(26b) Development and Experimental Validation of Hydrate-Philic Surfactants

Authors: 
Morrissy, S. A., University of Western Australia
Graham, B. F., University of Western Australia
Johns, M. L., University of Western Australia
May, E. F., University of Western Australia
Aman, Z. M., University of Western Australia
Clathrate hydrates are crystalline inclusion compounds which can form in subsea flowlines and lead to the formation of blockages. To mitigate the risk of hydrate blockages, conventional flow assurance approaches have deployed thermodynamic hydrate inhibitors (THI), such as methanol or monoethylene glycol, to move the pipeline out of the hydrate stability region. In deepwater operations, there is an increased driving force for hydrate formation and the amount of THI required to prevent hydrate formation in the flowline may be cost prohibitive. To maintain the viability of deepwater assets, alternative hydrate management strategies are required; anti-agglomerants (AAs) are one promising field, where surfactants are used to prevent hydrate particles from aggregating in the liquid phase or depositing on the flowline wall. However, the adoption and deployment of AAs may be limited, as the ionic nature of current-generation AAs may generate strong water-in-oil emulsions and may also have a deleterious effect on water quality. The development of surfactants that selectively adsorb to the hydrate crystal surface may remedy both operating challenges, but requires an experimental technique to characterize the hydrate-philicity of these chemicals. We present a new experimental protocol using a micromechanical force (MMF) apparatus and a pendant drop interfacial tensiometer to respectively measure hydrate cohesive force and oil-water interfacial tension. We have deployed this protocol to characterize several non-ionic surfactants, thereby identifying chemicals that reduce the hydrate cohesive force to a required level with minimal penalty to the water-oil interfacial tension. The application of this experimental protocol, based on an initial set of experiments, provides an attractive pathway to tailor the next generation of hydrate management chemicals, which are of particular importance in sensitive marine environments.