盐间泥岩裂缝超压油气藏成藏作用——以东濮凹陷文留构造为例

Overpressured fractured mudstone reservoir in salt-mud interbed—A case from Wenliu structure in Dongpu Sag

盐间泥岩裂缝性超压油气藏是一种特殊类型的油气藏,与一般泥岩裂缝性油气藏相比,其成藏作用具有以下特征:自生自储;泥岩裂缝发育于超压层段内;油气主要富集在断裂带附近。东濮凹陷文留地区盐间泥岩裂缝异常高压油气藏主要发育在以深湖—半深湖相沉积环境为主的Es32内,岩性为盐泥互层,砂岩不发育。盐间泥岩为优质烃源岩,成熟度较高,生烃潜力巨大;烃源岩上、下被盐岩所夹持,盖层条件较好;储集层为泥岩裂缝,裂缝的产生主要由断层活动、异常流体压力及盐丘上拱泥岩发生破裂所致,裂缝主要为剪切裂缝和张裂缝。

The overpressured fractured mudstone reservoir is a special type of reservoir, which has the following characteristics of formation： both hydrocarbon generation and accumulation occur in the same reservoir; mudstone fractures are developed in the section with abnormally high pressure; hydrocarbons collect in the vicinity of fault belts. The overpressured fractured mudstone reservoir in Wenliu is developed mainly in the second member of third section of Paleogene Shahejie Formation, where major sediments are deposited in deep and half-deep lacustrine environments. The lithology is salt-mud interbeds and sandstone is immature. It takes dark and thick rock rich in carbonate and organic matter as its source. The reservoir is related to the local tectonic deformation caused by fault, abnormal fluid pressure and salt plastic flow. The sealing of salt beds up and down the source rock made autogenous and in-situ-stored fractured mudstone reservoirs come into being.