不同开发方式下礁灰岩油藏驱油效率研究

王亚会 闫正和 张晓林

摘      要：南海东部礁灰岩油田具有储量开采程度低、裂缝发育复杂、非均质性强等特点，优化开发方式是提高开采效果的有效途径。以南海东部裂缝性中高渗礁灰岩L油田为例，选取目的层段的4塊全直径密闭岩心，拼接成直径10 cm，长度30 cm的长岩心组，在实际油藏条件下，模拟顶部注气、底部注水、底部注水驱至残余油后转顶部注气和底部高含水转注气段塞驱等实验，深入分析影响不同驱替方式下开采效果变化原因。结果表明：①顶部注气0.78 HCPV时，注入气处于临界突破点，大量形成油、气互溶混相驱，凝析混相驱和重力稳定驱效果明显，驱油效率高达70.7%，注入气突破临界点后，入口压力下降，驱油效率趋于稳定;②底部注水量从0到0.37 HCPV，驱油效率增长较快，最高仅为43.3%，较顶部注气效果差;③底水驱油后，不论顶部注气或底部注气段塞驱，渗流优势通道中气水混合流动均易形成贾敏效应，波及范围变大，随着注气倍数增加，驱油效率可提高3.0%～6.4%。该研究成果可为裂缝性中高渗礁灰岩油藏合理高效开采开发提供技术支持。。

关  键  词：全直径岩心;裂缝性高渗;礁灰岩;开发方式;驱油效率

中图分类号：TE327       文献标识码： A       文章编号： 1671-0460（2020）05-0821-05

Abstract： The reef limestone in the eastern South China Sea has the characteristics of low recovery， complex fracture development and strong heterogeneity. Therefore， optimizing the development mode is the key factor in determining the exploitation results. In this paper， L reef limestone reservoir in the eastern South China Sea was set as the target reservoir， and a long core set （diameter 10 cm and length 30 cm） consisting of 4 full diameter cores was selected from this reservoir. Crestal gas injection experiments， bottom water flooding experiments， experiments by converting bottom water flooding to crestal gas injection and experiments by converting bottom water flooding to gas slug injection were carried out，and the results of different development modes were analyzed. The results showed that ① When 0.78 HCPV gas was injected from the top， the injected gas reached the critical breakthrough point and the oil-gas miscible flooding statement was achieved. Condensing miscible flooding and gravity stable flooding were effective in this stage and the displacement efficiency reached 70.7%. After the injected gas broke through， the inlet pressure declined and the oil displacement efficiency tended to be stable. ② When bottom water was injected from 0 to 0.37 HCPV， the oil displacement efficiency increased rapidly but the final oil displacement efficiency was only 43.3%， which was lower than that of the crestal gas injection. ③ After the bottom water flooding， the gas-water mixture tended to cause the Jamin effect and the scope of sweeping was enlarged. With the increase of injection pore volume multiple， the oil displacement efficiency increased by 3.0%～6.4%. These experiments can give base data and technical support for the development of fractured reef limestone reservoirs.

Key words： Full diameter cores; High permeability with fracture; Reef limestone; Development modes; Oil displacement efficiency