Application of Strong Plugging Oil-based Drilling Fluid in a Horizontal Well in Tongnanba Block
A well is a horizontal well in Tongnanba area.In this area,the formation of sand and mud-stone is staggered,the pressure coefficient is high,there are coal seams,the formation drillability is poor,and overflow and collapse are easy to occur.According to the characteristics of formation lithology in this area,the technical difficulties of water-based drilling fluid system under complex conditions were analyzed,and a set of strong plugging oil-based drilling fluid system was constructed.The experimental results show that the selected composite plugging agent has good compatibility with oil-based drilling fluid.The high-temperature and high-pressure filtration loss at 120℃ is 1.0 mL,the PPA filtration loss is 0.6 mL,and the plugging rate is as high as 98.27％.The constructed strong plugging oil-based drilling fluid system has excellent wall-forming performance and plugging performance.The field application shows that the system solves the problem of annulus plugging and sticking caused by coal seam collapse in Tongnanba structural belt of northern Sichuan depression,Sichuan Basin.It can meet the needs of preventing fracture leakage and enhancing wellbore stability in the process of operation,and has been successfully applied in a horizontal well.
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