砂岩储层清水和污水混注对储层损害的实验评价

Experimental evaluation on formation damage caused by re-injection of mixture of fresh water and produced water in sandstone reservoir

注入水中乳化油含量和悬浮颗粒含量及粒径一直是控制砂岩油藏注入水水质的重要指标。利用正交试验原理,通过实验系统评价了乳化油和悬浮颗粒共存时乳化油滴浓度、固相颗粒含量及粒径、渗透率及注入孔隙体积的相互作用及其对中高渗储层吸水能力的影响。结果表明,对于污水回注或清水、污水混注的砂岩地层,乳化油和悬浮颗粒共存比其单一存在时对地层吸水能力的损害要严重。当油滴粒径小于10μm时,岩心损害程度大于70%,油滴粒径大于30μm时,岩心损害程度低于50%。对于给定孔喉的岩心,有一个临界颗粒粒径。临界固相颗粒粒径随渗透率(即孔喉大小)的变化而变化,而临界油滴粒径基本不随渗透率变化,粒径约为15μm。

The suspended particle and emulsion oil specifications are very important for water quahty control during produced-water re-injection in sandstone reservoirs. The mutual interactions and effects of particle content and size, oil content, core permeability and injected pore volume of water on fluid flowing efficiency in core were evaluated by orthogonal experiment design method. The coexistence of suspended particle and emulsion oil in produced water may lead to more serious damage of formation than the individual element in oily water re-injection. The damage extent was over 70 percent when the diameter of oil droplets was less than 10 μm, and the damage extent was below 50 percent when the diameter of oil droplets was over 30 μm. There is a critical value of particle diameter （about 15 μm） for a core with a certain pore-throat size. The critical diameter of solid particle changed with pore-throat size, but the size of oil droplets could not change with that.