Evaluation method of submarine hydrogen energy favorable exploration target in ultra-extended tectonic environment

Abstract

The application provides an evaluation method for favorable exploration targets of submarine hydrogen energy in an ultra-extended tectonic environment, and belongs to the field of submarine hydrogen energy exploration and development. The application integrates an evaluation index system for inorganic serpentinization hydrogen generation mechanism in a "hydrogen source-migration-reservoir-seal-thermal structure" five-in-one manner, so as to achieve the design purpose of significantly reducing exploration cost and risk and providing an industrialization target optimization tool for submarine hydrogen energy exploration of an ultra-extended passive continental margin. Specifically, by using existing seismic data and regional geological conditions, combining with geological environment and favorable reservoir-seal combination conditions required for submarine hydrogen energy generation, and aiming at tectonic units with hydrogen generation capacity in different basins, the development range of serpentinization is determined by comprehensively analyzing tectonic environment, extension, lithospheric change, large-scale detachment fault and deep fault characteristics, identifying upper and lower crust thickness and Moho depth, and combining temperature field and seismic reflection anomaly.

Description

Technical Field

[0001] This application relates to the field of seafloor hydrogen energy exploration and development, and specifically proposes a method for evaluating favorable seafloor hydrogen energy exploration targets in ultra-extensional tectonic environments through multi-attribute superposition and spatiotemporal matching scoring. Background Technology

[0002] Located at the intersection of several major tectonic plates, my country's coastal areas have undergone intense extensional forces since the Cenozoic era, forming a typical group of passive continental margin basins. Simultaneously, influenced by plate boundary faulting, deep-sea basin landforms have formed, constituting one of the most important oil and gas resource-rich zones in China's coastal waters. From a formation perspective, since the Late Cretaceous, the Pacific Plate has continuously subducted westward beneath the Eurasian Plate, adjusting its subduction rate and direction multiple times, accompanied by the retreat of the subduction zone. This led to a shift in the continental margin environment from compression to back-arc extension, triggering the formation of a series of rift basins, resulting in basins trending northeast or north-northeast. Beginning in the Late Eocene, the subduction direction of the Pacific Plate changed from north-northwest to northwest, and plate collisions caused fault zone activity to begin. In summary, controlled by a unique expansion process and the interaction of surrounding plates, the region is characterized by a stretching tectonic background with various tectonic processes such as compression, strike-slip, and extension. The continental crust is relatively thin, and the ocean-continent transition zone is widely distributed along the passive continental margin. Due to the lithospheric thinning, crustal extension, and multiple phases of magmatic underplating that formed the high-velocity lower crust, large detachment faults and metamorphic core complexes have developed. At the same time, the fault system is well-developed, and numerous detachment faults provide favorable channels for seawater entry. This unique regional geological feature provides uniquely favorable conditions for the generation and accumulation of natural hydrogen.

[0003] From the perspective of natural hydrogen generation environments, the most important natural hydrogen generation pathway is serpentinization, which mainly occurs in areas with basic to ultrabasic rocks. Crustal extension and thinning cause mantle material to rise, allowing ultrabasic rock masses to approach the surface. Under extensional conditions, the development of deep and large fault systems provides channels for seawater infiltration and hydrogen upwelling. Areas with high heat flow anomalies possess the reaction temperature conditions for hydrogen generation. In summary, natural hydrogen derived from serpentinization is considered the most promising hydrogen generation mechanism, and the optimal window for hydrogen generation occurs in the late rifting to early post-rifting stages of continental rift valleys and extensional margins.

[0004] In recent years, as oil and gas exploration has moved towards deeper layers and deeper parts of the Earth, a large amount of deep reflection and long-array seismic data has been collected, identifying clear Moho reflections and discovering evidence of serpentinization. Combined with current understanding of hydrogen production theories, the intense thinning of the continental crust, with some areas having crustal thicknesses of only a few kilometers, has formed "extensional zones." During the rifting period, sedimentary environments transitioned from terrestrial fluvial and lacustrine facies to littoral-shallow to semi-deep marine facies. The sandstone and carbonate rocks deposited during the rifting period and the early post-rift period possess good porosity and permeability, serving as potential hydrogen reservoirs. Due to the inactive tectonics in the post-rift period, a thick, fine-grained argillaceous cap was deposited, providing excellent sealing conditions for natural hydrogen accumulation. Simultaneously, within this tectonic unit, mantle material upwelled to the shallower parts of the Earth, and numerous brittle fractures developed within the crust, forming abundant underplated magma and magma sheets. This led to changes in the regional geothermal gradient, providing ideal material and spatial conditions for serpentinization reactions. The extensional tectonic environment is the most favorable tectonic unit for hydrogen generation and a promising area for submarine hydrogen energy exploration. Therefore, establishing an evaluation method for favorable seafloor hydrogen energy exploration targets in super-extensional tectonic environments is of great significance for the selection of future seafloor hydrogen energy exploration targets and drilling targets.

[0005] Existing technologies for research on natural hydrogen have the following main shortcomings: (I) At the academic and theoretical level, the focus is on exploring the formation mechanism and accumulation model of hydrogen, but a methodology for evaluating seabed hydrogen energy exploration targets has not yet been established. Existing research mainly starts from plate tectonic evolution, crustal thinning, and serpentinization reaction conditions, theoretically demonstrating that continental margins and other areas have hydrogen generation potential, and pointing out that ultra-extensional zones, detachment faults, and deep faults are key geological elements controlling hydrogen generation and migration. However, this research is essentially a verification and summary of basic geological theories, aiming to answer scientific questions such as "where does hydrogen come from and when is it generated," without further transforming the above theoretical understanding into a set of methods that can be directly used by engineering and technical personnel, including specific data acquisition, indicator extraction, and quantitative evaluation. In other words, existing academic achievements point out "where hydrogen may be generated," but have not solved the industrial application problem of "how to systematically, quickly, and cost-effectively find exploreable seabed hydrogen accumulation targets."

[0006] (II) Existing marine resource exploration patents target different resource objects, and their evaluation indicators cannot be transferred. In marine resource exploration and evaluation patents, the technical solutions are mostly constructed around specific resource objects such as hydrates and oil and gas, and the core evaluation indicators used are mostly aimed at the hydrocarbon gas accumulation process. The evaluation indicators and methodological frameworks of existing published patents cannot be directly transferred or modified for the evaluation of favorable seabed hydrogen energy exploration targets.

[0007] (III) Limited research on hydrogen relies on single indicators and lacks multi-factor systematic evaluation. In the few studies or reports involving natural hydrogen exploration, the identification of favorable exploration targets often relies on a single or a few indicators, such as identifying only surface or seafloor hydrogen leakage anomalies, only identifying serpentine outcrops, or only analyzing the degree of fault development. While this "single indicator method" is effective in some localized areas, it has significant limitations: First, seafloor hydrogen leakage anomalies only reflect the escape channels and cannot assess whether there is large-scale hydrogen generation and accumulation at depth; second, serpentine outcrops only indicate that serpentinization has occurred, but cannot determine whether the hydrogen generation time window matches the reservoir-seal conditions or whether it has been exhausted; finally, the results of single indicator evaluation are highly subjective and have low accuracy, easily leading to a large amount of ineffective exploration investment.

[0008] Currently, there is no systematic and quantitative comprehensive evaluation system that integrates multiple factors, including "hydrogen source (serpentinization potential + Moho morphology), migration pathway (detachment faults + deep and large faults), reservoir (rift-stage sandstone bodies + fractured rock bodies), caprock (sheet magma + mudstone), and thermal structure (temperature window at the top of the mantle)." This lack of a system leads to low efficiency, high cost, and unreliable prediction results in the early-stage target screening for submarine hydrogen exploration in ultra-extensional tectonic environments. In view of this, this application is hereby submitted. Summary of the Invention

[0009] The evaluation method for favorable seafloor hydrogen energy exploration targets in the super-extensional tectonic environment proposed in this application aims to solve the problems existing in the above-mentioned prior art by integrating an evaluation index system for the inorganic serpentinization hydrogen generation mechanism that integrates "hydrogen source, migration, reservoir, caprock, and thermal structure". Through multi-attribute superposition and spatiotemporal matching scoring, it can effectively achieve rapid delineation and classification of favorable hydrogen energy targets, thereby significantly reducing exploration costs and risks and providing an industrializable target selection tool for seafloor hydrogen energy exploration in the super-extensional passive continental margin.

[0010] Accordingly, the evaluation method for favorable exploration targets of submarine hydrogen energy in super-extensional tectonic environments utilizes existing seismic data and regional geological conditions, combined with the geological environment and favorable reservoir-seal combination conditions required for submarine hydrogen energy generation. For tectonic units with hydrogen generation capacity in different basins, the method comprehensively analyzes the tectonic environment, extensional processes, lithospheric changes, large-scale detachment faults, and deep and large fault characteristics to identify the thickness of the upper and lower crust and the depth of the Moho discontinuity, and determines the range of serpentinization development by combining temperature field and seismic reflection anomalies.

[0011] The method includes the following implementation process: Step (1): Based on the basin evolution characteristics and Moho discontinuity identification, determine the favorable areas for serpentinization; Regional geological data and long-array deep reflection seismic data of the study area were collected to clarify the main tectonic evolution environment and rifting stage of the basin. It was determined that the detachment rifting period was the key period for deep fluid communication in the ultra-extensional tectonic environment. The stratigraphic sequence and age were identified, and a group of areas with strong amplitude, continuous seismic reflection layer characteristics and depth characteristics consistent with the Moho surface were identified using deep reflection seismic profiles and Moho seismic identification. Step (2): Identify the depth of detachment faults and deep fractures inserted into the upper and lower crust and their contact relationship with the Moho discontinuity, and determine the potential for seawater to circulate downwards along the faults to the top of the mantle; Based on the location and thickness of the Moho discontinuity identified in step (1), identify large detachment faults and strike-slip faults, and analyze the relationship between gas and deep Moho discontinuity and shallow traps. Step (3): Analysis of favorable reservoirs for natural hydrogen accumulation and evaluation of magma and mudstone caprock; Using the structural-lithological composite traps of the hanging wall of the detachment fault identified in steps (1) and (2), the "source-sink" system technology is used to identify large braided river deltas or nearshore underwater fan sand bodies during the rifting period as reservoir spaces. Step (4): Assessment of geothermal field, heat flow and high-velocity body in the lower crust; By comparing the regional temperature change rate of the study area, the temperature of the serpentine layer is calculated based on the geothermal gradient and the depth of the Moho discontinuity identified in steps (1) and (2), and the deep thermal state is inverted by using the distribution of the high-velocity body in the lower crust. Step (5): Analysis of hydrogen source in gas geochemistry and serpentinization reaction simulation; By identifying the seabed topography and geomorphology features through existing multibeam and 3D seismic data collected during exploration, and by combining reflection seismic data at the locations of large seabed pocks, the relationship between the seabed pocks and deep fault systems and magma systems can be determined. Step (6): Based on the dual tectonic domain pattern, establish a quantitative assessment method for submarine hydrogen energy with multiple attributes and a zone target assessment method; including determining favorable target areas based on the regional tectonic evolution process through comprehensive scoring such as multi-attribute superposition, dynamic matching, and preservation condition deduction.

[0012] Step (1) involves using regional geological data of the study area and combining gravity, magnetic and seismic inversion to determine the reliability of the crust-mantle boundary.

[0013] Step (2) involves identifying the "slope-plateau" geometry at lower temperatures on two-dimensional or three-dimensional seismic profiles, with the fault converging downwards to the ductile shear zone or Moho discontinuity in the middle and lower crust.

[0014] Step (2) utilizes whether the fault cuts into the "thermal / tough" lower crust and induces brittle fracture, while identifying whether there is magmatic activity in the region to determine the source of the magmatic activity.

[0015] In step (5), if the pit is clearly related to a deep structure, further collect seabed surface sediment samples or gas samples from adjacent drilling sites to analyze the potential hydrogen and CO2 and CH4 content.

[0016] In step (5), firstly, the serpentinized peridotite is identified by analyzing the temperature field in step (4) and combining it with the high P-wave velocity obtained from reflection seismic inversion; then, the temperature window of the water-rock reaction is calculated using fluid inclusion thermometry; finally, the samples from ocean drilling or deep oil and gas drilling are analyzed; if strongly altered basalt is encountered, it confirms that the water-rock reaction is active and that it is an important hydrogen generation zone.

[0017] Step (6) involves first delineating the first-level favorable areas based on the regional location map, including areas with thinned crust, areas with developed detachment faults, and areas with high-velocity bodies in the lower crust; then, examining the spatiotemporal coupling between the magmatic activity period and the fault activity period, with higher matching degrees indicating higher deep fluid conduction efficiency; finally, removing areas with late-stage (after 23.8 Ma) volcanic conduits or severe caprock erosion to identify favorable target areas for submarine hydrogen energy.

[0018] In summary, the beneficial effects and advantages of this application compared with the prior art are as follows: 1. This application utilizes regional long-array seismic data, regional geological data, and multibeam bathymetry data. Through comprehensive analysis of multichannel seismic data, combined with attribute and amplitude anomalies, it identifies seafloor geological anomalies, the Moho discontinuity, and anomalous reflections of its serpentinized layer. Furthermore, by combining temperature fields, favorable tectonic environments for natural hydrogen formation, and reservoir-seal combinations, it determines favorable areas for seafloor hydrogen energy. The assessment process is simple and low-cost, providing a rapid identification method and system for my country's seafloor natural hydrogen and hydrogen energy resource-rich areas, reducing exploration costs, and achieving a leap from "theoretical site selection" to "engineering target determination."

[0019] 2. This application reinterprets and analyzes long-range, deep reflection data. If the two-way travel time of the deep reflection seismic profile is >8 seconds and the deep Moho discontinuity can be identified, the seismic data can be used directly. If the Moho discontinuity cannot be identified, targeted processing of the Moho discontinuity reflection is required, combined with regional tectonic environment differences. This allows for the effective identification of typical deep reflection multichannel seismic profiles in relevant terrains. By reinterpreting the elements of submarine hydrogen accumulation (such as the Moho discontinuity, serpentinized areas, detachment faults, large faults, and the location of the upper and lower crust and their contact relationships), this application innovatively conducts single-factor analysis of submarine natural hydrogen accumulation conditions and multi-attribute superposition, dynamic matching degree of magma and fault activity, and eliminates unfavorable factor areas where the caprock is destroyed. Then, it couples these with areas of large submarine pockmarks (diameter >1km) formed by deep influences to delineate the first-level favorable zone for submarine hydrogen energy. This application does not require extensive seismic exploration, drilling, or other operations. It only utilizes existing exploration and drilling data to assess favorable exploration zones for seafloor hydrogen energy in extended environments. Based on the assessment, it conducts target exploration for seafloor natural hydrogen, which is conducive to the low-cost and rapid discovery of favorable targets for seafloor hydrogen energy.

[0020] 3. This application adopts a zonal assessment method that is drastically different from existing technologies, exhibiting fundamental differences in genetic mechanisms, reservoir space, storage conditions, and geophysical response indicators. Specifically, it seeks "hydrogen sources" for natural gas by locating the Moho discontinuity, serpentinized layers, large faults and detachment faults, and their correlation with magmatic activity. It also analyzes the potential for seawater to circulate to the upper mantle along large faults. Then, using traditional hydrocarbon accumulation strategies, it compares and analyzes key elements of submarine hydrogen accumulation by matching reservoir conditions, caprock conditions, and migration channels (i.e., conduit systems). Therefore, the assessment of favorable exploration targets in this area is more efficient and structurally accurate. Attached Figure Description

[0021] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. Some specific embodiments of this application will be described in detail below with reference to the accompanying drawings in an exemplary and non-limiting manner. The same reference numerals in the drawings designate the same or similar parts or components. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale.

[0022] Figure 1 Flowchart of evaluation method for favorable exploration targets of submarine hydrogen energy in super-extensional tectonic environments; Figure 2 shows a comparison of submarine hydrogen reservoir formation elements in ultra-extensional tectonic environments of different regions; Figure 2(a) is a schematic diagram of identification based on deep reflection multi-channel seismic profiles for region 1; Figure 2(b) is a schematic diagram of identification based on different faults and stratigraphic structures for region 1; Figure 2(c) is a schematic diagram of identification based on deep reflection multi-channel seismic profiles for region 2; Figure 2(d) is a schematic diagram of identification based on different faults and stratigraphic structures for region 2. Figure 3 This is a schematic diagram of the favorable target area determined based on the comprehensive score of this application; Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0024] Example 1, as Figures 1 to 3 As shown, this application proposes a novel evaluation method for favorable exploration targets of submarine hydrogen energy in ultra-extensional tectonic environments. Utilizing existing seismic data and regional geological conditions, combined with the geological environment and favorable reservoir-seal combination conditions required for submarine hydrogen energy generation, this method comprehensively analyzes the tectonic environment, extensional processes, lithospheric changes, large-scale detachment faults, and deep and large fault characteristics of tectonic units with hydrogen generation capacity in different basins. It identifies the thickness of the upper and lower crust and the depth of the Moho discontinuity, and determines the range of serpentinization development by combining temperature field and seismic reflection anomalies. The implementation steps include the following: Step (1): Based on the basin evolution characteristics and Moho discontinuity identification, determine the favorable areas for serpentinization; Collect regional geological data and long-array deep reflection seismic data of the study area to clarify the main tectonic evolution environment and rifting stage of the basin, and determine that the detachment and rifting period is the key period for deep fluid communication in the ultra-extensional tectonic environment. Specifically, the stratigraphic sequence and age were identified, and a group of areas with strong amplitude, continuous seismic reflection layer characteristics, and depth characteristics consistent with the Moho depth were identified using deep reflection seismic profiles (two-way travel time > 8 seconds) and Moho earthquakes. For example, the continental crust region is more than ten kilometers, while the oceanic crust region is 6-7 kilometers. The reliability of the crust-mantle boundary can be determined by combining the reference regional data with gravity, magnetic and seismic joint inversion. Step (2): Identify the depth of the detachment fault and deep fractures inserted into the upper and lower crust and their contact relationship with the Moho discontinuity, and determine the potential for seawater to circulate downwards along the fault to the top of the mantle; Based on the location and thickness of the Moho discontinuity identified in step (1), large detachment faults and strike-slip faults are identified, and the relationship between hydrogen and deep Moho discontinuities and shallow traps is analyzed. For example, low-temperature (e.g., temperature <30°) "slope-plateau" geometry is identified on two-dimensional or three-dimensional seismic profiles, and faults converge downward to the ductile shear zone or Moho discontinuity of the middle and lower crust. Whether the fault cuts into the "thermal / ductile" lower crust and induces brittle fracture is used to identify whether there is magmatic activity in the area. Magma identification is consistent with traditional methods to determine the source of magmatic activity. For example, in region 1 of Figure 2, the fault in the region converges with the Moho discontinuity to the depths. When the crust is thinned to 5-6 km, the sharp decrease in the strength of the lithosphere will induce seawater to circulate downwards along the fault to the top of the upper mantle, triggering serpentinization reaction to generate hydrogen. Step (3): Analysis of favorable reservoirs for natural hydrogen accumulation and evaluation of magma and mudstone caprock; Because hydrogen molecules are small and easily diffuse, hydrogen preservation requires extremely high density of the reservoir and sealing performance of the caprock. Using the structural-lithological composite traps of the hanging wall of the detachment fault identified in steps (1) and (2), the existing "source-sink" system technology is used to identify large braided river deltas or nearshore underwater fan sand bodies during the rifting period as reservoir spaces. Because hydrogen molecules are small, volcanic rocks, which are traditionally considered low-quality reservoirs for oil and gas, can also serve as hydrogen reservoirs. As shown in Figure 2, Region 1 is mainly an extensional tectonic environment. In the later stages of rifting, the tectonic activity was not active, but the magmatic activity was intense, forming large-scale volcanic rocks that intruded into the overlying strata in a stratified manner. Dipipori was developed in areas of intense magmatic activity. Late-stage magma eruptions that pierced through the overlying mudstone caprock were not conducive to hydrogen preservation. However, in periods of relatively mild magmatic activity and in areas with developed sheet magma, natural gas and hydrogen were favorable capping areas.

[0025] Step (4): Assessment of geothermal field, heat flow and high-velocity body in the lower crust; From the perspective of geochemical temperature analysis of serpentinization, serpentinization occurs in the temperature range of 200-400℃. Collect geothermal gradient and heat flow data from oil and gas drilling in the basin, compare the temperature change rate in the region, and use the depth of the Moho discontinuity identified in steps (1) and (2) with the serpentinized area to calculate the temperature of the serpentinized layers based on the geothermal gradient and the depth of the Moho discontinuity. Then, use the distribution of high-velocity bodies in the lower crust (such as P-wave velocity > 7.0 km / s) to invert the deep thermal state. Among them, the high-velocity bodies in the lower crust indicate magma underplating and are a marker of local high heat flow areas (such as local heat flow value > 80 mW / m²).

[0026] Step (5): Analysis of hydrogen source in gas geochemistry and serpentinization reaction simulation; By identifying seafloor topography and geomorphological features using existing multibeam and 3D seismic data, and by combining large seafloor pits (such as those with a diameter > 1 km) with reflection seismic data, the relationship between seafloor pits and deep fault systems, magma systems, etc. (connecting the upper and lower crust of the Mohorovičić discontinuity) can be determined. If the pit is clearly related to a deep structure, it is recommended to collect further seafloor surface sediment samples or gas samples from adjacent drilling sites to analyze the potential hydrogen (H2) and CO2 and CH4 content. Alternatively, the temperature field analysis in step (4) above can be combined with the "high P-wave velocity (e.g., P-wave velocity > 7.0 km / s)" obtained from reflection seismic inversion to identify serpentinized peridotite; then, the temperature window of the water-rock reaction can be calculated using fluid inclusion thermometry, with 200-350℃ being suitable; finally, the samples from ocean drilling or deep oil and gas drilling can be analyzed. If strongly altered basalt is encountered, it confirms that the water-rock reaction is active and is an important hydrogen generation area. Step (6): Based on the dual tectonic domain pattern, establish a quantitative assessment method for seabed hydrogen energy with multiple superimposed attributes and an assessment method for exploration targets; Based on the regional tectonic evolution process, favorable target areas are determined through comprehensive scoring, including multi-attribute superposition, dynamic matching of seabed hydrogen energy conduction systems, and preservation condition deduction. Specifically, based on the regional location map, firstly, by overlaying thinning zones with a crustal thickness of <10km, zones with detachment fault development, zones with distribution of high-velocity bodies in the lower crust, and zones with distribution of high heat flow anomalies, first-level favorable areas are delineated; then, the spatiotemporal coupling between magmatic activity periods (e.g., the main phase from 43 to 23.8 Ma) and fault activity periods (e.g., 45 to 23.8 Ma) is examined, and the higher the matching degree, the higher the efficiency of deep fluid conduction; finally, areas with late-stage (after 23.8 Ma) volcanic conduits or severe caprock erosion are removed to determine favorable target areas for submarine hydrogen energy exploration.

[0027] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for evaluating favorable exploration targets for seafloor hydrogen energy in ultra-extensional tectonic environments, characterized in that: Using existing seismic data and regional geological conditions, combined with the geological environment and favorable reservoir-seal combination conditions required for submarine hydrogen energy generation, this study comprehensively analyzes the tectonic environment, extensional processes, lithospheric changes, large-scale detachment faults, and deep and large fault characteristics of tectonic units with hydrogen generation capacity in different basins. It identifies the thickness of the upper and lower crust and the depth of the Moho discontinuity, and determines the range of serpentinization development by combining temperature field and seismic reflection anomalies.

2. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 1, characterized in that: The implementation process includes the following steps: Step (1): Based on the basin evolution characteristics and Moho discontinuity identification, determine the favorable areas for serpentinization; Regional geological data and long-array deep reflection seismic data of the study area were collected to clarify the main tectonic evolution environment and rifting stage of the basin. It was determined that the detachment rifting period was the key period for deep fluid communication in the ultra-extensional tectonic environment. The stratigraphic sequence and age were identified, and a group of areas with strong amplitude, continuous seismic reflection layer characteristics and depth characteristics consistent with the Moho surface were identified using deep reflection seismic profiles and Moho seismic identification. Step (2): Identify the depth of detachment faults and deep fractures inserted into the upper and lower crust and their contact relationship with the Moho discontinuity, and determine the potential for seawater to circulate downwards along the faults to the top of the mantle; Based on the location and thickness of the Moho discontinuity identified in step (1), identify large detachment faults and strike-slip faults, and analyze the relationship between gas and deep Moho discontinuity and shallow traps. Step (3): Analysis of favorable reservoirs for natural hydrogen accumulation and evaluation of magma and mudstone caprock; Using the structural-lithological composite traps of the hanging wall of the detachment fault identified in steps (1) and (2), the "source-sink" system technology is used to identify large braided river deltas or nearshore underwater fan sand bodies during the rifting period as reservoir spaces. Step (4): Assessment of geothermal field, heat flow and high-velocity body in the lower crust; By comparing the regional temperature change rate of the study area, the temperature of the serpentine layer is calculated based on the geothermal gradient and the depth of the Moho discontinuity identified in steps (1) and (2), and the deep thermal state is inverted by using the distribution of the high-velocity body in the lower crust. Step (5): Analysis of hydrogen source in gas geochemistry and serpentinization reaction simulation; By identifying the seabed topography and geomorphology features through existing multibeam and 3D seismic data collected during exploration, and by combining reflection seismic data at the locations of large seabed pocks, the relationship between the seabed pocks and deep fault systems and magma systems can be determined. Step (6): Based on the dual tectonic domain pattern, establish a quantitative assessment method for seabed hydrogen energy with multiple superimposed attributes and a zone target assessment method; This includes determining favorable target areas based on the regional tectonic evolution process through comprehensive scoring such as multi-attribute superposition, dynamic matching, and preservation condition deduction.

3. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: Step (1) involves using regional geological data of the study area and combining gravity, magnetic and seismic inversion to determine the reliability of the crust-mantle boundary.

4. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: Step (2) involves identifying the "slope-plateau" geometry at lower temperatures on two-dimensional or three-dimensional seismic profiles, where faults converge downwards to the ductile shear zone or Moho discontinuity in the middle and lower crust.

5. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: Step (2) involves determining the source of magmatic activity by identifying whether a fault cuts into the "thermal / tough" lower crust and induces brittle fracture, while also identifying whether magmatic activity exists in the region.

6. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: In step (5), if the pit is clearly related to a deep structure, further collect seabed surface sediment samples or gas samples from adjacent drilling sites to analyze the potential hydrogen and CO2 and CH4 content.

7. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: In step (5), firstly, the serpentinized peridotite is identified by analyzing the temperature field in step (4) and combining it with the high P-wave velocity obtained from reflection seismic inversion; then, the temperature window of the water-rock reaction is calculated using fluid inclusion thermometry; finally, the samples from ocean drilling or deep oil and gas drilling are analyzed; if strongly altered basalt is encountered, it confirms that the water-rock reaction is active and that it is an important hydrogen generation zone.

8. The method for evaluating favorable exploration targets for submarine hydrogen energy in ultra-extensional tectonic environments according to claim 2, characterized in that: Step (6) involves first delineating the first-level favorable areas based on the regional location map, including areas with thinned crust, areas with developed detachment faults, and areas with high-velocity bodies in the lower crust; then, examining the spatiotemporal coupling between the magmatic activity period and the fault activity period, with higher matching degree indicating higher deep fluid conduction efficiency; finally, removing areas with developed late-stage volcanic conduits or severe cap erosion to determine favorable target areas for submarine hydrogen energy.

Images