DRILLING FLUID TECHNOLOGY FOR WELL GANGSHEN 69X1

Well Gangshen 69X1 is an extended reach exploratory well with its bottom depth at 5464.43m, and a horizontal displacement of 3118.04m. A period of 111.88 days are used for drilling this well, and it sets the records of the longest deviated section and longest horizontal displacement on land China to date. Drilling fluid technology is focused in this paper, more specifically, polymer based drilling fluid system is used to control the mud making tendency of clay by the effect of potassium polyacrylatic. To maintain well stability, polymer mud is used in the upper formation, and silicon based anti-sloughing drilling fluid is used in the lower section. Drilling fluid weight is determined referring to the formation pore pressure, fracturing pressure, and collapsing pressure profiles obtained from the offset loggings and core samples, together with the field condition. Four types of lubricating materials are selected to reduce friction and torque. White oil is used above 3000m, and multifunctional solid lubricant and plastic spheres are used below 3000m. In hole cleaning and reservoir protection, such measures as improving cuttings transportation, increasing pump rate and adopting temporary plugging are taken to enhance the field drilling.