Meeting the Challenges in Design and Execution of Two High Rate Acid Gas Injection Wells

Abstract

Abstract Two high rate acid gas injection wells were drilled in the LaBarge area of Wyoming. These wells were designed for injection of up to 65 million scf/day of a mixture of 65% H2S and 35% CO2. The primary engineering challenges in well design, casing selection, and cementing of the injection strings, along with the related operational challenges for both wells are discussed. Key drivers influencing zonal isolation, salt zone loading, casing and centralizer selection are presented. Casing selection was influenced by corrosive gas composition, high injection rates, and the potential for salt zone loading. The use of CRA tubulars, heavy wall casing for the salt loading, handling requirements, and centralizer selection are discussed. The primary driver in cement design was resistance to CO2, as past work has shown little H2S interaction with cement under these well conditions. A discussion of the development of a high alumina cement system with low fluid loss to address CO2 resistance and long liner length is coupled with the quality control steps taken from time of manufacture of the specialty cement to final placement in the well. Also described is the development of an alternate Portland cement system containing a reduced concentration of Portland cement by the use of sized particles to dilute the cement and reduce total system permeability. The unique engineering solutions resulted in operational challenges with casing running, cementing materials and equipment. A description of the location problems and the steps taken to resolve the issues are included.