Overcoming Accessibility Challenges in Open Hole Laterals Longer than 10,000 Feet

Abstract

Abstract Maximizing well productivity in extended reach wells with open hole completions in Saudi Arabia has been hampered by the difficulty encountered by coiled tubing (CT) to fully access open hole laterals with sections surpassing 6-in bore diameter and 10,000-ft in length. This paper discusses the innovative technologies, engineering string designs, and procedures that have been developed to increase the capabilities, dependability, and predictability of CT interventions in such wells. An exhaustive CT tubing force modeling analysis compared the performance of designs in 2.375-in and 2.875-in diameters and identified key operating parameters for future models and reach contribution from tractors and vibratory downhole tools. Records were reviewed and compiled for the most recent wells designs with varying bore sizes, target depths, open hole sections, and operating parameters. These open hole horizontal wells generated high frictional drag forces due to large completion diameters and tortuous wellbore trajectory. The presence of СО2 and H2S limited usable CT to sour service grades. Comprehensive tubing force and hydraulic pre-job analyses were used as basis of iteration for the versatile 2.375-in, and 2.875-in CT designs with up to 32,000-ft length and +90 MT in weight, combining engineered designs with novel CT heat treatment technologies. These CT designs were developed for a wide range of well configurations, conditions, and intervention treatments. The string designs feature wall thickness configurations selected to maximize reach and life in sour environments. The engineered CT strings were able to reach target depth (TD), comparable to the predicted results of the pre-job analyses. The engineered CT strings provided complete stimulation treatment over entire target zones, while minimizing risk and maximizing production economics for the operator. Extensive pre and post job analyses demonstrate the new designs’ capability of reaching all target depths, with allowances made for reach-assisting technologies in long, tortuous wells. The agitators, high expansion tractors, lubricants, high-pressure jetting tools, and the combined or isolated use-case of each to reach TD, are discussed in this document, as they were critical to maximizing the overall success of the intervention. This paper outlines the strategies used to reach deep well TDs through CT string design for various open hole completions longer than 10,000-ft. Operational and logistical procedures were changed for these unprecedented CT strings —including mobilizing the largest commercially available CT units and injector equipment in terms of capacity and power. The most recent CT manufacturing technologies that have helped cement and broaden the limits of extended reach stimulation interventions in open hole wells will be documented.