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The Shunbei oil-and-gas field in the Tarim Basin features a typical strike-slip fault-controlled fractured-vuggy reservoir. The formation of these reservoirs is primarily influenced by fracturing related to structural stress during periods of fault activity. This contrasts with reservoir types such as matrix vugs controlled by original sedimentary facies and caves modified by karst. To study the development mechanism and distribution patterns of strike-slip fault-controlled reservoirs under the influence of multi-stage structural stress, comprehensive analysis of field observations, core samples, well logging data, seismic surveys, and drilling dynamic data was conducted to characterize the development characteristics of fault-controlled reservoirs. This included different strike-slip faults, different parts along a single strike-slip fault, and different stratigraphic levels vertically. Combined with stress field numerical modeling, multi-stage structural stress recovery was carried out to predict the main development periods and distribution patterns of fault-controlled reservoirs. Significant variations in internal stress states were observed across different segments during periods of strike-slip fault activity. Tensile stress predominated in pull-apart segments, resulting in predominantly tensile fractures, whereas compressional stress state in push-up segments led to a variety of fracture types. The fault-controlled fractures in the top of the Yijianfang Formation in the Shunbei area were mainly developed during episode Ⅲ of the Middle Caledonian period and the Late Caledonian-Early Hercynian period. Few fractures were developed during the Middle to Late Hercynian period and thereafter. Compared to the Shunbei No.1 fault, the Shunbei No.18 fault exhibited higher fracture opening degree and density with a large displacement. Strike-slip fault-controlled reservoirs exhibit a cluster-like structure. Structural differences of the reservoirs are influenced by internal stress states in different segments during fault activity. Pull-apart segments typically feature a large fault core-damage zone with more cavities and 'double-cluster' structures, whereas push-up segments display more diverse fault core-damage zones with greater separability and 'multi-cluster' structures. The stress intensity during the strike-slip fault activity controls the types and scale of reservoir spaces, with smaller fault zones dominated by fractures and larger fault zones developing extensive fault core-damage zone architectures. The scale of fault-controlled reservoirs is positively correlated with fault activity intensity. Early fault activity promotes significant fracture development, while later stages, characterized by increased burial depths, result in few newly derived fractures due to reduced rock susceptibility to fracturing.

In recent years, the Ordos Basin has undergone a reevaluation, transitioning from a perception of a single block to a focus on understanding the influence of multiple stages and fault systems on hydrocarbon accumulation. This study utilizes the latest 3D seismic and drilling data alongside a theoretical model of strike-slip fault to analyze fault geometry and kinematics in the Xunyi-Yijun area of the basin's southern region. The mechanisms of fault formation are predicted and the related impacts on the formation and accumulation of deep carbonate rocks are also discussed. The results indicate the presence of three fault systems in the Xunyi-Yijun area, with decoupling between deep and shallow layers. The Lower Paleozoic strike-slip faults exhibit distinct characteristics, including high vertical structure, dip swing, and a "flower-shaped" structure in the section. The faults display "compression shear in the northwest, tension shear in the center, and segmental deformation on trunk fractures" on their planes.Moreover, the Lower Paleozoic strike-slip faults experienced two stages of tectonic activities with greater intensity observed from the Late Ordovician to the Silurian, marking the primary period of fault development. The activity intensity during the Middle to Late Permian was relatively weaker, with faults exhibiting inherited strike-slip characteristics. These faults formed two groups, one with a NE strike and the other with a NW strike. Additionally, during the second stage of the Caledonian period, ocean subduction and closure lead to stress being transferred to the basin interior. It is believed that the NE and NW strike basement weak zones existed in the southern Ordos Basin. As a result, the Lower Paleozoic strike-slip fault system likely formed due to the activation of oblique compression. This fault system has the potential to enhance the physical properties of deep carbonate reservoirs and create high-quality karst or tectonic fracture reservoirs in the Xunyi-Yijun area. Moreover, The formation of the "upper source and lower reservoir-lateral source and lateral reservoir" combination along the strike-slip fault belt is an area of interest for deep oil and gas exploration in the Xunyi-Yijun region.

Many Ordovician reservoirs discovered in the eastern section of Bachu-Maigaiti area ("Bamai area" for short) in the Tarim Basin are closely related to multi-stage active faults, making it the key to find oil and gas reservoirs in this area by identifying the source faults that cut through Cambrian gypsum-salt layers. Combined with the analysis of fault structure based on a large number of new seismic data and previous studies, the fault system in the eastern section of the Bamai area, especially the distribution and activity characteristics of strike slip faults are reunderstood. The results show that along with the migration and evolution of palaeo-uplift and the activities of large thrust fault zones in Bamai area, a series of high-angle and small-distance NE strike-slip faults that play a role of deformation and regulation are also developed, which together constitute the deformation tectonic system in the area. Two types of strike slip faults are developed in this area. One is superimposed and developed simultaneously or later with the NE and nearly EW Cambrian post-salt decollement zone of bruchfalten, with its strike consistent with that of the thrust fault belt, which is mainly distributed in the boundary and interior of the Hetian paleo-uplift. The other is developed in the compression-shortening zone confined by the large thrust fault belt, intersected with the nearly EW thrust fault belt at a large angle, and mainly distributed in the Hetian palaeo-uplift and Bachu faulted uplift. The former mainly formed in the late Hercynian period with weak local activities in the late Himalayan period, and the latter mainly formed in the late Himalayan period. The strike-slip faults superimposed with the Ordovician carbonate rocks that has experienced karst transformation in the middle and late Caledonian and early Hercynian are more conducive to the formation of effective fracture-karst vug reservoirs. They connect the upper and lower strata of the gypsum-salt layers, and their active period is consistent with the main hydrocarbon generation period of the deep subsalt source rocks, which is more conducive to transporting hydrocarbon source upward to the Ordovician system for accumulation. The large-scale reservoir located above the source and connected with two types of high-angle strike-slip faults is the favorable exploration direction of Ordovician.

In recent years, significant oil and gas discoveries have been achieved in the Permian Upper Wuerhe Formation and the Triassic Baikouquan Formation on the marginal slope of oil generation sag, Junggar Basin. However, in the central sag of the basin, no oil or gas show has been discovered in target formations, and low production has been made only by two wells. As a result, it is necessary to deepen the understanding of the mechanisms of oil and gas accumulation and clarify the main controlling factors. The analyses of the accumulation conditions in the central sag and some wells show that the direct reason for the failure to find oil and gas in the sag is the lack of local source-connecting faults and poor reservoir properties. An accumulation model with source in the lower section and reservoir in the upper section controlled by both source-connecting faults and favorable sand bodies was established for the Permian and Triassic strata in the sag. The sandbody lithologic reservoirs of fan-delta front subfacies in the Upper Wuerhe and Baikouquan formations under the background of stratigraphic overlap are the primary direction of exploration, covering an area about 3 600 km2. The comprehensive exploration of unconventional oil and gas in the Middle-Lower Permian source rocks and conventional oil and gas in multiple layers outside the source area should be targeted.

It is difficult to distinguish reservoirs and non-reservoirs based on the rock's physical properties. The quality of post-stack seismic data in the loess plateau is poor, which makes it a technical bottleneck for the prediction of reservoir of the Upper Paleozoic, and the exploration in the southern Ordos Basin was then constrained. Block evaluations have indicated that the northeastern part of Zhenjing district has a good potential for exploration, with the second member of Permian Shanxi Formation and the first member of Xiashihezi Formation as the main target beds. The results of 3D seismic facies analysis in Zhenjing area are consistent with the regional sedimentary facies studies on provenance and the distribution of sand bodies, indicating that seismic data can be used for the prediction of reservoir. The distribution of sedimentary facies of a series of seismic forward modeling showed that the sand bodies distributed with a certain distance and thickness in the second member of Shanxi Formation and the first member of Xiashihezi Formation formed recognizable seismic reflections. This vertical spatial combination of stratigraphic lithology is consistent with the depositional model of regional superimposed and thick single-type sand bodies, which is the typical form of reservoir-caprock combination that has been discovered in the surrounding gas reservoirs. The reservoir prediction based on the optimal number of wave crests from the forward simulation results confirmed that the superimposed and the thick single-type sand bodies of the second member of Shanxi Member were distributed in SW-NE directions. Furthermore, the picking and interpretation of co-phase axis and the structural mapping of seismic profile were carried out, which directly delineated the distribution range and burial depth of lithologic traps in the sand bodies of the second member of Shanxi Formation, and provided drilling targets for exploration and deployment in this area.

The Neoproterozoic Binggounan Formation mud shale in the Hongliugou Ⅰ section on the northwestern margin of the Altyn Tagh fault was deposited in a passive continental margin. They are shelf sediments about 60 m thick, interbedded with siliceous rocks, undergone a low temperature thermodynamic metamorphism, and had hydrocarbon generation potential. The tectonic background, provenance, weathering and sedimentary environment of the mud shale were discussed with regard to stratigraphic sections, mineralogy and geochemical analyses. The mud shale was mainly composed of silica-rich clay rock and mud-rich siliceous shale, followed by mud-silica mixed shale. They have simila-rities in Si, Mg, K, P, Sc, Y, Hf, Th Sc contents compared with the Post Archaean Australian shale (PAAS). The Ti, Mn, Fe, Ta contents and δEun, δCen, ΣREE values are higher, while the Al, Ca, Na, Nb and Zr contents are lower. The primitive sediment sources of the Binggounan mud shale were recycled sedimentary clasts, intermediate mafic and acid intrusive rocks, similar to a normal shale and arenites argillites and ensialic of continental upper crust in composition. The shale has undergone moderate chemical weathering in warm and humid conditions. The formation was divided into three sedimentary cycles from bottom to top, mainly anaerobic and anoxic, and occasionally oxidized. Hydrothermal alteration also occured in the lower section. The mud shale with a clay content of about 40% is rich in trace elements (REE) and organic matter, which was deposited in a suboxic to anoxic section on the shelf, showing a high productivity and hydrocarbon-generation potential.