抗高温油基钻井液封堵剂PF-MOSHIELD的研制与应用

针对层理和微裂缝发育的高温高压复杂井,从提高多尺度封堵效果和高温稳定性出发,研制了一种由独特的化学改性剂和磺化沥青、油溶性碳酸钙、纳米二氧化硅以及苯乙烯丙烯酸酯共聚物等组成的抗高温油基钻井液封堵剂PF-MOSHIELD。该封堵剂粒径分布在1～189.02 μm之间,热稳定性好,分解温度高达378℃,软化点为260℃,且能在油相中稳定分散。与传统的油基封堵剂相比,该封堵剂在压差的作用下挤入微裂缝,同时参与了“内滤饼”和“外滤饼”的形成,在高温下能对不同孔隙度的裂缝进行封堵,有效降低渗透滤失量和滤失速率。在南海海域WZ6-9、WZ12-1等区块井的应用表明,添加PF-MOSHIELD的钻井液体系流变稳定,电稳定性提高,减少页岩中孔隙压力传递效应,能够满足层理和微裂缝发育的硬脆性和破碎性地层井壁稳定要求。 

Development and Application of the High Temperature Plugging Agent PF-MOSHIELD for Oil Base Drilling Fluids

PF-MOSHIELD, a high temperature plugging agent, has been developed for use in oil base drilling fluids to enhance the efficiency of plugging fractures with wide size distribution at elevated temperatures in drilling high temperature high pressure wells complicated with developed beddings and microfractures. PF-MOSHIELD is made from a unique chemical modifier, sulfonated asphalt, acid soluble calcium carbonate, nanophase silica and styrene acrylate. PF-MOSHIELD, with its particle sizes distributed in the range of 1-189.02 μm, has good thermal stability; the decomposition temperature of PF-MOSHIELD is 378℃, and the softening point is 260℃. PF-MOSHIELD is dispersible in oil. Compared with conventional plugging agents for oil base drilling fluids, PFMOSHIELD can be squeezed into microfractures under pressure, taking part in the buildup of both the "inner filter cake" and the "surface mud cake". PF-MOSHIELD can, at high temperatures, plug fractures of different porosities, effectively reducing the amount of filtrate and the rate of filtration. Field application of PF-MOSHIELD on wells drilled in the Block WZ6-9 and Block WZ12-1 showed that drilling fluids treated with PF-MOSHIELD had stable rheology and enhanced electric stability, and pressure transferring in the pores in shale formations was weakened, all satisfying the needs of borehole wall stabilization in drilling hard brittle and fractured formations developed with beddings and microfractures.