Comprehensive ROP Enhancement and Efficiency Improvement Technologies for Exploratory Drilling in Wenchang Sea Area, Western South China Sea

During exploratory well drilling in the Wenchang sea area of the western South China Sea, several challenges are encountered, including low surface operation efficiency, difficult tripping-out in active soft mudstone formations, low rate of penetration (ROP) and severe bit wear in glutenite and basement granite formations, high friction and torque in complex trajectory wells, and difficulty in casing running, which lead to excessively high drilling costs. To address these engineering difficulties, technical studies were conducted on the optimization of a “two-in-one” casing program for surface and medium-deep sections, customized polycrystalline diamond compact (PDC) bit design, selection of novel ROP enhancement tools, stratified optimization of seawater-based drilling fluids, precise reaming techniques, and real-time dynamic intervention in drilling efficiency,etc. Through field practices, comprehensive ROP enhancement and efficiency improvement technologies suitable for drilling exploratory wells in the Wenchang sea area were developed. After the above technologies were applied in 29 exploratory wells in the Wenchang sea area, western South China Sea, compared with those of the 8 previously drilled wells, the average drilling cycle was reduced from 26.9 d to 20.5 d, and the drilling cost per meter was 22.19% lower than the budget. The significant achievements in ROP enhancement and cost reduction strongly supported the exploration discoveries of multiple oil and gas targets in the Wenchang Sea Area. The technologies provide a technical reference for optimized and fast drilling of similar wells in other sea areas.