Oil & Gas Geology ›› 2022, Vol. 43 ›› Issue (6): 1347-1358.doi: 10.11743/ogg20220606

• Petroleum Geology • Previous Articles    

Characteristics of strike-slip transition zone in southern Liaozhong Sag, Bohai Bay Basin and its control on large/medium-sized oilfields

Bingjie Wang(), Deying Wang, Xin Wang, Guanzhou Hui, Mingwang Xue   

  1. Tianjin Branch of CNOOC Ltd. ,Tianjin 300452,China
  • Received:2022-03-21 Revised:2022-09-08 Online:2022-12-01 Published:2022-11-21

Abstract:

The strike-slip transition zone developed in the southern Liaozhong Sag is a favorable position for the formation of large- and medium-sized oilfields. The study analyzes the characteristics of the strike-slip transition zone, as well as accumulation factors of the formation of structural traps, distribution of the Paleogene sand bodies and vertical hydrocarbon migration based on the interpretation results of three-dimensional seismic data, coupled with exploration practice. As indicated by the results, the study area develops three types of fault-edge transition zone, fault-overlapping transition zone and fault-terminal transition zone along five main strike-slip faults, each of which can be subdivided into transpressional subtype and transtensional subtype, corresponding to structural traps of the pressure buildup type and the pressure relief type produced thereby. Second, the structural traps developed in a transpressional strike-slip transition zone are large in scale (that is, the structural traps of the pressure buildup type are large in area), favorable for the formation of large- and medium-sized oilfields. Third, the Paleogene sand bodies in the strike-slip transition zone show obvious migration under strike-slipping, resulting in a wider lateral distribution, capable of accepting oil charging from different source rocks; thus the area features hydrocarbon enrichment in multiple structures on map view. Fourth, the strike-slip transition zone associated with the development of adjustment faults, is conducive to the vertical hydrocarbon migration, ultimately resulting in oil enrichment in multiple horizons and multiple fault blocks. In all, the strike-slip transition zone in southern Liaozhong Sag controls the basic hydrocarbon accumulation factors in the formation of large- and medium-sized oilfields, including the formation of large-scale structural traps, the lateral distribution of the Paleogene sand bodies, and the vertical hydrocarbon migration.

Key words: trap condition, migration condition, strike-slip fault controlling reservoir distribution, strike-slip transition zone, southern Liaozhong Sag, Bohai Bay Basin

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