Control of hydrocarbon accumulation by Lower Paleozoic cap rocks in the Tazhong Low Rise,Central Uplift, Tarim Basin, West China

• Published in: Petroleum science Vol. 11; no. 1; pp. 67 - 80
• Main Authors: Zhang, Yanping, Lü, Xiuxiang, Yang, Haijun, Han, Jianfa, Lan, Xiaodong, Zhao, Yue, Zhang, Jinhui
• Format: Journal Article
• Language: English
• Published: Beijing China University of Petroleum (Beijing) 01.03.2014; College of Geosciences, China University of Petroleum, Beijing 102249, China; State Key Laboratory of Petroleum Resources and Prospecting, China University of Petroleum, Beijing 102249, China%Tarim Oilfield Company, PetroChina, Korla, Xinjiang 841000, China%CNOOC Tianjin Branch Company, Tianjin 300452, China
• Subjects: Basins; Dolomite; Earth and Environmental Science; Earth Sciences; Economics and Management; Energy Policy; Exploration; Hydrocarbons; Industrial and Production Engineering; Industrial Chemistry/Chemical Engineering; Limestone; Migration; Mineral Resources; Mudstone; Rocks; 下古生界; 中央隆起带; 低层; 区域盖层; 塔里木盆地; 控制; 烃类; 积累; China, People's Rep., Xinjiang, Tarim Basin; China, People's Rep; hydrocarbon accumulation; Cap rock; Tazhong Low Rise; Lower Paleozoic; hydrocarbon destruction
• ISSN: 1672-5107; 1995-8226
• DOI: 10.1007/s12182-014-0318-5

Despite the absence of regional cap rocks in the Lower Paleozoic for the entire Tazhong Low Rise,several sets of effective local cap rocks are well preserved on the Northern Slope.Of these the best is the Ordovician mudstone of the Sangtamu Formation; the second is the Silurian Red Mudstone Member of the Tatairtag Formation and the marl of the Ordovician Lianglitag Formation; and the third is the gray mudstone of the Silurian Kepingtag Formation.The dense limestone of the Ordovician Yingshan Formation and the gypsum of the Middle Cambrian have shown initial sealing capacity.These effective cap rocks are closely related to the distribution of Lower Palaeozoic hydrocarbons in the Tazhong Low Rise.With well-preserved Sangtamu Formation mudstone and its location close to migration pathways,rich Lower Paleozoic hydrocarbon accumulation can be found on the Northem Slope.Vertically,most of the reserves are distributed below the Sangtamu Formation mudstone; areally,hydrocarbons are mainly found in the areas with well-developed Sangtamu Formation mudstone and Lianglitag Formation marl.Burial history and hydrocarbon charging history show that the evolution of Lower Palaeozoic cap rocks controlled the accumulation of hydrocarbon in the Tazhong Low Rise.Take the Red Mudstone Member of the Tatairtag Formation and Sangtamu Formation mudstone for examples：1） In the hydrocarbon charging time of the Late Caledonian-Early Hercynian,with top surfaces at burial depths of over 1,100 m,the cap rocks were able to seal oil and gas; 2） During the intense uplifting of the Devonian,the cap rocks with top surfaces at burial depths of 200-800 m and 500-1,100 m respectively were denuded in local areas,thus hydrocarbons trapped in earlier time were degraded to widespread bitumen; 3） In the hydrocarbon charging time of the Late Hercynian and Himalayan,the top surfaces of the cap rocks were at burial depths of over 2,000 m without intense uplifting and denudation thereafter,so trapped hydrocarbons were preserved.Based on cap rocks,the Ordovician Penglaiba Formation and Lower Cambrian dolomite could be potential targets for exploration on the Tazhong Northern Slope,and combined with hydrocarbon migration,less risk would be involved.