Feng, Qiao¹, Yiqun Liu¹, Wan Yang¹
(1) Northwestern University, Xian, China
(2) Wichita State University, Wichita, KS

ABSTRACT: Thermal History and Hydrocarbon Generation in Turpan Basin, Northwestern China

Superimposed sedimentary basins have experienced multiple tectonic episodes, thus, may contain several source rock successions with multiple thermal alterations. Evolution of the intermontane Turpan Basin in NW China exemplifies multiple tectonic-thermal regimes and resulting multiple episodes of hydrocarbon generations. The basin developed on an early Late Carboniferous folded igneous basement and has experienced late Hercynian, Indosinian, Yanshanian, and Himalayan orogenies, during each of which a unique basin type and tectonic-thermal regime developed. Five tectonic-thermal stages with a general cooling trend are identified: Late Carboniferous-Early Permian rifting, fast burial, and high thermal gradient (5^oC/100 m) ?Middle Permian drifting, moderately fast burial and moderately high thermal gradient (4.4^oC/100 m); Late Permian-Late Triassic steady thermal subsidence and decreased thermal gradient (3-4^oC/100 m); Jurassic-Cretaceous steady and extensive subsidence and low gradient (3-2.5^oC/100 m); Cenozoic compression, moderately fast subsidence, and low gradient (2.5-2.0^oC/100 m). Correspondingly, three source rocks were deposited: Middle Permian profundal-lacustrine shale, Middle and Upper Triassic littoral-lacustrine shale, and Lower and Middle Jurassic swamp-lacustrine coal. Burial and thermal history analyses indicate that Middle Permian and Middle and Upper Triassic source rocks have two episodes of hydrocarbon generation (late Late Triassic and Late Cretaceous, respectively), forming vertically-stacked different types of accumulations. Pre-Jurassic accumulations are remnant heavy oil in structural-lithologic traps; Jurassic-Cretaceous accumulations are light oil or gas in structural and/or lithologic traps.

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.