Drilling Difficulties and Technological Measures of the First Deep and Horizontal Well in Western Sichuan Basin

In this study, X21-1H well, the first deep and horizontal well in western Sichuan Basin, is analyzed. It is found that there are many difficulties during drilling horizontal wells in this area, such as a great difficulty in deviation prevention of a vertical section, a sand-carrying difficulty for drilling fluid in both deviated and horizontal sections, a poor drillability and a big risk of well control. In addition, the main technologies used to solve these difficulties are also presented, including wellbore-trajectory control technology, drilling assembly selection, drilling-fluid property optimization and matching fast-drilling technology. It is considered that the keys of successful drilling are the deviation prevention of vertical section, better wellbore trajectory and better sand-carrying and sidewall prevention of fluid drilling.