Design and Comparison of Two Drill String Solutions that Break Barriers in Extended Reach Drilling

Abstract To date, extended reach drilling (ERD) wells drilled on one of the main UAE offshore reservoirs have been delivered by using a tapered drill string design that combines two sizes of drill pipe. To reduce the number of days per well, a one-size only drill string concept has been considered, but such an option required some improvements in torque and geometry to meet specific well design requirements. An initial analysis of the drilling requirements in terms of torque, dimensions, tensile capacity, and hydraulics showed that the process limiter was the drill pipe connection as no option was available in the market that could meet the redesigned requirements. Two new technical solutions were separately developed that took into account the need for a reduced tool joint outer diameter (OD) for equivalent circulating density (ECD) and fishability in an 8½-in. hole. Once developed, the solutions were then validated for manufacturing and field trials. The first solution consisted of designing and developing an ultra-high torque thread profile, while the second solution suggested to upgrade the tool joint material grade of a new 4th generation double shouldered connection. Both newly designed drill pipe strings successfully passed the shop stress tests and were mobilized for operations. The drill pipes were used for drilling within the tight hydraulic window of such ERD wells, further validating the original drilling simulation parameters. The successful trial of these two single size string solutions enabled the saving of more than five days of rig operating time per well. This paper presents a detailed comparative evaluation of two innovative drill pipe design solutions that enable operators to run a single size string in challenging ERD wells. It also provides an insight into the operational benefits obtained by shifting to the new single size string.