Extended Reach Wells Record in Complex Formation with Remarkable Efficiency and Economy, China Bohai Bay

Extended Reach Drilling (ERD) is a particular challenge for directional drilling, especially in China Bohai Bay. For environment protection reason, oil based mud is forbidden to be used in Bohai Bay, and water based mud is only choice for that time. In the previous campaign, long time drilling has led to serious shale hydration and wellbore collapse in the sloughing formation with low operation efficiency. With the intention to eliminate the wellbore collapse events caused by shale hydration and high Drag and Torque (D&T), Synthetic Based Mud (SBM), which is similar to oil-based mud but is relatively non-toxic and has the potential to biodegrade, has been developed and applied for the first time. Based on the wellbore stability model, the adaptability of SBM and sloughing formation is analyzed, and the properties of SBM are optimized; moreover, the Continuous Circulation System is used to reduce equivalent circulating density of drilling fluid, and the micro reamer and cuttings bed breakers have also been employed to reduce equivalent circulating density of drilling fluid. These technologies have been successfully used in more than 10 extended reach wells, true vertical depth of 2000 m and horizontal displacement of 4300 m breaking the records of Bohai Oilfield.