Impact of Tubular Wear, Erosion, Deformation and Corrosion on Well Integrity During Extended Reach and HPHT Operations

Abstract Well components are routinely exposed to various thermal, mechanical and chemical stresses during drilling and production operations which can cause fatigue, deformation and damage. The impact of these stresses on common OCTG equipment is relatively well understood and can be mitigated/remedied to a certain extent through existing solutions. However, with the increasing focus on producing oil and gas from challenging and unconventional reservoirs - including deeper, extended reach, and HPHT plays, new technologies are being employed aggressively without properly accounting for potential well integrity issues. After being exposed to various drilling, completions and production operations, as well as downhole pressures, temperatures, and formation fluids, a deterioration in mechanical characteristics of the steel and other alloys are expected. This can seriously impair their thermal and mechanical properties - thereby weakening its collapse, burst and yield pressure ratings. Using data from drilling and completion programs, this study evaluates the extent of tubular wear caused by regular operations, corrosion, as well as erosion during operations. An analytical model which takes into account drilling data such as wellbore orientation, rotary speed, ROP, metal wear factors, corrosion and pitting volume as well as tripping statistics was used to evaluate common and specialized OCTG tools. The wear volume, and the average percentage decrease in casing string thickness was then correlated to the impairment in mechanical properties leading to casing deformation and failure. Studies and field data show that long term well integrity is heavily dependent on the casing and cementing program, as well as the standards of the OCTG equipment used. Therefore, weak spots around the casing and the joints—particularly those brought on by wear and corrosion—should be considered when designing unconventional operations such as those in HPHT and extended reach wells. Calculations show that during a well's operating lifecycle, losses of more than 40% of the initial volume may occur, resulting in a significant reduction in the casing string's thickness and stress ratings. These can in turn lead to fatigue through deformation, tension and compression, eventually leading to critical tubular damage, and a catastrophic well integrity failure. Erosion, wear and corrosion are significant challenges that affect well integrity, drilling efficiency and operational safety, especially in unconventional operations. The results of this work can be used to evaluate tubular properties for a well during operations, which can help determine protective measures to maintain well integrity throughout the life of the well.