玛湖凹陷风城组烃源岩特征与生烃模式

基于最新油气勘探成果及烃源岩有机地化分析数据和热模拟实验结果，评价了准噶尔盆地玛湖凹陷下二叠统风城组烃源岩的生烃能力，并进一步建立其生烃模式。研究区风城组发育一套沉积环境、岩性复杂多变的碱性湖泊相烃源岩，沉积水体盐度、碱度及成岩环境等变化快，致使源岩岩性复杂多变。其残余有机质丰度不高，类型为Ⅰ—Ⅱ型，大部分处于成熟阶段，热演化进程较慢。该组三个地层段均发育中—好烃源岩，少部分为很好烃源岩。风城组碱性湖泊相源岩生烃能力、模式与正常湖相源岩基本一致，为单峰式生油高峰，但其特点为生油持续时间长、总产油率远高于产气率、转化率高，主体处于生油阶段。油气勘探实践也证实玛湖凹陷是以含油为主的油气系统，在浅层或深层均以形成油藏为主。

Characteristics of Source Rocks and Hydrocarbon Generation Models of Fengcheng Formation in Mahu Depression

This study takes into account the most recent oil and gas exploration results， as well as experimental data from organic geochemical analysis of source rocks and the results of autoclave thermal simulation， to evaluate the hydrocarbon generation capacity of the lower Permian Fengcheng Formation in the Mahu Sag， Junggar Basin， and summarizes its hydrocarbon generation model. A set of alkaline lacustrine source rocks with complex sedimentary environment and lithology are developed in this formation. The salinity， alkalinity and diagenetic environment of the sedimentary water changed rapidly， which has caused the source rock lithology to be complex and variable. The abundance of residual organic matter is not high， and is mainly type I?II， most of which is mature stage， and the thermal evolution process was slow. The three strata have all developed medium?to?good source rocks； a few of them are very good source rocks. The hydrocarbon generation capacity and model of the basic lacustrine source rocks are basically similar to normal lacustrine source rocks， having a single oil?generation peak， but in this case it is characterized by a long oil generation duration， giving a total oil production rate far higher than the gas production rate and a high conversion rate， and the main body is at the oil generation stage. This life?cycle hydrocarbon model has been verified by oil and gas exploration results. The Mahu Depression is an oil?bearing oil/gas system， mainly formed in shallow or deep layers. This understanding has guiding significance for subsequent oil and gas exploration deployment.