Discovery and significant implication of the strike-slip faults in Kaijiang-Liangping Trough of the Sichuan Basin

Objective  The identification of strike−slip faults in sedimentary basins is of great significance to the study of the strike−slip fault−controlled reservoir and its exploitation deployment. However, the small−scale and low seismic resolution of strike−slip fault is the key issues restricting the exploration and development of strike−slip fault−controlled oil−gas reservoirs. Therefore, the identification of strike−slip faults is carried out on the basis of new 3D seismic data in the eastern Kaijiang−Liangping Trough of the Sichuan Basin.

Methods Steerable Pyramid reprocessing of the new 3D seismic data is used to enhance the seismic resolution on the strike−slip faults, the identification marks of the strike−slip faults are analyzed and the strike−slip faults are interpreted by seismic methods, and the fault effects on the gas accumulation and enrichment are discussed by the well data.

Results The Steerable Pyramid reprocessing has enhanced the seismic identified resolution of deep small (vertical fault displacement <30 m) strike−slip faults. Five marks in seismic section and six marks in plane attribute are proposed to form a method for seismic identification of small strike−slip faults. These include five section marks of vertical fault, flower structure, fault dip reversal, abrupt change of fault displacement and property, and six plane markers of echelon/oblique faults, horizontal offset of geological body, pull−apart micrograben, horsetail structure, horizontal variation of fault type and throw, and linear mutation of seismic attribute. A large strike−slip fault system is found that is consistent with the NW−trending platform margin. The strike−slip fault can not only connect source rocks and facilitate migration and accumulation, but also favor the gas enrichment and high production from the deep carbonate rocks.

Conclusions This paper proposes the identification markers of deep small strike−slip faults, and put forward the identification method of strike−slip fault. A large strike−slip fault system is found along the Kaijiang−Liangping Trough, and has significant effects on gas accumulation and distribution. This discovery provides a new exploration and development domain of strike−slip fault−controlled gas reservoirs in the Sichuan Basin.