油基钻井液用憎液性纳米封堵剂

Study on a Lyophobic Nanophase Plugging Agent for Oil Base Muds

为了解决油基钻井液在页岩气藏钻遇井壁失稳的难题,以纳米材料物理封堵和改变岩石表面润湿性为研究思路,通过溶胶-凝胶法对纳米二氧化硅进行表面改性,合成具有憎液性能的纳米封堵剂SNP-1。利用核磁共振进行分子结构表征,同时结合扫描电镜等微观实验和自然渗吸等宏观实验对其性能进行评价。结果表明,合成的纳米封堵剂SNP-1具有预先设计的基团,其能够使页岩表面液相接触角大于150°,反转毛细管附加压力为阻止液相进入孔喉的阻力,进一步降低岩心自然渗吸油含量;150℃老化后,使得油基钻井液的高温高压滤失量低至2.4 mL,破乳电压达800 V以上,能有效阻止页岩岩心的压力传递。

Physical plugging with nanophase materials and wettability alteration of rock surface were used to solve the borehole wall stability problem encountered in shale gas drilling with oil base muds.The surface of the nanophase silica was modified sol-gel method,turning the silica into a lyophobic nanophase plugging agent,SNP-1.Molecule structure characterization with NMR and laboratory evaluation with SEM and natural imbibition revealed that SNP-1 gains the functional groups it was expected to have.With SNP-1,the contact angle of liquid on the surface of shale is greater than 150°and the additional capillary pressure is reversed to a force resisting the liquid phase from entering the pore throats of shales,further reducing the oil content of rocks through natural imbibition.The HTHP filtration rate and electrical stability of the oil base mud treated with SNP-1,after being aged at 150℃,were 2.4 mL and above 800 V,respectively,effectively hindering the pressure transmission through shale cores.