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Junggar Basin, located in the northern Xinjiang, is one of the most important oil and gas bearing sedimentary basins in China. Zhong-4 Block, located in Fukang Sag at the southern edge of the basin, is rich in oil and gas resources but low in exploration. Strike slip faults in the study area play an important role in controlling the distribution of oil and gas. Based on seismic and logging data, the static characteristics of strike slip faults are determined, the formation mechanism of strike slip faults is clarified, and the relationship between strike slip faults and oil and gas distribution is clarified. The results show that: (1) North east trending R-type shear fault, northwest trending P-type shear fault and north-south trending T-type extension fracture fault are developed in Zhong-4 block. The cross section of the strike slip fault is steep, with flower like structure, and obvious dolphin effect and ribbon effect can be seen; On the plane, it is characterized by segmented development, consisting of oblique overlapping segment, linear segment and braided structure segment; (2) The faults in Zhong4 Block are generally strike slip faults formed under the single shear mechanism consisting of NWW, NE and NS directions. According to the comprehensive geometric and kinematic characteristics, the fault zone in the work area mainly follows the rightward Riedel single shear mode. The included angle between R shear fault, P shear fault and main fault is mostly 15 °~25 °, which is widely developed in the work area. There are two stages of strike slip activities in the study area. The first stage is left strike slip in the west of Dong 6 well area in the early Jurassic, and the second stage is right strike slip in the whole study area in the late Jurassic; (3) The fault block traps developed in the strike slip fault oblique overlap zone are the main places for oil and gas enrichment in the study area, while the vertical sealing of the fault controls the oil and gas enrichment horizon. When the normal stress of the section is large and the vertical sealing of the fault is strong, oil and gas are enriched in the deep Sangonghe Formation; When the vertical sealing of the fault is poor, oil and gas are distributed in deep Sangonghe Formation and shallow Toutunhe Formation.

The Bohai Bay Basin contains many depressions with varying degrees of hydrocarbon enrichment associated with the geological structures of different depressions. This study discussed the relationship between the geological structures and hydrocarbon enrichment of the depressions in the Bohai Bay Basin. Based on the Paleogene strata distribution and the length to width ratio of different depressions, their geological structures are divided into three types in plan-view: open (length/width 4) and transitional types (length/width 2–4). In cross section, the geological structures can be divided into dustpan I, dustpan II and double-faulted types. Based on tectonic evolution and sedimentary characteristics, the depressions are classified into early-formed, inherited and late-formed categories. Generally, narrow depressions are mainly located in the northeast and southwest of the Bohai Bay Basin, while open depressions are dominantly distributed in the central area of the basin; late-formed depressions are mainly around the Bohai sea area, and early-formed depressions are mostly located in the periphery of the basin. Geological structures of the depressions control the formation of the source, reservoir and cap rocks as well as hydrocarbon accumulation setting, and further influence the pay zones and oil-bearing sequence. In detail, dustpan II and double-faulted depressions mainly have A-type sags, which often possess better hydrocarbon generation conditions than dustpan I ones; hydrocarbons in open dustpan II depressions tend to accumulate in the central uplift areas or buried hill, while those in narrow dustpan I depressions always accumulate in gentle slope belts. The oil-bearing sequence for different evolutional depressions corresponds well with the sedimentary strata of the main development stages of depressions. In early-formed depressions, hydrocarbons are mainly enriched in deeply buried reservoirs, while in late-formed depressions hydrocarbons are abundant in the relatively shallow traps. In summary, most inherited and late-formed dustpan II depressions are enriched in hydrocarbons due to their extensive source rocks and good source–reservoir–seal assemblages, whereas dustpan I and early-formed depressions are relatively poor in hydrocarbons.