The evolution of the early Paleozoic carbonate platform in the Central uplift, Tarim Basin, northwestern China, and hydrocarbon accumulation

The Tarim Basin is the largest superimposed and oil-bearing basin in China, presented as an episodic tectonic superposition in the Central uplift. Understanding hydrocarbon differential accumulation in the Central uplift requires a proper view of the evolution of the early Paleozoic carbonate platform. Through detailed twodimensional seismic interpretation, paleogeographic and paleotectonic reconstructions of the carbonate platform are performed. Tying hydrocarbon accumulation elements to the dynamic evolutionary process of the carbonate platform, this paper provides new insights into hydrocarbon differential accumulation in the Tazhong and Bachu uplifts. Due to ongoing compression from the south, the Hetian paleohigh and the Tazhong uplift initially formed in the Cambrian -Middle Ordovician carbonate platform interior in the latest Middle Ordovician. The climax of uplifting and northward tilting of preexisting paleohighs occurred in the latest Ordovician and latest Middle Devonian, respectively. The carbonate platform suffered polyphase exposures in these paleohighs and strike -slip faulting in the northern slope of the Tazhong uplift, forming favorable karst reservoirs and strike -slip fault -controlled reservoirs. Following the latest Permian uplifting of the northwestern Hetian paleohigh, the Bachu uplift nucleated in the northern Hetian paleohigh in the Cenozoic. The southwestern Hetian paleohigh was inverted into a southwest -dipping monocline. In the Bachu uplift, the allochthonous hydrocarbons from the southwestern Hetian paleohigh underwent episodic migration, accumulation, adjustment, and destruction during the evolution of these uninherited paleohighs. The hydrocarbons mainly remain in structuralstratigraphic traps in the southern margin of the Bachu uplift. Multiple periods of gentle tilting have occurred in the Tazhong uplift since the Late Devonian. Episodic migrating hydrocarbons from autochthonous and neighboring source rocks in the north are enriched in the northern flank of the inherited Tazhong uplift.