A method and device for predicting the bottom boundary of hydrate stability region

Abstract

The present invention discloses a method and device for predicting the bottom boundary of a hydrate stability domain. The method comprises: obtaining a shallow seabed geothermal gradient by in-situ temperature measurement probe inclination correction; obtaining a first thermal conductivity of the shallow seabed by thermal conductivity test processing; obtaining a shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity; obtaining a second thermal conductivity based on hydrate drilling core measurement; obtaining the content of target radioactive elements in deep-sea sediments, and determining the average heat generation rate in combination with sediment density; establishing a vertical formation temperature field by geothermal extension technology; obtaining an apparent geothermal gradient of the hydrate layer by obtaining the derivative of the formation temperature of the hydrate layer to the depth; correcting the apparent geothermal gradient of the hydrate layer; and constructing the bottom boundary depth of the hydrate stability domain based on the corrected apparent geothermal gradient of the hydrate layer. The present invention can accurately predict the bottom boundary depth of the hydrate stability domain and can be widely used in the field of data processing technology.

Description

Technical Field

[0001] The present invention relates to the technical field of data processing, and in particular to a method and device for predicting the bottom boundary of a hydrate stability region. Background Art

[0002] Existing technologies are mainly based on numerical simulation or software simulation methods to characterize the temperature and pressure field and predict the hydrate stability domain of a single type of geological body such as salt diapir, mud diapir, or a certain ore body at a local spatial scale. The parameters involved in the simulation calculation are mostly based on the subjective settings of scientific researchers, based on empirical parameter values, or based on drilling measured data with high construction costs, and are often only applicable to areas with a high degree of investigation. The relevant methods have strong regional and ore body specificity and cannot effectively solve the problem of scientifically predicting the bottom boundary of the hydrate stability domain in a spatial region based on the actual geothermal field data of the shallow seabed. Summary of the invention

[0003] The present invention aims to solve the problem of related technical limitations at least to a certain extent. To this end, the present invention proposes a method and device for predicting the bottom boundary of the hydrate stability domain, which can accurately predict the bottom boundary of the hydrate stability domain.

[0004] On the one hand, an embodiment of the present invention provides a method for predicting the bottom boundary of a hydrate stability region, comprising:

[0005] Obtain the first stratum temperature data of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction;

[0006] Obtain shallow columnar sediments at a preset point on the seabed, and obtain the first thermal conductivity of the shallow seabed through thermal conductivity testing;

[0007] According to the product of the shallow geothermal gradient and the first thermal conductivity of the seafloor, the shallow geothermal heat flow value of the seafloor is obtained;

[0008] The second thermal conductivity from the shallow seabed to the hydrate layer is obtained based on the hydrate drilling core measurement;

[0009] Obtain the content of target radioactive elements in deep-sea sediments, and then determine the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density;

[0010] Based on the shallow seabed heat flow value, second thermal conductivity and average heat generation rate, the vertical formation temperature field is established through the geothermal extension technology;

[0011] Based on the vertical formation temperature field, the apparent geothermal gradient of the hydrate layer is obtained by calculating the derivative of the formation temperature of the hydrate layer with respect to depth.

[0012] The geothermal gradient of the hydrate layer is obtained based on the actual drilling measurement, and the error analysis is performed based on the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer. The apparent geothermal gradient of the hydrate layer is corrected based on the results of the error analysis;

[0013] The bottom depth of the hydrate stability zone is constructed based on the corrected apparent geothermal gradient of the hydrate layer.

[0014] Optionally, obtaining the first formation temperature data of the shallow seabed, and then obtaining the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction, includes:

[0015] Obtain the measured formation temperature data at different depths of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction;

[0016] Among them, the expression of the shallow seabed geothermal gradient is:

[0017] G s =(T max -T min ) / Lcosθ;

[0018] In the formula, G s represents the shallow seabed geothermal gradient; T max Indicates the formation temperature value measured by the in-situ temperature measurement probe at the bottom; T min represents the formation temperature value measured by the top in-situ temperature measurement probe; L represents the distance from the bottom to the top of the in-situ temperature measurement probe; θ represents the angle between the in-situ temperature measurement probe and the vertical direction.

[0019] Optionally, obtaining shallow columnar sediments at a preset point on the seabed, and obtaining a first thermal conductivity of the shallow seabed through thermal conductivity testing, includes:

[0020] Conduct thermal conductivity tests on each depth point in the preset points respectively to obtain the thermal conductivity value corresponding to each depth point;

[0021] The thermal conductivity values ​​at all depth points were summed and averaged to obtain the average thermal conductivity of the shallow columnar sediments on the seafloor.

[0022] Optionally, obtaining a second thermal conductivity from the shallow seabed to the hydrate layer based on hydrate drilling core measurement includes:

[0023] Thermal conductivity tests were performed at different locations of the hydrate drilling core at preset intervals to obtain the thermal conductivity of sediments at different depths from the shallow seabed to the hydrate layer;

[0024] The thermal conductivity obtained from all tests was summed and averaged to obtain the average thermal conductivity from the shallow seabed to the hydrate layer;

[0025] Among them, the expression of the average thermal conductivity from the shallow seabed to the hydrate layer is:

[0026]

[0027] Where K represents the average thermal conductivity from the shallow seabed to the hydrate layer; K i represents the thermal conductivity of the sediment at the i-th depth position; m represents the number of thermal conductivity tests.

[0028] Optionally, obtaining the content of the target radioactive element in the deep-sea sediments, and then determining the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density, includes:

[0029] The sediment heat generation rate at the sediment heat generation rate test point is calculated based on the U, Th and K element contents in the sediment obtained by the test at the preset sediment heat generation rate test point and the sediment density;

[0030] Among them, the expression of the sediment heat generation rate at the sediment heat generation rate test point is:

[0031]

[0032] In the formula, A i represents the sediment heat generation rate of the i-th sediment heat generation rate test point; ρ i represents the sediment density at the i-th sediment heat generation rate test point; represents the U content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the Th element content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the K content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point;

[0033] The sediment heat generation rates of all sediment heat generation rate test points were summed and averaged to obtain the average heat generation rate from the shallow seabed to the hydrate layer.

[0034] Optionally, based on the shallow seabed heat flow value, the second thermal conductivity and the average heat generation rate, a vertical formation temperature field is established by using a geothermal extension technology, including:

[0035] The seabed temperature and the formation temperature corresponding to the preset depth below the seabed are obtained, and then the vertical formation temperature field is calculated by the geothermal extension technology based on the one-dimensional heat conduction Laplace equation in combination with the shallow terrestrial heat flow value of the seabed and the second thermal conductivity and the average heat generation rate within the preset range; the preset range represents the depth range from 0 to the preset depth below the seabed;

[0036] Among them, the expression of vertical formation temperature field is:

[0037]

[0038] Where Z represents the preset depth below the seabed, T Z It represents the stratum temperature corresponding to the preset depth below the seabed; T0 represents the seabed temperature; Q represents the shallow terrestrial heat flow value of the seabed; K represents the second thermal conductivity within the preset range; A represents the average heat generation rate within the preset range.

[0039] Optionally, the apparent geothermal gradient of the hydrate layer is corrected based on the result of the error analysis, including:

[0040] When the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is greater than a preset threshold, the density of measuring points is increased, and then the process returns to the step of obtaining the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement, until the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is less than or equal to the preset threshold;

[0041] Among them, the content of target radioactive elements in deep-sea sediments and the corresponding sediment density are obtained according to the preset sediment heat generation rate test points; the increased measurement point density includes the measurement point density of hydrate drilling core measurement and the measurement point density of preset sediment heat generation rate test points.

[0042] Optionally, the bottom depth of the hydrate stability domain is constructed based on the corrected apparent geothermal gradient of the hydrate layer, including:

[0043] The formation temperature and formation depth function is constructed based on the corrected apparent geothermal gradient of the hydrate layer;

[0044] The bottom depth of the hydrate stability zone is obtained by solving the formation temperature and formation depth function together with the hydrate phase equilibrium simulation equation.

[0045] On the other hand, an embodiment of the present invention provides a device for predicting the bottom boundary of a hydrate stability region, comprising:

[0046] The first module is used to obtain the first stratum temperature data of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction;

[0047] The second module is used to obtain shallow columnar sediments at a preset point on the seabed, and obtain the first thermal conductivity of the shallow seabed through thermal conductivity testing;

[0048] The third module is used to obtain the shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity;

[0049] The fourth module is used to obtain the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement;

[0050] The fifth module is used to obtain the content of target radioactive elements in deep-sea sediments, and then determine the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density;

[0051] The sixth module is used to establish the vertical formation temperature field through the geothermal extension technology based on the shallow seabed heat flow value, the second thermal conductivity and the average heat generation rate;

[0052] The seventh module is used to obtain the apparent geothermal gradient of the hydrate layer by obtaining the derivative of the formation temperature of the hydrate layer with respect to the depth based on the vertical formation temperature field;

[0053] The eighth module is used to obtain the geothermal gradient of the hydrate layer based on the actual drilling measurement, perform error analysis based on the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and correct the apparent geothermal gradient of the hydrate layer based on the result of the error analysis;

[0054] The ninth module is used to construct the bottom depth of the hydrate stability domain based on the corrected apparent geothermal gradient of the hydrate layer.

[0055] On the other hand, an embodiment of the present invention provides an electronic device, including: a processor and a memory; the memory is used to store programs; the processor executes the program to implement the above-mentioned hydrate stability domain bottom boundary prediction method.

[0056] On the other hand, an embodiment of the present invention provides a computer storage medium, which stores a program executable by a processor. When the program executable by the processor is executed by the processor, it is used to implement the above-mentioned method for predicting the bottom boundary of the hydrate stability domain.

[0057] The embodiment of the present invention obtains the first formation temperature data of the shallow seabed, and then obtains the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction; obtains the shallow seabed columnar sediments at a preset point, and obtains the first thermal conductivity of the shallow seabed through thermal conductivity test processing; obtains the shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity; obtains the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement; obtains the content of the target radioactive element in the deep-sea sediment, and then determines the depth from the shallow seabed to the hydrate layer in combination with the corresponding sediment density. The average heat generation rate of the hydrate layer; based on the shallow seabed geothermal heat flow value, the second thermal conductivity and the average heat generation rate, a vertical formation temperature field is established through the geothermal extension technology; based on the vertical formation temperature field, the apparent geothermal gradient of the hydrate layer is obtained by calculating the derivative of the formation temperature of the hydrate layer with respect to the depth; the geothermal gradient of the hydrate layer is obtained based on the drilling measurement, and an error analysis is performed according to the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and the apparent geothermal gradient of the hydrate layer is corrected based on the result of the error analysis; the bottom boundary depth of the hydrate stability domain is obtained based on the corrected apparent geothermal gradient of the hydrate layer. The embodiment of the present invention is based on the acquisition of low-cost shallow seabed geothermal gradient data, and by implementing programmed calculations including "geothermal heat flow calculation", "thermal conductivity calculation", "average heat generation rate calculation", "vertical geothermal field construction", etc., to complete the correction of the shallow seabed geothermal gradient and obtain the "apparent geothermal gradient" of the hydrate layer, and finally accurately predict the bottom boundary depth of the hydrate stability domain. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] The accompanying drawings are used to provide a further understanding of the technical solution of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the technical solution of the present invention and do not constitute a limitation on the technical solution of the present invention.

[0059] Figure 1 This is a schematic diagram of an implementation environment for predicting the bottom boundary of a hydrate stability region provided by an embodiment of the present invention;

[0060] Figure 2 It is a schematic flow chart of a method for predicting the bottom boundary of a hydrate stability region provided by an embodiment of the present invention;

[0061] Figure 3 A schematic diagram of a process for calculating the thermal conductivity of a shallow seabed provided by an embodiment of the present invention;

[0062] Figure 4 A schematic diagram of a process for calculating the average thermal conductivity from the shallow seabed to the hydrate layer provided in an embodiment of the present invention;

[0063] Figure 5 A schematic diagram of a flow chart for calculating the average heat generation rate from the shallow seabed to the hydrate layer provided in an embodiment of the present invention;

[0064] Figure 6 A schematic diagram of a process for correcting the apparent geothermal gradient of a hydrate layer provided in an embodiment of the present invention;

[0065] Figure 7 A schematic diagram of a process for calculating the bottom depth of a hydrate stability zone provided in an embodiment of the present invention;

[0066] Figure 8 A schematic diagram of the overall process of a method for predicting the bottom boundary of a hydrate stability region provided in an embodiment of the present invention;

[0067] Fig. 9 A schematic diagram of the structure of a device for predicting the bottom boundary of a hydrate stability region provided in an embodiment of the present invention;

[0068] Fig.10 A schematic diagram of the structure of an electronic device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0070] It should be noted that, although the functional modules are divided in the system schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be performed in a different order than the module division in the system or the order in the flowchart. The terms "first / S100", "second / S200", etc. in the specification, claims and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence.

[0071] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0072] To facilitate the understanding of the technical solution of the present invention, the meanings of the parameters that may be cited in the embodiments of the present invention and their technical principles are first explained:

[0073] Hydrate: A mineral crystal formed by the combination of water molecules and gas molecules under low temperature and high pressure conditions. It is often found in marine environments or terrestrial permafrost zones and is a potential, huge clean energy source (hydrates in this invention specifically refer to hydrates in marine environments).

[0074] Geothermal gradient: Temperature always transfers from high temperature area to low temperature area. The parameter that measures the speed of temperature transfer is called geothermal gradient, which is usually expressed as the degree of temperature drop per kilometer (℃ / km).

[0075] Hydrate stability domain: Hydrates can only form under certain specific conditions of lower temperature and higher pressure. Beyond the corresponding temperature or pressure range, hydrates cannot form, or the formed hydrates will decompose. The area (or temperature and pressure range) where hydrates stably form and aggregate is usually called the hydrate stability domain, and the hydrate phase equilibrium curve (temperature and pressure relationship curve) is often used to indicate the range of the hydrate stability domain.

[0076] Heat generation rate: refers to the heat generated by the decay of radioactive elements (mainly U, Th, and K) contained in unit volume of rock per unit time.

[0077] Thermal conductivity: Thermal conductivity is also called "thermal conductivity" or "thermal conductivity", which is the amount of heat transferred through a unit heat conduction surface per unit time under a unit temperature gradient. Specifically, when the vertical downward temperature gradient is 1°C / m, the amount of heat transferred through a unit horizontal cross-sectional area per unit time is the thermal conductivity.

[0078] BSR: The full name of BSR is Bottom Simulating Reflector, which is similar to the seabed reflector. BSR is an important geophysical reflection interface for identifying hydrates. In the process of geological interpretation, it is usually used as the bottom boundary of the hydrate stability domain. In other words, in theory, there are hydrates above BSR, and there are no hydrates below BSR.

[0079] It is understandable that the method for predicting the bottom boundary of the hydrate stability domain provided in the embodiment of the present invention can be applied to any computer device with data processing and computing capabilities, and this computer device can be various terminals or servers. When the computer device in the embodiment is a server, the server is an independent physical server, or a server cluster or distributed system composed of multiple physical servers, or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN (Content Delivery Network), and big data and artificial intelligence platforms. Optionally, the terminal is a smart phone, tablet computer, laptop computer, desktop computer, etc., but is not limited to this.

[0080] To facilitate the understanding of the technical solution of the present invention, the technical feature terms that may appear in the embodiments of the present invention are first explained:

[0081] like Figure 1FIG. 1 is a schematic diagram of an implementation environment provided by an embodiment of the invention. Figure 1 The implementation environment includes at least one terminal 102 and a server 101. The terminal 102 and the server 101 can be connected to a network wirelessly or wired to complete data transmission and exchange.

[0082] Server 101 can be an independent physical server, or a server cluster or distributed system composed of multiple physical servers. It can also be a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communications, middleware services, domain name services, security services, CDN (Content Delivery Network), as well as big data and artificial intelligence platforms.

[0083] In addition, the server 101 can also be a node server in the blockchain network. Blockchain is a new application model of computer technologies such as distributed data storage, peer-to-peer transmission, consensus mechanism, and encryption algorithm.

[0084] The terminal 102 may be a smart phone, a tablet computer, a laptop computer, a desktop computer, a smart speaker, a smart watch, etc., but is not limited thereto. The terminal 102 and the server 101 may be directly or indirectly connected via wired or wireless communication, which is not limited in the embodiment of the present invention.

[0085] Based on the example Figure 1 In the implementation environment shown, an embodiment of the present invention provides a method for predicting the bottom boundary of a hydrate stability domain. The following is explained using the example of applying the method for predicting the bottom boundary of a hydrate stability domain in a server 101. It can be understood that the method for predicting the bottom boundary of a hydrate stability domain can also be applied in a terminal 102.

[0086] Reference Figure 2 , Figure 2 The flowchart of the method for predicting the bottom boundary of the hydrate stability region applied to the server provided in the embodiment of the present invention, the execution subject of the method for predicting the bottom boundary of the hydrate stability region can be any of the aforementioned computer devices (including servers or terminals). Figure 2 , the method comprises the following steps:

[0087] S100, obtaining the first stratum temperature data of the shallow seabed, and then obtaining the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction;

[0088] It should be noted that, in some embodiments, step S100 may include: obtaining measured formation temperature data at different depths of the shallow seabed, and then obtaining the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction;

[0089] Among them, the expression of the shallow seabed geothermal gradient is:

[0090] G s =(T max -T min ) / Lcosθ(1)

[0091] In the formula, G s represents the shallow seabed geothermal gradient; T max Indicates the formation temperature value measured by the in-situ temperature measurement probe at the bottom; T min represents the formation temperature value measured by the top in-situ temperature measurement probe; L represents the distance from the bottom to the top of the in-situ temperature measurement probe; θ represents the angle between the in-situ temperature measurement probe and the vertical direction.

[0092] For example, in some specific implementations, the calculation of the shallow seabed geothermal gradient is implemented as follows:

[0093] Based on the measured formation temperature data at different depths of the shallow seabed (generally within 6m below the seabed) obtained from field heat flow surveys, the shallow seabed geothermal gradient is calculated after in-situ temperature measurement probe inclination correction:

[0094] G s =(T max -T min ) / Lcosθ(1)

[0095] In the formula, G s is the shallow seabed geothermal gradient, unit: °C / km; T max T is the formation temperature value measured by the bottom in-situ temperature measurement probe, unit: °C; min is the formation temperature value measured by the top in-situ temperature measurement probe, in °C; L is the distance from the bottom to the top in-situ temperature measurement probe, in m; cosθ is the cosine value of the angle between the in-situ temperature measurement probe and the vertical direction.

[0096] In some specific embodiments, the in-situ temperature measurement probe position information, measured temperature information and angle information with the vertical direction are all derived from field measurement records and stored in the form of electronic documents, and the data can be directly retrieved for numerical calculation.

[0097] S200, obtaining shallow columnar sediments of the seabed at a preset point, and obtaining a first thermal conductivity of the shallow seabed through thermal conductivity testing;

[0098] It should be noted that in some embodiments, Figure 3As shown, step S200 may include: S201, respectively performing a thermal conductivity test on each depth point in the preset points to obtain a thermal conductivity value corresponding to each depth point; S202, summing and averaging the thermal conductivity values ​​of all depth points to obtain an average thermal conductivity of shallow columnar sediments on the seabed.

[0099] For example, in some specific implementations, the calculation of the thermal conductivity of the shallow seabed is implemented as follows:

[0100] Through field heat flow surveys, shallow columnar sediments of the seabed are obtained. The thermal conductivity of shallow columnar sediments at different depths is tested, and the average thermal conductivity of the shallow seabed is calculated.

[0101] In some optional embodiments, the thermal conductivity of the obtained shallow seabed columnar sediments is generally tested at five depth points.

[0102] K s =(K1+K2+K3+K4+K5) / 5 (2)

[0103] In the formula, K s is the average thermal conductivity of shallow columnar sediments on the seabed, in units of W / (mK); K1, K2, K3, K4, and K5 are the measured thermal conductivities of sediments at depths of 1m, 2m, 3m, 4m, and 5m below the seabed, respectively.

[0104] In some specific embodiments, a TK04 thermal conductivity meter is used to carry out thermal conductivity testing of shallow seabed sediments.

[0105] S300, obtaining a heat flow value of the shallow seabed according to the product of the shallow seabed geothermal gradient and the first thermal conductivity;

[0106] For example, in some specific implementations, the calculation of the shallow seabed heat flow is implemented as follows:

[0107] Based on the shallow seabed geothermal gradient data (according to formula 1) and the average thermal conductivity data (according to formula 2), the shallow seabed heat flow value is calculated.

[0108] Q=G s *K s (3)

[0109] Where Q is the shallow seabed heat flow value, unit is mW / m 2 ; G s is the shallow seabed geothermal gradient, unit: °C / km; K s It is the average thermal conductivity of shallow seabed sediments, in W / (mK).

[0110] S400, obtaining a second thermal conductivity from the shallow seabed to the hydrate layer based on hydrate drilling core measurement;

[0111] It should be noted that in some embodiments, Figure 4 As shown, step S400 may include: S401, performing thermal conductivity tests on different positions of the hydrate drilling core at preset intervals to obtain thermal conductivities of sediments at different depths from the shallow seabed to the hydrate layer; S402, summing and averaging the thermal conductivities obtained from all tests to obtain an average thermal conductivity from the shallow seabed to the hydrate layer; wherein the expression for the average thermal conductivity from the shallow seabed to the hydrate layer is:

[0112]

[0113] Where K represents the average thermal conductivity from the shallow seabed to the hydrate layer; K i represents the thermal conductivity of the sediment at the i-th depth position; m represents the number of thermal conductivity tests.

[0114] For example, in some specific implementations, the average thermal conductivity of the “seafloor shallow layer-hydrate layer” is calculated as follows:

[0115] Based on hydrate drilling cores (the depth can generally reach 200m below the seabed), the thermal conductivity of sediments at different depths from the shallow seabed to the hydrate layer is tested at certain depth intervals, and the average thermal conductivity is calculated.

[0116]

[0117] Where, K is the average value of the measured thermal conductivity from the shallow seabed to the hydrate layer; i is the i-th sediment thermal conductivity test point below the seabed (i = 1, 2, 3…m); m is the number of sediment thermal conductivity tests from the shallow seabed to the hydrate layer; K i is the measured value of sediment thermal conductivity at the i-th depth below the seafloor (i=1, 2, 3…m).

[0118] In some specific embodiments, the location of the hydrate layer is estimated by the depth of the BSR identified in the seismic profile.

[0119] More specifically, by identifying the two-way reflection time t corresponding to the BSR position in the seismic profile and multiplying it by the seismic reflection wave velocity, the BSR position is estimated, which is approximately the bottom boundary of the hydrate layer.

[0120] More specifically, the propagation velocity of shallow seabed seismic waves is v=1500 m / s.

[0121] S500, obtaining the content of the target radioactive element in the deep-sea sediment, and then determining the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density;

[0122] It should be noted that in some embodiments, Figure 5As shown, step S500 may include: S501, calculating the heat generation rate of the sediment at the sediment heat generation rate test point according to the U, Th and K element contents in the sediment obtained by the preset sediment heat generation rate test point combined with the sediment density; wherein the expression of the sediment heat generation rate at the sediment heat generation rate test point is:

[0123]

[0124] In the formula, A i represents the sediment heat generation rate of the i-th sediment heat generation rate test point; ρ i represents the sediment density at the i-th sediment heat generation rate test point; represents the U content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the Th element content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the K content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point;

[0125] S502. Sum and average the sediment heat generation rates of all sediment heat generation rate test points to obtain the average heat generation rate from the shallow seabed to the hydrate layer.

[0126] For example, in some specific embodiments, the average heat generation rate of the “shallow seafloor-hydrate layer” is calculated as follows:

[0127] Based on the contents of radioactive elements U, Th and K in deep-sea sediments, the heat generation rate of sediments from the shallow seabed to the hydrate layer is calculated.

[0128]

[0129] Where i is the i-th sediment heat generation rate test point below the seafloor (i = 1, 2, 3…m);

[0130] A i is the heat generation rate of the sediment at the i-th depth below the seafloor, in μW / m 3 ;

[0131] ρ i is the sediment density at the i-th depth below the seafloor, in g / cm 3 ;

[0132] is the U content in the sediment at the i-th depth below the seafloor, in ug / g;

[0133] is the Th content in the sediment at the i-th depth below the seafloor, in ug / g;

[0134] is the K content in the sediment at the i-th depth below the seafloor, in %;

[0135] In some specific embodiments, It can be calculated based on the element logging curve at the corresponding depth or obtained through element testing of sediment samples.

[0136]

[0137] A is the average heat generation rate of sediments from the shallow seabed to the hydrate layer, in μW / m 3 .

[0138] m is the measured sediment heat generation rate from the shallow seafloor to the hydrate layer;

[0139] In some specific embodiments, the location of the hydrate layer is estimated by the depth of the BSR identified in the seismic profile.

[0140] More specifically, by identifying the two-way reflection time t corresponding to the BSR position in the seismic profile and multiplying it by the seismic reflection wave velocity, the BSR position is estimated, which is approximately the bottom boundary of the hydrate layer.

[0141] More specifically, the propagation velocity of shallow seabed seismic waves is v = 1500 m / s

[0142] S600, based on the shallow seabed heat flow value, the second thermal conductivity and the average heat generation rate, the vertical formation temperature field is established through the geothermal extension technology;

[0143] It should be noted that, in some embodiments, step S600 may include: obtaining the seabed temperature and the formation temperature corresponding to a preset depth below the seabed, and then combining the seabed shallow terrestrial heat flow value and the second thermal conductivity and the average heat generation rate within the preset range to calculate the vertical formation temperature field through the geothermal extension technology according to the one-dimensional heat conduction Laplace equation; the preset range represents the depth range from 0 to the preset depth below the seabed; wherein the expression of the vertical formation temperature field is:

[0144]

[0145] Where Z represents the preset depth below the seabed, T Z It represents the stratum temperature corresponding to the preset depth below the seabed; T0 represents the seabed temperature; Q represents the shallow terrestrial heat flow value of the seabed; K represents the second thermal conductivity within the preset range; A represents the average heat generation rate within the preset range.

[0146] For example, in some specific implementations, the vertical formation temperature field construction is implemented as follows:

[0147] According to the one-dimensional heat conduction Laplace equation, the vertical formation temperature field is established by using the geothermal extension technology.

[0148]

[0149] Where Z is the depth of any position below the seabed, in km; T Z is the stratum temperature at depth Z below the seafloor, in °C; T0 is the seafloor temperature, in °C; Q is the shallow seafloor heat flow, in mW / m 2 (According to Formula 3); K is the average thermal conductivity of sediments within the depth range of 0 to Z meters below the seafloor, in W / (m·K) (According to Formula 4); A is the average heat generation rate of sediments within the depth range of 0 to Z meters below the seafloor, in mW / m 3 (According to formula 6).

[0150] S700, based on the vertical formation temperature field, obtaining the apparent geothermal gradient of the hydrate layer by obtaining the derivative of the formation temperature of the hydrate layer with respect to the depth;

[0151] For example, in some specific implementations, the calculation of the “apparent geothermal gradient” of the hydrate layer is implemented as follows:

[0152] On the basis of “constructing vertical formation temperature field”, the geothermal gradient of the hydrate layer is calculated by taking the derivative of the formation temperature of the hydrate layer with respect to the burial depth, which is the “apparent geothermal gradient” of the hydrate layer.

[0153]

[0154] In the formula, G h is the apparent geothermal gradient of the hydrate layer, in °C / km; Z is the depth of any position below the seabed, in km; A is the average heat generation rate of sediments from the shallow seabed to the hydrate layer, in μW / m 3 ; K is the average thermal conductivity from the shallow seabed to the hydrate layer, in W / (m·K); G is the geothermal gradient within the depth range of 0 to Z meters below the seabed, in ℃ / km;

[0155] In some specific embodiments, the value of Z is the burial depth of the BSR, that is, the bottom depth of the hydrate layer.

[0156] More specifically, by identifying the two-way reflection time t corresponding to the BSR position in the seismic profile and multiplying it by the seismic reflection wave velocity, the BSR position is estimated, which is approximately the bottom boundary of the hydrate layer.

[0157] More specifically, the propagation velocity of shallow seabed seismic waves is v=1500 m / s.

[0158] S800, obtaining the geothermal gradient of the hydrate layer based on actual drilling measurements, performing error analysis based on the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and correcting the apparent geothermal gradient of the hydrate layer based on the result of the error analysis;

[0159] It should be noted that in some embodiments, Figure 6 As shown, the apparent geothermal gradient of the hydrate layer is corrected based on the result of the error analysis, which may include: S801, when the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is less than or equal to the preset threshold, directly using the apparent geothermal gradient of the hydrate layer calculated in step S700 for step S900; S802, when the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is greater than the preset threshold, increasing the density of measuring points, and then returning to the step of obtaining the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement, until the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is less than or equal to the preset threshold; wherein the content of the target radioactive element in the deep-sea sediment and the corresponding sediment density are obtained according to the preset sediment heat generation rate test point test; the increased measuring point density includes the measuring point density of the hydrate drilling core measurement and the measuring point density of the preset sediment heat generation rate test point.

[0160] For example, in some specific implementations, the “apparent geothermal gradient” verification of the hydrate layer is implemented as follows:

[0161] The calculated apparent geothermal gradient of the hydrate layer “G h "Geothermal gradient of hydrate layer measured by drilling in adjacent areas" m "Perform error analysis.

[0162] Δ=|(G h -G m ) / G m |(9)

[0163] In the embodiment, if Δ≤5%, it means that the hydrate layer apparent geothermal gradient "G h " is accurate and can be used for the next step of calculation.

[0164] In the embodiment, if Δ>5%, it is necessary to return to "S400 to S700" to increase the density of measurement points of the thermal conductivity and heat generation rate of the "shallow seabed-hydrate layer" sediments to obtain more accurate calculation parameter information until Δ≤5%.

[0165] S900. The bottom depth of the hydrate stability domain is obtained based on the corrected apparent geothermal gradient of the hydrate layer.

[0166] It should be noted that in some embodiments, Figure 7As shown, step S900 may include: constructing a formation temperature and formation depth function based on the corrected apparent geothermal gradient of the hydrate layer; solving the formation temperature and formation depth function and the hydrate phase equilibrium simulation equation simultaneously to obtain the bottom depth of the hydrate stability domain.

[0167] For example, in some specific implementations, the calculation of the bottom boundary of the hydrate stability region is implemented as follows:

[0168] After the “apparent geothermal gradient” of the hydrate layer is verified, the bottom depth of the hydrate stability domain is calculated by constructing the formation temperature (T)-formation depth (D) function (Formula 10) and solving it together with the hydrate phase equilibrium simulation equation (Formula 11).

[0169] T D =T0+G h D(10)

[0170] D=aT D 4 +bT D 3 +cT D 2 +dT D +e(11)

[0171] Wherein, D is the depth of any position below the seabed, in km; in this embodiment, D is the bottom depth of the hydrate stability zone, in km; T0 is the seabed temperature, in °C;

[0172] T D is the formation temperature at a depth D below the seafloor, in °C. In this embodiment, T D is the bottom temperature of the hydrate stability region (i.e., the hydrate phase equilibrium temperature), in °C; a, b, c, d, e are constants;

[0173] In some specific embodiments, the hydrate phase equilibrium simulation equation is constructed by inputting the parameters of "pore water salinity" and "alkane gas composition".

[0174] In some specific embodiments, the data of "pore water salinity" and "alkane gas composition" are all from field measurement records and stored in the form of electronic documents, and the data can be directly retrieved for numerical calculations.

[0175] In order to explain the principle of the technical solution of the present invention in detail, the overall process of the present invention is described below in combination with some specific embodiments. It is easy to understand that the following is an explanation of the technical principle of the present invention and cannot be regarded as a limitation of the present invention.

[0176] First of all, it should be noted that natural gas hydrate resources are an important new type of mineral resources with huge resource potential. Major countries in the world are stepping up their efforts in hydrate exploration and development.

[0177] In nature, natural gas hydrates are mainly distributed in terrestrial permafrost zones and deep sea slope environments. The distribution of hydrates is closely related to the temperature and pressure conditions of the formation. Hydrates usually exist stably in low-temperature, high-pressure geological environments. When certain geological conditions change, such as crustal movement, sea level rise and fall, earthquakes, sedimentary landslides, etc., they may cause changes in the temperature and pressure conditions of the hydrate system, leading to the decomposition and release of hydrates, and even causing damage to the marine ecological environment or engineering geological disasters.

[0178] BSR is a geophysical reflection interface reflected in the seismic profile. It usually has the characteristics of strong amplitude, parallel to the seabed, and reflection polarity opposite to the seabed. It is the most important and reliable geophysical indicator for hydrate identification so far. Theoretically, there is a hydrate layer above the BSR and a free gas layer below the BSR. As far as marine hydrates are concerned, the bottom boundary of the hydrate stability domain is usually about 200m below the seabed. The deeper the bottom boundary of the hydrate stability domain, the larger the range of the hydrate stability domain, and the corresponding hydrate resources are greater. As far as hydrate drilling construction is concerned, the deeper the bottom boundary of the hydrate stability domain, that is, the greater the burial depth of the BSR, the greater the technical requirements and operational difficulty of drilling construction. Therefore, accurate prediction of the bottom boundary of the hydrate stability domain has important theoretical and practical significance for scientifically guiding hydrate exploration deployment and reducing the operational risks of engineering implementation.

[0179] In the process of hydrate exploration practice, the bottom depth of the hydrate stability zone is often obtained through the following methods.

[0180] (1) Determine the bottom boundary of the hydrate stability zone by identifying the BSR in the seismic profile. This method is widely used in the hydrate exploration process. However, due to the resolution of conventional seismic reflection data (usually greater than 10m), it is usually difficult to accurately determine the depth of the BSR, so it can only provide an auxiliary reference. In addition, in some complex geological backgrounds or fluid environments, the BSR in the seismic profile is not significant, or there are multiple reflections suspected to be "BSR", which often interferes with the accurate identification of the BSR. (2) Directly reveal the distribution of the hydrate layer through hydrate drilling (hydrate logging while drilling or drilling coring). This method is the most intuitive and reliable, but the cost of offshore drilling construction is extremely high and is not suitable for large-scale promotion and application. (3) Based on the hydrate phase equilibrium theory, the hydrate stability zone is calculated by numerical simulation of measured geological parameters. Based on the geothermal gradient, alkane gas composition, pore water salinity and other parameter information obtained by hydrate drilling and coring, the hydrate phase equilibrium equation is constructed to calculate the bottom boundary of the hydrate stability zone. The survey data required for this method have relatively low acquisition costs and can be obtained in batches, so it has a broad application prospect.

[0181] In the actual geological environment, the migration of deep gas-bearing fluids to shallow layers is accompanied by obvious heat transfer effects. Without considering the lateral propagation of heat, the heat flow Q at different layers or depths in the same well (or in the same vertical direction) is a constant. It is the product of the formation thermal conductivity (K) and the geothermal gradient (G). The thermal conductivity K is usually directly or indirectly related to the lithology, age, burial depth and compaction degree of the sample. For deep-sea sediments, thermal conductivity is mainly related to the degree of sediment compaction. Due to the low degree of compaction and high water content of shallow seabed sediments (generally within 6m below the seabed), their thermal conductivity (K) is lower than that of hydrate reservoirs (usually about 200m below the seabed), while the geothermal gradient (G) is higher than that of hydrate reservoirs. In addition, the heat generation rate will affect the distribution and evolution of the geothermal field, and the influence of the heat generation rate needs to be considered when analyzing the geothermal field.

[0182] Although the inference of the bottom boundary of the hydrate stability domain based on the hydrate phase equilibrium theory is highly scientific and economical, the use of this method also has limitations. Strictly speaking, only by accurately obtaining the measured geothermal gradient data of the hydrate layer and then based on the hydrate phase equilibrium equation, can the bottom boundary of the hydrate stability domain be accurately estimated. However, due to the high operating costs of hydrate drilling and deep formation temperature testing, the measured temperature (geothermal gradient) data of the hydrate layer is very limited in exploration practice. More commonly, the measured geothermal data at different depths of the shallow seabed strata are obtained by carrying an in-situ temperature measurement probe on a gravity column, and then the shallow seabed geothermal gradient is obtained. Since the measured geothermal gradient of the shallow seabed is high, it cannot accurately reflect the in-situ geothermal gradient information of the hydrate layer. The method of directly establishing the hydrate phase equilibrium equation based on the shallow seabed geothermal gradient data and inferring the hydrate stability domain based on this has errors to a certain extent, and may even mislead the drilling layer design and decision-making deployment. In view of the above problems, the present invention aims to propose a correction method for the shallow geothermal gradient of the seabed, in order to improve the prediction accuracy of the bottom boundary of the hydrate stability zone.

[0183] In view of the problems existing in the prior art, the present invention is based on the principles of heat transfer and numerical statistics. By making full use of the measured geothermal gradient data of shallow seabed with low acquisition operation cost, combined with auxiliary information such as seismic and well logging, the key parameters such as sediment thermal conductivity and heat generation rate are calculated or tested, so as to realize the correction of shallow seabed geothermal gradient data, obtain the geothermal gradient data of deep target layer (the hydrate layer in the present invention), and then realize the accurate prediction of the bottom boundary of the hydrate stability domain, effectively serving the implementation and deployment of hydrate drilling.

[0184] The present invention focuses on the high cost of hydrate drilling and geothermal in-situ testing, and the difficulty in predicting the hydrate stability domain. It intends to complete the shallow seabed geothermal gradient correction and obtain the "apparent geothermal gradient" of the hydrate layer by implementing programmed calculations including "terrestrial heat flow calculation", "average thermal conductivity calculation", "average heat generation rate calculation", "vertical geothermal field construction" based on the acquisition of low-cost shallow seabed geothermal gradient data. Finally, by constructing the formation temperature (T)-formation depth (D) function and solving it together with the hydrate phase equilibrium equation, the bottom boundary depth of the hydrate stability domain is accurately calculated.

[0185] like Figure 8 As shown, in some specific implementations, the embodiments of the present invention are based on the measured geothermal gradient data of the shallow seabed in a certain sea basin, and through the implementation of programmed calculations including "terrestrial heat flow calculation", "average thermal conductivity calculation", "average heat generation rate calculation", "vertical geothermal field construction", etc., the shallow seabed geothermal gradient correction is completed and the "apparent geothermal gradient" of the hydrate layer is obtained. Finally, by constructing the formation temperature (T)-formation depth (D) function and solving it together with the hydrate phase equilibrium equation, the bottom boundary depth of the hydrate stability domain is accurately calculated. The specific steps are as follows:

[0186] Step 1: Calculate the shallow seabed temperature gradient based on the measured formation temperature data at different depths of the shallow seabed during the field heat flow survey of the relevant sea basin.

[0187] G s =(T max -T min ) / Lcosθ(1)

[0188] In this embodiment, the bottom in-situ temperature measurement probe measures the formation temperature T max :3.32℃; The top in-situ temperature measurement probe measured the formation temperature T min : 2.82℃; the distance between the bottom and top in-situ temperature measurement probes is 4m; the angle between the in-situ temperature measurement probes and the vertical direction is 21°.

[0189] According to formula (1), the shallow seabed geothermal gradient is calculated as:

[0190] G s =(3.32-2.82) / 4 / cos(21°)=134℃ / km;

[0191] Step 2: Test the thermal conductivity of sediments at different depths in the shallow seabed (within 6m below the seabed) and calculate the average thermal conductivity of the shallow seabed sediments.

[0192] K s =(K1+K2+K3+K4+K5) / 5(2)

[0193] In this embodiment, thermal conductivity tests are performed at every 1 m depth on shallow seabed sediments obtained by gravity column sampling.

[0194] In this embodiment, the thermal conductivity of the sediments at five depths, namely, 1 m, 2 m, 3 m, 4 m, and 5 m below the seabed, was measured, and the average thermal conductivity value was calculated.

[0195] K s =(1.002+0.886+0.881+0.95+0.969) / 5=0.94W / (m·K);

[0196] Step 3: Calculate the shallow seabed heat flow value based on the shallow seabed temperature gradient (according to Formula 1) and the shallow seabed average thermal conductivity (according to Formula 2).

[0197] Q=G s *K s (3)

[0198] In this embodiment, the shallow seabed geothermal gradient G s :134℃ / km (according to formula 1); average thermal conductivity of the shallow seabed K s :0.94W / (m·K) (According to Formula 2), the shallow seabed heat flow value is calculated as:

[0199] Q=134*0.94=125.96mW / m 2 ;

[0200] Step 4: Based on the hydrate drilling core samples in the adjacent area (the depth can generally reach 200m below the seabed), the thermal conductivity of the sediments at different depths from the shallow seabed to the hydrate layer is measured at a certain depth interval, and the average thermal conductivity of "shallow seabed-hydrate layer" is calculated.

[0201]

[0202] In this embodiment, the depth of the hydrate layer is estimated based on the two-way reflection time in the seismic profile, which is 140 m below the seabed.

[0203] In this embodiment, thermal conductivity tests are performed on the drill core samples obtained at a depth of 5 m starting from the seabed.

[0204] In this embodiment, the thermal conductivity values ​​of 30 depth points of the "seafloor-hydrate layer" are obtained, and the average thermal conductivity is calculated (according to Formula 4).

[0205] K=(K1+K2+K3+…K 30 ) / 30=1.21W / (m·K);

[0206] Step 5: Calculate the heat generation rate of sediments based on the content of radioactive elements U, Th, and K in deep-sea sediments.

[0207]

[0208]

[0209] In this embodiment, the depth of the hydrate layer is estimated based on the two-way reflection time in the seismic profile, which is 140 m below the seabed.

[0210] In this embodiment, starting from the seabed at a depth of 5 m, the heat generation rate data corresponding to 30 sediment sample points within the depth range of "seabed shallow layer - hydrate layer" are calculated by actual measurement of core samples or based on logging data (according to Formula 5).

[0211]

[0212] After completing the heat generation rate of sediments at 30 different depths within the range of “shallow seabed-hydrate layer”, the average heat generation rate of sediments was calculated (Formula 6).

[0213]

[0214] Step 6: Based on the one-dimensional heat conduction Laplace equation, the vertical formation temperature profile is established using the geothermal extension technology to obtain the in-situ formation temperature corresponding to any depth below the seabed.

[0215]

[0216] In this embodiment, T0 is the seafloor temperature: 2.67°C; Q is the shallow seafloor heat flow value: 125.96 mW / m 2 (According to Formula 3); K is the average thermal conductivity of the sediments in the "shallow seabed-hydrate layer": 1.21W / (m·K) (According to Formula 4); A is the average heat generation rate of the sediments in the "shallow seabed-hydrate layer": 1.23μW / m 3 (According to Formula 6); Z is the burial depth of any position below the seabed; T Z is the formation temperature at depth Z below the seafloor.

[0217] Substituting the above parameters into Formula 7, the in situ formation temperature at any depth below the seafloor is calculated.

[0218]

[0219] Step 7: Calculate the “apparent geothermal gradient” of the hydrate layer by taking the derivative of the formation temperature of the hydrate layer with respect to the burial depth.

[0220]

[0221] In this embodiment, the value of Z is taken as the depth of the hydrate layer, and the “apparent geothermal gradient” of the hydrate layer is calculated.

[0222] In this embodiment, the depth of the hydrate layer is estimated based on the two-way reflection time in the seismic profile, which is 140 m below the seabed.

[0223]

[0224] Step 8: Hydrate layer apparent geothermal gradient "G h " and the geothermal gradient of the hydrate layer measured by drilling "G m "Error analysis.

[0225] Δ=|(G h -G m ) / G m | (9)

[0226] In this embodiment, through "steps 1 to 7", the shallow seabed geothermal gradient correction is completed to obtain the apparent geothermal gradient "G h ”:104.10℃ / km.

[0227] In this embodiment, the geothermal gradient of the hydrate layer measured by drilling in the adjacent area is “G m ”:107.00℃ / km.

[0228] In this embodiment, "G h ” and “G m The relative error is (107-104) / 107=2.80%, which meets the technical requirement of error less than 5%. This shows that the above method is reliable for estimating the "apparent geothermal gradient" of hydrate.

[0229] Step 9: Construct the formation temperature (T)-formation depth (D) function, solve it together with the hydrate phase equilibrium simulation equation, and calculate the bottom depth of the hydrate stability domain.

[0230] Based on the apparent geothermal gradient of the hydrate layer “G h ”, construct the formation temperature (T)-formation depth (D) function.

[0231] T D =T0+G h D (10)

[0232] In this example, the seafloor temperature T0 is 2.67°C; the hydrate layer has a geothermal gradient of “G h ”: 104℃ / km;

[0233] Therefore, in this embodiment, the formation temperature (T)-formation depth (D) function expression is:

[0234] TD =2.67+104.1*D (10-1)

[0235] The hydrate phase equilibrium equation is established based on the pore water salinity and alkane gas composition:

[0236] D=aT D 4 +bT D 3 +cT D 2 +dT D +e (11)

[0237] In this embodiment, the data of "pore water salinity" and "alkane gas composition" are from field measurement records, and the data can be directly retrieved for numerical calculation.

[0238] Further, in this embodiment, the pore water salinity is 35‰, and the alkane gas composition (converted into alkane gas content percentage) is CH4: 97.5%; C2H6: 2.49%; C3H8: 0.01%;

[0239] In this embodiment, the hydrate phase equilibrium equation established based on the pore water salinity and alkane gas composition is:

[0240] D=0.0021T D 4 +0.2654T D 3 -3.6674T D 2 +61.357T D -1454 (11-1)

[0241] In this embodiment, the equations 10-1 and 11-1 are solved simultaneously, and the only positive real number solution is taken to calculate the D value (i.e., the bottom boundary of the hydrate stability region) to be 150m.

[0242] In this embodiment, the calculated bottom depth of the hydrate stability zone (150 m below the seabed) and the bottom depth of the hydrate layer revealed by drilling in the adjacent area (148 m below the seabed) have an error of only 2 m, which meets the requirements of hydrate exploration and achieves accurate prediction of the bottom of the hydrate stability zone.

[0243] In summary, the technical solution of the present invention realizes:

[0244] 1. The present invention has formed a relatively complete and scientific geothermal gradient correction method system and technical process, which effectively reduces the cost of obtaining key scientific parameters.

[0245] Based on the basic principles of heat transfer, by using the measured geothermal gradient data of the shallow seabed, a series of programmed calculations including "terrestrial heat flow calculation", "average thermal conductivity calculation", "average heat generation rate calculation", and "vertical geothermal field construction" are carried out to complete the scientific correction of the shallow seabed geothermal gradient data, and finally achieve accurate calculation of the bottom boundary of the hydrate stability domain on this basis. Based on the above method system and technical process, the technical limitation of relying on high-cost drilling methods to obtain key scientific parameters in the past is effectively overcome. Therefore, this method has high scientificity, economy and expansive applicability.

[0246] 2. The present invention and related technical method systems realize the effective combination of multiple investigation methods and multi-dimensional data information, and achieve deep integration of data and information mining.

[0247] The present invention and related technical method systems realize the combination of multiple survey methods including heat flow measurement, geological sampling, seismic, well logging, etc., forming the advantages of multivariate data information clusters, and realizing an effective alternative to the traditional path of obtaining key geological information by relying only on high-cost technical means. In addition, the present invention also realizes the organic integration of data with different survey accuracies. For example, the depth of the hydrate layer is estimated using seismic data information with lower exploration accuracy (vertical resolution is generally greater than 10m); the heat generation rate of sediments at different depths is calculated using well logging data information with higher exploration accuracy (vertical resolution is generally less than 0.2m). The comprehensive application of data with different survey accuracies not only improves the operating efficiency, but also ensures the accuracy of the calculation results.

[0248] Compared with the prior art, the method of the present invention has at least the following beneficial effects:

[0249] The beneficial effect of the present invention is to effectively reduce the cost of acquiring key geological science data and improve the accuracy of hydrate exploration prediction.

[0250] Through the organic integration of various survey methods such as geological sampling, heat flow measurement, and seismic exploration, as well as the full mining of seismic, logging, and core information, based on the basic principles of heat transfer and scientific technical methods, through programmed calculations, scientific correction of shallow seabed geothermal gradient data is achieved, effectively reducing the cost of obtaining key scientific parameters in the hydrate exploration process.

[0251] The geothermal gradient is a key factor affecting the distribution of the hydrate stability domain, and is of great significance for guiding hydrate exploration. The deep formation temperature usually requires the drilling system to carry an in-situ temperature measurement probe that is resistant to high temperature and high pressure to carry out formation temperature detection, which has the disadvantages of high construction cost and complex operation process, and does not have the prospect of widespread promotion and application in the regional scope. The present invention is based on the collection of shallow seabed geothermal gradient data with low operation cost, combined with auxiliary information such as earthquakes and well logging, to calculate or test key parameters such as sediment thermal conductivity and heat generation rate, to achieve the correction of shallow seabed geothermal gradient data, obtain the geothermal gradient data of the deep target layer (the hydrate layer in the present invention), and then achieve accurate prediction of the bottom boundary of the hydrate stability domain, effectively serving the hydrate drilling deployment.

[0252] On the other hand, Fig. 9 As shown, an embodiment of the present invention provides a hydrate stability zone bottom boundary prediction device 900, which may include: a first module 910, used to obtain the first formation temperature data of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction; a second module 920, used to obtain the shallow seabed columnar sediments at a preset point, and obtain the first thermal conductivity of the shallow seabed through thermal conductivity test processing; a third module 930, used to obtain the shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity; a fourth module 940, used to obtain the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement; a fifth module 950, used to obtain the content of the target radioactive element in the deep-sea sediment, and then The average heat generation rate from the shallow seabed to the hydrate layer is determined in combination with the corresponding sediment density; the sixth module 960 is used to establish a vertical formation temperature field through geothermal extension technology based on the shallow seabed geothermal flow value, the second thermal conductivity and the average heat generation rate; the seventh module 970 is used to obtain the apparent geothermal gradient of the hydrate layer based on the vertical formation temperature field by calculating the derivative of the formation temperature of the hydrate layer with respect to the depth; the eighth module 980 is used to obtain the geothermal gradient of the hydrate layer based on drilling measurements, perform error analysis based on the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and correct the apparent geothermal gradient of the hydrate layer based on the results of the error analysis; the ninth module 990 is used to construct the bottom boundary depth of the hydrate stability domain based on the corrected apparent geothermal gradient of the hydrate layer.

[0253] The contents of the method embodiments of the present invention are all applicable to the device embodiments. The functions specifically implemented by the device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0254] On the other hand, an embodiment of the present invention further provides an electronic device, the electronic device comprising a memory and a processor, the memory storing a computer program, and the processor implementing the above-mentioned hydrate stability region bottom boundary prediction method when executing the computer program. The electronic device can be any intelligent terminal including a tablet computer, a car computer, etc.

[0255] It can be understood that the contents of the above method embodiments are all applicable to the present device embodiments, the functions specifically implemented by the present device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0256] like Fig.10 As shown, Fig.10 The hardware structure of an electronic device of another embodiment is illustrated, and the electronic device includes:

[0257] The processor 1001 may be implemented by a general-purpose CPU (Central Processing Unit), a microprocessor, an application-specific integrated circuit (Application Specific Integrated Circuit, ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of the present invention;

[0258] The memory 1002 can be implemented in the form of a read-only memory (ROM), a static storage device, a dynamic storage device, or a random access memory (RAM). The memory 1002 can store an operating system and other applications. When the technical solution provided in the embodiment of this specification is implemented by software or firmware, the relevant program code is stored in the memory 1002, and the processor 1001 calls and executes the network node population optimization method of the embodiment of the present invention;

[0259] Input / output interface 1003, used to implement information input and output;

[0260] The communication interface 1004 is used to realize the communication interaction between the device and other devices. The communication can be realized through a wired manner (such as USB, network cable, etc.) or a wireless manner (such as mobile network, WIFI, Bluetooth, etc.);

[0261] A bus 1005 , which transmits information between various components of the device (e.g., the processor 1001 , the memory 1002 , the input / output interface 1003 , and the communication interface 1004 );

[0262] The processor 1001 , the memory 1002 , the input / output interface 1003 and the communication interface 1004 are connected to each other in communication within the device via the bus 1005 .

[0263] The electronic device embodiments described above are merely illustrative, and the units described as separate components may or may not be physically separated, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0264] The contents of the method embodiments of the present invention are all applicable to the electronic device embodiments. The functions specifically implemented by the electronic device embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0265] Another aspect of an embodiment of the present invention further provides a computer-readable storage medium, wherein the storage medium stores a program, and the program is executed by a processor to implement the above method.

[0266] It should be noted that the computer-readable medium shown in the embodiment of the present invention may be a computer-readable signal medium or a computer-readable storage medium or any combination of the above two. The computer-readable storage medium may be, for example, but not limited to, an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, device or device, or any combination of the above. More specific examples of computer-readable storage media may include, but are not limited to: an electrical connection with one or more wires, a portable computer disk, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), a flash memory, an optical fiber, a portable compact disk read-only memory (Compact Disc Read to Only Memory, CD to ROM), an optical storage device, a magnetic storage device, or any suitable combination of the above. In the present invention, a computer-readable storage medium may be any tangible medium containing or storing a program, which may be used by or in combination with an instruction execution system, device or device. In the present invention, a computer-readable signal medium may include a data signal propagated in a baseband or as part of a carrier wave, which carries a computer-readable program code. Such propagated data signals may take a variety of forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination of the above. Computer readable signal media may also be any computer readable medium other than computer readable storage media, which may send, propagate, or transmit programs for use by or in conjunction with an instruction execution system, apparatus, or device. The program code contained on the computer readable medium may be transmitted using any suitable medium, including but not limited to: wireless, wired, etc., or any suitable combination of the above.

[0267] The contents of the method embodiments of the present invention are all applicable to the computer-readable storage medium embodiments. The functions specifically implemented by the computer-readable storage medium embodiments are the same as those of the above method embodiments, and the beneficial effects achieved are also the same as those achieved by the above method embodiments.

[0268] The embodiment of the present invention also discloses a computer program product or a computer program, which includes a computer instruction stored in a computer-readable storage medium. A processor of a computer device can read the computer instruction from the computer-readable storage medium, and the processor executes the computer instruction, so that the computer device executes the above method.

[0269] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to various embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a module, a program segment, or a part of a code, and the above-mentioned module, program segment, or a part of a code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram or flow chart, and the combination of the boxes in the block diagram or flow chart can be implemented with a dedicated hardware-based system that performs a specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0270] It should be noted that, although several modules of the device for action execution are mentioned in the above detailed description, this division is not mandatory. In fact, according to an embodiment of the present invention, the features and functions of two or more modules or units described above can be embodied in one module or unit. On the contrary, the features and functions of one module or unit described above can be further divided into being embodied by multiple modules or units.

[0271] Through the description of the above implementation, it is easy for those skilled in the art to understand that the example implementation described here can be implemented by software, or by software combined with necessary hardware. Therefore, the technical solution according to the implementation of the present invention can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD to ROM, a USB flash drive, a mobile hard disk, etc.) or on a network, including several instructions to enable a computing device (which can be a personal computer, a server, a touch terminal, or a network device, etc.) to execute the method according to the implementation of the present invention.

[0272] In some selectable embodiments, the function / operation mentioned in the block diagram may not occur in the order mentioned in the operation diagram. For example, depending on the function / operation involved, the two boxes shown in succession can actually be executed substantially simultaneously or the boxes can sometimes be executed in reverse order. In addition, the embodiment presented and described in the flow chart of the present invention is provided by way of example, for the purpose of providing a more comprehensive understanding of technology. The disclosed method is not limited to the operation and logic flow presented herein. Selectable embodiments are expected, wherein the order of various operations is changed and the sub-operation of a part for which is described as a larger operation is performed independently.

[0273] In addition, although the present invention is described in the context of functional modules, it should be understood that, unless otherwise specified, one or more of the functions and / or features can be integrated into a single physical device and / or software module, or one or more functions and / or features can be implemented in a separate physical device or software module. It is also understood that a detailed discussion of the actual implementation of each module is unnecessary for understanding the present invention. More specifically, in view of the properties, functions and internal relationships of the various functional modules in the device disclosed herein, the actual implementation of the module will be understood within the conventional skills of the engineer. Therefore, those skilled in the art can implement the present invention set forth in the claims without excessive experimentation using ordinary techniques. It is also understood that the specific concepts disclosed are merely illustrative and are not intended to limit the scope of the present invention, which is determined by the full scope of the appended claims and their equivalents.

[0274] If the function is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc. Various media that can store program codes.

[0275] The logic and / or steps represented in the flowchart or otherwise described herein, for example, may be considered as an ordered list of executable instructions for implementing logical functions, and may be embodied in any computer-readable medium for use by an instruction execution device, apparatus or device (such as a computer-based device, a device including a processor, or other device that can fetch instructions from an instruction execution device, apparatus or device and execute the instructions), or in conjunction with such instruction execution device, apparatus or device. For purposes of this specification, "computer-readable medium" may be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution device, apparatus or device, or in conjunction with such instruction execution device, apparatus or device.

[0276] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), a fiber optic device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0277] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0278] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0279] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0280] The above is a specific description of the preferred implementation of the present invention, but the present invention is not limited to the embodiments. Those skilled in the art can make various equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications or substitutions are all included in the scope defined by the claims of the present invention.

Claims

1. A method for predicting the bottom boundary of a hydrate stability region, characterized in that: include: Obtain the first stratum temperature data of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction; Obtaining shallow columnar sediments at a preset point on the seabed, and obtaining a first thermal conductivity of the shallow seabed through thermal conductivity testing; Obtaining a shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity; Based on the hydrate drilling core measurement, a second thermal conductivity from the shallow seabed to the hydrate layer is obtained; Obtaining the content of the target radioactive element in the deep-sea sediment, and then determining the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density; Based on the shallow seabed heat flow value, the second thermal conductivity and the average heat generation rate, a vertical formation temperature field is established by using a geothermal extension technology; Based on the vertical formation temperature field, obtaining the apparent geothermal gradient of the hydrate layer by calculating the derivative of the formation temperature of the hydrate layer with respect to the depth; Acquire the geothermal gradient of the hydrate layer based on actual drilling measurements, perform error analysis based on the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and correct the apparent geothermal gradient of the hydrate layer based on the result of the error analysis; Wherein, the correcting the apparent geothermal gradient of the hydrate layer based on the result of the error analysis comprises: When the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is greater than a preset threshold, the density of measuring points is increased, and then the step of obtaining the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement is returned to, until the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is less than or equal to the preset threshold; Wherein, the content of the target radioactive element in the deep-sea sediment and the corresponding sediment density are obtained according to the preset sediment heat generation rate test point test; the increased test point density includes the test point density of the hydrate drilling core measurement and the preset test point density of the sediment heat generation rate test point; The bottom depth of the hydrate stability zone is constructed based on the corrected apparent geothermal gradient of the hydrate layer.

2. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The method of obtaining the first formation temperature data of the shallow seabed and then obtaining the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction includes: Obtain the measured formation temperature data at different depths of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction; The expression of the shallow seabed geothermal gradient is: G s =(T max -T min ) / Lcosθ; In the formula, G s represents the shallow seabed geothermal gradient; T max Indicates the formation temperature value measured by the in-situ temperature measurement probe at the bottom; T min represents the formation temperature value measured by the top in-situ temperature measurement probe; L represents the distance from the bottom to the top of the in-situ temperature measurement probe; θ represents the angle between the in-situ temperature measurement probe and the vertical direction.

3. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The method of obtaining shallow columnar sediments of the seabed at a preset point and obtaining a first thermal conductivity of the shallow seabed by thermal conductivity testing includes: Performing a thermal conductivity test on each depth point in the preset points respectively to obtain a thermal conductivity value corresponding to each depth point; The thermal conductivity values ​​of all the depth points are summed and averaged to obtain the average thermal conductivity of the shallow columnar sediments on the seabed.

4. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The second thermal conductivity from the shallow seabed to the hydrate layer is obtained based on the hydrate drilling core measurement, including: Conducting thermal conductivity tests on different positions of the hydrate drilling core at preset intervals to obtain thermal conductivity of sediments at different depths from the shallow seabed to the hydrate layer; The thermal conductivities obtained from all tests are summed and averaged to obtain the average thermal conductivity from the shallow seabed to the hydrate layer; The expression of the average thermal conductivity from the shallow seabed to the hydrate layer is: Where K represents the average thermal conductivity from the shallow seabed to the hydrate layer; K i represents the thermal conductivity of the sediment at the i-th depth position; m represents the number of thermal conductivity tests.

5. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The obtaining of the content of the target radioactive element in the deep-sea sediment and then determining the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density includes: The heat generation rate of the sediment at the preset sediment heat generation rate test point is calculated based on the U, Th and K element contents in the sediment obtained by testing at the preset sediment heat generation rate test point and the sediment density; The expression of the heat generation rate of the sediment at the sediment heat generation rate test point is: In the formula, A i represents the sediment heat generation rate of the i-th sediment heat generation rate test point; ρ i represents the sediment density at the i-th sediment heat generation rate test point; represents the U content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the Th element content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; represents the K content in the sediment at the depth corresponding to the i-th sediment heat generation rate test point; The sediment heat generation rates of all the sediment heat generation rate test points are summed and averaged to obtain the average heat generation rate from the shallow seabed to the hydrate layer.

6. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The method of establishing a vertical formation temperature field by using a geothermal extension technology based on the seafloor shallow terrestrial heat flow value, the second thermal conductivity and the average heat generation rate includes: Acquire the seabed temperature and the formation temperature corresponding to the preset depth below the seabed, and then calculate the vertical formation temperature field by geothermal extension technology based on the one-dimensional heat conduction Laplace equation in combination with the shallow seabed terrestrial heat flow value and the second thermal conductivity and the average heat generation rate within a preset range; the preset range represents the depth range from 0 below the seabed to the preset depth; Wherein, the expression of the vertical formation temperature field is: Where Z represents the preset depth below the seabed, T z It represents the stratum temperature corresponding to the preset depth below the seabed; T0 represents the seabed temperature; Q represents the shallow terrestrial heat flow value of the seabed; K represents the second thermal conductivity within the preset range; A represents the average heat generation rate within the preset range.

7. The method for predicting the bottom boundary of the hydrate stability region according to claim 1, characterized in that: The bottom depth of the hydrate stability domain is constructed based on the corrected apparent geothermal gradient of the hydrate layer, including: The formation temperature and formation depth function is constructed based on the corrected apparent geothermal gradient of the hydrate layer; The formation temperature and formation depth function is solved together with the hydrate phase equilibrium simulation equation to obtain the bottom depth of the hydrate stability domain.

8. A device for predicting the bottom boundary of a hydrate stability region, characterized in that: include: The first module is used to obtain the first stratum temperature data of the shallow seabed, and then obtain the shallow seabed geothermal gradient through in-situ temperature measurement probe inclination correction; The second module is used to obtain shallow columnar sediments of the seabed at a preset point, and obtain the first thermal conductivity of the shallow seabed through thermal conductivity testing; The third module is used to obtain the shallow seabed geothermal flow value according to the product of the shallow seabed geothermal gradient and the first thermal conductivity; The fourth module is used to obtain the second thermal conductivity from the shallow seabed to the hydrate layer based on the hydrate drilling core measurement; The fifth module is used to obtain the content of the target radioactive element in the deep-sea sediment, and then determine the average heat generation rate from the shallow seabed to the hydrate layer in combination with the corresponding sediment density; A sixth module is used to establish a vertical formation temperature field through a geothermal extension technology based on the seafloor shallow terrestrial heat flow value, the second thermal conductivity and the average heat generation rate; A seventh module is used to obtain the apparent geothermal gradient of the hydrate layer by obtaining the derivative of the formation temperature of the hydrate layer with respect to the depth based on the vertical formation temperature field; An eighth module is used to obtain the geothermal gradient of the hydrate layer based on the actual drilling measurement, perform error analysis according to the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer, and correct the apparent geothermal gradient of the hydrate layer based on the result of the error analysis; The correction of the apparent geothermal gradient of the hydrate layer based on the result of the error analysis includes: When the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is greater than a preset threshold, the density of measuring points is increased, and then the steps executed by the fourth module are returned until the error between the apparent geothermal gradient of the hydrate layer and the geothermal gradient of the hydrate layer is less than or equal to the preset threshold; The content of the target radioactive element in the deep-sea sediment and the corresponding sediment density are obtained by testing the preset sediment heat generation rate test points; the increased test point density includes the test point density of the hydrate drilling core measurement and the test point density of the preset sediment heat generation rate test points; The ninth module is used to construct the bottom depth of the hydrate stability domain based on the corrected apparent geothermal gradient of the hydrate layer.

9. An electronic device, characterized in that: including a processor and a memory; The memory is used to store programs; The processor executes the program to implement the method according to any one of claims 1 to 7.

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