江汉盐湖盆地中高成熟原油的地球化学特征及油源探讨

江汉盐湖盆地中钟76井潜江组潜四段3300m以下发现的高成熟轻质原油，其基本特征是：饱和烃含量特高，非烃和沥青质含量很低；富含植烷、伽马蜡烷、C35升藿烷、孕甾烷和C27胆甾烷等指示高盐度、强还原环境的生物标志物。尤其明显的是C27-C29甾烷异构化程度高，αββ20R和20S峰十分突出，C29甾烷的两个参数值均大于等于0．5，指示了原油的成熟度已处于高成熟阶段。根据油源条件分析，认为该地区潜江组潜一段至潜四上段烃源岩埋深浅于3000m，P值小于1％，处于未成熟-成熟阶段，不具有形成高成熟原油的可能性，只有潜四下段烃源岩已进入生烃高峰高成熟早期阶段，能够提供轻质原油的油源。生物标志物多项地球化学资料及参数综合对比表明，本区两种成因类型的高成熟原油，其油源确系来自潜四下段两种不同沉积环境形成的泥质灰岩和灰质泥岩，明显具有近源运移聚集、自生、自储的特征，这展示了该地区潜四下段及其下覆的古潜山深层油气勘探有着良好的前景。

Geochemical characteristics and source rock identification of high mature oils in the Jianghan salt lake basins

The light crude oils found below 3300 m of Eq4 sand rocks in well Zhong 76 in Jianghan salt lake basins were characterized by: 1) high content of saturated hydrocarbons and non-hydrocarbons; 2) low asphaltene contents; 3) rich in phytane, gamacerane, C35 homohopanes, pregnant steranes and C27 regular steranes. These biological biomarkers indicated that light oils were derived from the source rocks deposited in saline and reduced environment. The isomerization ratios at C5, C14, C17 and C20 of C29 steranes w...