Occurrence and conceptual sedimentary model of Cambrian gypsum-bearing evaporites in the Sichuan Basin, SW China  

作　　者：Hong Liu Xiucheng Tan Yonghao Li Jian Cao Bin Luo 

机构地区：[1]State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University [2]Division of Sedimentology and Hydrocarbon Accumulation,Petro China Key Laboratory of Carbonate Reservoir,Southwest Petroleum University [3]School of Earth Science and Technology,Southwest Petroleum University [4]School of Earth Sciences and Engineering,Nanjing University [5]Research Institute of Exploration and Development,PetroChina Southwest Oil and Gas Field Company

出　　处：《Geoscience Frontiers》2018年第4期1179-1191,共13页地学前缘（英文版）

基　　金：funded by the Major State Basic Research Development Program of China ("973" project, Grant No. 2012CB214803);National Science and Technology Major Project of China (Grant No. 2016ZX05004)

摘　　要：During the Cambrian, gypsum-bearing evaporites formed in the Sichuan Basin, SW China. These rocks are important for oil and gas sealing, but details of their distribution and origin are not well established. This study examines the regional distribution and origin of the gypsum-bearing evaporites using a comprehensive analysis of drilling data from 34 wells, 5 measured cross-sections in the basin and surrounding area, and 96 maps of area-survey data. Results show that in the stratigraphic succession, the gypsum-bearing evaporites occur mainly in the Lower Cambrian Longwangmiao Formation, the Middle Cambrian Douposi Formation, and the Middle-Upper Cambrian Xixiangchi Group. Geographically, the rocks are found mainly in the southeastern part of the basin, and the distribution of deposits shows an overall SW-NE trend. The sedimentary environments for evaporite formation were evaporative lagoon and inter-platform basin in a platform setting. Gypsum was generated by the underwater concentration of sea water in a strongly evaporative environment. Both an evaporative restricted platform and a mixeddeposition restricted platform model appear to be applicable to the development of gypsum in the Sichuan Basin. The gypsum-bearing evaporites with the best sealing capacity are located mostly in the southeastern part of the basin. These constraints can be applied directly to regional exploration, and have implications for the regional paleogeography and paleoclimate.During the Cambrian, gypsum-bearing evaporites formed in the Sichuan Basin, SW China. These rocks are important for oil and gas sealing, but details of their distribution and origin are not well established. This study examines the regional distribution and origin of the gypsum-bearing evaporites using a comprehensive analysis of drilling data from 34 wells, 5 measured cross-sections in the basin and surrounding area, and 96 maps of area-survey data. Results show that in the stratigraphic succession, the gypsum-bearing evaporites occur mainly in the Lower Cambrian Longwangmiao Formation, the Middle Cambrian Douposi Formation, and the Middle-Upper Cambrian Xixiangchi Group. Geographically, the rocks are found mainly in the southeastern part of the basin, and the distribution of deposits shows an overall SW-NE trend. The sedimentary environments for evaporite formation were evaporative lagoon and inter-platform basin in a platform setting. Gypsum was generated by the underwater concentration of sea water in a strongly evaporative environment. Both an evaporative restricted platform and a mixeddeposition restricted platform model appear to be applicable to the development of gypsum in the Sichuan Basin. The gypsum-bearing evaporites with the best sealing capacity are located mostly in the southeastern part of the basin. These constraints can be applied directly to regional exploration, and have implications for the regional paleogeography and paleoclimate.

关 键 词：Sichuan Basin CAMBRIAN Gypsum-bearing evaporite Evaporative lagoon Inter-platform basin PLATFORM 

分 类 号：P618.13[天文地球—矿床学]