Cutting Mechanism Study of an Innovative Non-Planar Cutter PDC Bit and Its Field Application

Abstract

Tarim Kuqa tight sandstone reservoir is overlaid with extreme thick conglomerate, which has high compressive strength, strong heterogeneity and poor drill ability, resulting in low drilling ROP and less bit drilling footage. Through research study and analysis of PDC bit failure and wear modes, this paper described the development of an innovative non-planar PDC bit through cutting mechanism study and lab testing verification. When drilling through the strong homogeneity formation, it will still be surface contact between the non-planar cutter and the rock and therefore the rock-breaking mechanism is still the conventional shearing fracturing; When drilling through the heterogeneity formation, the convex ridges will generate the linear contact with the hard rock and the mechanical stress will be accumulated at the conglomerate surface to initially create the cracking and then break the rock with composite cutting mechanism of shearing and crushing to improve the rock breaking efficiency. Experimental results also showed that the non-planar cutter delivers several folds of impact resistance improvement over conventional cutter. The bit was successfully field tested in ultra-thick conglomerate layer in the Kuqa foreland thrust belt of the Tarim basin. The field test tripled bit footage and doubled ROP comparing to same intervals and formation in offset wells. It demonstrated the broader prospect of the non-planar PDC technology in conglomerate and highly heterogeneous applications.