PROPERTIES EVALUATION AND APPLICATION OF A NOVEL DRILLING FLUID WITH STRONG PLUGGING AND INHIBITION PERFORMANCE.

The shale formation in the Changning area is prone to complex engineering problems such as collapse of the wellbore, falling off the block and leakage during the drilling process. The reason is that the drilling fluid cannot effectively block the micro-cracks in the formation, and it is impossible to effectively suppress the internal hydration of the shale. In this paper, from the direction of improving the plugging and inhibition ability of the drilling fluid system, the strong plugging capacity plugging agent HXSZ-1 was added to the system to improve the plugging capacity of the system. Through the synergistic action of KCl, polyamine inhibitor and silicate, the inhibition performance of the system could be further improved. The indoor evaluation showed that the system had excellent plugging ability. The reduction rate of mud cake permeability at room temperature was 68.24%, and the HTHP static filtration loss was 2.7 mL, which was equivalent to the plugging performance of oil-based drilling fluid. The secondary recovery rate of shale was as high as 96.89% with the linear expansion rate of less than 4.8%, and the anti-pollution ability was strong. The EC50 value of the system was 11500 mg/L, which was non-toxic and could meet environmental protection requirements. The field application results showed that the system had stable performance during the drilling process. The average enlargement rate of well diameter was controlled within 4%, and the drilling cycle was shortened by 20%. The purpose of excellent and fast drilling was realized, and the field application effect was good. [ABSTRACT FROM AUTHOR]