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In recent years, breakthroughs in deep hydrocarbon exploration have been continuously achieved in the Tarim Basin of China. The Ordovician carbonate stratum has been shown to contain vast oil and gas resources. However, challenges remain in understanding the seismic response characteristics and accurately identifying the hydrocarbon reservoirs. These challenges can be attributed to factors including the significant burial depth of the target layers and complex geologic structures. To effectively support hydrocarbon exploration and resource assessment in the Tarim Basin, this study focused on the following three aspects in Region Y. First, according to the analysis of prestack amplitude versus offset (AVO) characteristics in well‐adjacent seismic traces and seismic forward modeling, we demonstrated that different fluid‐filled reservoirs have distinctly different AVO characteristics. This means that the hydrocarbon reservoirs in the study area can be identified by AVO inversion. Second, based on the theory that seismic waves exhibit amplitude attenuation and velocity dispersion when propagating through fluid‐filled media, the seismic dispersion AVO inversion technique was developed to obtain equations for the attributes of primary (P) and shear (S) seismic wave dispersion. Finally, this technique was applied in Region Y and further verified using actual drilling data from single wells and well profiles. The application results demonstrate that hydrocarbon reservoirs can be effectively identified using this technique and provide a technical reference for reservoir identification in other areas of the Tarim Basin. The AVO characteristic analysis is the prerequisite for the successful application of this method; the key is to find accurate inversion equations and parameters to recognize the AVO response patterns in the study area. [ABSTRACT FROM AUTHOR]

China's coal seam permeability is low, and the original coal seam gas extraction is difficult. CO2 displacement of coal seam CH4 technology is an effective gas extraction technology. CO2 is injected into the coal seam under pressure, and competitive adsorption occurs with CH4 in the pores. The gas composition is nonuniformly distributed, and its viscosity μ is the dynamic parameter. As the gas is compressible, the pressure drops, and migration distance does not satisfy a linear relationship. Therefore, the gas transport does not conform to Darcy's law. The mass transfer process and a multicomponent gas competitive adsorption were investigated theoretically and experimentally. The adsorption characteristics and gas compressibility determine the distribution of the gas components in pores and change the gas dynamic viscosity in different regions. The change in the gas dynamic viscosity in the channel is the direct reason for the nonlinear pressure gradient and gas flow curve. The permeability and gas component affect the degree of nonlinear deviation of the gas flow and pressure gradient curve. This affects the nonlinear deviation degree of the curve by changing the gas dynamic viscosity in the pore channel during displacement. The reasonable displacement pressure is the critical pressure (PO) through experimental and theoretical analysis. [ABSTRACT FROM AUTHOR]

Recent exploration efforts have revealed significant industrial gas flow from the Wujiaping Formation marine shale in the Longmen-Wushankan area of the eastern Sichuan Basin, underscoring its considerable exploration potential. In this study, the reservoir characteristics and exploration potential of the Wujiaping Formation shale gas in this area are further evaluated. On the basis of well rock electrical properties, experimental analyses, and depositional and structural patterns in the eastern region, we characterize the reservoir properties and identify the primary factors controlling shale gas accumulation. The results indicate that the Wujiaping shale is characterized by a high organic matter content, favorable pore types, high porosity, and a high content of brittle minerals, which are conducive to subsequent development and fracturing. A positive correlation is observed between the total organic carbon (TOC) content, porosity, brittle mineral content, and shale gas content. The TOC content is strongly correlated with the gas content (the correlation coefficient is 0.75). The high shale gas yield of the Wujiaping Formation is attributed to a combination of favorable sedimentary environments, pore conditions, roof and floor conditions, and fracturing capabilities. However, compared with the Longmaxi Formation in the Sichuan Basin, the Wujiaping Formation shale is characterized by a lower porosity, thinner shale, and deeper burial, posing challenges for exploration and development. In this study, criteria for evaluating Wujiaping Formation shale gas are established, and four favorable exploration areas are identified. Overall, the Permian Wujiaping Formation marine shale in the Longmen-Wushankan area holds promising exploration and development potential. Further exploration and an enhanced understanding of this formation will provide valuable guidance for future marine shale gas exploration and development in this area. [ABSTRACT FROM AUTHOR]

Obtaining higher-resolution and more realistic characteristics of tectonic stress fields is the goal of research into tectonic stress field simulations. In this study, a regional heterogeneous rock mechanics model was established on the basis of seismic, logging, and sample experimental data. The simulation results show that the minimum principal stress values in the lower Niutitang formation are between 25.0 and 120.0 MPa. The quantitative distribution prediction results for shale reservoir fractures based on the high-resolution tectonic stress field numerical model show that the fracture development zones in the Sangzhi block are mainly distributed near the fault, fold axis turning, and fold wing in an NE–SW orientation. There are two types of fractures developed in this region: shear fractures and tensile fractures. The shear fractures mainly developed near the NE–SW-oriented faults, with shear fracture rates ranging from 1 to 3, and the tensile fractures mainly developed in the southeast wing of the Wudaoshui anticline, with tensile fracture rates ranging from 1 to 2. The low fracture development zone is mainly located in the western slope of the block, with shear fracture rates and tensile fracture rates that are both < 1. [ABSTRACT FROM AUTHOR]

This study carried out a research on the distribution characteristics of the geostress field of ultra-deep strike-slip faults, aiming to improve the exploration efficiency and development benefits of ultra-deep fault-controlled reservoirs. This study combines multiple geological information, drilling information, seismic data, and seismic attribute analysis. Taking the FI12 fault zone in the Fengman Oilfield as an example, it carried out numerical simulation of the geostress field, clarified the distribution pattern of geostress, analyzed the effectiveness of fracture mechanics, and proposed a reservoir quality evaluation method and production increase strategy based on geostress analysis. The study includes the following three aspects: 1) research on the heterogeneity of fault-controlled fractured carbonate reservoirs: Due to the existence of faults, fractures, and pores, carbonate reservoirs exhibit strong heterogeneity. These discontinuous structures lead to local stress field decreases to varying degrees. By analyzing the changes in geostress, it is possible to infer the development of faults, fractures, and pores. This provides important basis for predicting and evaluating reservoirs. 2) research on the distribution pattern of geostress: The geostress of fractured bodies exhibits a "shell-type" distribution pattern. Inside the fractured body, the geostress values are lower, indicating that this part is a favorable reservoir body. On the outside of the fractured body, the geostress exhibits high-value concentration, and this part has relatively poor permeability and can be regarded as an unfavorable drilling target. 3) research on the relationship between fault-fracture mechanical activity and reservoir quality and production capacity: Geostress and its influence on fault-fracture mechanical activity are directly related to the quality and production capacity of fault-controlled fractured carbonate reservoirs. When deploying well locations and optimizing well trajectories, geostress factors should be fully considered, and reservoir reformation efficiency should be taken into account to promote single well production increases and reservoir economic devel. [ABSTRACT FROM AUTHOR]

With the development of shale gas exploration in China, the use of conventional logging tools has been introduced, and cross multipole array acoustic logging tools have gradually been used to determine the stress orientation in shale. The direction of fast shear waves (FSWs) is generally parallel to the horizontal maximum principal compression stress (SHmax). However, the azimuth of FSWs is found to be parallel to the main strike (but not to the SHmax) direction of structural fractures in shale reservoirs. Outcrop and image logging data indicate that the natural fractures in this area strike NE‒SW. If the shear wave anisotropy is caused by only the stress around the borehole and the FSWs are known to be NE‒SW, SHmax should be parallel to NE‒SW; however, according to statistics of land movement in adjacent areas, anelastic strain recovery, earthquake focal mechanism, borehole breakouts, hydraulic fracturing data, deviated well data, and drilling‐induced fracture data in local regions, SHmax is oriented in the NW‒SE direction, and the directions of FSWs are generally parallel to the structural fracture direction. This contradiction indicates that the development of structural fractures may affect the orientation of FSWs. Therefore, it is not reliable to use XMAC (Cross‐Multipole Array Acoustilog) logging only to determine the direction of in situ stress in fractured shale reservoirs. In addition, the direction of the FSWs in the middle of thick mudstones is NW‒SE, which may represent accurate information about the in situ stress direction. [ABSTRACT FROM AUTHOR]