Method, device and medium for identifying coexistence and occurrence types of hydrate and free gas

Abstract

The invention relates to the technical field of petroleum and natural gas hydrate exploration, and discloses a method and device for identifying coexistence and occurrence types of hydrate and free gas and a medium. The method comprises the following steps: establishing a temperature-depth relational expression of stratums below the seabed; determining the depths of the bottom boundaries of the stable zones of the type I and type II hydrates; calculating a bulk modulus ksat, a shear modulus Gsat, a longitudinal wave velocity Vp, a transverse wave velocity Vs and a saturated water formation resistivity R0; comparing logging data; determining a hydrate-containing layer; determining a hydrate and free gas coexistence layer; and determining a pore filling type hydrate and free gas coexistence layer and a fracture filling type hydrate and free gas coexistence layer. According to the technical scheme, on the basis of intersection analysis of the porosity and the resistivity difference and conjoint analysis of various logging data, the hydrate and free gas coexisting stratum and the occurrence form are rapidly and effectively recognized, and the optimal target and the reservoir characteristic difference can be rapidly determined on a hydrate drilling site.

Description

Technical Field

[0001] This invention relates to the field of oil and gas hydrate exploration technology, specifically to the evaluation of natural gas hydrate test production reservoirs, and more specifically to a method, apparatus, and medium for identifying the coexistence and occurrence types of hydrates and free gas. Background Technology

[0003] Hydrate exploration and drilling have revealed various types of hydrate and free gas coexistence phenomena in different lithological strata, such as pore-filling and fracture-filling hydrates and free gas coexisting. These coexisting strata may be located within Type I hydrate stability zones or between Type I and Type II hydrate stability zones, and these coexisting layers are currently the preferred areas for hydrate trial production. However, due to the differences in the causes and modes of hydrate and free gas coexistence, the physical characteristics of the formation rocks vary greatly. Traditional methods for rapid hydrate identification based on anomalies in logging data such as resistivity and P-wave velocity are not suitable for identifying hydrate and free gas coexisting layers.

[0004] Internationally, the identification and evaluation of hydrate and free gas reservoirs mainly rely on core samples, well logging data, and 3D seismic data obtained from drilling. While the identification features are generally quite reliable, it's difficult to directly determine the hydrate occurrence morphology without core samples. The main identifying characteristics of hydrate layers are high resistivity and high P-wave velocity. Core samples of fracture-filled hydrates often show visible vein-like or massive hydrate formations. Relatively rich hydrate layers, in the spatial distribution of 3D seismic profiles, exhibit chimney-like reflection characteristics such as amplitude gaps, formation arching, and abnormally shallow BSRs in local areas, serving as the main identifying indicators of hydrate anomalies. Free gas is identified by high resistivity and low P-wave velocity anomalies, which manifest as bright spot reflections in seismic data. Currently, there is no unified standard for identifying fracture-filled hydrate and free gas coexisting layers, and the following problems exist:

[0005] (1) In well logging data, formations containing free gas exhibit low P-wave velocities, while hydrate-bearing formations exhibit high P-wave velocities. However, in mixed hydrate and free gas layers, well logging data still shows low P-wave velocities for gas-bearing formations. In local layers, due to low or no gas content, high P-wave velocity anomalies may occur. However, as long as the formation contains free gas, the P-wave velocity is significantly lower than that of saturated water layers.

[0006] (2) The reservoir properties of pore-filled hydrates and fracture-filled hydrates differ significantly. Pore-filled hydrates exhibit isotropic characteristics, while fracture-filled hydrates show obvious anisotropic characteristics. If it is not possible to accurately determine whether the hydrate is pore-filled or fracture-filled, then choosing an inappropriate model will result in significant differences in the evaluated hydrate saturation. Among these, fractures developed in the sediments are the main cause of anisotropy, leading to significant changes in the measured physical property parameters. This anomaly is not necessarily due to the hydrate content, but rather to the anisotropy of the formation. Therefore, hydrate drilling and logging data record rich information about the filling medium and host sediments in the formation. How to use logging data to quickly determine the occurrence type and enrichment degree of hydrates and free gas in the formation is of great significance for accurately evaluating resource quantity and conducting coring.

[0007] Further analysis is needed.

[0008] Currently, there is a lack of methods for identifying formations containing both hydrates and free gas in pore-filled or fracture-filled types using well logging data. This is especially true in offshore hydrate drilling sites, where it is difficult to distinguish between hydrates and free gas in the drilled formation. In other words, it is difficult to quickly determine on-site whether a formation contains hydrates or free gas. This makes it difficult to accurately determine which locations have good reservoir characteristics when guiding subsequent sampling, leading to increased drilling costs and risks, and inaccurate prediction of resource potential.

[0009] In existing technologies, the research objective and formation extent of the hydrate site are first determined; then, the P-wave velocity, S-wave velocity, and resistivity data of the formation saturated water are calculated, and the hydrate saturation is calculated using a model. This method can identify whether the formation contains hydrates or free gas and calculate the saturation of either. However, when hydrates and free gas coexist, the logging response characteristics are similar to those of formations containing free gas, leading to problems in the judgment process. Furthermore, it is difficult to determine whether the hydrate type in a layer where hydrates and free gas coexist is a pore-filled hydrate or a fracture-filled hydrate. Summary of the Invention

[0010] This invention provides a method, apparatus, and medium for identifying the coexistence and occurrence types of hydrates and free gas, in order to solve the current lack of methods for identifying formations with coexisting hydrates and free gas in pore-filled or fracture-filled formations using well logging data, especially in offshore hydrate drilling sites where it is impossible to distinguish between the hydrate and free gas content of drilled formations.

[0011] According to a first aspect of the present invention, a method for identifying the coexistence and occurrence types of hydrates and free gas is provided, comprising the following steps:

[0012] S1. Based on the selected research target area, combined with the BSR identification method, determine whether multiple BSRs are locally developed in the strata; using the seabed temperature and strata temperature points measured by drilling, fit the geothermal gradient of the strata and establish the temperature-depth relationship of the strata below the seabed.

[0013] S2. Intersect the temperature-depth relationship described in step S1 with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components, and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively; wherein, the hydrate formed by pure methane is a type I hydrate, while the hydrate formed with ethane gas components is a type II hydrate.

[0014] S3. Calculate the bulk modulus k of a water-saturated formation. sat and shear modulus G sat The main lithologies of the strata are mudstone and sandstone.

[0015] S4. Calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s ;

[0016] S5. Combined density porosity Well logging was performed to calculate the resistivity R0 of the saturated water formation.

[0017] S6. Jointly analyze the logging data, and compare the saturated water P-wave velocity, S-wave velocity and resistivity calculated in steps S4 and S5 with the measured P-wave velocity, S-wave velocity and resistivity logging data.

[0018] S7. Analyze the well logging data from the bottom boundary of the Type I hydrate stability zone to the seafloor strata determined in step S2 to identify the hydrate-bearing layer;

[0019] S8. Compare and analyze the well logging data of the formation between the bottom boundary of the type I hydrate and type II hydrate stable zone determined in step S2 to determine the hydrate and free gas coexistence layer;

[0020] S9. Identify the hydrate and free gas coexistence layer described in step S8, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer.

[0021] Preferably, in step S2, the thickness of the bottom boundary of the type II hydrate stability zone calculated using the same geothermal gradient is greater than the bottom boundary of the type I hydrate stability zone calculated using pure methane gas.

[0022] Preferably, in step S4, the longitudinal wave velocity V p The transverse wave velocity V s The calculation formula is:

[0023]

[0024]

[0025] In the formula, ρ b This is the actual density logging data.

[0026] Preferably, in step S5, the resistivity R0 of the saturated water formation is calculated using the Archie equation, expressed as:

[0027]

[0028] In the formula, R w Let be the resistivity of the formation pore water, taken as 0.3 Ωm, and a and m be Archie's constants.

[0029] Preferably, in step S6, the joint analysis of logging data includes at least one of neutron and density porosity logging, P-wave velocity logging, S-wave velocity logging, density logging, gamma logging, and resistivity logging.

[0030] Preferably, in step S7, when the measured longitudinal wave velocity is higher than the longitudinal wave velocity of saturated water, the transverse wave velocity is higher than the transverse wave velocity of saturated water, and the measured resistivity is higher than the resistivity of saturated water, it is considered to be the hydrate layer; and / or

[0031] In step S8, if the measured resistivity is greater than the resistivity of saturated water, and the measured P-wave velocity is less than the P-wave velocity of saturated water, or if a local area exhibits a P-wave velocity greater than that of saturated water, and if a II-BSR exists in a local area on the seismic profile, then it is the hydrate and free gas coexisting layer; and / or

[0032] In step S9, the neutron porosity is significantly lower than the density porosity, indicating a coexistence layer of pore-filled hydrates and free gas; while the density porosity and neutron porosity curves are basically consistent, but the measured resistivity differs from the saturated water resistivity [△(R]]. t The presence of significant differences in the -R0) indicates that the layer is a coexistence of fissure-filled hydrate and free gas; the abnormally high resistivity indicates that the hydrate-containing layer has anisotropic characteristics.

[0033] Preferably, step S8 further includes the following step:

[0034] Further analysis of the hydrate and free gas coexistence layer revealed that when the measured shear wave velocity is similar to or the same as that of saturated water, it is a stratum dominated by free gas; when the measured shear wave velocity is significantly greater than that of saturated water, it is a stratum containing hydrates.

[0035] According to a second aspect of the present invention, an apparatus is provided for identifying the coexistence and occurrence types of hydrates and free gas, comprising:

[0036] A module was established to determine whether multiple BSRs are locally developed in the strata based on the selected research target area and the BSR identification method; the temperature-depth relationship of the strata below the seabed was established by fitting the geothermal gradient of the strata using the measured seabed temperature and strata temperature points from drilling.

[0037] The determination module is used to intersect the temperature-depth relationship obtained by the establishment module with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components, and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively; wherein, the hydrate formed by pure methane is a type I hydrate, while the hydrate formed with ethane gas components is a type II hydrate.

[0038] The first calculation module is used to calculate the bulk modulus k of the saturated water formation. sat and shear modulus G sat The main lithologies of the strata are mudstone and sandstone.

[0039] The second calculation module is used to calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s ;

[0040] The third calculation module is used to combine density and porosity. Well logging was performed to calculate the resistivity R0 of the saturated water formation.

[0041] The comparison module is used for joint analysis of logging data, and compares the saturated water P-wave velocity, S-wave velocity and resistivity obtained by the second calculation module and the third calculation module with the measured P-wave velocity, S-wave velocity and resistivity logging data.

[0042] The first analysis module is used to analyze the well logging data from the bottom boundary of the type I hydrate stability zone to the seafloor strata determined by the determination module, and to determine the hydrate-bearing layer.

[0043] The second analysis module is used to compare and analyze well logging data of the formation between the bottom boundary of the type I and type II hydrate stability zones determined by the determination module, and to determine the hydrate and free gas coexistence layer; and

[0044] The third analysis module is used to identify the hydrate and free gas coexistence layer mentioned in the second analysis module, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer.

[0045] According to a third aspect of the present invention, an electronic device is provided, comprising:

[0046] Memory; and

[0047] processor;

[0048] The memory is used to store one or more computer instructions; the one or more computer instructions are executed by the processor to implement the method described in any of the above.

[0049] According to a fourth aspect of the present invention, a readable storage medium is provided, wherein computer instructions are stored thereon; wherein, when executed by a processor, the computer instructions implement the method described in any of the preceding claims.

[0050] The technical solution of this invention, based on cross-analysis of porosity and resistivity differences and joint analysis of multiple logging data, can quickly and effectively identify the formations and occurrence morphologies in which hydrates and free gas coexist, which is beneficial for quickly determining the preferred targets and reservoir characteristic differences at the hydrate drilling site.

[0051] Among them, taking into account the development of II-BSR in seismic data, the analysis of rock property differences reflected by different porosities and well logging anomalies is applied to the rapid identification of hydrate and free gas coexisting layers and their occurrence types. Based on the identification and classification criteria of coexisting strata, it can quickly and effectively identify and distinguish hydrate and free gas strata at the hydrate drilling site, improve the efficiency of identifying coexisting layers and hydrate occurrence types using well logging data at the hydrate drilling site, guide the next step of hydrate drilling coring work, and provide a basis for subsequent fine exploration of hydrate reservoirs. Attached Figure Description

[0052] Figure 1 This is a flowchart of a method for identifying the coexistence and occurrence types of hydrates and free gas in one embodiment;

[0053] Figure 2 This is a schematic diagram of seismic profiles at different stations and the identification of multiple BSRs in one embodiment;

[0054] Figure 3 This is a schematic diagram of the bottom boundary of the stability zone of methane (type I) hydrate and the bottom boundary of the stability zone of type II hydrate in one embodiment;

[0055] Figure 4 This is a schematic diagram of well logging data and calculated saturation curve at the DC_E station in the Borneo waters of the South China Sea, as described in one embodiment.

[0056] Figure 5 This is a schematic diagram comparing the logging data and calculated curves of well W17 in the Shenhu area of ​​the northern South China Sea in one embodiment;

[0057] Figure 6 This is a cross-plot of porosity and resistivity differences in the hydrate and free gas coexistence layers in the Shenhu area of ​​the northern South China Sea and the Borneo area in one embodiment.

[0058] Figure 7 This is a flowchart of a method for identifying the coexistence and occurrence types of hydrates and free gas in one embodiment;

[0059] Figure 8 This is a schematic diagram of a device for identifying the coexistence and occurrence types of hydrates and free gas in one embodiment. Detailed Implementation

[0060] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0061] To enable those skilled in the art to better understand the present invention, the technical solution of one embodiment will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are merely some, not all, embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort should fall within the scope of protection of the present invention.

[0062] It should be noted that the terms "first," "second," etc., used in this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be used interchangeably where appropriate for the embodiments of the invention described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0063] It should be understood that when an element (such as a layer, film, region, or substrate) is described as being "on" another element, the element may be directly on the other element, or there may be an intermediate element present. Moreover, in this invention, when an element is described as being "connected" to another element, the element may be "directly connected" to the other element, or "connected" to the other element via a third element.

[0064] Example 1

[0065] Utilizing seismic and well logging data to quickly determine the coexistence morphology of hydrates and free gas before offshore drilling and coring is crucial for sampling and accurately assessing the degree of hydrate enrichment. Therefore, this invention proposes a rapid identification method for offshore hydrate and free gas coexistence layers by analyzing the trends in density porosity and neutron porosity, combined with well logging anomalies such as P-wave velocity and resistivity, to pinpoint the formations where hydrates and free gas coexist.

[0066] Please refer to Figure 1 , 7 This embodiment provides a method for identifying the coexistence and occurrence types of hydrates and free gas. Based on the cross-plotting of density and resistivity differences and the joint analysis of multiple well logging data, it enables rapid identification of the coexistence of hydrates and free gas in the lower part of the bottom boundary of the Type I hydrate stability zone. This method is based on seismic data BSR identification, calculation of P-wave and S-wave velocities in saturated water formations and comparison of well logging results, analysis of the difference between saturated water resistivity and measured resistivity, and its density-neutron porosity difference. Based on the calculation of the bottom boundary of Type I and Type II hydrate stability zones, it performs refined identification of the hydrate occurrence type and free gas formation between them. The stability zone thickness calculated using gas components does not necessarily perfectly match the BSR identified by seismic profiles. Generally, the BSR or I-BSR approximately matches the Type I hydrate stability zone, while the II-BSR approximately matches the bottom boundary of the Type II hydrate stability zone. Figure 1 This demonstrates the identification process for fracture-filled and pore-filled hydrate and free gas coexistence layers.

[0067] This method can quickly identify the formations and occurrence modes of hydrates and free gas, which is beneficial for quickly determining the preferred targets and reservoir characteristics differences at the hydrate drilling site.

[0068] The steps are explained in detail below:

[0069] S1. Select the target area for study and, based on the selected target area, determine whether multiple BSRs are locally developed in the formation using the BSR identification method. Figure 2 In the BSR identification method, the BSR characteristics on the seismic data are analyzed to identify the reflection characteristics of the strata above and below the BSR. Furthermore, the seabed temperature and stratum temperature points measured by drilling are used to fit the stratum geothermal gradient and establish the temperature-depth relationship of the strata below the seabed.

[0070] In one embodiment of step S1, when fitting the geothermal gradient, a value of 62.5℃ / km is used. The temperature-depth relationship between the subsea strata is established by combining the seafloor temperature (5℃), the depth of the subsea strata (D), and the stratum temperature (T).

[0071] D = (T - 5) / 0.0625

[0072] S2. Intersect the temperature-depth relationship described in step S1 with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components (calculated using the existing CSMHYD program), and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively. Figure 3The diagram illustrates the bottom boundaries of the stability zones for methane (Type I) hydrates and Type II hydrates, calculated based on the intersection of geothermal gradients and hydrate phase equilibrium curves with different gas components. Specifically, the hydrates formed from pure methane are primarily Type I hydrates, while those containing ethane gas components are Type II hydrates. Generally, the thickness of the bottom boundary of the Type II hydrate stability zone calculated using the same geothermal gradient is greater than that of the Type I hydrate stability zone calculated from pure methane gas.

[0073] S3. Calculate the bulk modulus k of a water-saturated formation. sat and shear modulus G sat The strata are primarily composed of mudstone and sandstone. The bulk modulus k can be calculated using existing traditional effective medium models. sat and shear modulus G sat The calculation methods and parameters are detailed in the references Dvorkin and Nur, 1996, Geophysics, and Ecker et al., 1998, Geophysics; the calculated bulk modulus k of saturated water sediments is also provided. sat and shear modulus G sat The main lithologies of the middle strata are mudstone and sandstone, with contents of 0.9% and 0.1%, respectively.

[0074] S4. Calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s The calculation formula is:

[0075]

[0076]

[0077] In the formula, ρ b For the measured density logging, k sat and G sat The bulk modulus and shear modulus of the saturated water formation are calculated in step S3.

[0078] S5. Combined density porosity Well logging is used to calculate the resistivity R0 of the saturated water formation; preferably, the Archie equation is used in conjunction with density and porosity. Well logging was used to calculate the resistivity R0 of the saturated water formation, expressed as follows:

[0079]

[0080] In the formula, R w Let be the resistivity of the formation pore water, taken as 0.3 Ωm, and a and m be Archie's constants.

[0081] In one embodiment of step S5, the values ​​of a and m in well W17 in the Shenhu area of ​​the South China Sea are 1.19 and 2.22, respectively, while the values ​​of a and m in well DC_E in the Borneo area of ​​the South China Sea are 1.77 and 0.99, respectively. The calculated density is porosity.

[0082] S6. Joint analysis of logging data, wherein the joint analysis includes at least one of neutron and density porosity logging, P-wave velocity logging, S-wave velocity logging, density logging, gamma logging, and resistivity logging; and simultaneously comparing the saturated water P-wave velocity, S-wave velocity, and resistivity calculated in steps S4 and S5 with the measured P-wave velocity, S-wave velocity, and resistivity logging data. Figure 4 , Figure 5 ).

[0083] S7. Analyze the well logging data from the bottom boundary of the Type I hydrate stability zone to the seafloor strata determined in step S2 to identify the hydrate-bearing layer. Preferably, the hydrate-bearing layer is defined as follows: the measured P-wave velocity is higher than the P-wave velocity of saturated water, the S-wave velocity is higher than the S-wave velocity of saturated water, and the measured resistivity is higher than the resistivity of saturated water (see Table 1).

[0084] S8. Compare and analyze the well logging data of the strata between the bottom boundary of the type I hydrate and type II hydrate stable zones determined in step S2 to determine the hydrate and free gas coexistence layer. Preferably, when the measured resistivity is greater than the resistivity of saturated water, and the measured P-wave velocity is less than the P-wave velocity of saturated water or there is a local P-wave velocity greater than that of saturated water, if a II-BSR exists in a local area on the seismic profile, then it is the hydrate and free gas coexistence layer (see Table 1).

[0085] In one embodiment of step S8, the coexistence layer of hydrates and free gas is further analyzed. When the measured shear wave velocity is similar to or the same as the shear wave velocity of saturated water, it is a formation mainly containing free gas; when the measured shear wave velocity is significantly greater than the shear wave velocity of saturated water, it is a formation containing hydrates (see Table 1).

[0086] Table 1. Logging parameters for different hydrate types

[0087]

[0088] S9. Identify the hydrate and free gas coexistence layer described in step S8, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer. Preferably, the neutron porosity is significantly lower than the density porosity (e.g., well W17 in the Shenhu area of ​​the northern South China Sea). Figure 5The image shows a comparison of logging data and calculated saturated water P-wave and S-wave velocities, resistivity data, and neutron porosity and density porosity curves from well W17 in the Shenhu area of ​​the northern South China Sea. The two porosities are significantly different, with a hydrate and free gas coexisting layer appearing between the bottom boundary of the methane hydrate stability zone and the bottom boundary of the type II hydrate stability zone. This is identified as a pore-filled hydrate and free gas coexisting layer. The density porosity and neutron porosity curves are basically consistent, without obvious abnormal changes (as seen in well DC_E in the Borneo area of ​​the South China Sea). Figure 3 However, the difference between the measured resistivity and the resistivity of saturated water is [Δ(R]]. t The presence of significant differences in the -R0) indicates that the layer is a coexistence of fissure-filled hydrate and free gas; the abnormally high resistivity indicates that the hydrate-containing layer has anisotropic characteristics.

[0089] in, Figure 6 The neutron porosity and density porosity difference for two different types of hydrates coexisting with free gas are clearly presented. With [Δ(R)] t The intersection diagram (-R0) shows data from well W17 in the Shenhu area of ​​the northern South China Sea, with square data representing data from well DC_E in the Borneo area of ​​the South China Sea.

[0090] The method for identifying the coexistence and occurrence types of hydrates and free gas in this invention innovatively proposes to utilize neutron and density porosity logging data obtained during drilling to analyze the differences in neutron and density porosity in layers with significant low P-wave velocity and high resistivity anomalies. This is combined with traditional methods such as P-wave velocity logging, S-wave velocity logging, and resistivity logging, as well as calculated P-wave velocity, S-wave velocity, and resistivity of saturated water, for joint analysis. By comparing the anomalies in logging parameters (see Table 1), the method identifies hydrate and free gas layers between the bottom boundaries of Type I and Type II hydrate stability zones. Finally, by using anomaly changes in resistivity, porosity, and seismic profile anomalies, the method quickly determines the coexistence layers of hydrates and free gas, and the occurrence status of hydrates and free gas in the coexistence layers. If the resistivity of the lower part of the methane (or type I) hydrate stability zone shows a high value anomaly, the velocity shows a high-low anomaly interval, and the neutron porosity is significantly different from the density porosity, then the hydrate in the hydrate and free gas coexisting layer is a pore-filling type. If the resistivity of the lower part of the methane (or type I) hydrate stability zone is abnormally high and the velocity is significantly reduced, but the difference between neutron and density porosity is not significant, then the hydrate and free gas coexisting layer is a fracture-filling type. The high resistivity anomaly is due to the anisotropy of fractures leading to increased resistivity, and the hydrate saturation of the formation is not necessarily very high.

[0091] This method makes full use of various logging response anomalies obtained from field drilling to quickly identify the formation containing hydrates and free gas. It can quickly and effectively identify and distinguish hydrate and free gas formations at the hydrate drilling site, and has guiding significance for determining the core location of hydrate drilling and making preliminary judgments on resource quantity.

[0092] Example 2

[0093] Please refer to Figure 8 One embodiment provides a device for identifying the coexistence and occurrence types of hydrates and free gas, employing the following structure:

[0094] 1. Module 10 is established to determine whether multiple BSRs are locally developed in the strata based on the selected research target area and the BSR identification method; using the seabed temperature and strata temperature points measured by drilling, the strata geothermal gradient is fitted to establish the temperature-depth relationship of the strata below the seabed.

[0095] 2. The determination module 20 is used to intersect the temperature-depth relationship obtained by the establishment module 10 with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components, and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively; wherein, the hydrate formed by pure methane is a type I hydrate, while the hydrate formed with ethane gas components is a type II hydrate.

[0096] 3. The first calculation module 30 is used to calculate the bulk modulus k of the saturated water strata. sat and shear modulus G sat The main lithology of the strata is mudstone and sandstone.

[0097] 4. The second calculation module 40 is used to calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s .

[0098] 5. The third calculation module 50 is used to combine density and porosity. Well logging was performed to calculate the resistivity R0 of the saturated water formation.

[0099] 6. The comparison module 60 is used for joint analysis of logging data, and at the same time compares the saturated water P-wave velocity, S-wave velocity and resistivity obtained by the second calculation module 40 and the third calculation module 50 with the measured P-wave velocity, S-wave velocity and resistivity logging data.

[0100] 7. The first analysis module 70 is used to analyze the well logging data from the bottom boundary of the type I hydrate stability zone to the seafloor strata determined by the determination module 20, and to determine the hydrate-bearing layer.

[0101] 8. The second analysis module 80 is used to compare and analyze the well logging data of the formation between the bottom boundary of the type I hydrate and type II hydrate stable zone determined by the determination module 20, and to determine the hydrate and free gas coexisting layer.

[0102] 9. The third analysis module 90 is used to identify the hydrate and free gas coexistence layer of the second analysis module 80, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer.

[0103] The device for identifying the coexistence and occurrence types of hydrates and free gas utilizes a combination of modules 10 (establishment), 20 (determination), 20 (calculation), 60 (comparison), and 60 (analysis) to rapidly identify hydrates in the field by analyzing the intersection differences in density and resistivity between the bottom boundaries of Type I and Type II hydrate stability zones. Through analysis of seismic data BSR identification, calculation of P-wave and S-wave velocities in saturated water formations, comparison of well logging results, and the difference between saturated water resistivity and measured resistivity, as well as the density-neutron porosity difference, the device determines whether the hydrate-free gas coexistence layer and its hydrates are of a pore-filling or fracture-filling type, providing rapid and accurate target selection for hydrate drilling and coring.

[0104] It should be noted that the above-mentioned apparatus for identifying the coexistence and occurrence types of hydrates and free gases is used to implement the methods for identifying the coexistence and occurrence types of hydrates and free gases in the above embodiments, and each module in the apparatus corresponds to each step in the method.

[0105] Example 3

[0106] Based on the same inventive concept, one embodiment of the present invention provides an electronic device, including: a memory and a processor; wherein the memory is used to store one or more computer instructions; the one or more computer instructions are executed by the processor using any of the methods described in the above embodiments.

[0107] Example 4

[0108] Based on the same inventive concept, one embodiment of the present invention provides a readable storage medium storing computer instructions; wherein, when the computer instructions are executed by a processor, they implement the method of any one of the above embodiments.

[0109] One or more of the aforementioned computer instructions can form a program.

[0110] The aforementioned program can run on a processor or be stored in memory (or computer-readable medium). Computer-readable medium includes both permanent and non-permanent, removable and non-removable media, and information storage can be achieved by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transferable medium that can be used to store information accessible by a computing device. As defined herein, computer-readable medium does not include transient computer-readable media, such as modulated data signals and carrier waves.

[0111] These computer programs may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes can be implemented using different modules, and different steps can be implemented using different modules.

[0112] Example 5

[0113] Please refer to Figure 1-7 This embodiment provides a technical solution for identifying the coexistence and occurrence types of hydrates and free gas. The following comparative analysis and explanation of the technical solution through several application cases will help to further understand its technical content.

[0114] The method for identifying the coexistence and occurrence types of hydrates and free gas, as described in the above embodiments, was applied to the logging-while-drilling data of well DC_E in the Borneo area of ​​the South China Sea and well W17 in the Shenhu area of ​​the South China Sea.

[0115] 1. Using steps S1 and S2, combined with seismic profiles, BSR and II-BSR on the seismic profiles of the two regions were identified, and the stability zones of type I and type II hydrates (i.e., I-BGHSZ and II-BGHSZ) were calculated using phase equilibrium curves.

[0116] 2. The P-wave velocity, S-wave velocity, and resistivity of the formation saturated water were calculated using steps S3-S5, and compared with the measured P-wave velocity, S-wave velocity, and resistivity. Figure 4 and 5 ).

[0117] 3. Using steps S6 and S7, the logging data anomalies between I-BGHSZ and II-BGHSZ were analyzed. Combined with Table 1, in the DC_E well in the Borneo area of ​​the South China Sea, high resistivity, low P-wave velocity, and a slightly increased S-wave velocity were observed in the formation between the bottom boundaries of the two stable zones (I-BGHSZ and II-BGHSZ). The neutron porosity and density porosity were basically consistent, indicating that the anomaly was not caused by free gas alone, as free gas alone would generally not result in an increased S-wave velocity. Therefore, the formation is considered to be a coexistence of hydrates and free gas. In the W17 well in the Shenhu area of ​​the South China Sea, between the bottom boundary of the methane hydrate stability zone and the bottom boundary of the type II hydrate stability zone, there is a change in high resistivity, high shear wave velocity, and high-low-high P-wave velocity. The high P-wave velocity anomaly indicates that the formation contains hydrates, while the low P-wave velocity may contain free gas. However, the shear wave velocity is also increasing, indicating that the formation contains both hydrates and free gas. The neutron porosity is significantly different from the density porosity, and a low neutron porosity anomaly is observed.

[0118] 4. Utilize the difference between neutron porosity and density porosity from step S9 The difference between the measured resistivity and the resistivity of saturated water [△(R]] t -R0)】Intersection diagram ( Figure 6 It can be seen that the curves of the two wells show obvious zoning. The intersection anomaly can be used to identify the hydrate occurrence morphology of the hydrate and free gas coexisting layer. Zone 1 is the DC_E well in the Borneo area of ​​the South China Sea. The porosity does not change significantly, but the resistivity is obviously abnormal, which is a fracture-filled hydrate. Zone 2 is the W17 well in the Shenhu area of ​​the South China Sea. The porosity changes significantly and the resistivity increases, but not as much as in Zone 1. It is a pore-filled hydrate.

[0119] Specifically, as shown in the attached diagram:

[0120] Figure 2 The image shows seismic profiles in the Borneo and Shenhu sea areas of the South China Sea, specifically seismic profiles from different stations and the identification of multiple BSRs, indicating potential areas for the coexistence of hydrates and free gas. II-BSRs developed beneath I-BSRs can be identified in both images, indicating that both regions are potential areas for the coexistence of hydrates and free gas.

[0121] Figure 4This paper presents well logging data for the DC_E station in the South China Sea Borneo region, which contains both free gas and hydrate-bearing layers. It compares the well logging data and calculated saturated water P-wave and S-wave velocities and resistivity data for the DC_E station, as well as the curves showing neutron and density porosity versus calculated hydrate saturation. The two porosities are consistent (I-BGHSZ represents the bottom boundary of the methane (Type I) hydrate stability zone; II-BGHSZ represents the bottom boundary of the Type II hydrate stability zone). As shown in the figure, the bottom boundary of the Type I hydrate stability zone is located 150m below the seabed. The formation exhibits anomalies of high resistivity, high P-wave velocity, and high S-wave velocity. Based on Table 1, it can be determined that two hydrate layers develop above it, namely between 100-132m and 143-150m. The calculated bottom boundary of the Type II hydrate stability zone is located 233m below the seabed. Between the bottom boundaries of the Type I and Type II hydrate stability zones, the logging curves show complex variations. According to the classification criteria, the strata with high resistivity, low P-wave velocity, and high S-wave velocity are hydrate layers, with two layers at 173-199m and 208-233m respectively. The strata with high resistivity, low P-wave velocity, and relatively small variations in S-wave velocity are free gas layers, with two layers at 151-173m and 199-208m respectively.

[0122] Figure 6 The porosity difference between the hydrate and free gas coexistence layers in well W17 (area 2, square) in the Shenhu area of ​​the northern South China Sea and well DC_E (area 1, dot) in the Borneo area is shown. With resistivity difference [△(R t -R0)】Cross plot; where fracture-filled hydrates (region 1, dots) and pore-filled hydrates (region 2, squares) are located in two distinct regions. Because the porosity characteristics of the pore-filled hydrate and free gas coexistence layer are significantly different from those of the fracture-filled hydrate and free gas coexistence layer, they exhibit distinct zoning; therefore, using With [△(R)] t Cross-plots and logging anomalies can quickly identify hydrate and free gas coexisting layers and their occurrence types.

[0123] In summary, this embodiment's application case compares the method of this invention with traditional techniques, utilizing well logging data of hydrates at the DC_E station in the cold seep area of ​​the South China Sea Borneo region, and through analysis of reflected seismic data and... With [△(R)] t By combining various data sources, including cross-plots and hydrate logging data, and comparing measured drilling data from different stations, it is possible to quickly determine the coexistence of hydrates and free gas, and whether the hydrate formation is pore-filled or fracture-filled. Furthermore, through application analysis of two wells—W17 in the Shenhu area of ​​the northern South China Sea and DC_E in the Borneo area—the identification of fracture-filled hydrate and free gas coexistence layers is mainly achieved through comprehensive analysis of seismic data, With [△(R)]t Cross-plot analysis was performed based on the classification criteria in Table 1 to identify the type of hydrate and free gas coexistence layer. Figure 6 ).from Figure 6 It can quickly identify that fracture-filled hydrates and pore-filled hydrates have obvious zoning characteristics. The porosity of the pore-filled hydrate and free gas coexistence zone is significantly greater than that of the fracture-filled hydrate and free gas coexistence zone.

[0124] The method of the present invention for identifying the coexistence and occurrence types of hydrates and free gas is simple and fast, and matches the actual drilling core results, indicating that the method can quickly identify the coexistence of hydrates and free gas and determine the occurrence type of hydrates.

[0125] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for identifying the coexistence and occurrence types of hydrates and free gas, characterized in that, Includes the following steps: S1. Based on the selected research target area, combined with the BSR identification method, determine whether multiple BSRs are locally developed in the strata; using the seabed temperature and strata temperature points measured by drilling, fit the geothermal gradient of the strata and establish the temperature-depth relationship of the strata below the seabed. S2. Intersect the temperature-depth relationship described in step S1 with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components, and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively; wherein, the hydrate formed by pure methane is a type I hydrate, while the hydrate formed with ethane gas components is a type II hydrate. S3. Calculate the bulk modulus k of a water-saturated formation. sat and shear modulus G sat The main lithologies of the strata are mudstone and sandstone. S4. Calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s ; S5. Combined density porosity Well logging was performed to calculate the resistivity R0 of the saturated water formation. S6. Jointly analyze the logging data, and compare the saturated water P-wave velocity, S-wave velocity and resistivity calculated in steps S4 and S5 with the measured P-wave velocity, S-wave velocity and resistivity logging data. S7. Analyze the well logging data from the bottom boundary of the Type I hydrate stability zone to the seafloor strata determined in step S2 to identify the hydrate-bearing layer; S8. Compare and analyze the well logging data of the formation between the bottom boundary of the type I hydrate and type II hydrate stable zone determined in step S2 to determine the hydrate and free gas coexistence layer; S9. Identify the hydrate and free gas coexistence layer described in step S8, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer.

2. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, In step S2, the thickness of the bottom boundary of the type II hydrate stability zone calculated using the same geothermal gradient is greater than that of the bottom boundary of the type I hydrate stability zone calculated using pure methane gas.

3. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, In step S4, the longitudinal wave velocity V p The transverse wave velocity V s The calculation formula is: In the formula, ρ b This is the actual density logging data.

4. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, In step S5, the resistivity R0 of the saturated water formation is calculated using the Archie equation, and the expression is: In the formula, R w Let be the resistivity of the formation pore water, taken as 0.3 Ωm, and a and m be Archie's constants.

5. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, In step S6, the joint analysis of logging data includes at least one of neutron and density porosity logging, P-wave velocity logging, S-wave velocity logging, density logging, gamma logging, and resistivity logging.

6. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, In step S7, when the measured P-wave velocity is higher than the P-wave velocity of saturated water, the S-wave velocity is higher than the S-wave velocity of saturated water, and the measured resistivity is higher than the resistivity of saturated water, it is considered to be the hydrate layer; and / or In step S8, if the measured resistivity is greater than the resistivity of saturated water, and the measured P-wave velocity is less than the P-wave velocity of saturated water, or if a local area exhibits a P-wave velocity greater than that of saturated water, and if a II-BSR exists in a local area on the seismic profile, then it is the hydrate and free gas coexisting layer; and / or In step S9, the neutron porosity is significantly lower than the density porosity, indicating a coexistence layer of pore-filled hydrates and free gas; while the density porosity and neutron porosity curves are basically consistent, but the measured resistivity differs from the saturated water resistivity [△(R]]. t The presence of significant differences in the -R0) indicates that the layer is a coexistence of fissure-filled hydrate and free gas; the abnormally high resistivity indicates that the hydrate-containing layer has anisotropic characteristics.

7. The method for identifying the coexistence and occurrence types of hydrates and free gas according to claim 1, characterized in that, Step S8 also includes the following steps: Further analysis of the hydrate and free gas coexistence layer revealed that when the measured shear wave velocity is similar to or the same as that of saturated water, it is a stratum dominated by free gas; when the measured shear wave velocity is significantly greater than that of saturated water, it is a stratum containing hydrates.

8. A device for identifying the coexistence and occurrence types of hydrates and free gas, characterized in that, include: A module was established to determine whether multiple BSRs are locally developed in a formation based on a selected research target area and in conjunction with a BSR identification method. By using the seabed temperature and formation temperature points measured during drilling, the formation geothermal gradient is fitted to establish the temperature-depth relationship of the strata below the seabed. The determination module is used to intersect the temperature-depth relationship obtained by the establishment module with the phase equilibrium curves of hydrates formed by pure methane and 96% methane and 4% ethane gas components, and use the phase equilibrium curves of the two gas components to determine the bottom boundary depth of the stability zone of type I and type II hydrates respectively; wherein, the hydrate formed by pure methane is a type I hydrate, while the hydrate formed with ethane gas components is a type II hydrate. The first calculation module is used to calculate the bulk modulus k of the saturated water formation. sat and shear modulus G sat The main lithologies of the strata are mudstone and sandstone. The second calculation module is used to calculate the longitudinal wave velocity V of the saturated water layer. p With transverse wave velocity V s ; The third calculation module is used to combine density and porosity. Well logging was performed to calculate the resistivity R0 of the saturated water formation. The comparison module is used for joint analysis of logging data, and compares the saturated water P-wave velocity, S-wave velocity and resistivity obtained by the second calculation module and the third calculation module with the measured P-wave velocity, S-wave velocity and resistivity logging data. The first analysis module is used to analyze the well logging data from the bottom boundary of the type I hydrate stability zone to the seafloor strata determined by the determination module, and to determine the hydrate-bearing layer. The second analysis module is used to compare and analyze well logging data of the formation between the bottom boundary of the type I and type II hydrate stability zones determined by the determination module, and to determine the hydrate and free gas coexistence layer; and The third analysis module is used to identify the hydrate and free gas coexistence layer mentioned in the second analysis module, and then compare the density porosity and neutron porosity curves to determine the pore-filled hydrate and free gas coexistence layer and the fracture-filled hydrate and free gas coexistence layer.

9. An electronic device, characterized in that, include: Memory; and processor; The memory is used to store one or more computer instructions; the one or more computer instructions are executed by the processor to implement the method according to any one of claims 1 to 7.

10. A readable storage medium, characterized in that, The readable storage medium stores computer instructions; wherein, when executed by a processor, the computer instructions implement the method described in any one of claims 1 to 7.

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