First 22" PDC Successful Run on Rotary Steerable System, Optimum Bit Design Selection for Challenging Directional Application

Abstract

Due to limited surface locations in developed fields, more and more deep well applications are requiring directional work in top sections, still drilling through interbedded challenging formations with severe dynamics issue. With the collaboration of Kuwait Oil Company, this paper introduces a new 22″ PDC bit selection method based on 3D simulations of dual UCS transitions and its impact on a given cutting structure arrangement. Stability and balancing of the PDC Drill Bit is key to success when drilling a directional section, specially when drilling larger size hole with dynamic events amplified by the inertia of the BHA. Balancing the cutting structure when encountering interbedded soft – hard transition with a variable dip angle is mandatory to achieve planned trajectory together with ensuring a good borehole quality and minimal tortuosity. The design presented in this paper and the optimization made on its cutting structure with an in-house 3D simulation software will demonstrate how these challenges have been solved over a wide range of drilling scenarios, including the proprietary capability to simulate rock transition. A series of different transition scenarios from soft to hard, hard to soft and with different dip angle have been conducted on a series of targeted 22″ bit designs aimed to be run in an application in North Kuwait. This process has been applied iteratively to estimate the adaptability of the bit design to these scenarios. Bit designs have been ranked with respect to different performance indicators like drillability, steerability, stability and tool face control. The top ranked bit design has been selected, manufactured and successfully run in the field. For the first time worldwide, RSS BHA in 22″ drilled S-Shape section of 1279 ft with inclination up to 10° and back to vertical while reaching 2.5° Dogleg severity. By using a PDC instead of Hybrid Roller cone bit, a 60% gain in ROP was possible and a 44% cost reduction achieved. This unique design configuration allowed an optimum directional behavior with reduced drilling dynamics recorded and enhanced borehole quality for smoother completion operation. By being the first ever S-Shape section Delivered by RSS worldwide and first 22″ RSS directional run in the Middle East, this success is opening the door to further development of existing field and more complex trajectory achievement. The performance is kept at the heart of the equation with optimized PDC cutting structure to deliver best ROP and lowest cost per foot each and every time.