安山岩双重介质底水油藏渗流特征研究及剩余油挖潜

Study on seepage characteristics of andesite dual media reservoirs with bottom water and potential tapping of remaining oil

大港南部安山岩油藏为典型的块状双重介质底水油藏,在20世纪90年代开发过程中,初期产能较高,含水较低,但油井含水上升速度非常快,在不到10年间,油藏含水达到98%,区块废弃停产,采出程度仅有6.1%。为了提高油藏的采收率,开展了区块精细分析,通过裂缝精细描述认为该区以高角度裂缝为主,在进行裂缝建模的基础上,进行了双重介质油藏数值模拟,研究了油藏开发过程中油水渗流特征,结果显示高角度裂缝作为优势渗流通道,纵向渗流能力较强,在直井开发的情况下容易沟通底水,导致油井含水快速上升。区块停产20年后,油藏在重力作用下油水发生了二次分异,油水界面下降明显,油气重新聚集在储集层高部位。据此针对剩余油富集区进行了井网井型论证,认为水平井在开发双重介质底水油藏方面比直井更具优势,在剩余油富集区部署水平井实施剩余油挖潜并取得了突出效果,对同类型油藏开发具有借鉴意义。

The andesite of southern Dagang,the typical massive dual media reservoir with bottom water,had higher productivity in the initial stage and lower water cut during development in the 1990s.While the water cut of reservoirs reached 98%in less than ten years due to the fast rising of water cut of oil wells,and the block production halted with the recovery efficiency of only 6.1%.In order to improve reservoir recovery efficiency,fine block analysis was conducted.The detailed description of fracture revealed that this area is dominated by high-angle fracture.On the basis of fracture modeling,numerical simulation of dual media reservoirs was carried out to study the oil-water seepage characteristics during reservoir development.It showed that high-angle fractures,as the dominant seepage channel,had strong longitudinal seepage ability and were easy to connect with the bottom water when developing a vertical well,leading to a fast rising of the water cut of oil wells.20 years after the production halt in this block,secondary differentiation occurred in the oil and water in the reservoir under gravity action.The oil-water interface dropped significantly,oil and gas re-accumulated in the higher part of the reservoir.On these grounds,well patterns and types directing at the remaining oil enrichment area were demonstrated,proving that horizontal wells had advantages over vertical wells in the development of dual-medium bottom water reservoirs.Horizontal wells were deployed in remaining oil enrichment area to tap the potential of remaining oil.Outstanding effect obtained had referential significance for the development of the same type of reservoir.