Evaluation of Defoamer Chemistries for Deepwater Drilling and Cementing Applications

Abstract The search for high performance defoaming agents has been intensified in recent years due to, for example, the challenging deepwater conditions and new environmental regulations for offshore drilling. The major task is to find suitable additives that pose little to no risk to the environment without compromising the performance and system integrity. The use of defoamers in drilling and cementing applications is of vital importance for controlling and preventing excessive foam that can lead to problems ranging from operational difficulties (e.g., pump cavitation) to quality control and performance interferences (e.g., miscalculation of slurry density as most field mixers determine the water/cement ratio by measuring the density of the slurry). The detrimental effect of foam in cementing and drilling operations becomes more serious in deepwater applications where not only new technical and logistic challenges are encountered (e.g., poorly consolidated formation, high potential for shallow-flow hazards, low temperatures, etc.), but also optimum drilling efficiency and reduced operational time are required to keep costs down. In this study, traditional blender tests and a novel dynamic foam analyzer were used to benchmark defoamer performance during simulated slurry mixing operations. In-depth evaluation of the initial and persistent efficiency enables accurate dosage comparisons in the lab, resulting in effective and reliable field operations. This paper presents a comprehensive study of various defoamer chemistries. Testing on high-foaming media comprising fluid loss additives, dispersants and gas migration control agents indicates that non-silicone outperform silicone chemistries. In the case of foaming agents for drilling, studies show that only silicone defoamers were a feasible alternative. The oilfield industry is presently facing several challenges both from increasing environmental restrictions and also from specific field application requirements. The focus on finding suitable replacement additives for cementing and drilling systems without compromising the properties of completion fluids is a priority for many oil service companies. The use of a systematic approach for material selection is instrumental in reducing or eliminating risks to ensure maximum operation efficacy and longevity of cementing and drilling jobs while accommodating the unique factors pertaining to each individual project.