Key Technology for Speeding up and Improving Efficiency of Ultra-Deep Slim-Hole Directional Drilling in Tarim Basin

In view of the problems such as low rate of penetration (ROP), short bit life, degumming and threading off of conventional screw drill tool, poor stability of drilling fluid, and simultaneous occurrence of blowout and leakage in pay zones in ultra-deep slim-hole directional drilling in the platform basin area of the Tarim Basin, the key technology for speeding up and improving efficiency in ultra-deep slim-hole directional drilling in Tarim Basin was developed. The technology used the standard drilling rate of a trip and bit footage as indicators and employed statistical analysis method to select bit KS1352DGRX with a diameter of ϕ149.2 mm / ϕ165.1 mm and bit KDM1062TR with a diameter of ϕ120.7 mm applicable to the target layer. By comparing the current situation of high-temperature resistant screws in China and abroad, Chinese high-temperature resistant screws were recommended for bottomhole temperatures below 180 °C. Otherwise, it was recommended to use metal screws or imported high-temperature resistant screws. The small-sized friction and drag reduction tools were designed using theoretical analysis combined with numerical simulation methods, and the tools’ position was optimized. Optimal salt-resistant, high-temperature, and high-pressure filtrate reducers and inhibitors were selected, and deoxidizers were developed. Reasonable pH control and calcium ion supplementation measures were made, and a temperature-resistant drilling fluid system for 200 °C was formed. The characteristics of blowout and leakage in the same layer in the pay zones of Shunbei Oilfield were analyzed, and the basic principle of well control featuring “density reduction + wellhead pressure control + optimized displacement” was determined. The key technology for speeding up and improving efficiency in ultra-deep slim-hole directional drilling in Tarim Basin was applied in five wells. The average ROP of the slim-hole section was increased by 113.24%, and the average hole diameter expansion rate was 5.57%. The average drilling cycle was shortened by 35.03%, and none of the wells had bottom hole failures and other complex conditions. The key technology for speeding up and improving efficiency in ultra-deep slim-hole directional drilling have provided the technical supports for the exploration and development of Tarim Basin.