A Study on the Influences of Alluvial Fan Sandbody and Its Internal Architecture on Remaining Oil Distribution

With the continuous deepening of development degree, the old oilfields in Eastern China have almost all entered the stage of ultra-high water content. In order to understand the distribution law of remaining oil in ultra-high water cut stage old oilfield, by using integrated deterministic three-dimensional architecture modeling and reservoir numerical simulation method under the constraint of 9-level architecture boundaries, this article discussed the influences of alluvial fan sandbody and its interior architecture on the residual oil distribution, taking the Xiaoji Oilfield in the eastern part of the Cangdong Sag, Bohai Bay Basin, China as an example. The research results show that: Four types of remaining oil controlled by alluvial fan sandbody and its internal architecture can be divided, namely the remaining oil in braided sand island, in braided river channel single sandbody, in poorly connected braided river water channel and overland sandbody; among them, the remaining oil in braided sand island includes remaining oil at the top and bottom of the accretion body. The inner part of the fan mainly has remaining oil in braided sand island, braided channel single sand body and overland sand body; the middle part of the middle fan has all the four types of remaining oil, the fan-outer belt-fan edge zone only has remaining oil in single channel sand body at the bottom of the braided channel with better reservoir properties. Four types of remaining oil can be exploited by infilled well pattern, horizontal well, adding perforation, profile control and water plugging, and separated layer water injection.