Lower Paleozoic Marine Source Rocks and Hydrocarbon Kitchens in the Tarim Basin, China

By

 Feiyu Wang¹, Shuichang Zhang²

(1) Petroleum University, Beijing, China (2) Research Institute of Petroleum Exploration and Development, CNPC, Beijing, China

 Exploration activity has increased significantly during the past 10 years in the Tarim basin, which is largest and least explored petroliferous basin in China. Although oils-source rock correlation have proved that petroleum may be mainly originated from Cambrian and Ordovician marine strata, the distribution of effective source rocks and evolution of hydrocarbon kitchen are still controversial in past years because the lower Paleozoic strata occur over the entire basin and its maximal thickness exceed 12000m in the interior of basin. According to more than 1,5000 rock samples geochemical screen analysis, the prime organic-rich interval exist in lower Cambrian and upper Ordovician, the former distribute in anoxic environment, the latter distribute in the slope with high productivity. Based on a detailed organic facies, oil-source correlation, organic maturity and thermal history reconstruction by organic geochemical and petrological techniques and Basin Modelling System, two lower Paleozoic hydrocarbon kitchens have been identified, the first is lower Cambrian euxinic source rock, located in the Awarti-Majaer depression, the second is upper Ordovicain carbonate mud mound source rock, located in the slope of Tazhong uplift and Tabei uplift to Majaer depression. The hydrocarbons in the gigantic Silurian tar sandstone and residual reservoir were derived from Cambrian source rock, the hydrocarbon in the Carboniferous and Devonian reservoir were from Ordovician source rock in recent 100Ma.