Optimal Bit, Reamer Selection and Operating Procedures Improve Hole Enlargement Performance in Deepwater Gulf of Mexico

Abstract

Abstract Hole enlargement using underreamers has become a necessary drilling practice in deepwater Gulf of Mexico. Underreaming while drilling saves operators an extra trip to open a hole, and improves drilling budgets. Further benefits include better equivalent circulating density management and optimal cement jobs because of the bigger annulus. With these benefits come great challenges that can be categorized into three classes: 1) Drilling dynamics 2) Drilling performance and 3) Hole quality. These challenges, if not addressed during the planning and execution phase, can lead to tool failure, lower penetration rates, and hole angle deflection. This paper presents a deepwater Gulf of Mexico success story where a total systems optimization approach was utilized to overcome the previously mentioned challenges, generating a scalable improvement in drilling efficiency. This paper presents the planning and results from two sections of the subject well - 18 1/8 x 21 in. and 16 ½ x 19 in. Each section had different sets of challenges. The first section was drilled through an inter-bedded formation entering at the top of the salt, while the second section was drilled entirely in salt. To overcome these challenges, an optimization approach was followed, which consisted of four steps - 1) Offset well analysis 2) Bit/underreamer selection 3) Development of optimum drilling parameters and 4) Roadmap to manage these parameters on the rig. According to field results, this approach improved the ROP by more than 15% in the 18 1/8 x 21-in. salt section. Drilling efficiency for both sections was enhanced by more than 65% when compared to previous offsets. For both sections, the maximum hole inclination was 0.13° or less, keeping the well vertical. Furthermore, lower axial and lateral vibrations were observed, eliminating downhole tool failures while the bit and underreamer came out with better dull conditions compared to the offsets.