Application of Gyro Shock-damping Tool combining with PDC bit in granite buried hill formation in Chad

Abstract

Stick-slip vibration is likely to occur while drilling in hard formation and soft-hard interbedded formation, especially when PDC bit is used, which further results in lower ROP and short footage. In this study, Gyro Shock-damping Tool and optimization PDC bit design were tested to reduce the stick-slip vibration and lengthen bit life while drilling in granite buried hill formation. Main parameters of the PDC bit include: 8 blades, short parabolic profile, Trident IV PDC, 10mm, 13mm cutter, totally 90 cutters, back rake of 19°-23°, double row of cutter (back row is impregnated string, with the height difference of 0.5mm). Gyro Shock-damping Tool combined with customized PDC bit was tested in 630-869m granite formation of a well in Chad, 239m footage was done in 54hrs, with a ROP of 4.44m/hr. In comparison, in an adjacent well, only 11m footage was completed with 3 PDC bits at the ROP of less than 1.23m/hr. Compared with some other adjacent wells drilled by 43 tri-cone bits, the specially designed bit increased by 97.33% in ROP and 54.19% in footage on average. All these prove that the technology outperforms the other bits, and can be used widely in granite buried hill horizontal well, hard formations and hard –soft interbedded formations.