大港油田沙一段中部泥岩盖层封闭油气能力和时间有效性

为了研究沙一段中部泥岩盖层在油气成藏中的作用,采用地质统计和历史演化的研究方法对大港油田沙一段中部泥岩盖层发育、微观封闭能力及封油气有效性进行研究。结果表明:沙一段中部泥岩盖层除北大港潜山构造带的南部局部缺失外,全区分布,是油气聚集与分布的区域性盖层。具有较强-强的封闭能力,在东营组中后期和明化镇组中期分别形成封闭低和中储量丰度油气藏的能力,2个时期均早于沙三段源岩的大量排烃期,在时间上封闭油气是有效的,但其目前尚未进入形成封闭高储量丰度油气藏的时期,只能形成封闭中低储量丰度的油气藏。大部分油气藏沙一段中部泥岩盖层排替压力均大于储层排替压力和油气藏剩余压力之和,在能力上封闭油气是有效的,只有少数油气藏剩余压力大在能力上无法有效封闭油气。沙一段中部泥岩盖层封闭油气有效性决定了其下油气富集但储量丰度不高。

Sealing oil-gas time and ability effectiveness of mudstone caprocks in middle Es1 in Dagang Oilfield

To study controlling of mudstone caprocks of middle Es1 to oil-gas accumulation,using the methods of geological statistics and historical evolution,the development,the micro-sealing ability and sealing effectiveness of mudstone caprocks in middle Es1 of Dagang Oilfield were studied.The results show that the mudstone caprocks of middle Es1 which distributes all over the research region except southern part of Beidagang buried-hill structural belt is regional caprock for oil-gas to accumulation and distribution.Moreover,mudstone caprock of middle Es1 owns stronger-strong sealing ability.In the late and middle of Ed and the middle of Nm it began forming separately sealing ability for oil-gas reservoirs with lower and middle reserves abundance.The two periods are earlier than expulsion oil-gas period in the great deal of Es3 sourcerock.It is effective to seal oil-gas in the time,but it has not yet gotten the formation period of oil-gas reservoirs with high reserves abundance now.Oil-gas reservoirs with middle and lower reserves abundance are only formed under mudstone caprock of middle Es1.The displacement pressure of mudstone caprock of middle Es1 in most oil-gas reservoirs is higher than the together of displacement pressure of reservoir and surplus pressure of oil-gas reservoirs.It is effective to seal oil-gas in ability.Sealing oil-gas effectiveness of the mudstone caprock of middle Es1 controls oil-gas accumulation under mudstone caprock of middle Es1,but reserves abundance of oil-gas reservoirs is lower.