A method and device for determining the lower limit of effective reservoir physical properties of a gas reservoir

Abstract

The application discloses a method and device for determining the lower limit of effective reservoir physical properties of a gas reservoir. The method comprises the following steps: according to the secondary migration and accumulation theory of natural gas reservoirs and the relationship between the driving force and resistance of the reservoirs, the relationship between the critical gas-containing pore throat radius of the gas reservoirs and the gas column height is established by using the mechanical balance principle; the relationship between the lower limit of the effective reservoir porosity and the gas column height is established according to the relationship between the median pore throat radius and the porosity and the relationship between the critical gas-containing pore throat radius and the gas column height; then, the relationship between the lower limit of the effective reservoir permeability and the gas column height is established according to the relationship between the porosity and the permeability; the lower limit determination model of the effective reservoir physical properties is obtained from the relationship between the lower limit of the effective reservoir porosity and the gas column height and the relationship between the lower limit of the effective reservoir permeability and the gas column height, and is used for determining the lower limit of the effective reservoir physical properties of the gas reservoir. Different lower limits of the physical properties can be determined according to the different gas column heights at different positions of the gas reservoir, and the lower limit of the physical properties of the gas reservoir can be determined reasonably, concisely and efficiently.

Description

Technical Field

[0001] This invention relates to the field of gas reservoir exploration and development technology, and in particular to a method and apparatus for determining the lower limit of effective reservoir properties in gas reservoirs. Background Technology

[0002] An effective reservoir refers to a reservoir saturated with oil and gas and capable of producing oil and gas, which can generate industrial oil and gas flow under existing technological conditions. The lower limit of effective reservoir properties is an important factor affecting the calculation of oil and gas geological reserves and the preparation of development plans. It is a difficult problem in reservoir and reserve evaluation research and a key issue directly related to the decision-making of oil and gas reservoir exploration and development.

[0003] Among the effective reservoir physical properties, porosity and permeability are the most representative. Currently, there are many methods for determining the lower limit of effective reservoir physical properties, both domestically and internationally, including the cumulative frequency statistical method, the core porosity-permeability relationship method, the minimum flow pore throat radius method, the bound water saturation method, oil and gas testing methods, and production capacity simulation methods. The current common practice is to determine a single lower limit for the same oil and gas reservoir, meaning that the lower limit values ​​for porosity and permeability are the same across all parts of the reservoir. Summary of the Invention

[0004] The inventors discovered that existing technologies typically determine a single lower limit for physical properties for an entire oil and gas reservoir. However, for gas reservoirs with significant structural variations, the effective reservoir physical property lower limits differ considerably across different locations, necessitating zonal determination. Otherwise, inaccurate geological reserve assessments and significant discrepancies between dynamic and static reserves can arise during reservoir development. To at least partially address these technical problems, the inventors developed this invention, providing a method and apparatus for determining the effective reservoir physical property lower limits of a gas reservoir through specific embodiments. This method can determine different physical property lower limits based on the varying gas column heights at different locations within the gas reservoir.

[0005] In a first aspect, embodiments of the present invention provide a method for determining the lower limit of effective reservoir properties in a gas reservoir, comprising:

[0006] Based on the theory of secondary migration and accumulation of natural gas and the relationship between accumulation dynamics and resistance, the first relationship between the critical gas-bearing throat radius and the height of the gas column is established using the principle of mechanical equilibrium.

[0007] Based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship, a third relationship is established between the effective reservoir porosity lower limit and the gas column height of the gas reservoir.

[0008] Based on the porosity-permeability relationship of the gas reservoir and the third relationship, a fourth relationship is established between the lower limit of the effective reservoir permeability and the height of the gas column.

[0009] Based on the third and fourth relations, an effective reservoir property lower limit determination model is obtained, which is used to determine the effective reservoir property lower limit of the gas reservoir.

[0010] In a second aspect, embodiments of the present invention provide an apparatus for determining the lower limit of effective reservoir properties in a gas reservoir, comprising:

[0011] The first relationship establishment module is used to establish the first relationship between the critical gas-bearing throat radius and the gas column height of a gas reservoir based on the theory of secondary migration and accumulation of natural gas and the relationship between reservoir dynamics and resistance, using the principle of mechanical equilibrium.

[0012] The third relationship establishment module is used to establish a third relationship between the effective reservoir porosity lower limit and the gas column height of the gas reservoir based on the second relationship between the median pore throat radius and porosity and the first relationship.

[0013] The fourth relationship establishment module is used to establish a fourth relationship between the lower limit of the effective reservoir permeability of the gas reservoir and the height of the gas column based on the porosity-permeability relationship of the gas reservoir and the third relationship.

[0014] The effective reservoir property lower limit determination model module is used to obtain the effective reservoir property lower limit determination model from the third relation and the fourth relation, and is used to determine the effective reservoir property lower limit of the gas reservoir.

[0015] Thirdly, embodiments of the present invention provide a computer program product, including a computer program / instruction, wherein the computer program / instruction, when executed by a processor, implements the above-described method for determining the lower limit of effective reservoir properties of a gas reservoir.

[0016] Fourthly, this disclosure provides a server, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for determining the lower limit of effective reservoir properties of a gas reservoir.

[0017] The beneficial effects of the above-described technical solutions provided in the embodiments of the present invention include at least the following:

[0018] (1) The method for determining the lower limit of effective reservoir properties of gas reservoirs provided in this embodiment of the invention is based on the theory of secondary migration and accumulation of natural gas reservoirs, takes into account the relationship between reservoir formation dynamics and resistance, and uses the principle of mechanical equilibrium to establish a method for determining the lower limit of effective reservoir properties of gas reservoirs, which is different from the commonly used statistical method or empirical value method.

[0019] (2) Considering the differences in gas column height, the effective reservoir physical property lower limit is determined for different locations of the gas reservoir. This method differs from the traditional single physical property lower limit method. For gas reservoirs with large differences in structural amplitude, it can more accurately evaluate the geological reserves of different regions of the gas reservoir.

[0020] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description, claims, and drawings.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0023] Figure 1 This is a flowchart of the method for determining the lower limit of effective reservoir properties in a gas reservoir according to Embodiment 1 of the present invention;

[0024] Figure 2 This is a schematic diagram showing the gas column height at different locations in the gas reservoir in Embodiment 1 of the present invention;

[0025] Figure 3 This is a flowchart illustrating the specific implementation of determining the lower limit of effective reservoir properties in gas reservoirs in Embodiment 2 of the present invention.

[0026] Figure 4 This is a contour map of the top surface structure of the SGP gas reservoir in Embodiment 2 of the present invention;

[0027] Figure 5a This is a reservoir well profile diagram of the SGP gas reservoir passing through wells G21-G7-G19-G3 in Embodiment 2 of the present invention;

[0028] Figure 5b This is a reservoir well profile diagram of the SGP gas reservoir via wells G10-G010-X1-G11-G29 in Embodiment 2 of the present invention;

[0029] Figure 6 This is a schematic diagram of the gas column height zoning of the SGP gas reservoir in Embodiment 2 of the present invention;

[0030] Figure 7 This is the curve showing the relationship between the gas column height and the critical gas-bearing throat radius in the SGP gas reservoir in Embodiment 2 of the present invention;

[0031] Figure 8 This is the curve showing the relationship between porosity and median pore throat radius in the SGP gas reservoir of Embodiment 2 of the present invention;

[0032] Figure 9 This is the curve showing the relationship between the gas column height and the lower limit of porosity in the SGP gas reservoir in Embodiment 2 of the present invention;

[0033] Figure 10This is the curve showing the relationship between the lower limit of porosity and the lower limit of permeability in the SGP gas reservoir in Embodiment 2 of the present invention;

[0034] Figure 11 This is a diagram showing the four properties of well logging interpretation in the G20 well of the SGP gas reservoir in Embodiment 2 of the present invention.

[0035] Figure 12 This is a schematic diagram of the device for determining the lower limit of effective reservoir properties in a gas reservoir according to an embodiment of the present invention. Detailed Implementation

[0036] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] To address the problems of inconsistent and inaccurate determination of the lower limit of effective reservoir properties in existing technologies, this invention provides a method and apparatus for determining the lower limit of effective reservoir properties in gas reservoirs. This method and apparatus can determine different lower limits of properties based on the different heights of the gas column at different locations within the gas reservoir, and can determine the lower limits of gas reservoir properties in a reasonable, simple, and efficient manner.

[0038] Example 1

[0039] Embodiment 1 of the present invention provides a method for determining the lower limit of effective reservoir properties in a gas reservoir, the process of which is as follows: Figure 1 As shown, it includes the following steps:

[0040] Step S11: Based on the theory of secondary migration and accumulation of natural gas reservoirs and the relationship between reservoir dynamics and resistance, the first relationship between the critical gas-bearing throat radius and the height of the gas column is established using the principle of mechanical equilibrium.

[0041] Based on the principle of secondary migration and accumulation of natural gas, the main driving force for the migration of conventional natural gas is buoyancy, while the main resistance is the capillary pressure in the pore throat. The magnitude of buoyancy depends on the height of the gas column, while the magnitude of resistance depends on the size of the pore throat. When the buoyancy exceeds the capillary resistance of the pore throat, natural gas is expelled into the pore throat, first into larger pore throats, then into smaller pore throats, until the buoyancy and capillary resistance reach equilibrium. The higher the continuous gas column, the greater the buoyancy during the natural gas migration and accumulation process, and the smaller the corresponding critical gas-bearing pore throat radius. Therefore, the effectiveness of a reservoir is closely related to the reservoir pore throat size and gas column height. Different gas column heights correspond to different critical gas-bearing pore throat radii, thus corresponding to different lower limits of effective reservoir properties.

[0042] Based on the theory of secondary migration and accumulation of natural gas reservoirs, considering the relationship between reservoir formation dynamics and resistance, and using the principle of mechanical equilibrium, the critical pore throat radius corresponding to different gas column heights is calculated, and the first relationship between the critical pore throat radius of the gas reservoir and the gas column height is established.

[0043] The aforementioned critical gas-bearing pore throat radius is the pore throat radius at which natural gas reaches a balance between dynamics and resistance during migration. If the pore throat radius is less than this critical value, the pore throat usually contains only formation water; if the pore throat radius is greater than this critical value, gas usually begins to fill the pore throat.

[0044] The driving force for the migration of conventional natural gas is buoyancy:

[0045] F=Δρ gw gh g (1)

[0046] In equation (1), F is the buoyancy force, MPa; Δρ gw It is the gas-water density difference under gas reservoir conditions, in g / cm³. 3 g is the acceleration due to gravity, typically 9.8 m / s². 2 h g It is the height of the continuous air column, in meters (m).

[0047] The main resistance to natural gas migration is the pore throat capillary pressure. The capillary pressure experienced when natural gas enters from a large pore into a small pore is:

[0048]

[0049] In equation (2), It is the pore throat capillary pressure, MPa; σ gw θ represents the surface tension between the gas and water phases under gas reservoir conditions, in mN / m; gw R1 is the air-water wetting angle; R2 is the radius of the large throat (mm); R2 is the radius of the small throat (mm).

[0050] When natural gas reaches a balance between dynamics and resistance during its migration, the small pore throat radius R2 in equation (2) is the critical gas-bearing pore throat radius R. c R1 is taken as the average throat radius R p Equation (2) satisfies the following relationship:

[0051]

[0052] In equation (3), R c R is the critical pore throat radius, in mm; p Let be the average pore throat radius, in mm. Then, from equation (3) above, the expression for the critical pore throat radius can be derived as:

[0053]

[0054] Therefore, based on the theory of secondary migration and accumulation of natural gas reservoirs and the relationship between reservoir dynamics and resistance, and using the principle of mechanical equilibrium, the first relationship between the critical gas-bearing pore throat radius and the gas column height can be established by the above equation (4) through the pore throat parameters and gas-water interface parameters of the gas reservoir.

[0055] Step S12: Based on the second and first relationships between the median pore throat radius and porosity of the gas reservoir, establish the third relationship between the effective reservoir porosity lower limit and the gas column height.

[0056] The second relationship between the median pore throat radius and porosity of a gas reservoir can be obtained from mercury intrusion porosimetry data of gas reservoir samples.

[0057] Multiple sample points containing median pore throat radius and porosity were obtained from the mercury injection data of the rock samples. A second relationship between median pore throat radius and porosity was obtained by fitting the sample points.

[0058] Generally, a gas saturation exceeding 50% indicates a pure gas layer. Therefore, the critical gas-bearing pore throat radius can be taken as equal to the median pore throat radius. At the same time, the critical gas-bearing pore throat radius is taken as the lower limit of porosity. Based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship mentioned above, a third relationship between the effective reservoir porosity lower limit and the gas column height can be established.

[0059] Step S13: Based on the porosity-permeability relationship and the third relationship of the gas reservoir, establish the fourth relationship between the lower limit of the effective reservoir permeability and the height of the gas column.

[0060] The porosity-permeability relationship of a gas reservoir can be derived from the porosity-permeability relationship of a rock sample.

[0061] By determining the lower limit of permeability corresponding to the lower limit of porosity based on the porosity-permeability relationship, a fourth relationship between the lower limit of effective reservoir permeability and the gas column height can be obtained from the third relationship between the lower limit of effective reservoir porosity and the gas column height.

[0062] Step S14: Based on the third and fourth relations, obtain the effective reservoir property lower limit determination model, which is used to determine the effective reservoir property lower limit of the gas reservoir.

[0063] The method for determining the lower limit of effective reservoir properties of gas reservoirs provided in Embodiment 1 of this invention is based on the theory of secondary migration and accumulation of natural gas, considers the relationship between reservoir dynamics and resistance, and establishes a method for determining the lower limit of effective reservoir properties of gas reservoirs using the principle of mechanical equilibrium, which is different from commonly used statistical methods or empirical methods.

[0064] Considering the differences in gas column height, the effective reservoir physical property lower limit is determined for different locations of the gas reservoir. This method differs from the traditional single physical property lower limit method and can more accurately evaluate the geological reserves of different regions of the gas reservoir for gas reservoirs with large differences in tectonic amplitude.

[0065] In some embodiments, the first relationship between the critical gas-bearing throat radius and the gas column height of the gas reservoir, namely equation (4), is complex in form and includes parameters such as the surface tension between the gas and water phases (σ). gw air-water wetting angle θ gw Average throat radius R p The density difference between air and water Δρ gw Both gravitational acceleration (g) and the acceleration due to gravity are essentially constant under the same reservoir conditions. Therefore, in practical applications, they can also include:

[0066] The gas column heights at multiple locations in the reservoir are obtained, and the critical pore throat radius at each location is obtained based on the gas column height and the first relationship. Based on the critical pore throat radius at each location and the gas column height, the fitting relationship between the critical pore throat radius and the gas column height is obtained by fitting.

[0067] Accordingly, based on the second and first relationships between the median pore throat radius and porosity of a gas reservoir, a third relationship is established between the lower limit of effective reservoir porosity and the gas column height, which may specifically include:

[0068] Based on the second relationship between the median pore throat radius and porosity of a gas reservoir and the fitting relationship between the critical gas-bearing pore throat radius and the gas column height, a third relationship between the lower limit of effective reservoir porosity and the gas column height is established.

[0069] After obtaining the model for determining the lower limit of effective reservoir properties using the above method, for any location within the gas reservoir, as long as the gas column height at that location is determined, the lower limit of effective reservoir properties at that location can be obtained through the model, including the lower limits of effective reservoir porosity and permeability.

[0070] In some embodiments, the method may include: determining a gas column height map using a top surface structural map of the gas reservoir and the initial height of the gas column; dividing the gas reservoir into multiple regions based on the gas column height map and determining the average gas column height of each region; and determining a model based on the average gas column height of each region and the lower limit of effective reservoir properties to determine the lower limit of effective reservoir properties for that region.

[0071] Furthermore, refer to Figure 2 As shown, the initial height of the gas column is the height of the gas-water interface in the gas reservoir, or the height of the trap overflow line.

[0072] Similarly, for wells within a gas reservoir, the gas column height is determined based on the well logging data; by determining the model based on the gas column height and the lower limit of effective reservoir properties, the lower limit of effective reservoir properties of the well can be determined.

[0073] Using the above methods, the effective reservoir property lower limit can be determined for each region of the gas reservoir; it is also possible to determine the effective reservoir property lower limit for each well location individually.

[0074] Example 2

[0075] Embodiment 2 of the present invention provides a specific implementation flow of a method for determining the lower limit of effective reservoir properties in a gas reservoir. Taking the SGP gas reservoir as an example, the flow is as follows: Figure 3 As shown, it includes the following steps:

[0076] Step S31: Using the top surface structural map and reservoir profile map of the gas reservoir, determine the height of the continuous gas column in different parts of the gas reservoir.

[0077] Figure 4 , Figure 5a , Figure 5b These are the top structural diagram and reservoir profile of the SGP gas reservoir, respectively. Figure 5a for Figure 4 Cross-sectional view of the central survey line AA' Figure 5b Figure 4 Cross-sectional view of the central survey line BB'.

[0078] The SGP gas reservoir's proven reserves begin at an elevation of -4400m. A water-producing layer is found at -4350m in the eastern part of the reservoir, but no water layer was observed during gas testing in the southern part. During production, the proven reserves exhibited overall internal connectivity, with better inter-well connectivity at higher structural levels and relatively poorer connectivity at lower levels. Using -4400m as the starting point for the gas column height of the SGP gas reservoir, the reservoir is divided into several regions, A, B, C, and D, based on the gas column height. Figure 6 As shown.

[0079] Step S32: Based on the gas reservoir temperature, pressure, and fluid properties, calculate the critical pore throat radius corresponding to different gas column heights, and establish R. c ~h g Relationship diagram.

[0080] The SGP gas reservoir has a temperature of 120℃ and an original formation pressure of 60.6 MPa. Under these reservoir conditions, the gas-water interfacial tension σ gw =25mN / m, air-water wetting angle θ gw =0°, air-water density difference Δρ gw =0.73g / cm 3 Average throat radius R p =0.5μm, the critical pore throat radius corresponding to different gas column heights in the SGP gas reservoir can be calculated by equation (4), and the fitting relationship is R c =6896h g -0.998 ,like Figure 7 As shown.

[0081] Step S33: Based on the mercury intrusion porosimetry data of the rock samples, statistically analyze the relationship between the median pore throat radius and porosity, and establish a graph R showing the relationship between porosity and the median pore throat radius.50 ~φ.

[0082] R was obtained by fitting mercury injection data from 31 rock samples of the SGP gas reservoir. 50 ~φ has a good exponential relationship, and its expression is R 50 =3.9643e 0.6312φ ,like Figure 8 As shown.

[0083] Step S34: According to R c ~h g Relationship diagram and R 50 ~φ Relationship Chart Establishes the Relationship Between Porosity Lower Limit and Gas Column Height φ c ~h g .

[0084] Take R c =R 50 The fitting yielded h of the SGP gas reservoir. g ~φ c It forms a good exponentiation relationship, and its expression is φ. c =15.616h g -0.3465 ,like Figure 9 As shown.

[0085] Step S35: Calculate the lower limit of permeability corresponding to the lower limit of porosity using the relationship between the porosity and permeability parameters of the rock sample.

[0086] By fitting the parameters of the SGP gas reservoir rock samples, k was obtained. c ~φ c The relation is ,like Figure 10 As shown.

[0087] Step S36: According to φ c ~h g and k c ~φ c The relationship is used to determine the lower limit of effective reservoir properties corresponding to different gas column heights.

[0088] Table 1 shows the lower limit range of porosity and permeability in different regions of the SGP gas reservoir, and Table 2 shows the lower limit of effective reservoir properties for gas wells in different locations.

[0089] Table 1 Lower Limits of Effective Reservoir Properties in SGP Gas Reservoir Zones

[0090]

[0091] Table 2 Lower limits of effective reservoir properties in gas wells at different locations in SGP

[0092]

[0093]

[0094] Step S37: Determine the effective reservoir properties of the gas well using logging parameters based on the lower limit of effective reservoir properties in different locations.

[0095] Figure 11 The logging interpretation diagram for well G20 in the SGP gas reservoir shows a data point every 0.125m. According to the method of this invention, the gas column height of well G20 is 690m. The lower limit of effective reservoir porosity is determined to be 1.62%, and the lower limit of permeability is 0.025mD. Under these conditions, the effective reservoir thickness is 27.375m, the average porosity is 6.75%, and the average gas saturation is 80.85%. The lower limit of effective reservoir porosity determined in the SGP gas reservoir development plan is 2.5%. Under these conditions, the effective reservoir thickness of well G20 is 24.125m, the average porosity is 7.05%, and the average gas saturation is 82.69%. Based on the above data, the geological reserves of well G20 evaluated using this method are 6.28% higher than those in the development plan.

[0096] The evaluation table shows the geological reserves of gas wells in different locations within the SGP. Compared to the development plan, this method increased the average geological reserves of gas wells in Zone A by 3.64%, Zone B by 2.35%, Zone C by 0.26%, and Zone D by 32.81%. The area with the greatest change in geological reserves is Zone D. This area is located on the edge of the gas reservoir, with a small gas column height, poor reservoir properties, and low well-controlled dynamic reserves. The method of determining the effective reservoir property lower limit by zoning effectively reduces the difference between dynamic and static reserves of gas wells. Considering the differences in gas column height, the effective reservoir property lower limit is determined separately for different locations within the gas reservoir. This differs from the traditional single property lower limit method and can more accurately evaluate the geological reserves of different regions of the gas reservoir for gas reservoirs with significant structural differences.

[0097] Based on the inventive concept of this invention, embodiments of this invention also provide a device for determining the lower limit of effective reservoir properties in gas reservoirs, the structure of which is as follows: Figure 12 As shown, it includes:

[0098] The first relationship establishment module 121 is used to establish the first relationship between the critical gas-bearing throat radius and the gas column height of a gas reservoir based on the theory of secondary migration and accumulation of natural gas and the relationship between reservoir dynamics and resistance, using the principle of mechanical equilibrium.

[0099] The third relationship establishment module 122 is used to establish a third relationship between the effective reservoir porosity lower limit and the gas column height of the gas reservoir based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship.

[0100] The fourth relationship establishment module 123 is used to establish a fourth relationship between the lower limit of the effective reservoir permeability of the gas reservoir and the height of the gas column based on the porosity-permeability relationship of the gas reservoir and the third relationship.

[0101] The effective reservoir property lower limit determination model establishment module 124 is used to obtain the effective reservoir property lower limit determination model from the third relationship and the fourth relationship, and is used to determine the effective reservoir property lower limit of the gas reservoir.

[0102] Based on the inventive concept of the present invention, embodiments of the present invention also provide a computer program product, including a computer program / instruction, wherein the computer program / instruction, when executed by a processor, implements the above-mentioned method for determining the lower limit of effective reservoir properties of gas reservoirs.

[0103] Based on the inventive concept of the present invention, embodiments of the present invention also provide a server, including: a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the above-described method for determining the lower limit of effective reservoir properties of gas reservoirs.

[0104] Unless otherwise specifically stated, terms such as processing, calculation, operation, determination, display, etc., may refer to the actions and / or processes of one or more processing or computing systems or similar devices that represent the manipulation and conversion of data representing physical (e.g., electronic) quantities within the registers or memory of the processing system into other data similarly representing physical quantities within the memory, registers, or other such information storage, transmission, or display devices of the processing system. Information and signals can be represented using any of a variety of different techniques and methods. For example, data, instructions, commands, information, signals, bits, symbols, and chips mentioned throughout the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or particles, light fields or particles, or any combination thereof.

[0105] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to the specific order or hierarchy described.

[0106] In the above detailed description, various features are combined together in a single embodiment to simplify the embodiments of this subject matter. It would be necessary to clearly state more features in each claim. Instead, as reflected in the appended claims, the invention is presented with fewer features than all of the disclosed individual embodiments. Therefore, the appended claims are hereby clearly incorporated into the detailed description, wherein each claim stands alone as a preferred embodiment of the invention.

[0107] Those skilled in the art will also understand that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments herein can be implemented as electronic hardware, computer software, or a combination thereof. To clearly illustrate the interchangeability between hardware and software, the various illustrative components, blocks, modules, circuits, and steps described above are generally described in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. Those skilled in the art can implement the described functionality in alternative ways for each specific application; however, such implementation decisions should not be construed as departing from the scope of this disclosure.

[0108] The steps of the methods or algorithms described in conjunction with the embodiments herein can be directly embodied in hardware, software modules executed by a processor, or a combination thereof. The software modules can reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium well known in the art. An exemplary storage medium is connected to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and storage medium can reside in an ASIC. The ASIC can reside in a user terminal. Alternatively, the processor and storage medium can exist as discrete components in the user terminal.

[0109] For software implementation, the techniques described in this application can be implemented using modules (e.g., procedures, functions, etc.) that perform the functions described in this application. This software code can be stored in memory units and executed by a processor. The memory units can be implemented within the processor or outside the processor; in the latter case, they are communicatively coupled to the processor via various means, as is well known in the art.

[0110] The foregoing description includes examples of one or more embodiments. It is certainly impossible to describe all possible combinations of components or methods in order to describe the above embodiments, but those skilled in the art will recognize that further combinations and arrangements of the various embodiments are possible. Therefore, the embodiments described herein are intended to cover all such changes, modifications, and variations that fall within the scope of the appended claims. Furthermore, the term “comprising” as used in the specification or claims is interpreted in a manner similar to the term “including,” as it is understood when used as a conjunction in the claims. Additionally, the use of any term “or” in the specification of the claims is intended to mean “non-exclusive or.” The terms “first” and “second,” etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

Claims

1. A method for determining the lower limit of effective reservoir properties for gas reservoirs, characterized in that, include: Based on the theory of secondary migration and accumulation of natural gas and the relationship between accumulation dynamics and resistance, and utilizing the principle of mechanical equilibrium, the first relationship between the critical gas-bearing pore throat radius and the gas column height is established using the following formula through the pore throat parameters and gas-water interface parameters of the gas reservoir: ； in, The critical pore throat radius. The surface tension between the gas and water phases under gas reservoir conditions. To moisten the corner with air and water, The average pore throat radius, Due to the density difference between air and water, It is the acceleration due to gravity. This refers to the height of the air column; Based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship, a third relationship is established between the effective reservoir porosity lower limit and the gas column height of the gas reservoir. Based on the porosity-permeability relationship of the gas reservoir and the third relationship, a fourth relationship is established between the lower limit of the effective reservoir permeability and the height of the gas column. Based on the third and fourth relations, an effective reservoir property lower limit determination model is obtained, which is used to determine the effective reservoir property lower limit of the gas reservoir.

2. The method of claim 1, wherein, Also includes: The gas column heights at multiple locations in the gas reservoir are obtained, and the critical gas-bearing throat radius at each location is obtained based on the gas column height at each location and the first relationship. Based on the critical pore throat radius and gas column height at each location, a fitting relationship between the critical pore throat radius and gas column height of the gas reservoir is obtained; correspondingly, The establishment of a third relationship between the effective reservoir porosity lower limit and the gas column height, based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship, specifically includes: Based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the fitting relationship, a third relationship between the effective reservoir porosity lower limit and the gas column height is established.

3. The method of claim 1, wherein, The establishment of a third relationship between the effective reservoir porosity lower limit and the gas column height, based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship, specifically includes: The critical gas-bearing pore throat radius is taken as equal to the median pore throat radius. The critical gas-bearing pore throat radius is taken as the lower limit of porosity. Based on the second relationship between the median pore throat radius and porosity of the gas reservoir and the first relationship, a third relationship between the effective reservoir porosity lower limit and the gas column height of the gas reservoir is established.

4. The method of claim 1, wherein, Also includes: Using the top surface structure diagram of the gas reservoir and the initial height of the gas column, a gas column height diagram is determined; The gas reservoir is divided into multiple regions based on the gas column height map, and the average gas column height of each region is determined. The model is determined based on the average gas column height of each region and the lower limit of the effective reservoir properties, thereby determining the lower limit of the effective reservoir properties for that region.

5. The method of claim 4, wherein, The initial height of the gas column is the height of the gas-water interface of the gas reservoir, or the height of the trap overflow line.

6. The method of claim 1, wherein, Also includes: For the wells within the gas reservoir, the gas column height of the well is determined based on the well logging data. The model is determined based on the gas column height of the well and the lower limit of the effective reservoir properties, thereby determining the lower limit of the effective reservoir properties of the well.

7. The method according to any one of claims 1 to 6, characterized in that, The second relationship between the median pore throat radius and porosity was obtained from the mercury injection data of the rock samples from the gas reservoir; The porosity-permeability relationship of the gas reservoir is the porosity-permeability relationship of the rock sample.

8. A device for determining the lower limit of effective reservoir properties for gas reservoirs, characterized in that it comprises: include: The first relationship establishment module is used to establish the first relationship between the critical gas-bearing pore throat radius and the gas column height of a gas reservoir based on the theory of secondary migration and accumulation of natural gas and the relationship between reservoir dynamics and resistance, using the principle of mechanical equilibrium and the pore throat parameters and gas-water interface parameters of the gas reservoir, through the following formula: ； wherein, Rc is the critical gas pore throat radius, is the surface tension between gas and water under gas reservoir conditions, is the gas-water wetting angle, is the average pore throat radius, is the gas-water density difference, is the gravitational acceleration, is the gas column height; The third relationship establishment module is used to establish a third relationship between the effective reservoir porosity lower limit and the gas column height of the gas reservoir based on the second relationship between the median pore throat radius and porosity and the first relationship. The fourth relationship establishment module is used to establish a fourth relationship between the lower limit of the effective reservoir permeability of the gas reservoir and the height of the gas column based on the porosity-permeability relationship of the gas reservoir and the third relationship. The effective reservoir property lower limit determination model module is used to obtain the effective reservoir property lower limit determination model from the third relation and the fourth relation, and is used to determine the effective reservoir property lower limit of the gas reservoir.

9. A computer program product comprising computer programs / instructions, characterized in that, When the computer program / instruction is executed by the processor, it implements the method for determining the lower limit of effective reservoir properties of gas reservoirs as described in any one of claims 1 to 7.

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