辽西凹陷沙四段烃源岩特征及生烃潜力

Characteristics of source rocks and hydrocarbon generation potential of the Member 4 of Shahejie Formation in Liaoxi Depression,China

研究辽西凹陷沙四段烃源岩品质及生烃潜力,探讨该边缘凹陷油气勘探前景。在现有钻井资料分析的基础上,结合地震属性特征,通过烃源岩地球化学分析、古环境分析以及盆地模拟,综合评价沙四段烃源岩生烃潜力,结果显示:①沙四段沉积时期整体处于干热气候、微咸水、弱氧化-还原沉积环境,由于中洼陆源输入较大,形成Ⅱ2型干酪根,烃源岩TOC平均质量分数为1%,为一般烃源岩;中-北洼远离陆源输入,具有较高的藻类丰度,形成Ⅱ1型干酪根,烃源岩TOC平均质量分数高达4%,为高丰度优质烃源岩。②沙四段烃源岩排烃门限深度大约在2.8 km,整个沙四段烃源岩都已成熟,进入生烃高峰。辽西凹陷中-北洼烃源岩丰度高、类型好,生烃潜力大,将是今后围绕沙四段勘探的主力洼陷。

Based on the previous drilling data and seismic attribute characteristics,the hydrocarbon generation potential of E s 4 source rocks is comprehensively evaluated by means of geochemical analysis,paleo-environmental analysis and basin modeling so as to unravel the oil and gas exploration prospect of the Liaoxi Depression.It shows that the sedimentary environment of E s 4 source rocks was under a hot-dry climate with brackish water and weak oxidization-reduction conditions.Terrigenous input in the central sag of Liaoxi depression is abundant and mainly forms typeⅡ2 kerogen with average TOC value of 1%.The central-northern sag keeps far away from the terrigenous input with high algae abundance and forms typeⅡ1 kerogen with average TOC value of 4%.The hydrocarbon expulsion threshold of E s 4 source rocks is 2.8 km at depth in Liaoxi Depression,and the entire source rocks are mature and in the peak of hydrocarbon generation.It proves that the E s 4 source rocks in the study area are characteristic of high abundance,favorable hydrocarbon type and great hydrocarbon formation potential.Therefore,the central-northern sag of Liaoxi Depression is a favorable target for the oil and gas exploration.