海上多层稠油聚合物驱产液指数变化主控因素

Main Controlling Factors on Liquid Productivity Index for Polymer Flooding in Offshore MultiLayered Heavy Oil Reservoirs

针对海上稠油聚合物驱过程中部分井产液能力存在明显下降的问题,通过构建基于渗流力学理论的多层油藏聚合物驱产液指数计算模型,研究了影响产液指数变化的主控因素。结果表明,油井产液指数在转注聚合物后依次经历上升段、下降段、平稳段和回升段;无因次产液指数最大降幅受聚合物黏度、注聚合物时机以及渗透率级差的影响显著,波谷时机受原油黏度、渗透率级差、低渗层相对厚度以及聚合物吸附能力倍数的影响显著,据此进一步提出了无因次产液指数最大降幅及波谷时机计算公式;海上油田典型注聚合物条件下,产液指数平均最大降幅为53.1%,波谷时机对应聚合物平均累计注入孔隙体积倍数为0.250 PV.研究成果对聚合物驱产液指数预测、方案设计与调整具有重要指导意义。

To address the apparent decline of liquid productivity index during polymer flooding in some offshore heavy oil wells,a sophisti-cated mathematical model to predict productivity behavior in multi-layered reservoirs is established,then the main controlling factors on the variations of liquid productivity index of polymer flooding are studied.The results show that the productivity index after conversion into polymer flooding undergoes 4 phases-rise,decline,stabilization and rise again;the largest drop of the dimensionless liquid productivity index is significantly influenced by polymer viscosity,polymer injection timing and permeability ratio,and the trough timing is highly impacted by crude oil viscosity,permeability ratio,relative thickness of low-permeability zone and absorption capacity.Based on which formu-las to calculate the largest drop of dimensionless liquid productivity index and trough timing are proposed.Under the typical polymer flood?ing conditions in offshore oilfields,the average largest drop of liquid productivity index is 53.1%,and the average cumulative injection pore volume corresponding to the trough timing is 0.250 PV.The research results are of guiding significance for the liquid productivity index pre?diction,program design and adjustment for polymer flooding.