涠洲12-1油田水平井无固相有机盐钻井液技术

涠洲12-1油田在应用无固相有机盐钻井液钻进储层时，存在钻井液流变性不能满足长裸眼水平段井眼清洁要求、暂堵剂粒径分布不合理和储层保护性能差的问题。为此，通过优化增黏剂的加量和暂堵剂的粒径分布对无固相有机盐钻井液配方进行了优化。性能评价表明:优化后的无固相有机盐钻井液具有较高的低剪切速率黏度，可以提供良好的携岩和悬浮岩屑的能力；储层保护性能优良，岩心的渗透率恢复率大于90%；抑制性能较强，泥页岩线性膨胀率仅为10%，岩屑滚动回收率高达96.48%。4口井的现场应用结果表明:采用优化的无固相有机盐钻井液后，涠洲12-1油田水平井段未发生起下钻遇阻；表皮系数由20.0以上降为-3.0，产油量为配产的2倍。这表明，优化后的无固相有机盐钻井液能满足涠洲12-1油田水平段钻进的要求，可解决水平井段井眼清洁和储层保护效果差的问题。 

Solid-Free Organic Salt Drilling Fluid for Horizontal Wells in the Weizhou 12-1 Oilfield

Solid-free organic salt drilling fluids used for drilling reservoirs in the Weizhou 12-1 Oilfield have rheological problems that resulted in a failure to perform borehole cleaning in long open horizontal intervals.Therefore, a solid-free organic salt drilling fluid was formulated by optimizing the additive quantity and particle size distribution.Performance evaluation showed that optimized solid-free organic salt drilling fluids had a high low shearing rate viscosity,and may provide satisfactory for cutting,carrying and suspension capacities.In addition,these drilling fluids perform well in protecting reservoirs,with permeability recovery rate of cores contaminated by these fluids more than 90%.The drilling fluids also have high inhibition capacities with linear expansion rate of mud shale as low as 10%,with rolling cutting recovery rate up to 96.48%.Field application results indicated that no pipe sticking has been observed during tripping operations in horizontal intervals in the Weizhou 12-1 Oilfield when using the new fluid.More specifically,by using optimized solid-free organic salt drilling fluids,skin factors were reduced from over 20.0 to -3.0,oil production was 2 times of that expected.It was concluded that optimized solid-free organic salt drilling fluid could meet the requirement of drilling horizontal intervals in the Weizhou 12-1 Oilfield,and effectively improve well cleaning and reservoir protection in horizontal intervals.