimum horizontal principal stress curve, minimum horizontal principal stress value of stress barrier section, average value of minimum horizontal principal stress of each small layer and stress segmentation; S8, dividing the development layer system according to the small layer thickness, reserve abundance of each small layer and longitudinal stress difference.

2. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S4, when calculating the reserve abundance corresponding to different recovery efficiencies, the lower limit of the reserve abundance is determined by taking the shale gas recovery efficiency of 50%.

3. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S5, the geophysical logging technology includes dipole sonic logging method.

4. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S6, the fracturing data includes cluster number, proppant type, sanding intensity, liquid adding intensity, fracturing technology, the dynamic monitoring data includes microseismic monitoring, tracer, adjacent well pressure excitation response during fracturing, well test analysis, and the production dynamic analysis includes production pressure, daily gas production and daily water production of adjacent wells before and after the well is put into production.

5. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S7, the conventional logging curves include gamma, resistivity, compensated sonic, lithologic density and compensated neutron.

6. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S8, when dividing the development layer system, the thickness of the development layer system is not less than the sum of the predicted upper fracture height and lower fracture height.

7. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S8, when dividing the development layer system, the reserve abundance of the development layer system is not less than the reserve abundance corresponding to the economic limit recoverable reserves.

8. The method for fine division of development layer series of shale gas reservoir based on multi-factor analysis according to claim 1, characterized in that, In step S8, when dividing the development layer system, the stress barrier layer serves as the top and bottom interface of a set of development layer system.

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