Removal of Wellbore Scales From High Temperature Depleted Gas Wells

摘要

Mixed mineral scales were observed in production tubulars of many Mobile Bay gas wells. These wells are mostly ultra-high temperature (about 400°F) sour gas producers with condensed formation water. Reservoir pressure (about 5000psi) is considered low for the 21,000 ft deep wells due to depletion. Hydrochloric and organic acids have been used historically for scale removal in these wells with mixed results. Scale analysis of the samples retrieved from these wells confirmed the presence of salts and mineral scales. Six commercial treatment products were evaluated kinetically and thermodynamically for their dissolution efficiency on these field scale samples. One product with non-acid nature was identified to be the best to dissolve the scales efficiently with minimum operational risks of scale re-precipitation, corrosion of tubulars, and potential formation damage. Treatment candidate wells were analyzed based on well performance evaluation. Three wells with skins significantly higher than expected due to scale formation in the production systems, were selected as treatment candidates. These wells were treated with the nitrified non-acid system to dissolve the skin damage. Treatments are considered successful with an additional gas production gain of 1,867 BEQ/day. The paper discusses the laboratory evaluation and field validation of the non-acid operationally simple system for the scale removal