Technology Update: New Antifoam Additive Shows Superior Ability To Reduce Air Entrainment in Cement Slurry

Abstract

Technology Update Zonal isolation is a critical part of wellbore construction. To achieve zonal isolation, cement must be properly mixed before pumping downhole. Air entrainment that occurs during mixing can lead to errors in cement density readings. The use of powder antifoaming additives can enable a reduced level of air entrainment in the matrix of the cement slurry, but often requires liquid defoaming additives to reduce the surface air entrainment. The X-Air P cement powder antifoam, developed by Hexion, is designed to prevent air entrainment in cement systems. The reduced air entrainment achieved results in an improved density control for a more accurately mixed slurry. The additive uses a unique chemistry that has been proven in the field to be at least 50% more efficient than an alternative, widely available commercial formulation, with more stable cement slurries achieved as a result. The Hexion cement antifoam additive (CAA) is applicable in a variety of cement formulations, including those that contain dispersants, accelerators, retarders, and fluid-loss additives. The CAA is a free-flowing powder that is stable in wide temperature and humidity ranges and resists clumping. Its performance may also eliminate the need for a liquid defoamer on location. Development and Testing Following the effort that identified the need for a more effective powder antifoam, extensive laboratory testing was performed by in-house domain experts, service company specialists, and other third-party laboratories. Initial internal performance testing involved mixing the CAA at 0.1% by weight of cement (BWOC) into Portland cement, blending it with water and common cement additives, and measuring the density of the slurry. Portland cement classes A, C, G, and H were tested. Variations of fluid-loss additives, dispersants, and accelerators were used. The same test procedure was followed with the use of an alternative commercial formulation. The results in Fig. 1 show that the CAA had measurably lower air entrainment than the alternative mixture, which led to more consistent results with a variety of cement additives. Third-party testing showed that the CAA had negligible effects on rheology, free water, thickening time, compressive strength, and fluid loss.