塔河油田缝洞型油藏单井注氮气采油机理及实践

塔河油田缝洞型碳酸盐岩油藏储集层类型特殊、开发难度大，前期通过实施单井及单元注水，在一定程度上取得了良好的增油效果；随着注水量增加，开发效果逐渐变差，大量剩余油富集在缝洞单元高部位，注水无法波及。针对此类剩余油，开展了注氮气吞吐驱油实验研究，结合数值模拟技术，论证了注氮气能有效动用这部分剩余油。注入地层中的氮气与原油混合并发生重力分异，将高部位剩余油向下置换并采出，注入氮气在原油中溶解也能起到一定的降低原油黏度、补充地层能量的作用。该项技术2012年开始在塔河油田奥陶系缝洞型碳酸盐岩油藏开展现场试验，已投产试验井123口，累计产油16.13×104 t，增油效果显著，验证了缝洞型碳酸盐岩油藏注气吞吐置换剩余油是一项可行的提高采收率技术。

Mechanism and Practice of Nitrogen Injection for EOR in Fractured-Vuggy Carbonate Reservoir in Tahe Oilfield,Tarim Basin

The fractured-vuggy carbonate reservoirs in Tahe oilfield are characterized by special reservoir types and difficult exploitation. The previous single well water injection and element pattern water flooding obtained better oil incremental effects to some extent. However, the development effect was getting poor with the continuous water flooding for the plentiful oil that water flooding can’t sweep was remained in high parts of fractured-vuggy units. This paper studied and proved the possibility of nitrogen huff and puff process for the remained oil by means of numerical simulation technique. When injecting nitrogen gas into the formation, it will mix up with the crude oil and appear gravitational segregation to replace downward and produce the oil, also, the injected nitrogen dissolved in the remained oil can play a role of reducing the oil viscosity and complementing the formation energy or pressure. This technology has been applied to 123 wells in Ordovician fracture-vuggy carbonate reservoirs in Tahe oilfield since 2012, and the cumulative oil production amounted to 16.13×104 t. It is verified that it is a feasible EOR technology for such a reservoir