牛东火山岩油藏立体注水开发技术与应用

牛东火山岩油藏为异常低温正常压力系统的特殊油藏,具有火山喷发期次多、油藏规模小的特点。储集层裂缝发育,裂缝以低角度缝和水平缝为主;油层垂向跨度大,单层厚度大,非均质性强。油藏开发初期,采用衰竭式开采的单井产量递减率大,开展直井井组注水先导试验,邻井日产油量略有上升,注水见效程度低,水平井注水吞吐先导试验提高采收率幅度有限。针对油藏开发中存在的问题,对注水吞吐、井网调整和压裂进行不断优化,形成了水平井与直井混合立体注水开发技术,可以有效改善火山岩油藏的注水开发效果。后经推广实施,牛东火山岩油藏注水见效比例达44.4%,见效后单井初期平均日增油量为1.7 t,预计提高采收率5.7%,油藏立体注水开发取得了较好效果,可为其他同类型油藏的开发提供借鉴。

Stereoscopic Waterflooding Technology and Its Application in Niudong Volcanic Oil Reservoir

Niudong volcanic oil reservoir is a kind of special oil reservoir of abnormal temperature and normal pressure. It was formed by multiple stages of volcanic eruption, so the reservoir is on a small scale. In the reservoir, there are developed fractures that are dominated by almost low-angle and horizontal cracks, and oil layers cover a large span vertically, and each layer is very thick and heterogeneous. During the early development, rapid production decline occurred in the wells developed by depletion method; water flooding pilot test was carried out in vertical well groups, the daily oil production of adjacent wells increased slightly; and the EOR result of cyclic water injection pilot test in horizontal wells was not very good, indicating that the waterflooding effect was not oblivious. Regarding these problems, a vertical-horizontal well-mixed, stereoscopic waterflooding technology has been established based on the optimizations of cyclic water injection, well pattern adjustment and fracturing program, which can effectively improve the waterflooding effect in volcanic oil reservoirs. The actual application of the technology in horizontal wells exhibits a good effect with the well response rate of 44.4%, the initial incremental oil production of 1.7 t/d per well, and the expected enhanced oil recovery of 5.7%, which can provide references for the development of the other similar oil reservoirs.