Search for a command to run...
Abstract This paper presents the development and field qualification of a 2.375″ outer diameter (OD) quench-and-tempered (Q&T) grade 95 coiled tubing (CT) specifically engineered for sour service unconventional wells in Saudi Arabia. It highlights the metallurgical innovation, mechanical design integration, and operational deployment that enabled reliable performance in high pressure (over 8,000 psi working pressure), extended reach gas wells. Emphasis is placed on safe sour-service operation, CT well accessibility, extended fatigue life, and reliable execution of post-frac plug millouts in laterals exceeding 15,000+ ft. The Q&T grade 95 material was developed to overcome sour service limitations of high strength CT while meeting mechanical demands for extended-reach laterals. Metallurgical refinement targeted uniform microstructure and hardness <26 HRC (Rockwell Hardness C) for sulfide stress cracking (SSC) and hydrogen embrittlement (HE) resistance, verified through mechanical and NACE compliant testing. String modeling was conducted using advanced fatigue, buckling, and tubing force sensitivity analysis. Multiple 2.375-in OD designs were manufactured, deployed, and iteratively refined with operational feedback. Field implementation integrated BHA optimization, fluid system design, and continuous engineering support across multiple high-pressure, extremely sour gas wells classed as NACE SSC region 3. Field deployment of 2.375″ Q&T Grade 95 CT demonstrated a step-change in sour-service performance. Compared to conventional CT grades, results showed longer fatigue life, improved abrasion resistance, and superior reliability in abrasive cleanouts. Higher yield strength provided greater pressure margin during high-rate pumping, while SSC testing validated suitability for high H2S wells (pH2S <200 psi). Force modeling and field validation confirmed enhanced lateral reach up to 1,000 ft farther than legacy strings allowing full post-frac plug millouts beyond 15,000+ ft laterals with consistent weight-on-bit (WOB) delivery. Optimized wall thickness configurations met pressure containment standards, balancing strength with sour service resistance. The integration of metallurgy, design, and operational practices reduced non-productive time, improved consistency, and minimized the need for higher wall thicknesses. These results establish Q&T grade 95 as a reliable, field proven CT solution for unconventional shale interventions in Saudi Arabia, offering enhanced safety, efficiency, and cost performance under demanding sour service conditions. This work introduces a fit-for-purpose Q&T grade 95 CT material that bridges the gap between sour service resistance and mechanical strength requirements for current high-pressure/high-temperature (HPHT) unconventional wells. The proven metallurgy and optimized string design enable extended reach, pressure capacity, and wear resistance without compromising sour service integrity. The demonstrated field success offers a scalable pathway for deploying next generation of CT solutions in high-pressure, sour unconventional gas plays worldwide.