Method for evaluating effective gas storage space of buried hill gas storage

Abstract

The invention relates to a buried hill gas storage effective gas storage space evaluation method, and belongs to the technical field of oil-gas exploration. The method comprises the following specific steps: acquiring fracture development parameters; determining the type of a storage space; reservoir logging response characteristics are determined; extracting buried hill cracks; establishing a bedrock geologic model and a bedrock buried hill discrete fracture model of the target area; and importing the results into a gas storage simulation model in the form of data flow, extracting effective gas storage spaces of a substrate and a crack of the buried hill gas storage, and determining a final buried hill building effective gas storage space. Through research on the method for calculating the reservoir space of the buried hill oil and gas reservoir rebuilt gas storage, the problem of invalid reservoir space calculation is deducted, the calculation accuracy is improved, and theoretical support is provided for calculation of the buried hill reservoir building capacity and later injection and production well position deployment.

Description

Technical Field

[0001] This invention relates to a method for evaluating the effective gas storage space of buried hill gas storage facilities, belonging to the field of oil and gas exploration technology. Background Technology

[0002] Underground gas storage facilities are a crucial link in the natural gas industry chain, serving as essential infrastructure to ensure a safe and stable gas supply. With the increasing proportion of natural gas in my country's energy consumption, underground gas storage facilities have become a key element in ensuring the safe supply of natural gas in my country in recent years. Buried hill oil and gas reservoirs are among the most popular exploration and development targets both domestically and internationally, possessing large reserves, excellent capping conditions, and significant value for gas storage facility construction.

[0003] In the prior art, Chinese invention patent authorization announcement number: CN 109710968 B, discloses a method and device for predicting fractures in bedrock buried hills. The method includes: performing whole-core mineral analysis and element capture logging on the target area to obtain lithological distribution; establishing a bedrock geological model based on seismic data, conventional logging data, imaging logging data, and core data of the target area; determining effective fracture characteristic parameters of the target area through core observation, imaging logging, and logging data analysis; generating rock mechanics test data through rock mechanics testing; establishing the relationship between fracture controlling factors and fracture development parameters; and establishing a discrete fracture model for bedrock buried hills based on the determined effective fracture characteristic parameters, the established relationship between fracture controlling factors and fracture development parameters, and the bedrock geological model, thereby predicting fractures in the target area. By integrating multi-source data and multiple methods, the method identifies and predicts fracture development in buried hill bedrock reservoirs, ultimately establishing a discrete fracture model to guide the exploration and development of buried hill bedrock reservoirs.

[0004] Chinese Invention Patent Application Publication No. CN 106096249 A discloses a quantitative evaluation method for fractured oil and gas reservoirs, comprising the following steps: (1) determining the matrix porosity and oil and gas enrichment patterns, analyzing reservoir heterogeneity, and dividing reservoir units; (2) predicting fracture distribution patterns, evaluating fracture permeability anisotropy, and dividing seepage units; (3) evaluating the matching relationship between matrix porosity and fractures, and dividing reservoir-seepage units; (4) quantitatively evaluating the contribution rate of fractures to reservoir production. This quantitative evaluation method for fractured oil and gas reservoirs can effectively reflect the heterogeneity of the reservoir matrix pore system (the main storage space for oil and gas), the heterogeneity of the fracture system (the main seepage channels for oil and gas), and their matching relationship, objectively evaluating the contribution of fractures to the production capacity of this type of oil and gas reservoir, improving the evaluation efficiency of complex fractured reservoirs, and better guiding the oil and gas exploration and development of complex dual-medium reservoirs, thereby reducing their exploration and development risks and costs.

[0005] Bedrock buried hills are assemblages of metamorphic or igneous rocks below sedimentary sequences, containing sedimentary rocks with extremely low porosity or no matrix porosity. Compared to sedimentary reservoirs, buried hill reservoirs exhibit greater lithology and lithofacies complexity, with significant vertical and horizontal variations, making lithological identification more challenging. They also exhibit stronger reservoir heterogeneity, further complicating the prediction of gas storage space after conversion into underground gas storage facilities. Therefore, accurate calculation of gas storage space in the conversion of buried hill oil and gas reservoirs into underground gas storage facilities is difficult, leading to significant deviations in storage capacity calculations. To address this, a method for evaluating the effective gas storage space of buried hill gas storage facilities has been developed. Summary of the Invention

[0006] To better address the conversion of buried hill oil and gas reservoirs into underground gas storage facilities, this invention proposes a method for determining the effective gas storage space of buried hill gas storage facilities based on lithology, well logging, and geological modeling methods. This provides theoretical support for calculating the storage capacity of buried hill gas storage facilities and for the subsequent deployment of injection and production well locations.

[0007] The technical solution adopted in this invention is a method for evaluating the effective gas storage space of a buried hill gas storage facility, and the specific steps are as follows:

[0008] Step 1: Obtain crack development parameters;

[0009] Step 2: Determine the type of storage space;

[0010] Step 3: Determine the reservoir logging response characteristics;

[0011] Step 4: Extract the fissures in the buried hill;

[0012] Step 5: Establish a bedrock geological model and a bedrock buried hill discrete fracture model for the target area;

[0013] Step 6: Import the above results into the gas storage simulation model in the form of a data stream, extract the matrix and effective gas storage space of the buried hill gas storage, and determine the final effective gas storage space for the buried hill gas storage.

[0014] Furthermore, step one specifically involves obtaining regional lithofacies distribution data based on dynamic and static data, using core samples to observe and describe the development of fractures in buried hills, thereby obtaining fracture development parameters.

[0015] Furthermore, the crack development parameters in step one include the number of crack groups, the number of cracks, the crack density, the crack aperture, the crack dip angle, and the degree of filling.

[0016] Furthermore, step two specifically involves using thin sections of the cast body, scanning electron microscopy, and other crack data to analyze the development characteristics of cracks and dissolution pores under microscopic conditions, and to clarify the type of buried hill reservoir space.

[0017] Furthermore, step two also includes classifying the buried hill reservoir space type according to porosity.

[0018] Furthermore, the other fracture data includes wellbore imaging logging images.

[0019] Furthermore, step three specifically involves using core samples, calibration data, and well logging data, combined with gas logging production data, to classify the single-well buried hill fracture system and matrix system, thereby determining the reservoir logging response characteristics.

[0020] Furthermore, step four specifically involves using the seismic data volume after structural smoothing to obtain the fracture dip angle, azimuth angle, and length based on well logging data, and using the fracture dip angle, azimuth angle, and length parameters to select different fracture scales, and then using the ant volume module of the Petrel software to extract the buried hill fractures.

[0021] Furthermore, step five specifically involves establishing a bedrock geological model of the target area based on seismic data, conventional logging data, imaging logging data, and core data of the target area; using the fracture development parameters as constraints, and based on the established bedrock geological model, obtaining a buried hill discrete fracture model according to the relationship between fractures and dissolution pores, and establishing a buried hill gas storage model.

[0022] Furthermore, the prerequisite for extracting the effective gas storage space of the matrix and fractures in the buried hill gas storage is to use natural gas-driven saturated oil core tests with different injection pressure differentials, combined with nuclear magnetic resonance and core mercury injection experiments, to study the minimum usable pore throat radius of the core when each flow unit of the gas storage reaches the maximum injection volume. Based on the correspondence between pore throat radius and porosity, the lower limit of usable porosity is calculated to be 5%, thereby studying the changes in the effective storage capacity of the flow unit.

[0023] This invention discloses a method for evaluating the effective gas storage space of buried hill gas reservoirs. Its advantages, compared to existing technologies, are that it establishes a method based on the understanding that dissolution pores are mainly distributed along fractures, indicating an inherent causal relationship between their formation and the degree of fracture development controlling the distribution of dissolution pores. This method determines the reservoir logging response characteristics and extracts buried hill fractures. Based on the establishment of a bedrock geological model and a bedrock buried hill discrete fracture model for the target area, the above results are imported into the gas reservoir simulation model in the form of a data stream to extract the effective gas storage space of the matrix and fractures in the buried hill gas reservoir. Furthermore, by conducting research on the calculation method for the storage space of buried hill oil and gas reservoir reconstruction, this invention eliminates the problem of calculating ineffective storage space, improving calculation accuracy and providing theoretical support for calculating the storage capacity of buried hill gas reservoirs and the subsequent deployment of injection and production wells. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 The diagram shown is a schematic cross-sectional view of the lithology distribution of a buried hill in Embodiment 1 of the present invention;

[0026] Figure 2 The diagram shown is a schematic diagram of well logging lithology classification in Embodiment 1 of the present invention;

[0027] Figure 3 The diagram shown is a schematic representation of the distribution relationship between cracks and dissolution pores in Embodiment 1 of the present invention.

[0028] Figure 4 The image shown is a schematic diagram of the reservoir identification diagram in Embodiment 1 of the present invention;

[0029] Figure 5 The image shown is a schematic cross-sectional view of the crack distribution in an ant body in Embodiment 1 of the present invention;

[0030] Figure 6 The diagram shown is a schematic representation of the bedrock geological model in Embodiment 1 of the present invention;

[0031] Figure 7 The figure shown is a schematic diagram of the discrete crack model in Embodiment 1 of the present invention. Detailed Implementation

[0032] 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. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. 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.

[0033] To further understand the content of this invention, the technical solution will be further described below in conjunction with specific embodiments.

[0034] Example 1: As Figures 1-7 As shown in the figure, this embodiment provides a method for evaluating the effective gas storage space of a buried hill gas storage facility, taking the calculation of the effective gas storage space of a buried hill gas storage facility in the MG block of a certain oilfield as an example:

[0035] Step 1: Obtain regional lithofacies distribution data based on dynamic and static data, and describe the development of fractures in the buried hill using core observations to obtain fracture development parameters. These parameters include the number of fracture groups, the number of fractures, fracture density, fracture aperture, fracture dip angle, and degree of filling. Specifically, based on mineral content and elemental composition, the Archean buried hill rocks in the MG block are divided into two major categories: metamorphic rocks and igneous rocks, with eight subcategories and fifteen rock types. Using core observations and well logging interpretation results, macroscopic fracture characteristics are obtained, with the following parameters: 2 fracture groups, 16 fractures, a fracture density of 26 fractures / m, a fracture aperture of 0.2-0.5 mm, a fracture dip angle of 30-90°, and a filling degree from partially filled to unfilled. Well logging interpretation shows that the fracture direction is mainly northeast and near east-west; the fracture dip angle is mainly medium to high angle fractures of 40°-80°.

[0036] Step Two: As Figure 3 As shown, using cast thin sections, scanning electron microscopy, and other fracture data, including available fracture data such as wellbore imaging logging images, the development characteristics of fractures and dissolution pores under microscopic conditions are analyzed to clarify the buried hill reservoir space type. This embodiment analyzes that the main reservoir spaces in a buried hill are fractures and dissolution pores. The dissolution pores are mainly distributed along the fractures, indicating an intrinsic genetic link between their formation, with the degree of fracture development controlling the distribution of dissolution pores. Microscopic pore structure analysis based on capillary force, mercury injection, pore throat distribution, and cast structure reveals severe reservoir heterogeneity. In this embodiment, the reservoir space is divided into three categories based on physical property parameters: Category I: Porosity greater than 5%, reservoir space combination type is macroscopic fracture + microfracture + broken intergranular pore type, which is a good reservoir; Category II: Porosity between 5% and 1%, reservoir space combination type is microfracture + micropore type, which is a reservoir with fracture as the main seepage feature; Category III: Porosity less than 1%, reservoir space combination type is microfracture + micropore type, which is a non-reservoir.

[0037] Step 3: As Figure 1 , 2 As shown in Figure 4, single-well buried hill fracture systems and matrix systems are delineated using core samples, calibration logs, and well logging data, combined with gas logging production data, to determine reservoir logging response characteristics. Specifically, core-calibrated logging is used to establish qualitative and quantitative identification patterns for major lithologies. Logging data identifies four main categories: mixed granite, mixed gneiss, amphibolite, and igneous rocks. The lithologies are primarily mixed gneiss and mixed granite, followed by igneous rocks and amphibolite. Combined with gas logging production data, single-well buried hill fracture systems and matrix systems are delineated, reservoir logging response characteristics are determined, and an effective buried hill reservoir identification chart is established. This is supplemented with local oil testing and production data to identify effective reservoirs.

[0038] Step Four: As Figure 5As shown in the figure, the black lines represent fractures. Using seismic data volume after structural smoothing, the fracture dip angle, azimuth angle, and length are obtained from well logging data. Different fracture scales are selected using the fracture dip angle, azimuth angle, and length parameters. The Petrel software ant module is then used to extract buried hill fractures. In this embodiment, the fractures in the Class I reservoir area are developed in a network, while the Class II and Class III reservoirs are unusable areas.

[0039] Step 5: As Figure 6 and 7 As shown, a bedrock geological model of the target area is established based on seismic data, conventional logging data, imaging logging data, and core data of the target area. With the fracture development parameters as constraints, a discrete fracture model of the buried hill is obtained based on the relationship between fractures and dissolution pores, and a buried hill gas storage model is established.

[0040] Step Six: Import the results from Steps One through Five into the gas storage simulation model as a data stream to extract the effective gas storage space of the matrix and fractures in the buried hill gas storage, and determine the final effective gas storage space for buried hill gas storage construction. The prerequisite for extracting the effective gas storage space of the matrix and fractures in the buried hill gas storage is to use natural gas-driven saturated oil core tests with different injection pressure differentials, combined with nuclear magnetic resonance and core mercury injection experiments, to study the minimum usable pore throat radius of the core when each flow unit of the gas storage reaches its maximum injection volume. Based on the correspondence between pore throat radius and porosity, the lower limit of usable porosity is calculated to be 5%, thereby studying the changes in the effective storage capacity of the flow units. The final effective gas storage space for the MG block is 1295.9 × 10⁻⁶. 6 m 3 .

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for evaluating the effective gas storage space of a buried hill gas storage facility, characterized in that, Step 1: Obtain fracture development parameters; Step 2: Identify reservoir space type; Step 3: Determine reservoir logging response characteristics; Step 4: Extract buried hill fractures; Step 5: Establish bedrock geological model and bedrock buried hill discrete fracture model for the target area; Step 6: Import the above results into the gas storage simulation model in the form of a data stream, extract the matrix and effective gas storage space of the buried hill gas storage, and determine the final effective gas storage space for buried hill construction.

2. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step one specifically involves obtaining regional lithofacies distribution data based on dynamic and static data, using core samples to observe and describe the development of fractures in buried hills, thereby obtaining fracture development parameters.

3. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, The crack development parameters in step one include the number of crack groups, the number of cracks, the crack density, the crack aperture, the crack dip angle, and the degree of filling.

4. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step two involves using thin sections of the cast body, scanning electron microscopy, and other fracture data to analyze the development characteristics of fractures and dissolution pores under microscopic conditions, and to identify the type of buried hill reservoir space.

5. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step two also includes classifying buried hill reservoir space types based on porosity.

6. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 4, characterized in that, Other fracture data includes peri-well imaging logging images.

7. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step three involves using core samples, calibration data, and well logging data, combined with gas logging production data, to classify the single-well buried hill fracture system and matrix system, thereby determining the reservoir logging response characteristics.

8. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step four involves using the seismic data volume after structural smoothing to obtain the fracture dip angle, fracture azimuth angle, and fracture length based on well logging data. Different fracture scales are then selected using these parameters, and the buried hill fractures are extracted using the ant volume module of the Petrel software.

9. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, Step five specifically involves establishing a bedrock geological model of the target area based on seismic data, conventional logging data, imaging logging data, and core data of the target area; using the fracture development parameters as constraints, and based on the established bedrock geological model, obtaining a discrete fracture model of the buried hill according to the relationship between fractures and dissolution pores, and establishing a buried hill gas storage model.

10. The method for evaluating the effective gas storage space of a buried hill gas storage facility according to claim 1, characterized in that, The prerequisite for extracting the effective gas storage space of the matrix and fractures in a buried hill gas storage facility is to use natural gas-driven saturated oil core tests with different injection pressure differentials, combined with nuclear magnetic resonance and core mercury injection experiments, to study the minimum usable pore throat radius of the core when each flow unit of the gas storage facility reaches the maximum injection volume. Based on the correspondence between pore throat radius and porosity, the lower limit of usable porosity is calculated to be 5%, and the effective storage capacity of the flow unit is studied accordingly.

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