东营凹陷广饶海相灰岩油藏的勘探与成因机制探讨

Exploration and Origin Mechanism of Marine Limestone Oil-Pool in Guangrao of Dongying Depression

山东东营凹陷南部的广饶油藏为一奥陶系灰岩残丘山整带含稠油的大潜山油藏,其埋藏深度为634.4～1575.0m,现已探明含油面积30.7 km^2。1990年发现一个山头含油,1991—1993年发现多个山头含油,1996—1997年在各山头之间的部位钻探,结果探明潜山带南部整带含油。地质和地球化学资料分析证实,该油藏不仅是今生古储潜山油藏,还是烃类经基岩风化壳运移、聚集而形成的稠油油藏。形成稠油的主要原因是,油藏形成后,构成潜山圈闭的明化镇组、馆陶组浅层泥岩封堵条件差,使原油中轻质组分大量散失,重质组分浓缩。由初期的一个至几个出油点至目前探明为一个大油藏的事实表明,在盆地边缘找油,只要油源充足,运移通道和成藏条件好,就有可能发现大油藏。研究这类油藏的发现史和成因机制,对海相灰岩发育盆地的油气勘探有一定的理论和实际意义。

Guangrao oil-pool to south of Dongying depression,an Ordovician limestone residual mountain of wholly bearing visceus oil,is a big buried-hill oil-pool.it is buried at the depth of 634.4～1575.0m,and the proven oil-bearing area so far is B0.7km^2.The first oil-bearing hill was discovered in 1990.A lot of ones were then found in 1991-1993.In 1996- 1997 drilling between hills suggests that the whole south of buried hills bear oil.The oil-pool is not only a buried hill pool with young source rock and old reservoir,but also a viscous oil -pool.The main reason of viscous oil formation is that Minghuazhen and Guantao shales as a caprock are shallow burial in poor sealing conditions,which result in light compositions of the oil lost in great deal and heavy ones concentrated.Study on the discovery history and origin mechanism has a certain theoretical and practical significance on oil-gas exploration of marine limestone developed basin.