聚合物类型、注液方式和层系组合方式对聚驱效果的影响实验

Experiment on influence of polymer type,injection mode and strata series combination mode on polymer flooding effect

目前大庆油田聚合物驱油技术的应用对象已经由一类储层向二、三类储层转移,原注入体系在注聚初期阶段的适应性较差,对高渗层的封堵能力弱,需要进一步评价注入体系和优化注入方式,以提高聚驱效果。因此开展了聚合物类型、注液方式和层系组合方式对聚驱效果影响实验研究。结果表明:实验所用“抗盐”聚合物低剪切强度表现为内摩擦力即视黏度损失较小,但高剪切强度条件下结构易于破坏,致使黏度保留率较低、滞留和液流转向能力较差;考虑到矿场注入压力受到储层岩石破裂压力限制,与“恒速”注入方式相比较,“恒速/恒压”注入方式和现场注入方式更为贴近;采用“分步注入”,模型中“层内非均质”岩心打开时机较晚,最终采收率增幅较大。实验结果可以为矿场局部注聚技术的推广提供技术支持。

At present,the application object of polymer flooding technology in Daqing Oilfield is transferred from ClassⅠreservoirs to ClassⅡand ClassⅢreservoirs.Original injection system has relatively low adaptability in early stage of polymer injection and low plugging capability for high permeability reservoirs.It is necessary to fur-ther evaluate injection system and optimize injection mode to improve polymer flooding effect.Therefore,experi-mental study on influence of polymer type,injection mode and strata series combination on polymer flooding effect is carried out.The results show that“salt-resistant”polymer used in experiment presents as small loss of internal friction,i.e.,apparent viscosity,in low shearing strength condition,but its structure is easily destroyed in high shearing strength condition,causing low viscosity retention rate and poor detention and liquid flow inverting capa-bility.Considering that injection pressure is limited by reservoir rock breakdown pressure in the field,“constant rate/constant pressure”injection mode and field injection mode are more appropriate than“constant rate”injection mode.When the opening time of“inner-layer heterogeneous”cores in“step injection”model is late,the ultimate recovery increases greatly.The experimental results provide technical support for promotion of localized polymer flooding in field.