A Comprehensive Evaluation of Properties of Common and Regional Cement Formulations from a Well Integrity Standpoint
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AbstractOilfield cements have been an integral part of any drilling operation and forms the primary barrier when it comes to ensuring wellbore integrity. The strength of the cement layer is one of the primary factors that confirms the success of the drilling job and ensures the well remains productive and without issues throughout its productive years.The type of cements used in any oilfield operation depends on several factors including, but not limited to lithology, type of formation, pressures and temperatures, type of formation fluids and the overall purpose of the cement job. This requires customized cement jobs and recipes specific to the well and the section being drilled, and this is ensured by the use of specialized additives to the base cement mixtures to control its properties. Due to major differences in lithology, standardization, and properties of hydrocarbon reservoirs in the Middle East and the rest of the world, several customized recipes and formulations are used which are specific to the region. This paper is aimed at aggregating available information from common cement recipes in the Middle East and North America, and evaluating properties based on laboratory results available from representative experiments done as part of developing a cement database.The differences in geology have resulted in fundamental variations in cement formulations used in Middle East and North America. Literature from the Middle East region overwhelmingly indicated that API Class G is more commonly used, while Class H cement is more commonly favored in North America and the rest of the world. The differences further extend to the type of additives used as well. Formations in the Middle East have a higher occurrence of vugs and fractures, as well as gaseous hydrocarbons and/or H2S needing the use of LCM and other additives. Cement recipes vary from well to well, as does the use of sea water versus fresh water. Additives such as accelerators, retarders, defoamers, as well as fluid-loss control agents, are also commonly used. All these impact the properties of the cement, especially when monitored over time, and when accounting for ageing effects. Several teams have conducted stand-alone evaluations of various cement formulations, and documented their properties, though the presence of a comprehensive database of literature and laboratory-based results are lacking.Documenting such variations in the cement formulations and comparing the differences can help in better understanding the functionalities and efficiencies of cements used. Integrating these into a comprehensive database with laboratory-tested results can help in creating a knowledge base which could be utilized by the industry to better understand the performance of these cement mixtures over time and identify potential wellbore integrity issues.
