欢26块(杜)氮气驱适应性评价及应用研究

Research on Adaptability Evaluation and Application of Nitrogen Drive in Du Oil Reservoir of Huan26 Block

欢26块(杜)油藏先后经历天然能量和水驱两个开发阶段,随着油藏注水开发的不断深入,受油藏非均质性和油藏构造条件影响,油藏动用不均;主要表现为构造高部位注水不见效,其原因是受地层构造倾角大的影响,地层亏空严重,导致注入水沿倾角下倾方向流动并在构造高部位聚集,使构造高部位能量达不到补充,生产效果差。解决这一问题的关键是使驱替介质向构造高部位运移、补充构造高部位能量。提出了改变驱替介质流动方向的解决思路,并结合目前技术现状,提出了非烃类气体驱油的技术思路。通过对比几种非烃类气体驱油技术的优缺点,最终确定了氮气驱为最佳技术,通过数值模拟和物理模型实验确定了氮气驱现场实施的各项参数:注入方式为气水交替,交替周期为6个月,选用上倾部位氮气波及体积的0.45PV、气水比为1∶1设计各单井氮气总注入量。现场应用表明:氮气辅助水驱技术能够解决欢26块(杜)构造高部位井注水不见效的问题。

Dujiatai oil reservoir of Huan26 block in has been developed at two stages of natural energy and water drive.Along with the continuous deepening of water flooding,the oil reservoir was produced irregularly for heterogeneity and structure conditions.Poor effect of water injection was gained at high position of the structure,whose reason is serious reservoir voidage affected by high structure dip results in the downdip flow along the dip and accumulation of the injected water at the high position of the structure without energy supply.The key of solving the problem is to make displacing medium migrate to the high position of the structure for energy supply.The idea of flow direction change of the displacing medium is put forward.Com-bined with present technical status,the idea of non-hydrocarbon gas displacement is put forward.Nitrogen drive was considered as the best after the comparison of advantages and disadvantages among several tech-nologies of non-hydrocarbon gas displacement.Parameters of the nitrogen drive in the field were determined through numerical simulation and physical model experiments.Injection way is water alternating gas in six months per cycle.Total nitrogen injection rate of single well was designed according to 0.45 PV of the nitro-gen swept volume at upward positions and 1 ∶1 of gas-water ratio.Field application shows that nitrogen assisted water flooding may solve the problem of poor effect of water injection at the high positions of the struc-ture in Dujiatai oil reservoir of Huan26 block.