Improving Horizontal Well Performance with PDC Bits Designed to Increase Aggressiveness through the Run

Abstract

Abstract A substantial development effort, backed by drilling simulator and field testing, has delivered a directional PDC drill bit optimized for drilling the curve and lateral sections of horizontal wells. The PDC drill bit employs a new technology that controls the aggressiveness of the PDC in specific portions of the well and delivers reduced drilling and operating costs. With an increased focus on fewer days on a well necessitated by reduced natural gas prices in the North American land market, the need to reduce cost and eliminate bit trips has increased substantially over the past year. Operators in North America Oil/Gas Shale plays have migrated to drilling a combined curve and lateral section with a single bit to reduce operating expenses and rig time. With these changes, the PDC drill bit must maintain toolface control in the curve section, while being able to attain an increased rate of penetration (ROP) in the lateral section. To maintain toolface control and achieve the desired build-up rates, the axial and lateral aggressiveness of the bit must be managed. To do this, the aggressiveness (Mu) of the PDC drill bit is initially controlled at the kick-off point from the vertical section through the curve section. As the PDC bit drills the curve section, the feature that controls the torsional oscillations is systematically reduced allowing the aggressiveness, thus the ROP, to increase for the lateral section. In atmospheric lab testing, the aggressiveness was increased from 0.38 (curve) to 0.64 (lateral) for the new design. This represents an increase of 68% in the aggressiveness from the beginning of the curve to the end of the lateral section. This has been substantiated in field performance. The goal for this innovative feature is to control the torsional oscillations at the beginning of the curve section of the well, where control drilling is generally used to achieve the desired build-up rates. Once in the lateral section, the predominant method of drilling changes from sliding to rotating thus the need for the bit to have increased aggressiveness. This paper demonstrates how selectively managing the torsional oscillations of the PDC drill bit in the curve and lateral sections can increase on-bottom drilling time and decrease operating expenses due to increased toolface control and increased rate of penetration. By efficiently managing the bit's torsional response, a single PDC drill bit can be used in both sections, which allows for a single bottomhole assembly to be run without a trip.