Key Technology of Optimized and Fast Slim Hole Drilling in Shenfu Block, Ordos Basin

The Shenfu Block in Ordos Basin is a tight gas-producing area. In this study, optimized and fast drilling technology for slim holes was explored to further increase the rate of penetration (ROP) and reduce the drilling cost in this block. The wellbore trajectory was optimized from "vertical–build–hold–build–hold" to "vertical–build–drop–hold" matching the formation strike, which improved the drilling efficiency. The drill bit was optimized, including the change of tooth density, adjustment of cutting tooth size and caster angle, and enhancement of stability and wear resistance. The drilling assembly, size of the drill pipe, and postive displacement motor (PDM) were optimized, and a three-dimensional (3D) vibration impactor was developed for enhancing the ROP. Additionally, the performance of the drilling fluid was improved by the introduction of a biomimetic lubricant and the optimization of the drilling fluid formula. Further, drilling parameters were also optimized. The key technology of optimized and fast slim hole drilling relying on the above measures was applied in 8 wells in Shenfu Block, realizing the one-trip drilling of the second-spud section. The ROP was increased by more than 50% and the drilling cycle was shortened by 45%. This technology provides technical support for future drilling of tight gas wells in Shenfu Block and a reference for the drilling of tight gas wells in other regions in China.