Abstract: Mature oilfields in eastern China are in an ultra-high water-cut stage, comprehensive water cut exceeding 90%, while the average recovery rate remains at only about 30%. However, the remaining oil is highly dispersed, and conventional infill drilling is costly, which limits the economic feasibility of well pattern reconstruction and further oil recovery enhancement. To address these challenges, specialized tools were developed, including high-torque-resistant casing, casing string driving tools, drillable bits, and retrievable logging-while-drilling instruments, and a full-process casing drilling technology was established to enable integrated single-trip drilling and casing operations. Pilot field trials in the Shengli Oilfield demonstrated significant improvements in drilling efficiency, substantial cost reductions, and enhanced reservoir protection. This technology offers a cost-effective and efficient approach for well pattern reconstruction in ultra-high water-cut mature oilfields, and is also applicable to the development of complex fault-block oilfields and heterogeneous reservoirs. It opens new avenues for enhancing oil recovery in mature oilfields and enabling the efficient development of hard-to-recover reserves.