低渗储层PRD钻井液微细固相的絮凝性能优化

以东方某低渗透气田储层为例,分别测试了重晶石粉、超细碳酸钙、膨润土粉、泥岩钻屑(储层段)在液相里的粒径分布情况,评价了他们对储层的损害程度,发现造浆膨润土和水化后泥岩,由于大部分颗粒在微米和亚微米级,对岩心渗流通道造成了堵塞。因此优选出了絮凝剂PL-1,其在加量为0.1%时对微细固相具有好的絮凝能力,并能明显增强钻井液的储层保护能力,被优化后的PRD钻井液污染的岩心,渗透率恢复值由优化前的66.9%提高到79.7%,而且钻井液的滤失造壁性也得到了改善。

Optimization of Flocculation Performance of PRD Drilling Fluid for Fine Solids

Particle size distribution was tested for barite, ultra-fine calcium carbonate, bentonite and shale cuttings (from reservoir section) dispersed in liquids, and their effects on the permeability of reservoir formations were evaluated. It was found that the bentonite and shale cuttings, which contain large numbers of micron and submicron particles, blocked the flow channel of the cores. Based on the test results, a flocculant, PL-1, was selected to flocculate these fine solids. In laboratory core flooding test, the PRD drill-in mud (for low-permeability reservoir drilling) treated with 0.1% PL-1 gave a percent permeability recovery of 79.7%, while PRD drill-in fluid not treated with PL-1 gave a percent permeability recovery of 66.9%, showing the efficiency of PL-1 in reservoir protection. PL-1 also helped reduce the filter loss of PRD.