Historically, acid gas injection well completions have typically consisted of low alloy steels internally plastic coated or fiberglass lined. However, costly workovers and environmental have caused operators and engineering companies to reevaluate these well completions. CRA often supports engineering companies in these evaluations, helping determine the ideal metallurgy based on the operator’s goals and expectations. On occasion, higher alloy materials are chosen as an alternative to prolong the life of the well, reduce workovers, and eliminate environmental casualties.
Acid gas is a classification of natural gas containing impurities such as hydrogen sulfide (H2S) and carbon dioxide (CO2) in quantities large enough to designate it as acidic. Acid gas injection (AGI) is the injecting or disposing of acid gas into underground zones or reservoirs. AGI projects are not producers or money makers but are often a necessary part of the natural gas purification process. Operators often outsource the well design and engineering to a knowledgeable third-party engineering firm.
AGI wells are typically designed to be “water-free,” and as such, low alloy steels are commonly used. However, low compressor discharge temperatures can result in water formation even in dry acid gas wells. In addition, casing and tubing are exposed to groundwater below the packer. When water is present in acid gases, the conditions may be very corrosive. In these cases, stainless steels or nickel base alloys may be a more suitable alternative to low alloy steels.
With a metallurgist on staff, CRA is often enlisted to help engineering companies evaluate their well conditions and determine the appropriate metallurgy for the application. Often, low alloy steels are suitable. However, if stainless steels or nickel base alloys are required, CRA works to find the most cost-effective option that effectively eliminates the need for workovers and risks of leaks or failures. CRA works with customers to find innovative win-win solutions to their unique needs. Material trades, contingency and lease programs, and hard-to-find surplus solutions are a few of the options sometimes considered.
This article highlights CRA’s work assisting engineering companies with well design and material selection on acid gas injection applications. CRA is able to offer well-analysis, metallurgical support, and unique, cost-effective solutions for stainless steel or nickel base alloys when required. With this assistance, engineering companies can recommend tubing and casing options that best fit the operator’s needs.
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