Study of Residual Oil in Tahe 4th Block Karstic/Fractured Heavy Oil Reservoir

Tahe 4th block karstic/fractured Heavy Oil Reservoir is a block bottom water reservoir with the greater heterogeneity. By the end of 2009, the yearly rate oil production is 7.23×106tons, and the oil recovery efficiency is 11.4%. But after a long period of development, many deficiencies of fast producing are exposed gradually: the water breaks through early in the oil wells, the water cut increase fast; the natural decline rate is high, and the development degree of the reservoir is lower. By physical simulation experiments, the residual oil types and their effect factors have been investigated. The five main residual oil types in karstic/fractured reservoir have been determined. Furthermore, according to the dynamic and static information of wells, the production wells have been divided into three types by clustering method. And the 4th block of Tahe oil field have been divided into three zones in accordance with the well types, including a zone with a lot of caves, a zone with caves and fractures and a zone with fractures. Meanwhile, the main residual oil types and the research direction of EOR technologies in different zones have been pointed out. The knowledge gained from this study can be a foundation to increase the well controllability and improve oil recovery in fractured/karstic carbonate reservoirs.