Innovative Conical Diamond Element Bits Drill Back-to-Back Tight Curves in One Run, Improving Economics While Reducing Risk in Avalon Shale Play, New Mexico

Abstract

Abstract An operator challenged drillbit providers to deliver fixed cutter bits that could drill high-dogleg curves and improve ROP in the Avalon shale play in Lea County, New Mexico. The heavily interbedded lithology is unpredictable and contains thick sections of limestone in some areas. The challenging transitional nature of the formations has caused major difficulties in achieving the planned 12°/100-ft build rate with conventional PDC bits and has resulted in slow ROP and potential reliability issues with roller cone hybrid bits. The operator wanted to maximize ROP and increase build rates to kick off the curve deeper in the lithology column to land the borehole in the precise location and to increase reservoir exposure in the lateral. The service provider proposed using an 8¾-in conical diamond element (CDE) bit to achieve the high doglegs at a fast ROP, using a holistic design and simulation software to optimize the placement of the CDEs across the bit face based on the application and directional drilling objectives. The CDE's unique conical shape enables it to drill with significantly less torque compared with conventional PDC cutters. This reduces reactive torque fluctuations with the CDE bit when drilling directionally, enabling higher build rates with better toolface control to stay on target with fewer adjustments by the directional driller and to complete the curve in less time. The new CDE bit would be part of an integrated drilling system designed to produce a tight curve and position the wellbore to increase reservoir contact. The bit would be coupled with a positive displacement motor with a high-performance power section purposely designed for directional drilling. The first CDE bit drilled the curve in one run with an overall ROP of 30.2 ft/h, 39% faster than the average roller cone hybrid offsets (26 runs). This was the first time a fixed-cutter bit has completed the curve in New Mexico's Avalon play in one run on a conventional assembly with this operator. The curve was completed in only 944 ft, with a build rate of 12°/100 ft, achieving the tight geometry required by the operator to land early in the reservoir. Since the CDE bit has no moving parts like previous roller cone-hybrid benchmark bits, any risks associated with costly fishing trips due to lost cones were eliminated. Based on the success of the initial run, the operator elected to run another CDE bit on the next well. This bit matched the performance of the first CDE bit, drilling the curve in one run with an overall ROP of 30.1 ft/h, completing the curve in 947 ft. The runs confirmed that the CDE bit can consistently deliver the required build rate at above average ROP with fewer reliability concerns compared with the roller cone-hybrids used in offset wells.