低自由水钻井液体系

A novel drilling fluid with less free water

基于对钻井液中自由水流动状态的研究,研制了自由水络合剂,其能有效络合钻井液中的自由水,提高自由水进入地层的毛管阻力,减少滤液侵入地层的量和深度;同时络合剂络合自由水后形成特殊的分子胶束,能形成致密的低渗透封堵膜,有效封堵孔喉和微裂缝,提高地层承压能力,降低钻井液密度。构建了低自由水钻井液体系,CST毛细管吸水实验、岩心自吸水实验和自由水含量测定均证实该体系具有较好的络合自由水的能力,能有效减少钻井液中液相向地层的侵入量。现场应用结果表明,该体系具有良好的流变性、润滑性及抑制性,可有效解决井壁稳定性问题,且能有效提高地层承压能力、降低钻井液密度、提高机械钻速、缩短钻井周期。

Through research on the flowing state of free water in drilling fluids,a special complexing agent was developed.This additive can increase the capillary force for free water to invade reservoirs and thus control filtrate invasion by effectively complexing the free water in drilling fluids.The invasion quantity and invasion depth of water into reservoirs can be reduced.In addition,the complexed free water can form a kind of special micelle and low-pemeability membrane so that it can effectively plug pore throats and microfractures,increase the bearing pressure of formations and decrease the required density of drilling fluids.Based on the results of CST tests,spontaneous water imbibition test of cores and measurement of free water content,it is concluded that the newly formulated drilling fluid with less free water can effectively complex free water in drilling fluids and reduce liquid invasion to formations.Field application shows that the less free water drilling fluid has good behaviors of rheology,lubricity and inhibition.It can increase the bearing capability of the formation,decrease the required density of drilling fluid,and shorten the drilling time.