Characteristics and origin of the Sinian-Permian fault system and its controls on the formation of paleo-carbonate reservoirs: A case study from Central Paleo-Uplift, Sichuan Basin, China

摘要

We have evaluated the existence of good paleo-carbonate reservoirs in fault damage zones with a burial depth exceeding 5800 m in the Central Paleo-Uplift, Sichuan Basin, China. The relationships between fault system and sedimentation, and the formation of the paleo-carbonate reservoirs have been explored, which have long been ignored by previous studies due to the low-quality seismic data and the prevalent assumption of weak tectonic movement. Data from different sources such as newly acquired and processed seismic data, cores, and well-logs are used to study the characteristics and origin of the fault system and their controls on the formation of paleo-carbonate reservoirs. The main findings are as follows: (1) The Sinian-Permian fault system in the study area mainly comprises strike-slip faults with different scales plus a small number of locally developed collapserelated concentric faults. (2) The Sinian-Permian fault system, which usually has normal throw, mainly developed in an extensional stress field and its evolution spanned five stages including the basement-fault formation stage in the Yangtze cycle, extensional dextral strike-slip faults formation stage in the Xingkai cycle, weakly compressional sinistral strike-slip faults formation stage in the Caledonian cycle, extensional faults formation stage in the Hercynian cycle, and compressional transformation stage in the Indosinian-Himalayan cycles. Most faults formed in the Xingkai and Caledonian cycles, whereas the Indosinian-Himalayan cycles had a weak effect on the Sinian-Permian fault system in the study area. (3) Different types of faults have different effects on the sedimentation, formation, and preservation of the paleo-carbonate reservoirs. The synsedimentary faults provide necessary tectonic background for the sedimentation of high-energy facies, whereas the successive faults and coalesced fractures determine the formation, distribution, and preservation of the porous karst carbonate reservoirs. Th