聚合物滞留率对特低渗透非均质油藏调堵效果的影响——以长庆西峰油田某边底水天然能量开发油藏为例

Effect of polymer retention on conformance control in ultra-low permeability heterogeneous reservoirs:A case study on reservoir with edge and bottom water produced by natural energy in Changqing Xifeng Oilfield

为研究聚合物的滞留率对特低渗透非均质油藏调堵效果的影响,利用人造非均质储层模型开展注聚合物-天然能量开采模拟实验。借助自主设计的边底水油藏天然能量开采模拟实验装置,实现了室内开采实验对目标油藏矿场开发特征的精准模拟,明确了聚合物滞留率对控水、保压、稳油和提高采收率效果的影响。实验结果表明,提高聚合物在高渗透层的滞留有助于控制水窜、抑制油藏压力降低速度,对延长油井稳产期效果明显。此外,采收率与聚合物滞留率为非单调变化规律,即存在一个采收率达到峰值的最佳聚合物滞留率;以最佳聚合物滞留率为界,聚合物滞留率过小或者过大,采收率均明显降低。对于目标油藏,适宜的聚合物滞留率为70%~82%,其适宜的注入量为高渗透层孔隙体积的0.3~0.6倍。由此可知,特低渗透非均质油藏调堵工艺需要控制聚合物适宜的注入量和适度的滞留率。

In order to study the effect of polymer retention on conformance control and production performance in an ultralow permeability heterogeneous reservoir,the artificial heterogeneous core models are used to perform a series of polymer conformance control experiments followed by production under the natural energy.Based on the novel designed experimental apparatus for reservoirs with an edge and bottom water and produced by the natural energy,the similarity simulation for the production characteristics of a practical oilfield is achieved in laboratory.The effect of polymer retention rate on water channeling control,reservoir pressure maintaining,oil production stabilization and enhanced oil recovery were analyzed.The results show that the increase of the polymer retention in the high-permeability layer is helpful to control water channeling,inhibit the decline rate of reservoir pressure,and extend the relatively high production period of production wells.Additionally,the oil recovery and the rate of polymer retention are non-monotonic,namely,there is an optimal retention rate(RC)to reach the highest oil recovery.Taking the optimal retention rate of polymer as the benchmark,higher or lower polymer retention rate leads to an obvious decline in oil recovery.For the target reservoir,the laboratory results show that the optimal polymer retention rate are 70%to 82%,and the optimal polymer injection volume are 0.3 PV to 0.6 PV(PV represents the pore volume of the high-permeability layer).An effective conformance control technology for an ultra-low permeability heterogeneous reservoir needs to provide both optimal polymer injection volume and polymer retention rate.