Unique Hybrid Drill Bit with Novel PDC Cutters Improves Performance in Ultra-Deepwater Brazil Pre-Salt Application

Abstract

The Brazil ultra-deepwater, pre-salt application has been a very challenging drilling environment since exploration activity began in 2005. The initial pre-salt section contains limestone with random silicified nodules. Over the last few years, operators have collected large amounts of data for service companies to analyze to improve drilling performance through bit design. Using this information, a hybrid bit design with the most advanced cutter and bit technology was developed successfully increasing the distance drilled by 138% and the rate of penetration (ROP) by 171%.Prior to advanced hybrid bit technology, a variety of other drill bit technologies such as polycrystalline diamond compact (PDC) bits and impregnated designs were used in the pre-salt. Historically, impregnated bits had longer runs, but with high mechanical specific energy (MSE) and low ROP, drilling with these bits was not economical. Contrarily, PDC bits can deliver higher ROP but cannot drill as far as impregnated bits. Three hybrid designs, the last one using dual-chamfer technology, were brought into this application to reduce cost-per-meter through better drilling efficiency and ROP. Each successive design managed to exceed customer expectations.Extensive laboratory tests were conducted on the hybrid designs to address the demanding needs of pre-salt applications. These unique bits showed promising results on atmospheric surface rig tests and in pressurized bottomhole simulator testing. Hybrid bits produced much less torque, with smoother torque fluctuations and faster ROPs than roller-cone and PDC bits through the simulated interbedded formations in laboratory testing. Novel dual-chamfer cutters used in the bit have been lab tested on a vertical turret lathe (VTL), a visual pressurized single-point-cutter (VSPC) test machine and a monotonic loading test. Cutter testing showed positive VTL results and increased resistance to diamond fractures.Ultra-deepwater drilling is very demanding and expensive, so operators want to achieve total depth in just one run by avoiding trips to change out the bit or bottomhole assembly (BHA). The improved bit and cutter technology resulted in significant cost savings and confidence for the customer. The performance of the hybrid bit with dual-chamfer cutters was significantly better than offsets, saving the operator approximately USD 9769/m.

Simulation and Experimental Study on Rock Disintegration Characteristics of Special-shaped PDC Cutters

“…Up to now, various new special-shaped PDC cutters such as conical, ridged PDC cutter have been developed [9]. Field drilling tests show that, special-shaped PDC cutters show certain advantages in hard rock drilling, for example, the conical PDC cutter developed by Smith Company can better concentrate the load on one point to break the rock, and its thicker diamond layer helps to improve the wear resistance and stability of the cutter [10,11]; the diamond layer of the ridged PDC cutter has a ridge-like structure, which shows higher hardness and toughness [12,13]; the multi-dimensional special-shaped PDC cutter developed by Baker Hughes Company (https://www.bakerhughes.com/) helps to improve the heat conversion efficiency, and maintain its aggressiveness for a long time [14,15].…”

Experimental research on torque characteristic and weight distribution of the polycrystalline diamond compact–roller hybrid bit

“…The test results showed that this type of hybrid bits was capable to drill in hard or heterogeneous formation with high efficiency, more particularly, both the torque and the torsional vibration of the bit were lowered, and the stick-slip effect was reduced. [17][18][19][20] As a new bit type, study on the rock-breaking method of this hybrid drill bit can seldom be found. For further study on it, the Rock Bit Laboratory of SWPU (Southwest Petroleum University) has conducted a series of systematic research on the hybrid bit technology 21,22 and has achieved some research findings.…”