Abstract
Recent years, progress has been made in hydrocarbon exploration of Shaximiao Formation in Sichuan Basin. The Shaximiao formation is fluvial facies deposit, the reservoir is channel sandstone with a low porosity and permeability, oil and gas generate from black shale of the Lianggaoshan formation and the Da’anzhai section of Ziliujing formation. In Longgang, immigration channel is the key condition of accumulation of Shaximiao formation. There are two kinds of immigration channels, fractures caused by hydrocarbon generation overpressure release and faults. Oil generated from Lianggaoshan shale immigrated to the sandstone of bottom part of Sha1, oil and gas generated from Da’anzhai black shale immigrated to upper part sandstone though faults. There is no water in the reservoir. Channel sandstone and source faults interpretation is the key point of exploration success.
Highlights
Jurassic is the only oil-producing stratum in Sichuan Basin
During this period bivalves flourished, as did some gastropods, ostracoda and fish, the deep and semi deep lake was mainly located in Gongshanmiao, Longgang and Pingchang, black calcareous organic rich shale, 30 to 60 meters thick, was deposited in the Da’anzhai section there
Controlled by the orogenic belt, a complete sedimentary evolution sequence of delta fringe, shallow lake, semi deep lake and deep lake was formed from bottom to top, 30 to 60 meters thick black organic rich shale was deposited in the Lianggaoshan top part
Summary
In the early and middle Jurassic, Sichuan Basin is a large depression basin formed on the basis of Triassic foreland basin. During the Da'anzhai period, the Sichuan basin was a large freshwater lake basin and carbonate rocks were widely distributed, only a few delta facies clastic rocks distributed along the periphery of the basin During this period bivalves flourished, as did some gastropods, ostracoda and fish, the deep and semi deep lake was mainly located in Gongshanmiao, Longgang and Pingchang, black calcareous organic rich shale, 30 to 60 meters thick, was deposited in the Da’anzhai section there. In the early Shaximiao period, the clastic material in the periphery of the basin was abundant, and the delta deposits with long-distance distributary channels are distributed in most areas of Sichuan basin At this time, the basin water became shallow, the climate changed to semi-arid, and the tectonic activity weakened.
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