Design and Optimization of Horizontal Well Structure in Sub-salt Reservoir in Tarim Basin

Kuche aera under sub-salt reservoir in Tarim Basin is rich in resources. Due to the influence of inverted strike-slip structure, the faults of the above salt formation in some blocks are generally developed. If the vertical well is used to exploit the reservoir, there are 7–9 sealing points, and 8–10 casings needed. The current casing and related drilling technique can not meet the requirements. In order to avoid the weak layer and faults, the team optimized the drilling technique by using horizontal wells. Firstly, the initial geological borehole trajectory to avoid the fault is determined based on the fine characterization technology of the formation, and the geological sealing point of the formation is determined based on the pressure profile prediction results. Secondly, based on the creep property of salt, mudstone and gypsum, the position of the kick-off point is determined. Thirdly, the final orientation of the target and the final wellbore trajectory are determined according to the optimal fracture opening pressure and the optimal wellbore stability orientation of the reservoir. Finally, the casing strength and wear in salt layer are predicted and checked. At the same time, the wellbore trajectory is optimized based on the analysis of string running ability. The successful implementation of this technology in Keshen 1002 well in Tarim Basin proves the feasibility of using horizontal wells to exploit multi-fault subsalt reservoirs, and effectively develop the reserves that cannot be exploited by traditional technology, and greatly improves the benefits of exploitation.