A method for predicting a salt-under fracture-cave type carbonate reservoir

Abstract

The application discloses a method for predicting a salt-under fracture-vug type carbonate reservoir, and relates to the technical field of oil geological exploration, and comprises the following steps: S1, acquiring 3D seismic fine interpretation and horizon calibration of a research area, and building a stratigraphic framework; S2, fine interpretation of faults / fractures, classifying and grading the faults / fractures, and constructing a fracture network; S3, identifying relatively dominant sedimentary facies types on the basis of the dense carbonate rock, and restoring a palaeogeomorphology; S4, analyzing main control factors of the reservoir, and establishing a development mode of the salt-under fracture-vug type carbonate reservoir; and S5, predicting the salt-under fracture-vug type reservoir, solving the problems of great difficulty in reservoir prediction and low success rate of target exploration in the prior art, and being especially favorable to identification of the fracture-vug type reservoir formed by the fracture corrosion modification of some matrix lithology-dense carbonate rock and prediction of a favorable development area of the fracture-vug type carbonate rock.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil geological exploration, and particularly relates to a method for predicting a salt-under fractured-vuggy carbonate reservoir. BACKGROUND

[0002] Among the global proven oil and gas reserves, evaporites are developed in many large basins such as the Middle East, Central Asia, North America and the like. According to technical research, due to the influence of thick salt rock, the degree of salt-under structure implementation is low, the reservoir prediction is difficult, and the target exploration success rate is not high.

[0003] In the prior art, the related literatures of the salt-under carbonate reservoir prediction technology are disclosed, such as the publication number "CN113109875A", the name is "a salt-under carbonate reservoir inversion method under the constraint of full waveform velocity field", which is published on July 13, 2021, the publication number "CN111983683A", the name is "a salt-under lacustrine limestone reservoir prediction method and system under the condition of few wells", which is published on November 24, 2020, the publication number "CN110211226A", the name is "a deep water salt-under carbonate reservoir structure interpretation method", which is published on September 06, 2019, the publication number "CN110068862A", the name is "a salt-under super-deep faulted anticline oil and gas reservoir high-quality reservoir prediction method and device", which is published on July 30, 2019.

[0004] The following are some literatures on the prediction of carbonate reservoirs under salt: Hao Jinjin, He Weiwei, Zhang Yajun, et al. took the Amu Darya BP gas field as an example, and used layer flattening, phase conversion and inversion technology to qualitatively and quantitatively describe the reflection characteristics and reservoir thickness of the reef flat reservoir under salt (2020); Shan Tianyou took the deepwater carbonate rock under salt in Brazil as the research object, combined high-precision post-stack seismic facies controlled reservoir inversion with pre-stack precise equation fluid inversion to predict the spatial distribution of reef flat reservoir and fluid under salt (2019); Tian Yu, Zhang Xingyang, Zhu Guowei, et al. took the Callovian-Oxfordian of Amu Darya as the research background, found that there were often reef flat bodies under salt domes, which were important drilling targets, and the distribution of salt rock had obvious control effect on oil and gas migration and enrichment (2016); Yang Xiaolin carried out research on the under-salt fractured carbonate rock reservoir in the eastern mountain front thrust belt of the right bank of Amu Darya, and clearly defined the development mode of biological reefs and fractures in the region, identified the distribution of reef flat bodies through seismic attribute data, and finally accurately described the high-quality carbonate rock reservoir under the thrust belt through inversion impedance body (2013); Wang Ling, Zhang Yan, Ma Xiaoyu, et al. took the Amu Darya Basin as an example, analyzed the seismic response characteristics of different reef bodies and salt rock, and optimized the sequence framework constrained sparse inversion method to effectively eliminate the influence of salt rock deformation on the prediction of biological reef reservoir (2010); He Xiaosong, Sun Lin, Zhang Hongbin, et al. started from the seismic reflection characteristics of biological reefs in Block A in Central Asia, analyzed the seismic reflection characteristics of biological reefs in carbonate rock section, and confirmed the oil and gas target area in the biological reef development area (2009); Aikebier Shadi carried out comprehensive evaluation on the under-salt carbonate rock reservoir in Tahe Oilfield, studied the Ordovician carbonate rock paleokarst and reservoir development law in the salt body coverage area, and comprehensively used amplitude extraction technology, amplitude variation rate analysis technology, fine coherence analysis (fracture zone prediction), and favorable reservoir seismic reflection pattern analysis technology to predict reef flat reservoirs (2006).

[0005] The research results of the above patent application literatures and journal literatures show that the combination of biological reef flat and overlying salt rock is easy to form structural-lithologic composite traps, so the prediction of carbonate rock reservoirs under salt is mostly concentrated in the description of reef flat body distribution. However, with the increase of exploration and development efforts in gas fields, some carbonate rocks with relatively dense matrix lithology can also form fracture-cave type reservoirs under the transformation of fractures and dissolution, which are favorable exploration targets. However, there is currently no prediction method for such reservoirs. The method is aimed at studying dense carbonate rocks, taking fracture identification and prediction as the core, establishing a fracture-cave type carbonate rock development mode, and providing a method for predicting under-salt fracture-cave type reservoirs. SUMMARY

[0006] The purpose of the present application is to provide an under-salt fracture-cave type carbonate rock reservoir prediction method, which solves the problem of high difficulty in reservoir prediction and low success rate of target exploration in the prior art, and is particularly beneficial to the prediction of fracture-cave type reservoirs formed by some carbonate rocks with relatively dense matrix lithology under the transformation of fractures and dissolution.

[0007] The application is achieved by the following technical solutions:

[0008] A method for predicting a subsalt fracture-vug carbonate reservoir, comprising the following steps:

[0009] S1, obtaining a three-dimensional seismic fine interpretation and horizon calibration of a study area, and building a stratigraphic framework;

[0010] S2, fine interpretation of faults / fractures, classification and hierarchical identification of faults / fractures, and construction of a fracture network;

[0011] S3, identifying a relatively dominant sedimentary facies type on the basis of a dense carbonate rock, and restoring a paleogeomorphology;

[0012] S4, analyzing main control factors of a reservoir, and establishing a subsalt fracture-vug carbonate reservoir development model;

[0013] S5, predicting a subsalt fracture-vug reservoir.

[0014] Further, in step S1, the method for building the stratigraphic framework is:

[0015] S1-1, obtaining seismic data of a study area, performing target processing, improving a signal-to-noise ratio, and improving a seismic imaging effect;

[0016] S1-2, combining well drilling information to perform time-depth calibration, and accurately determining isochronous interfaces, including a gypsum-salt rock top and bottom interface, a carbonate rock top surface, and a basement top surface;

[0017] S1-3, using the isochronous interfaces to build a stratigraphic horizon framework.

[0018] Further, in step S2, the method for classifying and hierarchically identifying faults / fractures is:

[0019] S2-1, combining structural interpretation to identify faults, and performing element summarization and hierarchical identification of the faults, wherein a first-order fault controls a structural belt, a second-order fault controls the distribution and morphology of a trap, and a third-order fault affects the fracture development density of a reservoir;

[0020] S2-2, combining core and imaging logging data to analyze fracture properties;

[0021] S2-3, using seismic data to extract fracture-related attributes, focusing on easy fault development areas, and constructing a fracture network.

[0022] Further, in step S2-2, when analyzing the fracture properties, the occurrence, period, and genesis of the fractures are included.

[0023] Further, in step S2-3, the easy fault development areas include stress extrusion areas, stress conversion areas, and anticline shaft parts.

[0024] Further, in step S3, the method for identifying the relatively dominant sedimentary facies type and restoring the paleogeomorphology is:

[0025] S3-1: Determine the sedimentary facies type according to petrological and paleontological markers using core and thin section data. The water energy of the Callovian-Oxfordian in the right bank of the Amu River is low as a whole, and local dune beach bodies develop on a gentle slope background;

[0026] S3-2: Summarize the seismic reflection structure corresponding to different sedimentary types, and use related seismic attributes to characterize the distribution of dune beach bodies. The dune beach facies is a weak amplitude and weak continuity chaotic reflection structure, the interdune sea facies of the gentle slope is a parallel reflection structure with a weak amplitude and medium-strong continuity, and the overlying gypsum rock is a strong amplitude and strong continuity "eyeball" reflection structure;

[0027] S3-3: Predict the distribution range of dune beach bodies in combination with the configuration relationship between the shape of gypsum rock and dune beach bodies. The "eyeball" gypsum rock is mostly a favorable area for the development of dune beach bodies;

[0028] S3-4: Layer the top boundary of salt gypsum rock to restore the paleogeomorphology during the carbonate rock deposition period.

[0029] Further, in step S4, the method for establishing a subsalt fracture-cave carbonate reservoir development model is:

[0030] S4-1: Analyze the configuration relationship between different periods of fractures and fracture-cave reservoir development. The tectonic fractures of the Yanshan period are the main seepage channels for dissolution fluid;

[0031] S4-2: Analyze the configuration relationship between different periods of dissolution and fracture-cave reservoirs. Acidic fluid during the burial period is the dominant dissolution;

[0032] S4-3: Analyze the configuration relationship between different sedimentary facies and fracture-cave reservoirs. If the fracture development area is superimposed with dune beach sedimentary microfacies, the fracture-cave type reservoir development degree is the highest;

[0033] S4-4: Based on steps S4-1, S4-2, and S4-3, establish a fracture-cave type reservoir development model. The reservoir type is divided into dense reconstruction type and dune beach reconstruction type.

[0034] Further, in step S4-2, the acidic fluid includes organic acid fluid and hydrothermal fluid.

[0035] Further, in step S5, the subsalt fracture-cave reservoir prediction method is:

[0036] S5-1: Fracture prediction, use multi-attribute to characterize fracture connectivity;

[0037] S5-2: Find the possible buried anticline under the salt. The anticline structure axis is prone to develop more fractures due to the influence of compressive stress;

[0038] S5-3: predicting the matrix reservoir distribution, combining with the paleogeomorphologic features, using seismic inversion to depict the dune beach body distribution;

[0039] S5-4: based on steps S5-1, S5-2, S5-3, multi-factor superposition is used to predict the distribution of the salt-underlying fracture-cave reservoir, wherein the fractures are developed near the anticline axis of the fault, the acid fluid has strong dissolution and reconstruction on the matrix reservoir, and the dense reconstruction fracture-cave type reservoir is formed; if the dune beach phase is superimposed, the size of the fracture-cave will be larger, and the dune beach reconstruction fracture-cave type reservoir is formed.

[0040] Further, in step S5-1, the attributes include coherence, illumination, likelihood, and discontinuity.

[0041] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0042] 1. In the present application, the salt-underlying fracture-cave type carbonate reservoir prediction method can be used to guide the salt-underlying fracture-cave type carbonate reservoir prediction in overseas Paralic Basin, Amu Darya Basin, domestic Ordos Basin, Tarim Basin and the like, has certain guiding significance for finding the salt-underlying lithology relatively dense fracture-cave type carbonate rock or the structure-lithology composite trap related to the biological dune beach, can reduce the drilling risk and improve the reservoir prediction accuracy.

[0043] 2. In the present application, the method is based on the clear regional geological background of the research area, combined with the seismic data, drilling and logging data, core slice data for research. In view of the problem that the imaging is affected by the overlying thick salt rock of the target layer, the seismic processing is carried out. The time-depth calibration is carried out by using the actual drilling, and the isochronous stratigraphic framework is established. The faults and fractures are finely identified, the faults are classified, the fracture occurrence, period and cause are judged, and the fracture network is constructed. The core and slice data are used to determine the sedimentary facies type of the target layer in the research area, the seismic reflection structure of different sedimentary facies types is summarized, the configuration relationship between the gypsum salt rock and the dominant sedimentary facies is combined, and the dominant sedimentary facies is identified on the basis of the recovery of the paleogeomorphology. The relationship between different period fractures, different period dissolution and different sedimentary facies and the fracture-cave type reservoir is analyzed, the main control factors of the reservoir development are clarified, and finally the salt-underlying fracture-cave type carbonate reservoir distribution is predicted by comprehensively superimposing the dune beach body distribution, the present anticline axis and the fracture development area. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 The salt-underlying fracture-cave type carbonate reservoir prediction method route in the present application. DETAILED DESCRIPTION

[0045] The present application will be further described in detail below in combination with the embodiments, but the implementation mode of the present application is not limited thereto.

[0046] In the present application, the prediction of the fractured-vug carbonate reservoir under salt is centered on fractures. In addition to the conventional attribute methods such as coherence and illumination volume, geological knowledge is added in the fracture identification process to study the stress extrusion zone, stress conversion zone, and structural anticline shaft under the structural background, and to establish a fracture network. Meanwhile, a technique for identifying mound and beach bodies is created. The mound and beach bodies are different from reef and beach bodies in that they have small thickness and are difficult to predict. After the sedimentary microfacies types of the mound and beach bodies are determined by using core and logging data, the seismic reflection structure of the mound and beach bodies is summarized, and the distribution characteristics of the reservoir matrix of the mound and beach bodies are predicted in combination with the shape of the overlying gypsiferous rock. In addition, a development model of the fractured-vug reservoir under salt is established based on the mechanism understanding of fractures and dissolution. The favorable reservoir development zone is predicted by superimposing the fracture development zone and the dominant mound and beach bodies. For the convenience of the public to understand the present application, the present application is further described below in combination with specific examples.

[0047] Example 1

[0048] In this example, a gas field is selected as an example to further illustrate the prediction method of the fractured-vug carbonate reservoir under salt. The main producing layer of the gas field is a set of fractured-vug carbonate rock. The overlying gypsiferous rock of nearly one kilometer causes the reflection of the seismic data to be weak, and the reservoir response characteristics on the seismic profile are blurred. In combination with the existing research results and literature research, it is found that the gas field is subjected to plate extrusion stress, and is subjected to strong lateral rotation extrusion to cause strong deformation, and is mainly a high-amplitude faulted anticline. Referring to Figure 1 , the prediction method of the fractured-vug carbonate reservoir under salt includes the following steps:

[0049] Step 1: Based on the regional geological background, logging data, core thin section data, and seismic data of the study area, the 3D seismic fine interpretation and horizon calibration of the study area are obtained, and the stratigraphic framework is built

[0050] S1-1: Obtain the seismic data of the study area of the gas field, perform target processing on the gas field, improve the signal-to-noise ratio, and make the top surface of the carbonate rock imaging clearer, the internal reflection characteristics of the carbonate rock more reasonable, and the deep imaging effect obviously improved;

[0051] S1-2: Time-depth calibration is performed in combination with drilling information to accurately determine the isochronous interface, including the top and bottom interfaces of the gypsiferous rock, the top surface of the carbonate rock, and the top surface of the basement;

[0052] S1-3: Build a stratigraphic horizon framework by using the isochronous interface.

[0053] Step 2: Fine interpretation of faults / fractures, classification and hierarchical identification of faults / fractures, and construction of a fracture network

[0054] S2-1: Identify faults by structural interpretation, summarize and classify the elements of faults, where the first-order faults control the structural belt, the second-order faults control the distribution and form of traps, and the third-order faults affect the fracture development density of the reservoir;

[0055] S2-2: Analyze the fracture properties in combination with core and imaging logging data, including fracture occurrence, period, and origin when analyzing fracture properties;

[0056] S2-3: Extract fracture-related attributes using seismic data, focus on areas prone to fault development, and build a fracture network, including stress extrusion zones, stress conversion zones, and anticline shafts.

[0057] According to the above method, a plurality of faults with high reliability are finely identified, and the faults are mainly in the near-south-north direction. Vertical fractures and high-angle oblique fractures develop near the main fault, and vertical fractures develop less in the area away from the main fault, mainly in low-angle fractures.

[0058] There are three periods of fractures in the study area, the first period of ineffective fractures, the second period of dissolution and expansion fractures, and the third period of structural fractures. The first period of pressure solution fractures is fully filled with calcite, which is ineffective. The group of fractures is complex in origin, mainly the earliest diagenetic fractures and pressure solution filling fractures. The second period of superimposed structural fractures is mainly dissolution and expansion fractures, mainly high-angle or vertical fractures, and dissolution and expansion along the two sides of the fracture surface, forming a very developed dissolution zone with holes. It can be a good reservoir section. The third period of structural fractures is mainly high-angle fractures, and oblique fractures and a small amount of horizontal fractures also develop. The fracture and karst hole system are in a cutting relationship and have no genetic relationship. Most of them are not filled and form good reservoirs with matrix dissolution holes, which can greatly improve oil and gas production.

[0059] Step 3: Identify relatively dominant sedimentary facies types on the basis of dense carbonate rocks and restore the paleogeomorphology

[0060] S3-1: Use core and thin section data to determine sedimentary facies types based on petrological and paleontological markers, where the overall water energy is low in the Amu Darya right bank Callovian Oxfordian stage, and local hill and beach bodies develop on a gentle slope background;

[0061] S3-2: Summarize the seismic reflection structure corresponding to different sedimentary types, and use related seismic attributes to depict the distribution of hill and beach bodies, where the beach facies is a weak amplitude and weak continuity chaotic reflection structure, the inter-beach sea facies of the gentle slope is a sheet-like weak amplitude and medium-strong continuity parallel reflection structure, and the overlying gypsum salt rock is a strong amplitude and strong continuity "eyeball" reflection structure;

[0062] S3-3: Predict the distribution range of hill and beach bodies in combination with the configuration relationship between gypsum salt rock morphology and hill and beach bodies, where the "eyeball" gypsum salt rock is mostly a favorable area for the development of hill and beach bodies;

[0063] S3-4: The top boundary of the salt-gypsum rock layer is flattened to restore the paleogeography of the carbonate rock deposition period.

[0064] Based on the above methods, the target strata of this gas field are mainly composed of bioclastic and algal nodule micritic limestone, with relatively deep water, representing a quiet intermontane marine sedimentary microfacies. Locally, bioclastic sandstone-limestone, composite grain limestone, spherulitic limestone, and algal nodule-bearing spherulitic limestone are deposited, representing a bioclastic hillock sedimentary microfacies with relatively strong water energy. The hillock facies exhibits a shoal-like, weak-amplitude, weak-continuity, and chaotic reflection structure; the gently sloping intermontane marine facies exhibits a sheet-like, weak-amplitude, medium-strong-continuity parallel reflection structure; and the overlying gypsum-salt rock exhibits a strong-amplitude, strong-continuity "eyeball" reflection structure.

[0065] Step 4: Analyze the main controlling factors of the reservoir and establish a development model for subsalt fractured-cavity carbonate reservoirs.

[0066] S4-1: Analysis of the configuration relationship between fractures and fracture-vuggy reservoirs in different stages, among which the tectonic fractures of the Yanshanian period are the main channels for the seepage of dissolution fluids;

[0067] S4-2: Analysis of the relationship between different stages of dissolution and the configuration of fractured-vuggy reservoirs. Among them, acidic fluids are the dominant dissolution during the burial period. Acidic fluids include organic acid fluids and hydrothermal fluids.

[0068] S4-3: Analyze the configuration relationship between different sedimentary facies and fracture-vuggy reservoirs. Among them, if the fracture development zone happens to overlap with the hill and shoal sedimentary microfacies, the fracture-vuggy reservoir will have the highest degree of development.

[0069] S4-4: Based on steps S4-1, S4-2, and S4-3, establish a fracture-vuggy reservoir development model, and classify the reservoir types into tight modified type and hill-shoal modified type.

[0070] The above methods indicate that the dissolution of the target layer in this gas field occurs in two phases. The first phase, with a geothermal temperature range of approximately 80-120℃, was subsequently filled with calcite. The second phase, with a geothermal temperature range of approximately 120-160℃, involved dissolution by CO2, H2S, and organic acid fluids. The second phase, characterized by acidic fluid dissolution, is crucial for the formation of dissolution cavities, while the fracture system influences the extent of the dissolution.

[0071] The reservoir development in the study area is affected by sedimentation, structure and dissolution. The gas field was in a lower ramp-outer ramp environment during the sedimentary period, and local hill-beach sedimentary bodies were developed. The overall matrix reservoir was underdeveloped, and there were few residual primary pores. The first stage of tectonic extrusion was accompanied by the formation of the second stage of fractures, which was the key geological action for the formation of large-scale reservoirs. Acidic fluids (organic acid fluids, hydrothermal fluids, TSR reaction) entered the dissolution reconstruction along the thrust faults and the associated fractures, forming a dissolution reservoir. The second stage of extrusion activated the subsalt basement and formed the third stage of fractures, which superimposed and modified the early fracture-cave type system, and was beneficial to the formation of high-quality reservoirs. The reservoir development model is that a large number of fractures are developed in the anticline axis of the thrust fault zone during the strong extrusion period, and the dissolution fluid along the thrust fault zone forms a fracture-cave type reservoir.

[0072] Step 5, prediction of subsalt fracture-cave reservoir

[0073] S5-1: fracture prediction, multi-attribute is used to describe fracture connectivity, the attributes include coherence, illumination, likelihood, discontinuity, etc.

[0074] S5-2: search for possible subsalt buried anticline, the anticline structure axis is easy to develop more fractures due to the influence of extrusion stress;

[0075] S5-3: prediction of matrix reservoir distribution, combined with paleogeomorphological characteristics, use seismic inversion to describe the distribution of hill-beach bodies;

[0076] S5-4: based on steps S5-1, S5-2, S5-3, multi-factor superposition is used to predict the distribution of subsalt fracture-cave reservoir, where the fractures are developed near the anticline axis of the fault, the acid fluid has strong dissolution and reconstruction on the matrix reservoir, forming a dense reconstructed fracture-cave type reservoir; if the hill-beach facies is superimposed, the size of the fracture-cave will be larger, forming a hill-beach reconstructed fracture-cave type reservoir.

[0077] Finally, multi-attribute is used to describe fracture connectivity, the attributes include coherence, illumination, likelihood, discontinuity, etc. Search for possible subsalt buried anticline, the anticline structure axis is easy to develop more fractures due to the influence of extrusion stress. Predict the distribution of matrix reservoir, combined with paleogeomorphological characteristics, use seismic inversion to describe the distribution of hill-beach bodies, and use multi-factor superposition to predict the distribution of subsalt fracture-cave reservoir, and determine the favorable development area of fracture-cave type subsalt rock.

[0078] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change made on the basis of the technical essence of the present application to the above embodiment falls within the protection scope of the present application.

Claims

1. A method of predicting a subsalt vugular carbonate reservoir, characterized by, Comprise the following steps: S1, obtain the three-dimensional seismic fine interpretation and horizon calibration of the study area, build the stratigraphic framework; S2, fault / fracture fine interpretation, fault / fracture classification, hierarchical identification, and fracture network construction; In step S2, the method for classifying and identifying faults / fractures is: S2-1: Identify faults in combination with structural interpretation, summarize and classify the elements of faults, wherein the first-order faults control the structural belt, the second-order faults control the distribution and shape of traps, and the third-order faults affect the fracture density of the reservoir; S2-2: Analyze the fracture properties in combination with core and imaging logging data; S2-3: Extract fracture-related attributes using seismic data to construct a fracture network; S3, identify relatively dominant sedimentary facies types on the basis of dense carbonate rocks, and restore the paleogeomorphology; In step S3, the method for identifying relatively dominant sedimentary facies types and restoring the paleogeomorphology is: S3-1: Use core and thin section data to determine sedimentary facies types according to petrological and paleontological markers; S3-2: Summarize the seismic reflection structures corresponding to different sedimentary types, and use related seismic attributes to depict the distribution of dunes and banks; S3-3: Predict the distribution range of dunes and banks in combination with the configuration relationship between gypsosalt rock morphology and dunes and banks, wherein the "eyeball" gypsosalt rock is mostly a favorable area for the development of dunes and banks; S3-4: Flatten the top boundary of salt and gypsum rock, and restore the paleogeomorphology during the carbonate rock deposition period; S4, analyze the main controlling factors of the reservoir, and establish a development model of the subsalt fracture-cave carbonate rock reservoir; S5, subsalt fracture-cave reservoir prediction; In step S5, the method for subsalt fracture-cave reservoir prediction is: S5-1: Fracture prediction, use multiple attributes to depict fracture connectivity; S5-2: Find possible buried anticlines under the salt, and more fractures are likely to develop in the axial part of the anticline structure due to the influence of extrusion stress; S5-3: Predict the distribution of matrix reservoirs, combine with the paleogeomorphology characteristics, and use seismic inversion to depict the distribution of dunes and banks; S5-4: Based on steps S5-1, S5-2, and S5-3, superimpose multiple factors to predict the distribution of subsalt fracture-cave reservoirs.

2. The method according to claim 1, wherein, In step S1, the method for building the stratigraphic framework is: S1-1: Obtain seismic data in the study area, perform target processing, improve signal-to-noise ratio, and improve seismic imaging effect; S1-2: Time-depth calibration combined with drilling information, accurate determination of isochronous interface, including gypsosalt rock top and bottom interface, carbonate rock top surface and basement top surface; S1-3: Build a stratigraphic framework using isochronous interfaces. 3.The method according to claim 1, wherein, In step S2-3, when extracting fracture-related attributes using seismic data, pay attention to the easy fracture development area to construct a fracture network.

4. The method according to claim 1, wherein, In step S2-2, analyze the fracture properties, including the occurrence, period, and origin of the fractures.

5. The method according to claim 1, wherein, In step S2-3, the easy fracture development area includes stress extrusion area, stress conversion area, and anticline axis.

6. The method according to claim 1, wherein, In step S3-2, when depicting the distribution of dunes and banks, the bank facies is a weak-amplitude weak-continuity chaotic reflection structure, the interdune marine facies of gentle slope is a sheet-like weak-amplitude medium-strong continuity parallel reflection structure, and the overlying gypsosalt rock is a strong-amplitude strong-continuity "eyeball" reflection structure.

7. The method according to claim 1, wherein, In step S4, the method for establishing a development model of the subsalt fracture-cave carbonate rock reservoir is: S4-1: analyze the configuration relationship between different periods of cracks and fracture-cavity reservoir development, wherein the tectonic cracks of Yanshan period are the main seepage channels of dissolution fluid; S4-2: analyze the configuration relationship between different periods of dissolution and fracture-cavity reservoir, wherein the acid fluid in the burial period is the dominant dissolution; S4-3: analyze the configuration relationship between different sedimentary facies and fracture-cavity reservoir, wherein if the fracture development area is superimposed with the dune beach sedimentary microfacies, the fracture-cavity type reservoir development degree is the highest; S4-4: based on steps S4-1, S4-2, S4-3, establish the fracture-cavity type reservoir development model, and the reservoir type is divided into dense reconstruction type and dune beach reconstruction type.

8. The method according to claim 7, wherein, In step S4-2, the acid fluid includes organic acid fluid and hydrothermal fluid.

9. The method according to claim 1, wherein, In step S5-4, when predicting the distribution of sub-salt fracture-cavity reservoir by multi-factor superposition, the cracks are developed near the anticline axis of fault, the acid fluid has strong dissolution and reconstruction to the matrix reservoir, and the dense reconstruction fracture-cavity type reservoir is formed.

10. The method according to claim 1, wherein, In step S5-1, the attributes include coherence, illumination body, likelihood body and discontinuity.

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