History of hydrocarbon accumulations spanning important tectonic phases in marine sedimentary basins of China: Taking the Tarim Basin as an example

Abstract

Subaerial marine sedimentary basins in China have undergone three phases of important tectonic changes at the end of the Early Paleozoic, Late Paleozoic-Early Mesozoic and Late Cenozoic. These tectonic changes have exerted strong impacts on hydrocarbon generation, migration and accumulation as well as on the occurrence and distribution of hydrocarbon reservoirs. The Tarim Basin is a typical example of multiphase hydrocarbon accumulations in a marine basin of China. The Early Paleozoic tectonic framework laid a geological basis for the marine setting of hydrocarbon formation in the Tarim Basin, but most accumulations were destroyed later due to frequent tectonic movements so that only bitumen is left at present. In the Late Paleozoic, the Ordovician source rock located in the western Manjar Sag entered peak generation stage and hydrocarbons successively accumulated at its southern and northern uplifted positions. Tectonic compressional deformation developed in the Early Mesozoic and the subsequent uplift and denudation allowed hydrocarbons accumulated at this phase to suffer from bacterial degradation. In the Late Cenozoic, the superimposition of basinal margin reconstruction and terrestrial molasse formation accelerated the formation of secondary cracking of hydrocarbons to gases in the platform of the basin, the influx of deeper natural gases dissolved in crude oils accumulated early and a unique large-scale condensate pool was then formed. The three tectonic changes controlled not only the formation of the marine basin, the sedimentation and evolution of source rocks, and the formation of reservoirs, but also the accumulation process and alteration of hydrocarbons in the marine sedimentary basin. Key words: important tectonic change phase, marine sedimentary basin, hydrocarbon accumulation history, hydrocarbon accumulation composite effect, multiple hydrocarbon reservoir, Tarim Basin