TECTONIC EVOLUTION FROM LATE SINIAN TO EARLY PALEOZOIC AND NATURAL GAS EXPLORATION IN THE NORTHWESTERN SICHUAN BASIN, SW CHINA

Sichuan Basin is located in the northwest of Upper Yangtze platform of Southwest China, and research area is situated in the northwestern Sichuan Basin. Based on the fields, drilling and seismic data of Sichuan Basin, this paper systematically discusses tectonic evolution characteristics from Late Sinian to Early Paleozoic, and analyzes the petroleum geology significance of this area, as well as points out recent favorable exploration directions. There are mainly three stages of tectonic evolution during Late Sinian to Early Paleozoic: ‡@During Late Sinian to early stage of Early Cambrian, this area was affected by tension action and formed two sets of nearly north-south trend intracontinental rifts, and two sets of carbonate platform margins in Upper Sinian Dengying Formation. ‡ADuring middle stage of Early Cambrian to Middle Ordovician, this area was eroded strongly because of multi-period uplifting of the northwestern Bikou paleo-land. ‡BDuring Late Ordovician to Late Silurian, this area was eroded strongly again because of contractional action of Guangxi movement, and the northwest was stronger than southeast. During Late Sinian to Early Cambrian, the formation of intracontinental rifts controlled the development of bioherm beach facies reservoirs on the carbonate platform margins in Upper Sinian Dengying Formation and the high quality source rock in Lower Cambrian. During middle stage of Early Cambrian, the uplifting of Bikou paleo-land controlled the distribution of oolitic beach facie reservoirs around the paleo-land. Comprehensive research shows that Jiulongshan structure is the most beneficial exploration belts recently.