Tectonic-lithofacies paleogeography, large-scale source- reservoir distribution and exploration zones of Cambrian subsalt formation, Tarim Basin, NW China

WEI Guoqi,ZHU Yongjin,ZHENG Jianfeng,YU Guang,NI Xinfeng,YAN Lei,TIAN Lei,HUANG Lili

Table 1 Comprehensive analysis of favorable area of Cambrian subsalt dolomite reservoirs in the Tarim Basin.

Zones Paleohigh setting and features Source rocks Reservoirs Cap rocks Area with buried depth below 8500 m/km2 Evaluation and expectation Exploration activities North slope in Tazhong Central basement paleohigh and inherited stable paleohigh finalized in the Hercynian South margin of Yurtusi source rocks and potential Sinian source rocks Xiaoerbulak algal mound- shoal and Qigbulak microbial mound-shoal Yurtusi argillaceous rocks and Middle Cambrian gypseous salt rocks and gypseous dolomitic flats 2764 for the lower assemblage 7305 for the upper assemblage Breakthrough in Cambrian subsalt exploration 4 wells completed, Zhonghan2 deployed, discoveries of the upper assemblage in Zhongshen1, and Zhongshen5 to be tested South slope in Tazhong Original Tabei basement paleohigh and residual paleohigh reconstructed in the Hercynian-Indosinian Above major Yurtusi source rocks and in the north margin of potential Sinian source rocks Wusonger platform marginal mound- shoal and Qigbulak microbial mound-shoal Yurtusi argillaceous rocks and Middle Cambrian gypseous salt rocks and argillaceous dolomitic flats 11 511 for the lower assemblage 601 for the upper assemblage Exploration of large weathering dolomites in Tabei and favorable area in Wusonger Formation 6 wells finished, Luntan2 and Luntan3 deployed, discoveries of the upper assemblage in Luntan1 Keping-Wensu periphery Wensu low uplift and residual paleohigh reconstructed in the Late Caledonian- Early Hercynian Major Yurtusi source rocks superimposed with potential Sinian source rocks Wusonger platform marginal mound- shoal, Xiaoerbulak algal mound- shoal, and Qigbulak microbial mound-shoal Yurtusi argillaceous rocks and Middle Cambrian gypseous salt rocks and gypseous dolomites 682 for the lower assemblage 26 580 for the upper assemblage Exploration of favorable areas of subsalt primary hydrocarbon reservoirs in tectonically stable regions and gas reservoirs adjusted in the Himalayan 5 wells finished, feasibility study of Yutan1 and Shentan1, and discoveries of the upper assemblage in Ketan1 by Beijing Energy Holding Co., Ltd. and the lower assemblage in Hongtan1 penetrated by ZPEC Upper Makit slope Western Tarim paleohigh tilted by the Himalayan movement, migrated paleohigh Yurtusi source rocks Xiaoerbulak algal mound- shoal Middle Cambrian gypseous salt rocks 32 820 for the upper assemblage Great improvement in exploration potential and attempt to make a breakthrough in subsalt reservoirs in southwestern Tarim 2 wells finished, and Matan1 being penetrated