Evaluation of Carboniferous hydrocarbon source rocks in the eastern Qaidam basin,China

Carboniferous dark-colored mudstone, carbonate rocks, coals and carbonaceous mudstone are well developed in the eastern Qaidam basin. Regional geological survey and organic geochemical analysis indicate that Carboniferous hydrocarbon source rocks consists predominantly of dark-colored mudstone and carbonate rocks, and coals and carbonaceous mudstone probably have hydrocarbon-generating capacity. The dark-colored mudstone has an average organic carbon content of 1.13% and the organic matter is mainly of Ⅱ2 and Ⅲ types, so it belongs to moderate to good source rocks. The carbonate rocks has a low organic carbon content, averaging 0.26% and the organic matter is of Ⅱ1 and Ⅱ2 types, so they belong to poor to moderate hydrocarbon source rocks. All the source rocks are in a peak period of oil generation and expulsion with a moderate maturity of organic matter and have good petroleum prospects, except those in the Dulan area, which contain overmature organic matter and are in an overmature, dry gas-generating stage. The source rocks developed in Shihuigou are very thick and have a high organic matter abundance. The dark-colored mudstone and carbonate rocks reach the standards of good and moderate hydrocarbon source rocks with a moderate organic matter maturity and have larger hydrocarbon- generating potential.