Abstract
Extended-reach drilling target records in the Upper Zakum region have now reached 50,000-ft depth, surpassing manufacturing, equipment, and operational boundaries of the coiled tubing (CT) industry. However, custom-fit CT manufacturing equipment and logistical procedures are being evaluated to boost manufacturing capabilities that will allow to build multipurpose CT strings configurations with larger operating envelopes that can perform well across a variety of wellbore designs and target depths, including the recent record of 50,000-ft.
Over the past five years, highly engineered 2.375-in CT strings ranging from 31,000-ft to 43,000-ft in length have been deployed in the region, to service and maintain these complex wells trajectories over 4.5:1 MD/TVD ratios. The CT design makeups and length have progressed over time to have heavy reliance on extended reach hydraulic tractors by utilizing quench and temper materials that allowed greater diameter to wall thickness ratios (D/t), while satisfying pressure, load, and fatigue ratings. Nevertheless, the newest target depths require significant upgrades to CT manufacturing equipment, extended reach downhole tools and surface equipment.
CT has become an integral component to reduce cost and time in the region, and its utilization has increased because of the collaboration between the well operator, CT service providers, extended reach tool companies and CT manufacturers to improve its suitability, reliability, and predictability. The CT string engineering for 50,000-ft mega-reach wells required an iterative string design methodology that heavily considered the actual field reliability (actual tensile load ratings) of the CT hydraulic tractors and chemical friction reducers to determine the optimal CT lengths and wall thickness configurations. The CT manufacturing capabilities and surface equipment were maximized to optimize wellbore accessibility. A thorough evaluation of each stage of the CT manufacturing process revealed areas where equipment would reach capacity based on the CT design specifications. The resultant studies discuss comprehensive ground-up development, engineering, testing, and qualification of CT manufacturing requiring capital investments to produce the massive CT strings. The strings are 10 miles long weighing around 100 – 110 MT including the working drum. Funding for such a large-scale project is currently pending, with the operators’ demand for such strings and the projected return on investment influencing the decision.
The ability to intervene with CT is crucial to the field development strategy, and as the new wellbore designs become increasingly difficult to service, fit-for-purpose CT solutions are needed. CT manufacturing industry is engineering and developing equipment that expands the limits of CT production to bridge this gap.
