Lacustrine carbonate rock types and sedimentary environments of the Lower Jurassic Daanzhai Member of Heping Reservoir section in Beibei area, Chongqing
Shi Kailan1,2, Chen Fangwen1,2, Duan Zhuo3, Luo Sicong2, Su Chengpeng1,2, Ma Teng1,2, Tang Hao1,4, Tan Xiucheng1,4
1 Sichuan Province Key Laboratory of Natural Gas Geology,Southwest Petroleum University,Chengdu 610500,Sichuan 2 School of Geoscience and Technology,Southwest Petroleum University,Chengdu 610500,Sichuan 3 Geophysical Prospecting Company and Chuanqing Drilling Engineering Corporation,PetroChina, Chengdu,610213,Sichuan 4 The Sedimentary and Accumulation Department of Key Laboratory of Carbonate Reservoirs, PetroChina,Southwest Petroleum University,Chengdu 610500, Sichuan
Abstract：The Da-anzhai Member of Lower Jurassic Ziliujing Formation in Sichuan Basin is one of the important horizons of dense oil exploration,and has been studied over half a century. However, due to rough classification of the rock types and unclear understanding of the sedimentary environments and reservoir types, no major breakthrough has been achieved. For this reason, the study of lacustrine carbonate rock types and their sedimentary environments in the Da-anzhai Member of Heping Reservoir section in Beibei area,Chongqing,eastern Sichuan Basin was carried out. The results indicate that those mixed sediments recorded in the Da-anzhai Member largely comprise of terrigenous clastic rocks and carbonate rocks. And 5major rock categories and 14 rock types accordingly are further classified. Carbonate rocks evidently dominates through the thickness occupying more than 60％,of which micrite ranks the first,followed by the shell limestone and the bioclastic limestone. Each microfacies assemblage ordered vertically,where 4 representive upward-shallowing sequences existed. Sedimentary environments of various rock types are further analyzed according to their macro-micro characteristics and vertical combination forms. The results show that the Da-anzhai Member in Beibei area is shore-shallow lake with weak hydrodynamic condition,mainly featured by low-energy carbonatite,while the shell shoal developed in high- and low-energy environments is not the main part of carbonate sedimentation. The initiation of carbonate sedimentation phase and the massive blooming of calcareous skeleton fauna are the main causes for sedimentation of the Da-anzhai lacustrine carbonates. Crystal line bioclastic limestone and micritic dolomite of shore-shallow lacustrine facies may be the reservoir rock for dense oil in eastern Sichuan Basin. In further exploration, more attentions should be paid to the shore-shallow lacustrine rocks which could be easily dissolved by meteoric water.
. Lacustrine carbonate rock types and sedimentary environments of the Lower Jurassic Daanzhai Member of Heping Reservoir section in Beibei area, Chongqing[J]. JOPC, 2015, 17(2): 198-212.
