Step Change in Drilling Optimization Resulted in A Country Record

Abstract

Abu Dhabi National Oil Company (ADNOC) offshore and Schlumberger jointly initiated a project to drill the longest 12¼-in section ever drilled in United Arabs Emirates (UAE) as part of the integrated drilling service for an extended-reach project. The plan involved drilling 14,400 ft in an extended-reach drilling (ERD) well in the field. The objective was to reach section TD in one run, drilling from 5,194-ft MD and reaching TD at 19,494 ft MD. In the well in study, Well 29, the trajectory crossed different formations—including limestones, shales, and dolomites—and built inclination from 30° to 78° to achieve an optimal step-out for the following sections to reach the boundaries of the reservoir at 27,000 ft. Different formation challenges throughout the section required a step change in engineering to complete the objective successfully. ADNOC needed a robust steerable system selection with metal-to-metal sealing that would be exposed to severe downhole conditions, a new bit technology design, anti-collision analysis to help reduce additional gyroscopic operations, and optimized drilling parameters with an enhanced drillstring design. The section was planned to drill in 17.7 days. The total section was finished 10 days ahead of planned AFE, setting the record for the longest 12¼-in section ever drilled in ADNOC and UAE of 14,400 ft, which was 58% longer lateral than field average. Through increased cutting efficiency and superior impact resistance, the new bit design with ridged diamond elements drilled the fastest 12¼-in section on the field in 0.91 d/1,000 ft. Good hole conditions facilitated successfully running and cementing the longest 9⅝-in casing, meeting ADNOC well integrity barrier requirements. The 12¼-in section had the fastest IADC-recorded ROP in the field, with an on-bottom ROP of 105 ft/h, which was 110% faster than the field average. The Geomagnetic Reference Service correction was implemented for the first time and was allowed to drill in proximity with a high anti-collision risk well, eliminating a gyro trip in the middle of the run. Downhole drilling parameters analysis from the drilling mechanics module was crucial for understanding downhole energy transmission and implementation of efficient drilling strategy and reducing shocks and vibrations. The drillstring was redesigned, replacing the traditional 5-in × 5⅞-in drillpipe and enabling a stiffer BHA, which helped maximize the bit performance.