Key Coring Technologies for the Dainan Formation and Funing Formation in North Jiangsu Basin

The goal of this study was to develop a coring bit that can overcome the challenges of challenging mudstone rocks. In the mudstone strata of the Dainan Formation and Funing Formation in the North Jiangsu Basin, there are problems such as less footage for each coring, low core recovery and lower coring ROP. After analyzing the geological characteristics and drillability of cored stratum, a PDC coring bit suitable for the Dainan and Funing mudstone strata was developed. This bit adopts the " G series” teeth as the main cutters, and it is fitted with the large nozzle and inner gauge flow channel and applies the optimally designed the slot slope for removing cuttings. It is able to reduce the friction between the cuttings and cutters, improve the cutting migration state and enhance the ROP. Furthermore, it can clean the cutters effectively, and facilitate the core entering the inner barrel, which improves the core recovery significantly. The new coring bit and optimal coring barrel were jointly used to core the Dainan Formation and Funing Formation in 48 exploration wells, with an average core recovery of greater than 98.0% and maximum ROP of 24.80 m/h. By aligning the new coring bit with technologies, researchers solved the coring problems of the Dainan Formation and Funing Formation in North Jiangsu Basin, with good on-site promotion and application value for best practices