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Coiled tubing abrasion from well completion interference is a prominent failure mode in the industry. Variables influencing the severity of the abrasion include string design, completion design, well tortuosity and the well environment. The complexity of wells has increased which has required the industry to use higher strength coiled tubing materials and, larger diameters of coiled tubing. In doing so, the tubing force analyses suggest higher normal forces against the casing has become standard. SPE 81724 (Larsen, Reichert 2003) studied the wet and dry abrasion relationship of 90ksi yield coiled tubing against L80 and L80-13Cr completion materials and found dry abrasion to be 250 times more aggressive compared to wet abrasion in those tests. Furthermore, despite the impression that abrasion occurs more often in chrome completions, the results showed chrome completion abraded the coiled tubing at approximately the same rate as the standard L80 in those tests. Since then, the use of quench and tempered coiled tubing typically in the range of 110-140 ksi. minimum yield strength is mainstream to navigate the increased length and tortuosity of the wells currently being drilled. As a result, abrasion appears to be more frequent, though intermittently reported because failures near the whip end and bottom hole assembly are commonly dismissed in the field near as normal for operations. In instances where the abrasion occurs in the middle of the string, the results can be more challenging for well control. The purpose of this paper is to further explore the abrasion relationship between conventional 90 grade coiled tubing and some of the newer high strength quench and tempered materials in the 110-140ksi yield range. These coiled tubing materials were mated with various well completion materials including L80, L80-13Cr, P110 and P110-13Cr. Only dry abrasion was investigated at this time to carefully examine the abrasion relationship of each material. In summary, the data further supports the conclusions in SPE 81724 (Larsen, Reichert 2003) where coiled tubing materials showed similar abrasion rates against the various casing materials with and without chrome additions. Furthermore, the casing abrasion rates could be shown to be consistent with their relative hardness: the harder the material, the lower the abrasion rate. Additional future work will also consider friction reducers and varying normal forces.
Coiled tubing abrasion from well completion interference is a prominent failure mode in the industry. Variables influencing the severity of the abrasion include string design, completion design, well tortuosity and the well environment. The complexity of wells has increased which has required the industry to use higher strength coiled tubing materials and, larger diameters of coiled tubing. In doing so, the tubing force analyses suggest higher normal forces against the casing has become standard. SPE 81724 (Larsen, Reichert 2003) studied the wet and dry abrasion relationship of 90ksi yield coiled tubing against L80 and L80-13Cr completion materials and found dry abrasion to be 250 times more aggressive compared to wet abrasion in those tests. Furthermore, despite the impression that abrasion occurs more often in chrome completions, the results showed chrome completion abraded the coiled tubing at approximately the same rate as the standard L80 in those tests. Since then, the use of quench and tempered coiled tubing typically in the range of 110-140 ksi. minimum yield strength is mainstream to navigate the increased length and tortuosity of the wells currently being drilled. As a result, abrasion appears to be more frequent, though intermittently reported because failures near the whip end and bottom hole assembly are commonly dismissed in the field near as normal for operations. In instances where the abrasion occurs in the middle of the string, the results can be more challenging for well control. The purpose of this paper is to further explore the abrasion relationship between conventional 90 grade coiled tubing and some of the newer high strength quench and tempered materials in the 110-140ksi yield range. These coiled tubing materials were mated with various well completion materials including L80, L80-13Cr, P110 and P110-13Cr. Only dry abrasion was investigated at this time to carefully examine the abrasion relationship of each material. In summary, the data further supports the conclusions in SPE 81724 (Larsen, Reichert 2003) where coiled tubing materials showed similar abrasion rates against the various casing materials with and without chrome additions. Furthermore, the casing abrasion rates could be shown to be consistent with their relative hardness: the harder the material, the lower the abrasion rate. Additional future work will also consider friction reducers and varying normal forces.
During the completion phase of four unconventional wells in the United Arab Emirates (UAE), a detailed engineering approach enabled overcoming challenges presented by the extreme conditions of pressure, temperature, and sour environment across long horizontal sections to successfully carry out cleanout activities. The methods implemented to address those conditions prioritized personnel safety and asset integrity. The unconventional wells in this campaign were characterized by a reservoir pressure of approximately 13,000 psi and a bottomhole temperature of approximately 325°F. Gas was expected as reservoir fluid. The environment was sour, with 5% mol of H2S and 5% mol of CO2. After fracturing, the shut-in pressure was approximately 8,000 psi. Those conditions triggered a new engineering approach to design a customized coiled tubing (CT) pipe that could reach depths of 20,700 ft and perform efficient cleanouts. Other considerations included the selection of the appropriate pressure control equipment (PCE), downhole tools, and intervention fluids that could withstand the harsh working conditions. The wells were completed with 5 1/2-in. fracturing strings; horizontal sections ranged from 5,000 to 8,200 ft. Each of the 95 fracturing stages was isolated by dissolvable plugs. The CT pipe design considered well trajectories, working pressures, and downhole environment. The highly engineered 22,000 ft, 2 3/8-in. CT string was manufactured with quench and tempered (Q&T) material with yield strength of 110,000 psi. A custom-fit CT string integrity program was implemented to ensure safe intervention in high-pressure sour environment. Pipe life was then monitored in real time using magnetic flux leakage. Downhole tools (CT connector and check valves) and the PCE stack were designed to hold pressures up to 15,000 psi. The PCE configuration was thoroughly reviewed, and since the wellhead stack exhibited a maximum height of approximately 120 ft, a stack stress analysis through finite-element modeling software was conducted to validate structure stability, to confirm forces and bending moments remained within safe working limits, and to determine the optimal setting for guy wires. Job execution highlighted challenges linked to the high-pressure cycling and the need to optimize the number of achievable sweeps in the horizontal section. Well trajectories also proved challenging for the cleanout, with solids accumulation in specific intervals. This operation, the first of its kind in the country for the operator, yielded lessons for design considerations and the execution process and recommendations for CT intervention in similar working environments. It also confirms that 110,000-psi yield strength Q&T CT strings can be safely deployed in a high-pressure sour environment by implementing proper risk mitigation strategies.
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