Permian Basin: Cementing Solutions for CO2 and Other Corrosive Environments
Well cementing is a fundamental and essential part during the exploration of a well. The primary goals of the annular cement sheath in wells are zonal isolation, supporting the casings and protecting them from corrosion. The cement sheath must withstand downhole stresses induced by pressure and temperature fluctuations, as well as corrosive attacks from aggressive formation and injection fluids (such as the CO2 floods used extensively throughout the Permian Basin) without failures during the life of well (ideally including after abandonment).
Cement sheath failures leading to loss of zonal isolation are the biggest concerns since they affect the wellbore integrity and so the life of the well with economic consequences: decline in production, loss of production time because of remedial cementing, and in the worst case even complete well failure/collapse and well abandonment. Therefore, it is critically important to design cement systems that counteract all negative impacts on the sheath integrity during the life of the well, to ensure maximal durability. Synthetic and resin-based binders provide high chemical resistance and good mechanical properties in the well, but conventional cement is still preferred because of its economic and practical advantages and its ready availability.
Harsh wellbore conditions (corrosive environments combined with high temperatures and pressures) have been always challenging for scientists and engineers developing improved cement systems. Early cement technology progress was based on empirical discoveries, but the advances have become more scientific in the last few decades due to improved analytic methods as well as the demand from the industry to develop more effective, economical and sustainable systems. We have a much better understanding of physical and chemical interactions among minerals during cement hydration, the impact of additives and secondary cementitious materials, and the mechanisms of cement corrosion. This knowledge has been fundamental to achieving the goal of economical cement systems for corrosive environments that perform for the full life of a well.
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