Geochemical characteristic and origin of solid bitumen in the Jurassic and Triassic sandstone reservoir of Santai Area,Junggar Basin,NW China

Solid bitumen was identified in the pore spaces of the Jurassic and Triassic sandstone reservoir in the Santai Area, Junggar Basin, NW China, which limits economic petroleum production, even influencing hydrocarbon accumulation. Organic geochemical techniques were figured out the origin of bitumen and its formation mechanisms. Carbon isotope characteristics of the crude oil and bitumen-reservoir extracts suggests the bitumen mainly derived from sapropelic-type source rock of Pingdiquan Formation, which was deposited in the semideep and deep lacustrine environment. Biomarker date indicates bitumen was formed from petroleum in low thermally mature stage and biodegradation was responsible for formation of the bitumen.