Method, device, equipment and medium for determining the maximum air column height that can be tolerated by the cap layer

Abstract

The present application provides a method, device, equipment and medium for determining the maximum tolerable gas column height of a cap layer, wherein the method comprises: obtaining the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in a hydrate accumulation zone at different depths; wherein the cap layer in the hydrate accumulation zone is a shallow hydrate accumulation zone cap layer under a tensile stress state; determining the minimum fracture pressure of the cap layer in the hydrate accumulation zone according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation zone; determining the maximum tolerable gas column height of the cap layer in the hydrate accumulation zone according to the minimum fracture pressure, which can improve the accuracy of the determined maximum tolerable gas column height, thereby improving the safety during hydrate exploitation and reducing the risk of gas leakage.

Description

Technical Field

[0001] The present application relates to the technical field of geological exploration and development of oil and gas reservoirs, and in particular to a method, device, equipment, and medium for determining the maximum tolerable gas column height of a cap layer. Background Art

[0002] Natural gas hydrates, which usually exist in shallow unconsolidated sediments in the deep sea, are a potential clean energy source. The cap rock in these hydrate accumulation areas, that is, the sedimentary layer covering the hydrates, is crucial to ensure the stable exploitation of natural gas hydrates, because during the hydrate exploitation process, once the height of the gas column accumulated below the cap rock exceeds the tolerable range of the cap rock, the cap rock will rupture, leading to the risk of disasters such as gas leakage.

[0003] Therefore, there is an urgent need for a method to determine the maximum tolerable gas column height of the caprock to improve the safety of hydrate mining and reduce the risk of gas leakage. Summary of the invention

[0004] The present application provides a method, device, equipment, and medium for determining the maximum tolerable gas column height of a cap rock, so as to improve the safety during hydrate mining.

[0005] In a first aspect, an embodiment of the present application provides a method for determining a maximum tolerable air column height of a cap layer, comprising:

[0006] Obtaining the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; wherein the cap layer in the hydrate accumulation area is a cap layer in the shallow hydrate accumulation area under a tensile stress state;

[0007] Determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area;

[0008] The maximum tolerable gas column height of the caprock in the hydrate accumulation zone is determined according to the minimum value of the fracture pressure.

[0009] Optionally, the horizontal minimum principal stress of the caprock in the hydrate accumulation area at different depths is obtained, including:

[0010] Obtaining rock mechanical parameters of the caprock in the hydrate accumulation area; wherein the rock mechanical parameters are obtained by conducting a rock mechanical property test on core samples in the caprock in the hydrate accumulation area;

[0011] Obtaining the formation density of the target formation at different depths, and determining the vertical principal stress of the cap layer in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths; the target formation includes the cap layer in the hydrate accumulation area and the formation above the cap layer;

[0012] The vertical principal stress, pore fluid pressure and rock mechanics parameters are substituted into Huang's model for calculation to obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation zone at different depths.

[0013] Optionally, determining the vertical principal stress of the caprock in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths includes:

[0014] Using the formula Calculating the vertical principal stress of the caprock in the hydrate accumulation area at different depths;

[0015] Among them, σ v is the vertical principal stress; h is the depth value corresponding to the depth to be calculated of the cap layer in the hydrate accumulation zone; ρ(h) is the function of the target formation density changing with depth; g is the gravitational acceleration; ρ w is the seawater density above the hydrate accumulation area; h0 is the seawater depth above the hydrate accumulation area.

[0016] Optionally, determining the minimum value of the fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths includes:

[0017] According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined;

[0018] According to the fracture pressure of the cap layer in the hydrate accumulation area at different depths, the minimum fracture pressure of the cap layer in the hydrate accumulation area is determined.

[0019] Optionally, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, including:

[0020] Using the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths;

[0021] in, is the minimum horizontal principal stress; P w is the pore fluid pressure; is the tensile strength of rock.

[0022] Optionally, determining the maximum tolerable gas column height of the caprock in the hydrate accumulation zone according to the minimum value of the fracture pressure includes:

[0023] The maximum tolerable gas column height of the caprock in the hydrate accumulation area is calculated using the following formula:

[0024]

[0025] Among them, h g is the maximum tolerable air column height; ρ w is the seawater density above the hydrate accumulation area; ρ g is the density of the gas accumulated under the cap layer of the hydrate accumulation area; It is the minimum fracture pressure of the cap rock in the hydrate accumulation area.

[0026] Optionally, determining the minimum value of the fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths includes:

[0027] Determine the minimum fracture pressure of the cap layer in the hydrate accumulation zone and the depth corresponding to the minimum fracture pressure according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths;

[0028] Accordingly, the method further includes:

[0029] Obtaining a depth contour map of the cap layer in the hydrate accumulation area;

[0030] The position corresponding to the minimum rupture pressure value is determined according to the minimum rupture pressure value and the depth contour map.

[0031] In a second aspect, an embodiment of the present application provides a device for determining a maximum tolerable air column height of a cap layer, comprising:

[0032] An acquisition module is used to obtain the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer of the hydrate accumulation area at different depths; wherein the cap layer of the hydrate accumulation area is the cap layer of the shallow hydrate accumulation area under the tensile stress state;

[0033] The first determination module is used to determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area;

[0034] The second determination module is used to determine the maximum tolerable gas column height of the caprock in the hydrate accumulation area according to the minimum value of the fracture pressure.

[0035] In a third aspect, an embodiment of the present application provides an electronic device, comprising: a processor, and a memory communicatively connected to the processor;

[0036] The memory stores computer-executable instructions;

[0037] The processor executes the computer-executable instructions stored in the memory to implement the method according to the first aspect.

[0038] In a fourth aspect, an embodiment of the present application provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions, and when the computer-executable instructions are executed by a processor, they are used to implement the method described in the first aspect.

[0039] In a fifth aspect, an embodiment of the present application provides a computer program product, including a computer program, which implements the method described in the first aspect when executed by a processor.

[0040] The present application provides a method, device, equipment, and medium for determining the maximum tolerable gas column height of the cap layer, the method comprising: obtaining the horizontal minimum principal stress, pore fluid pressure, and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; wherein the cap layer in the hydrate accumulation area is a shallow hydrate accumulation area cap layer under a tensile stress state; according to the horizontal minimum principal stress, pore fluid pressure, and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, determining the minimum value of the fracture pressure of the cap layer in the hydrate accumulation area; the minimum value of the fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area; according to the minimum value of the fracture pressure, determining the maximum tolerable gas column height of the cap layer in the hydrate accumulation area. The accuracy of the determined maximum tolerable gas column height can be improved, thereby improving the safety during hydrate mining and reducing the risk of disasters such as gas leakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0042] Figure 1 An application scenario diagram provided for an embodiment of the present application;

[0043] Figure 2 A schematic flow chart of a method for determining the maximum tolerable air column height of a cover layer provided in an embodiment of the present application;

[0044] Figure 3A schematic diagram of a seismic profile provided in an embodiment of the present application;

[0045] Figure 4 A histogram of fracture pressures at different positions of a cap layer provided in an embodiment of the present application;

[0046] Figure 5 A histogram of the tolerable air column height at different positions of a cover layer provided in an embodiment of the present application;

[0047] Figure 6 A schematic diagram of the structure of a device for determining the maximum air column height that a cover layer can withstand provided in an embodiment of the present application;

[0048] Figure 7 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application.

[0049] The above drawings have shown clear embodiments of the present application, which will be described in more detail later. These drawings and text descriptions are not intended to limit the scope of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0050] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0051] Natural gas hydrates, which usually exist in shallow unconsolidated sediments in the deep sea, are a potential clean energy source. The cap rock in these hydrate accumulation areas, that is, the sedimentary layer covering the hydrates, is crucial to ensure the stable exploitation of natural gas hydrates, because during the hydrate exploitation process, once the height of the gas column accumulated below the cap rock exceeds the tolerable range of the cap rock, the cap rock will rupture, leading to the risk of disasters such as gas leakage.

[0052] In addition, during the geological storage of carbon dioxide in the sea, if the gas injection pressure is too high and exceeds the upper pressure limit of the cap rock, the risk of carbon dioxide leakage will be greatly increased.

[0053] In view of this, the present application provides a method for determining the maximum tolerable gas column height of a cap layer, which is used to determine the maximum tolerable gas column height corresponding to the cap layer in a shallow hydrate accumulation area under a tensile stress state. First, the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths are obtained, and the minimum fracture pressure corresponding to the cap layer in the hydrate accumulation area is determined according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; finally, according to the minimum fracture pressure, the maximum tolerable gas column height corresponding to the cap layer in the hydrate accumulation area is determined. The present application determines the minimum fracture pressure corresponding to the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, fluid pressure and rock tensile strength corresponding to the strata at different depths, and then determines the maximum tolerable gas column height corresponding to the cap layer in the hydrate accumulation area according to the minimum fracture pressure. The accuracy of the determined maximum tolerable gas column height can be improved, thereby improving the safety during hydrate exploitation and reducing the risk of disasters such as gas leakage.

[0054] Figure 1 An application scenario diagram provided for an embodiment of the present application, such as Figure 1 As shown, the user inputs the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths through the user device, wherein the input form of the horizontal minimum principal stress and the pore fluid pressure can be a function. For example, the user inputs the function of the horizontal minimum principal stress varying with depth and the function of the pore fluid pressure varying with depth through the user device, and clicks the confirmation button after the input is completed. The user device sends the function of the horizontal minimum principal stress varying with depth, the function of the pore fluid pressure varying with depth, and the rock tensile strength to the server. The server determines the minimum fracture pressure corresponding to the cap layer in the hydrate accumulation zone according to the received function of the horizontal minimum principal stress varying with depth, the function of the pore fluid pressure varying with depth, and the rock tensile strength, and then determines the maximum tolerable gas column height corresponding to the cap layer in the hydrate accumulation zone according to the minimum fracture pressure. Finally, the server sends the maximum tolerable gas column height to the user device, and the user device displays the maximum tolerable gas column height on the display page after receiving it.

[0055] The technical solution of the present application and how the technical solution of the present application solves the above-mentioned technical problems are described in detail below with specific embodiments. The following specific embodiments can be combined with each other, and the same or similar concepts or processes may not be repeated in some embodiments. The embodiments of the present application will be described below in conjunction with the accompanying drawings.

[0056] Figure 2The flowchart of a method for determining the maximum air column height that a cover layer can withstand provided in an embodiment of the present application is shown in FIG. The execution subject of this embodiment can be any device with data processing function. This application uses a server as the execution subject for specific description. Figure 2 As shown, a method for determining the maximum tolerable air column height of a cap layer provided in an embodiment of the present application may include:

[0057] Step 201, obtaining the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the hydrate accumulation zone cap layer at different depths; wherein the hydrate accumulation zone cap layer is a shallow hydrate accumulation zone cap layer under a tensile stress state.

[0058] It should be noted that the geostress field refers to the distribution of stress at each point in the earth's crust. The forces in the geostress field include: vertical principal stress, horizontal minimum principal stress and horizontal maximum principal stress.

[0059] Among them, the direction of the vertical principal stress is the vertical direction, and the horizontal minimum principal stress and the horizontal maximum principal stress are both in the horizontal direction; among them, under the tensile stress state, the vertical principal stress is the stress with the largest value among the three principal stresses, the horizontal maximum principal stress is the stress with the middle value among the three principal stresses, and the horizontal minimum principal stress is the stress with the smallest value among the three principal stresses.

[0060] Pore ​​fluid pressure refers to the pressure of the fluid in the pores of underground formation rocks. Since shallow unconsolidated formations usually have normal formation pressure, the pore fluid pressure is equal to or close to the hydrostatic pressure, that is, the pressure generated by the weight of a static water column. It can be expressed by the formula Calculate, where is the pore fluid pressure, in MPa; h is the depth, in m; ρ w is the seawater density above the hydrate accumulation area, in g / cm 3 ; g is the acceleration due to gravity, which can be taken as 9.80m / s 2 The density of seawater above the hydrate accumulation area is 1.025 g / cm 3 When , the formula for the variation of pore fluid pressure at different depths in the caprock of the hydrate accumulation zone with depth is: .

[0061] Rock tensile strength refers to the ability of rock to resist damage under tensile load. It is a measure of the maximum stress value that rock materials can withstand under tensile stress.

[0062] The rock tensile strength is obtained by conducting rock mechanical property tests on core samples in the caprock of the hydrate accumulation area.

[0063] Specifically, the server obtains the horizontal minimum principal stress and pore fluid pressure of the cap layer in the hydrate accumulation area at different depths, as well as the rock tensile strength of the cap layer in the hydrate accumulation area.

[0064] Optionally, the horizontal minimum principal stress of the caprock in the hydrate accumulation area at different depths is obtained, including:

[0065] Obtaining rock mechanical parameters of the caprock in the hydrate accumulation area; wherein the rock mechanical parameters are obtained by conducting a rock mechanical property test on core samples in the caprock in the hydrate accumulation area;

[0066] Obtaining the formation density of the target formation at different depths, and determining the vertical principal stress of the cap layer in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths; the target formation includes the cap layer in the hydrate accumulation area and the formation above the cap layer;

[0067] The vertical principal stress, pore fluid pressure and rock mechanics parameters are substituted into Huang's model for calculation to obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation zone at different depths.

[0068] Among them, rock mechanics parameters refer to parameters related to the mechanical properties of rocks under stress, such as elasticity, elastoplasticity, rheology, brittleness, toughness, heat generation, etc., which may include: compressive strength, tensile strength, shear strength, elastic modulus, plastic modulus, Poisson's ratio, friction angle and failure criterion parameters.

[0069] There is still strata covering the cap layer in the hydrate accumulation area, and there is seawater above the strata. The target strata include the cap layer in the hydrate accumulation area and the strata above the cap layer.

[0070] Specifically, sediment cores are taken out from the cap layer in the hydrate accumulation area, and rock mechanical parameters can be obtained by conducting rock mechanical property tests on the sediment core samples. The user inputs the rock mechanical parameters of the cap layer in the hydrate accumulation area and the formation density of the target formation at different depths through the user device, wherein the formation density of the target formation at different depths can be a function of the change of the target formation density with depth. Click the confirmation button, and the user device sends the rock mechanical parameters and the formation density of the target formation at different depths to the server.

[0071] After the server obtains the formation density of the target formation at different depths, the vertical principal stress of the cap layer in the hydrate accumulation area at different depths is determined according to the formation density of the target formation at different depths.

[0072] Substitute the vertical principal stress and the obtained rock mechanics parameters into the Huang model The calculations were performed to obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation area at different depths.

[0073] Among them, σ v is the vertical principal stress, in MPa; P w is the pore fluid pressure, MPa; μ is the static Poisson's ratio, α is the Biot coefficient; β2 is the tectonic stress coefficient. The Biot coefficient is a parameter used in rock mechanics and geomechanics to describe the relationship between the effective stress and the total stress of porous media (such as rock or soil) under external stress. The tectonic stress coefficient is an important parameter used in geomechanics and rock mechanics to describe the stress state of the crust, which reflects the characteristics of the tectonic stress field of the crust; the static Poisson's ratio and Biot coefficient are obtained by testing the rock mechanical properties of core samples in the caprock of the hydrate accumulation area; the tectonic stress coefficient β2 can be an empirical value selected based on the actual situation of the hydrate accumulation area.

[0074] In this way, the rock mechanical parameters obtained from the rock mechanical properties test of the sediment core samples in the cap rock in the hydrate accumulation area and the vertical principal stress at different depths determined according to the formation density are substituted into the Huang model for calculation to obtain the horizontal minimum principal stress at different depths, which can improve the accuracy of the determined horizontal minimum principal stress.

[0075] Optionally, determining the vertical principal stress of the caprock in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths includes:

[0076] Using the formula Calculating the vertical principal stress of the caprock in the hydrate accumulation area at different depths;

[0077] Among them, σ v is the vertical principal stress; h is the depth value corresponding to the depth to be calculated of the cap layer in the hydrate accumulation zone; ρ(h) is the function of the target formation density changing with depth; g is the gravitational acceleration; ρ w is the seawater density above the hydrate accumulation area; h0 is the seawater depth above the hydrate accumulation area.

[0078] Specifically, for each stratum at each depth, the vertical principal stress corresponding to the stratum includes the pressure generated by the gravity of all strata above the stratum and the pressure generated by the gravity of the entire water body above the seabed.

[0079] Vertical principal stress of caprock in hydrate accumulation area at different depths , where σ v is the vertical principal stress, in MPa; h is the depth value corresponding to the depth to be calculated of the cap layer in the hydrate accumulation zone, in m; ρ(h) is the function of the target formation density changing with depth, which is obtained from density logging; g is the gravitational acceleration, which can be taken as 9.80 m / s2 ρ w is the seawater density above the hydrate accumulation area, in g / cm 3 ; h0 is the seawater depth above the hydrate accumulation area, in meters.

[0080] Thus, using the formula Calculating the vertical principal stress of the caprock in the hydrate accumulation zone at different depths can improve the accuracy of the determined vertical principal stress.

[0081] Step 202: determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area.

[0082] Specifically, the server determines the minimum fracture pressure corresponding to the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths.

[0083] Optionally, determining the minimum value of the fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths includes:

[0084] According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined;

[0085] According to the fracture pressure of the cap layer in the hydrate accumulation area at different depths, the minimum fracture pressure of the cap layer in the hydrate accumulation area is determined.

[0086] Specifically, the server determines the fracture pressure of the cap layer in the hydrate accumulation zone at different depths based on the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths, wherein the fracture pressure at different depths may be a function of the variation of the fracture pressure with depth.

[0087] The server calculates the minimum value of the function of fracture pressure changing with depth, and obtains the minimum fracture pressure of the cap rock in the hydrate accumulation area.

[0088] In this way, the function of how the fracture pressure changes with depth is first determined, and then the minimum fracture pressure is determined by calculating the minimum value of the function, thereby improving the accuracy of the determined minimum fracture pressure.

[0089] Optionally, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, including:

[0090] Using the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths;

[0091] in, is the minimum horizontal principal stress; P w is the pore fluid pressure; is the tensile strength of rock.

[0092] Specifically, the server uses the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths, where: is the minimum horizontal principal stress, is the pore fluid pressure, is the tensile strength of rock. and Both can be functions that vary with depth.

[0093] Thus, using the formula The accuracy of the calculated fracture pressure of the caprock in the hydrate accumulation zone at different depths can be improved.

[0094] Optionally, determining the minimum value of the fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths includes:

[0095] Determine the minimum fracture pressure of the cap layer in the hydrate accumulation zone and the depth corresponding to the minimum fracture pressure according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths;

[0096] Accordingly, the method further includes:

[0097] Obtaining a depth contour map of the cap layer in the hydrate accumulation area;

[0098] The position corresponding to the minimum rupture pressure value is determined according to the minimum rupture pressure value and the depth contour map.

[0099] Specifically, the server determines the fracture pressure of the cap layer in the hydrate accumulation area at different depths according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, wherein the fracture pressure at different depths can be a function of the fracture pressure varying with depth. The server calculates the minimum value of the function of the fracture pressure varying with depth and the depth corresponding to the minimum value, and obtains the minimum fracture pressure of the cap layer in the hydrate accumulation area and the depth corresponding to the minimum fracture pressure.

[0100] Afterwards, the server obtains the depth contour map corresponding to the cap layer in the hydrate accumulation area; the position corresponding to the minimum fracture pressure can be determined based on the depth corresponding to the minimum fracture pressure and the depth contour map.

[0101] Among them, the Depth Contour Map is a chart used to represent topography or underwater topography (such as the seabed, lake bottom or riverbed). It uses contour lines (contours or isobaths) to show areas of different depths.

[0102] In this way, not only the minimum fracture pressure corresponding to the cap rock can be determined, but also the depth corresponding to the minimum fracture pressure can be determined. Then, combined with the depth contour map, the position corresponding to the minimum fracture pressure can be determined. The position corresponding to the minimum fracture pressure is the location where leaky hydrates develop after the cap rock ruptures. This is very important for revealing the distribution law of leaky hydrates and clarifying the dynamic evolution mechanism of leaky hydrates, because only when the height of the gas column accumulated under the cap rock reaches a certain value, exceeding the tolerable range of the cap rock, will the cap rock rupture, leading to the development of leaky hydrates.

[0103] Step 203: Determine the maximum tolerable gas column height of the caprock in the hydrate accumulation area according to the minimum value of the fracture pressure.

[0104] Specifically, the server determines the maximum tolerable gas column height corresponding to the caprock in the hydrate accumulation area according to the minimum fracture pressure.

[0105] The present application provides a method for determining the maximum tolerable gas column height of the cap layer, and obtains the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; wherein the cap layer in the hydrate accumulation area is a shallow hydrate accumulation area cap layer under a tensile stress state; according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the minimum fracture pressure of the cap layer in the hydrate accumulation area is determined; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area;

[0106] According to the minimum value of the fracture pressure, the maximum tolerable gas column height of the caprock in the hydrate accumulation area is determined, which can improve the accuracy of the determined maximum tolerable gas column height, thereby improving the safety of the hydrate mining process and reducing the risk of disasters such as gas leakage.

[0107] Optionally, determining the maximum tolerable gas column height of the caprock in the hydrate accumulation zone according to the minimum value of the fracture pressure includes:

[0108] The maximum tolerable gas column height of the caprock in the hydrate accumulation area is calculated using the following formula:

[0109]

[0110] Among them, h g is the maximum tolerable air column height; ρ w is the seawater density above the hydrate accumulation area; ρ g is the density of the gas accumulated under the cap layer of the hydrate accumulation area; It is the minimum fracture pressure of the cap rock in the hydrate accumulation area.

[0111] Specifically, the server uses the formula The maximum tolerable gas column height of the cap rock in the hydrate accumulation zone is calculated, where: is the maximum tolerable air column height, in m; is the seawater density above the hydrate accumulation area, in g / cm 3 ; is the gas density accumulated under the cap layer of the hydrate accumulation area, in g / cm 3 ; It is the minimum fracture pressure of the caprock in the hydrate accumulation area, in MPa.

[0112] In this way, the maximum tolerable gas column height of the caprock in the hydrate accumulation zone is determined using the above formula, which can improve the accuracy of the determined maximum tolerable gas column height.

[0113] The method of the present application is used to determine the maximum tolerable gas column height of the caprock in a shallow hydrate accumulation zone under a certain tensile stress state.

[0114] First, the situation of the hydrate accumulation area is introduced. The gas source in the hydrate accumulation area mainly comes from deep gas reservoirs, and the accumulation forms are hydrates, low-saturation natural gas and medium-to-high saturation natural gas reservoirs. Relatively high porosity and permeability reservoirs are developed in the area, which are the main accumulation strata of hydrates and natural gas. Above the reservoirs are cap rocks formed by fine-grained mud deposits. The cap rocks are widely distributed and continuous in the plane, providing good sealing conditions for the accumulation of natural gas and hydrates. The cap rocks above the relatively high porosity and permeability reservoirs in the hydrate accumulation area have good 3D seismic and logging data, and the interpretation of the 3D seismic and logging data of the target cap rocks has been completed.

[0115] Implementation process:

[0116] 1. Calculation of vertical principal stress: The water depth above the seabed in the hydrate accumulation area is 1725m. Based on density logging, the vertical principal stress of the caprock in the hydrate accumulation area at different depths is obtained. The relationship with depth h is: .

[0117] 2. Calculation of pore fluid pressure: Since the hydrate accumulation zone is in the shallow unconsolidated formation, the pore fluid pressure adopts the hydrostatic pressure, that is, ,in, is the pore fluid pressure at different depths, in MPa.

[0118] 3. Calculation of rock tensile strength: Rock mechanical properties tests were conducted on sediment core samples in the caprock of the hydrate accumulation area, and the rock tensile strength was T = 1.197MPa.

[0119] 4. Calculate the minimum horizontal principal stress: Substitute the rock mechanical parameters obtained from the rock mechanical properties test of the sediment core sample, such as the static Poisson's ratio μ=0.26, the tectonic stress coefficient β2 of 0.235, and the vertical principal stress and pore fluid pressure at different depths into the Huang model to calculate the minimum horizontal principal stress. h The relationship with depth h is:

[0120] h

[0121] 5. Calculate the fracture pressure: Substitute the rock tensile strength, pore fluid pressure and horizontal minimum principal stress into P g =σ h -P w +T calculates the burst pressure P g The relationship with depth h is:

[0122] P g =0.003955h-5.7594

[0123] 6. Calculate the maximum gas column height: the gas density of the hydrate accumulation area ρ g =0.168g / cm 3 Substitution The calculated relationship between the maximum bearing air column height and the depth h is:

[0124] h g =0.47h-685.76

[0125] Table 1 shows some corresponding data of the fracture pressure and depth corresponding to the bottom boundary of the cap rock in the hydrate accumulation area.

[0126]

[0127]

[0128] Figure 3 A schematic diagram of a seismic profile provided in an embodiment of the present application, such as Figure 3 As shown, there are 10 positions, namely P1, P2, P3, P4, P5, P6, P7, P8, P9, and P10. The fracture pressures corresponding to the formations at different depths are arranged in order from small to large to obtain a fracture pressure sequence. The first 10 values ​​in the fracture pressure sequence are taken, and the positions corresponding to the first 10 values ​​are the 10 positions in the figure. Among them, the fracture pressure corresponding to P1 is 1.402MPa, the fracture pressure corresponding to P2 is 1.412MPa, the fracture pressure corresponding to P3 is 1.423MPa, the fracture pressure corresponding to P4 is 1.405MPa, the fracture pressure corresponding to P5 is 1.435MPa, the fracture pressure corresponding to P6 is 1.448MPa, the fracture pressure corresponding to P7 is 1.447MPa, the fracture pressure corresponding to P8 is 1.440MPa, the fracture pressure corresponding to P9 is 1.445MPa, and the fracture pressure corresponding to P10 is 1.433MPa.

[0129] Figure 4 A histogram of the fracture pressure at different positions of the cap layer provided in the embodiment of the present application is shown in FIG. Figure 4 As shown, the figure contains Figure 3 The bursting pressure corresponding to each of the 10 positions from P1 to P10.

[0130] Figure 5 A histogram of the tolerable air column height at different positions of the cover layer provided in the embodiment of the present application is shown in FIG. Figure 5As shown, the air column height corresponding to P1 is 165.231m, the air column height corresponding to P2 is 166.439m, the air column height corresponding to P3 is 167.796m, the air column height corresponding to P4 is 165.670m, the air column height corresponding to P5 is 169.241m, the air column height corresponding to P6 is 170.691m, the air column height corresponding to P7 is 170.585m, the air column height corresponding to P8 is 169.767m, the air column height corresponding to P9 is 170.336m, and the air column height corresponding to P10 is 168.999m.

[0131] The minimum value of the air column height corresponding to each of the 10 positions from P1 to P10 is taken, which is the maximum tolerable air column height corresponding to the cap layer, which is 165.231m, and the corresponding position is P1.

[0132] Corresponding to the above-mentioned method for determining the maximum tolerable air column height of the cover layer, an embodiment of the present application also provides a device for determining the maximum tolerable air column height of the cover layer. Figure 6 This is a schematic diagram of the structure of a device for determining the maximum air column height that a cover layer can withstand provided in an embodiment of the present application. Figure 6 As shown, the device comprises:

[0133] An acquisition module 601 is used to acquire the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; wherein the cap layer in the hydrate accumulation area is a cap layer in the shallow hydrate accumulation area under a tensile stress state;

[0134] The first determination module 602 is used to determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area;

[0135] The second determination module 603 is used to determine the maximum tolerable gas column height of the caprock in the hydrate accumulation area according to the minimum value of the fracture pressure.

[0136] Optionally, when acquiring the horizontal minimum principal stress of the cap layer in the hydrate accumulation area at different depths, the acquisition module 601 is specifically used to:

[0137] Obtaining rock mechanical parameters of the caprock in the hydrate accumulation area; wherein the rock mechanical parameters are obtained by conducting a rock mechanical property test on core samples in the caprock in the hydrate accumulation area;

[0138] Obtaining the formation density of the target formation at different depths, and determining the vertical principal stress of the cap layer in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths; the target formation includes the cap layer in the hydrate accumulation area and the formation above the cap layer;

[0139] The vertical principal stress, pore fluid pressure and rock mechanics parameters are substituted into Huang's model for calculation to obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation zone at different depths.

[0140] Optionally, when determining the vertical principal stress of the caprock in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths, the acquisition module 601 is specifically used to:

[0141] Using the formula Calculating the vertical principal stress of the caprock in the hydrate accumulation area at different depths;

[0142] Among them, σ v is the vertical principal stress; h is the depth value corresponding to the depth to be calculated of the cap layer in the hydrate accumulation zone; ρ(h) is the function of the target formation density changing with depth; g is the gravitational acceleration; ρ w is the seawater density above the hydrate accumulation area; h0 is the seawater depth above the hydrate accumulation area.

[0143] Optionally, the first determining module 602 is specifically configured to:

[0144] According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined;

[0145] According to the fracture pressure of the cap layer in the hydrate accumulation area at different depths, the minimum fracture pressure of the cap layer in the hydrate accumulation area is determined.

[0146] Optionally, when determining the fracture pressure of the cap layer in the hydrate accumulation area at different depths according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the first determination module 602 is specifically used to:

[0147] Using the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths;

[0148] in, is the minimum horizontal principal stress; P w is the pore fluid pressure; is the tensile strength of rock.

[0149] Optionally, the second determining module 603 is specifically configured to:

[0150] The maximum tolerable gas column height of the caprock in the hydrate accumulation area is calculated using the following formula:

[0151]

[0152] Among them, h g is the maximum tolerable air column height; ρ w is the seawater density above the hydrate accumulation area; ρ g is the density of the gas accumulated under the cap layer of the hydrate accumulation area; It is the minimum fracture pressure of the cap rock in the hydrate accumulation area.

[0153] Optionally, the first determining module 602 is specifically configured to:

[0154] Determine the minimum fracture pressure of the cap layer in the hydrate accumulation zone and the depth corresponding to the minimum fracture pressure according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths;

[0155] Accordingly, the first determining module 602 is further configured to:

[0156] Obtaining a depth contour map of the cap layer in the hydrate accumulation area;

[0157] The position corresponding to the minimum rupture pressure value is determined according to the minimum rupture pressure value and the depth contour map.

[0158] The specific implementation principle and effect of the device for determining the maximum tolerable air column height of the cover layer provided in the embodiment of the present application can be found in the aforementioned embodiment and will not be repeated here.

[0159] Figure 7 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present application. Figure 7 As shown, the electronic device of this embodiment may include:

[0160] at least one processor 701; and

[0161] A memory 702 communicatively connected to the at least one processor;

[0162] The memory 702 stores instructions that can be executed by the at least one processor 701, and the instructions are executed by the at least one processor 701 to enable the electronic device to execute the method described in any of the above embodiments.

[0163] Optionally, the memory 702 may be independent or integrated with the processor 701 .

[0164] The implementation principle and technical effects of the electronic device provided in this embodiment can be found in the aforementioned embodiments and will not be described in detail here.

[0165] An embodiment of the present application further provides a computer-readable storage medium, wherein the computer-readable storage medium stores computer-executable instructions. When a processor executes the computer-executable instructions, the method described in any of the above embodiments is implemented.

[0166] An embodiment of the present application further provides a computer program product, including a computer program, which implements the method described in any of the above embodiments when executed by a processor.

[0167] In the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are only schematic, for example, the division of the modules is only a logical function division, and there may be other division methods in actual implementation, such as multiple modules can be combined or integrated into another system, or some features can be ignored or not executed.

[0168] The above-mentioned integrated module implemented in the form of a software function module can be stored in a computer-readable storage medium. The above-mentioned software function module is stored in a storage medium, including a number of instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) or a processor to perform some steps of the method described in each embodiment of the present application.

[0169] It should be understood that the above-mentioned processor can be a processing unit (Central Processing Unit, CPU), or other general-purpose processors, digital signal processors (Digital Signal Processor, DSP), application-specific integrated circuits (Application Specific Integrated Circuit, ASIC), etc. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc. The steps of the method disclosed in the application can be directly embodied as being executed by a hardware processor, or executed by a combination of hardware and software modules in the processor. The memory may include high-speed random access memory (Random Access Memory, RAM), and may also include non-volatile memory (Non-Volatile Memory, NVM), such as at least one disk storage, and can also be a USB flash drive, a mobile hard disk, a read-only memory, a disk or an optical disk, etc.

[0170] The above storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk or optical disk. The storage medium can be any available medium that can be accessed by a general or special-purpose computer.

[0171] An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an application specific integrated circuit (ASIC). Of course, the processor and the storage medium can also exist as discrete components in an electronic device or a main control device.

[0172] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0173] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0174] Through the description of the above implementation methods, those skilled in the art can clearly understand that the above-mentioned embodiment methods can be implemented by means of software plus a necessary general hardware platform, and of course by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present application, or the part that contributes to the prior art, can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for enabling a terminal device (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) to execute the methods described in each embodiment of the present application.

[0175] The above are only preferred embodiments of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for determining the maximum tolerable air column height of a cap layer, characterized in that: include: Obtaining the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; wherein the cap layer in the hydrate accumulation area is a cap layer in the shallow hydrate accumulation area under a tensile stress state; Determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the minimum horizontal principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area; Determining the maximum tolerable gas column height of the caprock in the hydrate accumulation area according to the minimum value of the fracture pressure; According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap rock in the hydrate accumulation zone at different depths, the minimum value of the fracture pressure of the cap rock in the hydrate accumulation zone is determined, including: According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined; Determining a minimum value of the rupture pressure of the cap layer in the hydrate accumulation area according to the rupture pressure of the cap layer in the hydrate accumulation area at different depths; According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap rock in the hydrate accumulation area at different depths, the fracture pressure of the cap rock in the hydrate accumulation area at different depths is determined, including: Using the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths; in, is the minimum horizontal principal stress; P w is the pore fluid pressure; is the tensile strength of rock.

2. The method according to claim 1, characterized in that Obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation area at different depths, including: Obtaining rock mechanical parameters of the caprock in the hydrate accumulation area; wherein the rock mechanical parameters are obtained by conducting a rock mechanical property test on core samples in the caprock in the hydrate accumulation area; Obtaining the formation density of the target formation at different depths, and determining the vertical principal stress of the cap layer in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths; the target formation includes the cap layer in the hydrate accumulation area and the formation above the cap layer; The vertical principal stress, pore fluid pressure and rock mechanics parameters are substituted into Huang's model for calculation to obtain the horizontal minimum principal stress of the caprock in the hydrate accumulation zone at different depths.

3. The method according to claim 2, characterized in that Determining the vertical principal stress of the cap rock in the hydrate accumulation area at different depths according to the formation density of the target formation at different depths includes: Using the formula Calculating the vertical principal stress of the caprock in the hydrate accumulation area at different depths; Among them, σ v is the vertical principal stress; h is the depth value corresponding to the depth to be calculated of the cap layer in the hydrate accumulation zone; ρ(h) is the function of the target formation density changing with depth; g is the gravitational acceleration; ρ w is the seawater density above the hydrate accumulation area; h0 is the seawater depth above the hydrate accumulation area.

4. The method according to any one of claims 1 to 3, characterized in that: Determining the maximum tolerable gas column height of the caprock in the hydrate accumulation zone according to the minimum value of the fracture pressure includes: The maximum tolerable gas column height of the caprock in the hydrate accumulation area is calculated using the following formula: Among them, h g is the maximum tolerable air column height; ρ w is the seawater density above the hydrate accumulation area; ρ g is the density of the gas accumulated under the cap layer of the hydrate accumulation area; is the minimum fracture pressure of the caprock in the hydrate accumulation area; g is the gravitational acceleration.

5. The method according to claim 1, characterized in that According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap rock in the hydrate accumulation zone at different depths, the minimum value of the fracture pressure of the cap rock in the hydrate accumulation zone is determined, including: Determine the minimum fracture pressure of the cap layer in the hydrate accumulation zone and the depth corresponding to the minimum fracture pressure according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation zone at different depths; Accordingly, the method further includes: Obtaining a depth contour map of the cap layer in the hydrate accumulation area; The position corresponding to the minimum rupture pressure value is determined according to the minimum rupture pressure value and the depth contour map.

6. A device for determining the maximum air column height that a cover layer can bear, characterized in that: include: An acquisition module is used to obtain the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer of the hydrate accumulation area at different depths; wherein the cap layer of the hydrate accumulation area is the cap layer of the shallow hydrate accumulation area under the tensile stress state; The first determination module is used to determine the minimum fracture pressure of the cap layer in the hydrate accumulation area according to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths; the minimum fracture pressure is used to indicate the minimum pressure value required to fracture the cap layer in the hydrate accumulation area; A second determination module is used to determine the maximum tolerable gas column height of the caprock in the hydrate accumulation area according to the minimum value of the fracture pressure; The first determining module is specifically configured to: According to the horizontal minimum principal stress, pore fluid pressure and rock tensile strength of the cap layer in the hydrate accumulation area at different depths, the fracture pressure of the cap layer in the hydrate accumulation area at different depths is determined; Determining a minimum value of the rupture pressure of the cap layer in the hydrate accumulation area according to the rupture pressure of the cap layer in the hydrate accumulation area at different depths; The first determining module is specifically configured to: Using the formula Calculate the fracture pressure of the caprock in the hydrate accumulation area at different depths; in, is the minimum horizontal principal stress; P w is the pore fluid pressure; is the tensile strength of rock.

7. An electronic device, characterized in that: include: A processor, and a memory communicatively connected to the processor; The memory stores computer-executable instructions; The processor executes the computer-executable instructions stored in the memory to implement the method according to any one of claims 1 to 5.

8. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer-executable instructions, which are used to implement the method according to any one of claims 1 to 5 when executed by a processor.

9. A computer program product comprising a computer program, characterized in that When the computer program is executed by a processor, the method according to any one of claims 1 to 5 is implemented.

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