深海挥发性油藏注气开发气油比变化规律研究及应用

Study on the variation law of gas-oil ratio in gas injection development of deep sea volatile oil reservoirs and its application

西非深海AKPO油田挥发性M油藏为浊积复合朵叶体沉积,流体纵向上存在明显的组分梯度特征;基于流体性质及油气两相渗流规律,研究了注入气突破前后气油比的变化规律。注入气突破前,生产井气油比变化规律与原始溶解气油比变化规律一致,呈缓慢上升趋势;注入气突破后,从油气两相渗流规律和物质平衡出发,结合出口端含气饱和度和平均含气饱和度的关系,建立了注气开发油藏气驱特征曲线,推导得到了气油比与采出程度、气油比上升率与采出程度的指数型关系式,并绘制了气油比、气油比上升率与采出程度图版用于表征气油比变化规律。M油藏应用表明,本文理论分析结果与实际油藏气油比变化规律吻合,所提出以“扩大注气波及”为核心的注气井工作制度调整方法可以有效控制单井气油比上升速度,延缓产量递减,稳油控气效果显著。

The M volatile oil reservoir of the AKPO oilfield in the deep sea of West Africa belongs to the turbidite composite lobe deposition, and there are obvious compositional gradient characteristics of the fluids in the longitudinal direction. Based on the fluid properties and the two-phase seepage law of oil and gas, the variation law of gas-oil ratio before and after the breakthrough of injected gas was studied. Before the breakthrough of injected gas, the variation law of gas-oil ratio in production wells is consistent with the variation law of original dissolved gas-oil ratio, showing a slow rising trend;after the breakthrough of injected gas, starting from the two-phase seepage law and material balance of oil and gas, combined with the relationship between gas saturation at the outlet end and the average gas saturation, the gas flooding characteristic curve of the gas injection reservoir was established;the exponential relationship between gas-oil ratio and recovery degree, gas-oil ratio increase rate and recovery degree was derived and plotted, and the gas-oil ratio, gas-oil ratio increase rate and recovery degree plate were used to characterize the variation law of gas-oil ratio under different recovery degrees. Its application in M reservoir shows that the theoretical analysis results of this paper are in consistent with the variation law of gas-oil ratio of actual reservoirs, and the proposed gas injection wells working system adjusting method of focusing on "expanding gas injection sweepage" can effectively control the rising rate of gas-oil ratio of single well and delay the production decline, hence achieving a significant effect of oil stabilization and gas control.