Highly Engineered 2.375-in CT Provides Effective and Reliable Interventions in 30,000-ft Mega Reach Wells in Offshore Abu Dhabi

Abstract

Abstract With the aim of long-term sustainable production in the Persian Gulf, wells are being developed on artificial islands to maximize reservoir contact using extended reach drilling technologies with liner completions. This drilling strategy has many advantages and efficiencies, albeit, it results in complex 3-D well trajectories which challenge service operations throughout the well's life cycle. The ability to perform interventions in these wells with challenging laterals using Coiled Tubing (CT) is critical for achieving field development goals. With well cleanouts and stimulation as the primary scope of work, a CT string was custom-engineered to maximize reach capabilities and injection rates, in well trajectories of up to 4.5:1 MD/TVD ratios that extend up to ~20,000-ft laterals through the reservoir. The challenging operating requirements incorporate several constraints, including accessibility of +30,000-ft target depths, minimizing the use of high cost extended reach tools, and achieving injection rates of at least 5 BPM, all within acceptable pressure limits to maximize CT service life, without exceeding surface equipment capabilities available in the area. An iterative CT design methodology that incorporated the use of patented CT manufacturer strip technology, extensive tubing forces and hydraulics analyses, traction-force generating tool capabilities, fatigue simulations, and improved operation practices, enabled safe and successful deployment of 70-T (155,000-lbs) 2.375-in CT strings with 31,500-ft continuous length on the artificial islands. CT strings reached target depths, with the bottom-hole assembly (BHA) generating 7,500-lbf of traction force in the most difficult wells, while delivering up to 5 BPM injection rates during the stimulation operations. These extended reach CT strings are the largest (by weight) ever produced and deployed on the artificial islands, which enabled the well operator to maximize well performance and productivity in ultra-long lateral wells. This paper demonstrates the extensive design process to provide support and custom-engineer CT strings to perform complex operations - including matrix stimulation, mechanical isolation, scale inhibition, water control, and well cleanouts. Analysis of the field data, and performance of the strings will also be discussed to demonstrate increased efficiencies achieved by the well operator. As future wells are being designed with greater laterals, further development in downhole tools technology will allow the deployment of +35,000-ft CT in continuous length to economically and efficiently achieve extended reach CT operational goals in the field. Engineered solutions for 2.375-in CT over 36,500-ft are currently in the design stage. These strings are expected to surpass the 73 T (tube only) weight -becoming a future milestone for CT interventions.