Cement Expansion in Cased Hole Environments: A Novel Laboratory Testing and Evaluation Method with Successful Field Implementation

Abstract

Abstract Preventing bulk shrinkage of cement in cased hole wells is important when dealing with the risk of sustained casing pressure (SCP). Current studies based on membrane tests suggest that even with a high percentage content of expanding agents, cement systems show little or no expansion in dry media. An alternative laboratory method, for measuring cement expansion followed by a successful field application, has been used to evaluate the total bulk volume change of the cement based on curing in a dry environment and in water. A major operator in the Caspian region who experienced some occasions of SCP in the past, is adopting various measures to prevent and mitigate the SCP. This paper presents laboratory testing and successful field implementation of an expanding cement system capable of expanding in the absence of water. This expanding cement system is tested with the American Petroleum Institute (API) membrane and ring test methods, which resulted in proposing a comprehensive procedure modification. The expanding cement system behavior is presented in terms of rheological, filtration, and mechanical properties. The operator accepted the methodology and successfully implemented the recommended solution on their selected wells. Test results using the API membrane and expansion ring methods are presented. Testing procedure modifications, including curing environment, placement time, shear history, and gel and compressive strength development for measuring bulk volume change of cement are proposed. Contrary to all expectations, a cement system with simple modifications provided measurable expansion in a dry environment while being stable and not over expanding in water. Optimal cement slurry properties were obtained. The developed cement system, which was successfully implemented in the field, provided long-term zonal isolation with no indication of sustained casing pressure to date. For the first time, an alternative method is being used to evaluate the bulk volume change of cement that has been exposed to a dry environment. The research results and field data indicate that the expanding cement systems perform well and can be used in intervals with no access to water. Results of this effort will undoubtedly assist operators deal with sustained casing pressures by adopting the methodology.