柴达木地区上古生界石炭系烃源岩评价

Evaluation of Carboniferous source rocks in Qaidam area

通过柴达木盆地周缘地区上古生界暗色泥岩、碳酸盐岩、煤及碳质泥岩的有机地球化学的测试分析,研究结果表明,石炭系烃源岩主要以暗色泥岩为主,炭质泥岩和煤可能具有生烃能力。下石炭统暗色泥岩有机碳含量一般达到了差到中等,而上石炭统暗色泥岩有机碳含量达到好或者很好;上、下石炭统的暗色灰岩有机碳含量均比较低,一般仅为非到差等烃源岩。有机碳评价较好的泥岩主要发育在潮坪、泻湖、沼泽相沉积相类型中;剖面上评价较好的层位为怀头他拉组的中部和克鲁克组及其扎布萨尕秀组的下段,评价结果已经达到好到很好等级。样品中的有机质类型均以Ⅲ型和Ⅱ2型为主。除都兰、格尔木地区有机质成熟度过高、处于过成熟的生干气阶段外,其他地区有机质成熟度中等,正处于生烃、排烃高峰期,具有良好的油气勘探前景。

Organic geochemistry measurements and analyses were conducted on Carboniferous dark-colored mudstones,carbonates,coals and carbonaceous mudstones in marginal areas around the Qaidam Basin.The results indicated that the Carboniferous source rock consists predominantly of dark-colored mudstones among which coals and carbonaceous mudstones probably have hydrocarbon-generative potential.The lower Carboniferous dark-colored mudstone generally has poor to moderate contents of organic carbon,while the upper Carboniferous one contains a good or very good abundance of organic carbon.However,the upper and lower Carboniferous dark-colored limestone shows a lower content of organic carbon,constituting only a non-to poor-source rock.Mudstones with good source potential developed mainly in deposits of tidal flat,lagoon and marsh facies and horizons occurring in the middle Huaitoutala Formation,Keluke Formation and the lower Zhabusagaxiu Formation were evaluated as a good or very good source rock.Organic matter in the samples is mainly dominated by type II and III kerogens,and all the source rocks,except for the Dulan and Geermu areas where they have been at the post-mature stage to generate dry gases,are in a peak period of oil generation and expulsion with a moderate maturity of organic matter,thus,they have a good petroleum prospect.