A rapid estimation method for the average thickness of gas reservoirs within a certain trap range

Abstract

The present invention belongs to the field of oil and gas field exploration and development, and specifically relates to a method for rapidly estimating the average thickness of a gas reservoir within a certain trap range. The method comprises classifying the morphology of a geological body into several different types of geometric bodies based on the geometric morphological characteristics of the structural trap; setting equivalent average thicknesses based on the structure of the geometric body, and collecting the geometric bodies and their corresponding equivalent average thicknesses together to establish a comparison table; determining the type of geological body based on the geometric morphological characteristics of the actual structural trap by comparing the thickness comparison table, and selecting the corresponding weighted average thickness based on the type of geological body to complete the estimation of the weighted average thickness of the corresponding geological body. This method requires minimal data, requiring only that the geometric characteristics roughly match, rather than strictly conforming to mathematically defined geometric body types. It is easy to implement in actual work, has high estimation efficiency, and produces scientific, reasonable, and highly accurate results. It can be widely used in matrix gas field resource evaluation.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field exploration and development technology, and in particular relates to a method for quickly estimating the average thickness of a gas reservoir within a certain trap range. Background Art

[0002] Oil and gas field reserves are fundamental to developing exploration and development strategies. Calculating reserves has comprehensive standards and systems, enabling accurate calculations to determine reserve size. However, as data becomes available, reserves are constantly updated. Technical discussions and research presentations often require a quick assessment of the accuracy and rationality of reserve calculations, or a quick estimate of reserve size, without requiring a precise result, or even without it being possible. This necessitates a fast and effective estimation method to provide a reasonable estimate of reserve size and enable rapid decision-making.

[0003] The static reserve calculation methods for gas and oil reservoirs are similar. However, compared to oil reservoirs, gas reservoirs typically have a more complex distribution of oil-water interfaces. Gas-water interfaces are easier to identify, and the spatial relationship between gas and water is more defined. Gravity differentiation causes gas to accumulate at the top of the structure, so a quick and simple calculation method is desirable. Among the reserve calculation parameters, the average effective thickness can be calculated by multiplying the average gas reservoir thickness by the net-to-gross formation ratio. In other words, once the net-to-gross formation ratio is determined, the average effective thickness required for reserve calculation only needs to be known.

[0004] The purpose of determining the average thickness of a gas reservoir is to solve the problem of calculating gas reservoir reserves or resources. The current method for determining the average thickness of a gas reservoir is mainly through the area-weighted average method, but this method has high data requirements and requires detailed drawings and calculations, which cannot meet the requirements of rapid estimation. Summary of the Invention

[0005] The present invention helps to quickly determine the reserve scale by judging the geometric type of the geological body within the trap and selecting the approximate value of the weighted average thickness of the gas reservoir, thereby facilitating rapid decision-making and improving the efficiency and accuracy of judgment.

[0006] This is achieved specifically through the following technical solutions:

[0007] Formula for calculating natural gas geological reserves in gas reservoirs or oil reservoir gas caps based on volumetric method ,in, is the geological reserves of natural gas, in units of ; is the gas-bearing area, unit ; is the average effective thickness, unit ; is the average effective porosity, decimal; is the average initial gas saturation, is the average formation gas volume coefficient under original conditions, dimensionless. There are many geological types of natural gas reservoirs. Since we want to achieve a rapid estimation of reserves, we only consider volumetric reserves here, and mainly for porous (cavity) gas reservoirs (including oil reservoir gas caps). In the reserve calculation formula, the gas-bearing area It can be directly read and used through the structural map, the average effective porosity and average initial gas saturation All of them are obtained through well logging interpretation. The parameters are obtained by temperature, pressure and composition. Even different people can get basically the same results. Only the average effective thickness (i.e. weighted average effective thickness) The present invention is to create a method for quickly estimating the average thickness, thereby realizing a rapid estimation of reserves.

[0008] A method for quickly estimating the average thickness of a gas reservoir within a certain trap range is characterized by: including geological classification, establishing a thickness comparison table, and confirming the type;

[0009] A method for quickly estimating the average thickness of a gas reservoir within a certain trap range is characterized by: including geological classification, establishing a thickness comparison table, and confirming the type;

[0010] The geological classification is to classify the morphology of geological bodies into several different types of geometric bodies according to the geometric characteristics of structural traps;

[0011] The thickness comparison table is established by setting an equivalent average thickness according to the structure of the geometric body, where the equivalent average thickness of the geometric body is the weighted average thickness of the corresponding geological body; all geometric bodies and their corresponding equivalent average thicknesses are collected together to establish a comparison table for selecting the weighted average thickness;

[0012] The type of confirmation is as follows: the type of geological body is determined by comparing the geometric features of the actual structural trap with a thickness comparison table, and the corresponding weighted average thickness is selected according to the type of geological body to complete a rapid estimation of the weighted average thickness of the corresponding geological body.

[0013] Preferably, in the process of geological classification, the shapes of geological bodies are summarized into A-type geometric bodies that are hemispherical, B-type geometric bodies that are cone-shaped, and C-type geometric bodies that are inverted concave funnel-shaped.

[0014] Preferably, in the process of establishing the thickness comparison table, the bottom area of the A-type geometric body is , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the volume of the hemisphere is ,Will Set to the equivalent average thickness of type A geometry.

[0015] Preferably, in the process of establishing the thickness comparison table, the bottom area of the B-type geometric body is , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the cone volume is ,Will Set to the equivalent average thickness of type B geometry.

[0016] Preferably, in the process of establishing the thickness comparison table, the bottom area of the C-shaped geometric body is , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; based on the volume integral expression of the inverted concave funnel ,Will Set to the equivalent average thickness of type B geometry.

[0017] Preferably, in the process of confirming the type, the equivalent average thickness of the geological body between the A-type geometry and the B-type geometry and the geological body between the B-type geometry and the C-type geometry is obtained by interpolation.

[0018] Preferably, in the process of confirming the type, if the vertical section of the actual geological body through the structural vertex presents a plane geometry close to a semicircle, and the structural height is close to half the length of the bottom side of the section, then the geological body is judged to be a type A geometric body.

[0019] Preferably, in the process of confirming the type, if the vertical section of the actual geological body passing through the structural vertex presents a triangular plane geometric shape, the geological body is determined to be a type B geometric body.

[0020] Preferably, in the process of confirming the type, if the vertical section of the actual geological body through the structural vertex presents a plane geometry of an inverted concave funnel, and the structural height is close to half the length of the bottom side of the section, then the geological body is judged to be a C-type geometric body.

[0021] Preferably, a quarter arc with the x-axis and the y-axis as tangents is set in the first quadrant or the second quadrant of the plane rectangular coordinate system, and the inverted concave funnel is a three-dimensional figure formed by the quarter arc around the y-axis.

[0022] Beneficial effects brought by this technical solution:

[0023] 1) This technical solution classifies geological body types. Based on the vertical profile characteristics through the vertex of the target geological body, the target geological body type can be determined, and the corresponding approximate equivalent average effective thickness can be selected. Research results: "Average effective thickness" not only determines the scale of the geological body but also allows for rapid estimation of reserves and resources, facilitating decision-makers' rational judgment and deployment, and improving work efficiency. Furthermore, this technical method offers the advantages of high estimation reliability, convenient and quick application, low cost requirements, and strong operability.

[0024] 2) This method requires minimal data; it only requires that the geometric features roughly conform to the geometric body type defined in mathematics. It is easy to implement in practice, has high estimation efficiency, and produces scientific and reasonable results with high accuracy. It can be widely used in matrix gas field resource evaluation.

[0025] 3) Classification by geological body type solves the problem of lack of mathematical basis for estimating the average thickness of gas reservoirs. As long as the geological body types are reasonably classified and the equivalent average thickness values are accurately selected, the error in the calculated average effective thickness of gas reservoirs will not exceed 20%;

[0026] 3) This technical solution is particularly suitable for estimating the average thickness of gas reservoirs in geological storage layers of matrix pore type and fracture-pore type. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The foregoing and following detailed description of the present invention will become more apparent when read in conjunction with the following drawings, in which:

[0028] Figure 1 It is a cross-sectional view of type A geometry;

[0029] Figure 2 It is a cross-sectional view of type B geometry;

[0030] Figure 3 It is a cross-sectional view of a C-shaped geometry;

[0031] Figure 4 Thickness comparison table. DETAILED DESCRIPTION

[0032] The following is a further explanation of the technical solution for achieving the purpose of the present utility model through several specific embodiments. It should be noted that the technical solution claimed for protection by the present utility model includes but is not limited to the following embodiments.

[0033] Example 1

[0034] This embodiment discloses a method for quickly estimating the average thickness of a gas reservoir within a certain trap range, as a preferred embodiment of the present invention, which is characterized by: including geological classification, establishing a thickness comparison table, and confirming the type;

[0035] Geological classification: According to the geometric features of structural traps, the morphology of geological bodies is classified into several different types of geometric bodies; specifically, Figures 1-3 As shown in the figure, the morphology of the geological body can be summarized as a type A geometric body that is a hemisphere, a type B geometric body that is a cone, and a type C geometric body that is an inverted concave funnel (it should be noted that the hemisphere / cone / inverted concave funnel described in this technical solution is not an absolute hemisphere / cone / inverted concave funnel. The geometric body that is similar to the hemisphere / cone / inverted concave funnel can also be regarded as a hemisphere / cone / inverted concave funnel). Among them, the so-called inverted concave funnel is a 1 / 4 arc with the x-axis and the y-axis as tangents set in the first quadrant or the second quadrant of the plane rectangular coordinate system. The inverted concave funnel is a three-dimensional figure formed by the 1 / 4 arc around the y-axis.

[0036] Establish a thickness comparison table: set the equivalent average thickness according to the structure of the geometric body. The equivalent average thickness of the geometric body is the weighted average thickness of the corresponding geological body; bring all geometric bodies and their corresponding equivalent average thicknesses together to establish a comparison table for selecting the weighted average thickness.

[0037] Confirm the type: According to the geometric characteristics of the actual structural trap, the type of geological body is determined by comparing it with the thickness comparison table, and the corresponding weighted average thickness is selected according to the type of geological body to complete the rapid estimation of the weighted average thickness of the corresponding geological body.

[0038] This technical solution categorizes geological body types and establishes a corresponding comparison table. By determining the type of target geological body, the corresponding approximate equivalent average effective thickness can be selected. The research results show that "average effective thickness" not only determines the size of the geological body but also allows for rapid estimation of reserves and resources, facilitating decision-makers' rational judgment and deployment, thereby improving work efficiency.

[0039] Example 2

[0040] This embodiment discloses a method for quickly estimating the average thickness of a gas reservoir within a certain trap range, as a basic implementation scheme of the present invention, which is characterized by: including geological classification, establishing a thickness comparison table, and confirming the type;

[0041] Geological classification: Based on the geometric characteristics of structural traps, the morphology of geological bodies can be classified into several different types of geometric bodies; that is, the morphology of geological bodies can be summarized as type A geometric body that is a hemisphere, type B geometric body that is a cone, and type C geometric body that is an inverted concave funnel.

[0042] Establish a thickness comparison table: set the equivalent average thickness according to the structure of the geometric body. The equivalent average thickness of the geometric body is the weighted average thickness of the corresponding geological body. Collect all geometric bodies and their corresponding equivalent average thicknesses together to establish a comparison table for selecting the weighted average thickness, where:

[0043] For a geometric body of type A, let the bottom area of the geometric body of type A be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the volume of the hemisphere is ,Will Set to the equivalent average thickness of type A geometry;

[0044] For the B-type geometry, let the base area of the B-type geometry be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the cone volume is ,Will Set to the equivalent average thickness of the B-type geometry;

[0045] For a C-shaped geometry, let the base area of the C-shaped geometry be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; based on the volume integral expression of the inverted concave funnel ,Will Set to the equivalent average thickness of type B geometry.

[0046] Confirm the type: According to the geometric characteristics of the actual structural trap, the type of geological body is determined by comparing it with the thickness comparison table, and the corresponding weighted average thickness is selected according to the type of geological body to complete the rapid estimation of the weighted average thickness of the corresponding geological body.

[0047] This technical solution classifies geological bodies based on their structural characteristics and establishes corresponding comparison tables. Based on the vertical profile shape characteristics of the target geological body's apex, the type of the target geological body can be judged, and the corresponding approximate equivalent average effective thickness can be selected, thereby achieving rapid estimation of reserves and resources, providing convenience for decision makers to make reasonable judgments and deployments, and improving work efficiency. In addition, this technical method has the advantages of high estimation reliability, convenient and fast application, low cost requirements, and strong operability. Furthermore, this method requires little data, requiring only a rough conformance of geometric features, and does not require strict conformance to mathematically defined geometric body types. It is easy to implement in actual work, has high estimation efficiency, and the results are scientific and reasonable with high accuracy. It is particularly suitable for estimating the average thickness of gas reservoirs in matrix pore-type and fracture-pore-type geological body storage layers, and can be well promoted in matrix-type gas field resource evaluation.

[0048] Example 3

[0049] This embodiment discloses a method for quickly estimating the average thickness of a gas reservoir within a certain trap range, as a basic implementation scheme of the present invention, which is characterized by: including geological classification, establishing a thickness comparison table, and confirming the type;

[0050] Geological classification: Based on the geometric characteristics of structural traps, the morphology of geological bodies can be classified into several different types of geometric bodies; that is, the morphology of geological bodies can be summarized as type A geometric body that is a hemisphere, type B geometric body that is a cone, and type C geometric body that is an inverted concave funnel.

[0051] Establish a thickness comparison table: set the equivalent average thickness according to the structure of the geometric body. The equivalent average thickness of the geometric body is the weighted average thickness of the corresponding geological body. Collect all geometric bodies and their corresponding equivalent average thicknesses together to establish a comparison table for selecting the weighted average thickness, where:

[0052] For a geometric body of type A, let the bottom area of the geometric body of type A be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the volume of the hemisphere is ,Will Set to the equivalent average thickness of type A geometry;

[0053] For the B-type geometry, let the base area of the B-type geometry be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the cone volume is ,Will Set to the equivalent average thickness of the B-type geometry;

[0054] For a C-shaped geometry, let the base area of the C-shaped geometry be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; based on the volume integral expression of the inverted concave funnel ,Will Set to the equivalent average thickness of type B geometry.

[0055] Confirm the type: According to the geometric features of the actual structural trap, the type of geological body is determined by comparing it with the thickness comparison table, and the corresponding weighted average thickness is selected according to the type of geological body to complete the rapid estimation of the weighted average thickness of the corresponding geological body.

[0056] If the vertical section of the actual geological body through the structural vertex presents a plane geometry close to a semicircle, and the structural height is close to half the length of the bottom side of the section, then the geological body is judged to be a type A geometric body;

[0057] If the vertical section of the actual geological body through the structural vertex presents a triangular plane geometry, then the geological body is judged to be a type B geometry;

[0058] If the vertical section of the actual geological body through the structural vertex presents a plane geometry of an inverted concave funnel, and the structural height is close to half the length of the bottom side of the section, then the geological body is judged to be a C-type geometry;

[0059] For the geological bodies between type A and type B geometry, and between type B and type C geometry, the equivalent average thickness is obtained by interpolation.

[0060] This technical solution provides a mathematical basis for estimating average thickness, establishing a method for rapidly determining equivalent average thickness through table lookup. This method changes the previous unstructured estimation method and improves the accuracy of the obtained results. Unlike the cumbersome method of calculating weighted average thickness by drawing detailed isopach maps, this method simplifies the calculation process, improves the efficiency of obtaining results, and achieves the goal of rapidly estimating gas reservoir reserves.

Claims

1. A method for rapidly estimating the average thickness of a gas reservoir within a certain trap range, characterized by: Including geological classification, establishing thickness comparison table, and confirming type; The geological classification is as follows: based on the geometric features of structural traps, the morphology of geological bodies is classified into several different types of geometric bodies, specifically, the morphology of geological bodies is classified into type A geometric bodies that are hemispherical, type B geometric bodies that are cone-shaped, and type C geometric bodies that are inverted concave funnel-shaped; The thickness comparison table is established by setting an equivalent average thickness according to the structure of the geometric body, where the equivalent average thickness of the geometric body is the weighted average thickness of the corresponding geological body; all geometric bodies and their corresponding equivalent average thicknesses are collected together to establish a comparison table for selecting the weighted average thickness; wherein: Let the base area of A be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the volume of the hemisphere is ,Will Set to the equivalent average thickness of type A geometry; Let the base area of the B-type geometric body be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; the calculation formula based on the cone volume is ,Will Set to the equivalent average thickness of the B-type geometry; Let the base area of the C-shaped solid be , the structural amplitude above the air-water interface is , the structural amplitude above the air-water interface is the height of the corresponding geometric body; based on the volume integral expression of the inverted concave funnel ,Will Set to the equivalent average thickness of the B-type geometry; The type of confirmation is as follows: the type of geological body is determined based on the geometric features of the actual structural trap and compared with a thickness comparison table, and the corresponding weighted average thickness is selected according to the type of geological body to complete a rapid estimation of the weighted average thickness of the corresponding geological body; among which, for geological bodies between type A and type B geometries and between type B and type C geometries, the equivalent average thickness is obtained by interpolation.

2. A method for rapidly estimating the average thickness of a gas reservoir within a certain trap range as claimed in claim 1, characterized in that: In the process of confirming the type, if the vertical section of the actual geological body through the structural vertex presents a plane geometry close to a semicircle, and the structural height is close to half of the length of the bottom side of the section, then the geological body is judged to be a type A geometric body.

3. The method for rapidly estimating the average thickness of a gas reservoir within a certain trap range as claimed in claim 1, characterized in that: In the process of confirming the type, if the vertical section of the actual geological body passing through the structural vertex presents a triangular plane geometric shape, the geological body is determined to be a type B geometric body.

4. The method for rapidly estimating the average thickness of a gas reservoir within a certain trap range as claimed in claim 1, characterized in that: In the process of confirming the type, if the vertical section of the actual geological body through the structural vertex presents a plane geometric shape of an inverted concave funnel, and the structural height is close to half the length of the bottom side of the section, then the geological body is judged to be a C-type geometric body.

5. The method for rapidly estimating the average thickness of a gas reservoir within a certain trap range as claimed in claim 1, characterized in that: A quarter arc with the x-axis and the y-axis as tangents is set in the first quadrant or the second quadrant of the plane rectangular coordinate system, and the inverted concave funnel is a three-dimensional figure formed by the quarter arc around the y-axis.

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