OS4C-5：MINIMIZING CLATHRATE HYDRATE ADHESION FORCES WITH CHEMICAL AND PHYSICAL MODIFICATIONS TO STEEL

Zachary M. AMAN1,2, E. Dendy SLOAN1, Amadeu K. SUM1, Carolyn A. KOH1
1. Center for Hydrate Research, Chemical & Biological Engineering Department, Colorado School of Mines, USA; 2. Centre for Energy, The University of Western Australia, Australia

    Clathrate hydrate adhesion to steel surfaces can lead to deposits of gas hydrates forming on the surfaces of oil and gas pipelines, enhancing the risk of hydrate plug formation in pipelines. The ability to reduce the adhesion forces between hydrate—steel surfaces could help to minimize hydrate deposition. Such a strategy could be applicable in a number of hydrate applications, including hydrates in flow assurance to avoid pipeline blockages and containment of oil/gas during a deepwater blowout. In the latter application, hydrate adhesion to the surface of the caisson structure may interfere with containment operations. In this study, different chemical and physical treatments were used to modify the steel surface, such that hydrate particle – steel surface adhesion could be reduced. A micromechanical force apparatus was used to measure the hydrate-surface adhesion forces without and with surface treatment/modification of grade 309 stainless steel surfaces. Experiments were performed with cyclopentane hydrate (structure II, which is the structure of most hydrates formed in oil/gas systems) and stainless steel coated with oleomide solution, graphite, an organic acid, 1,9-nonanedithiol, and Rain-X chemical additives.  Micromechanical studies revealed that some chemical additives induced morphological changes in the hydrate particle, increasing variability between force measurements in a single experiment; strong surfactants weakened the capillary bridge and prevented hydrate from growing along the steel; weak surfactants draw free water to the surface without satisfactorily weakening the bridge strength (leading to an overall increase in capillary force). The effects of contact time and contact angle on hydrate-steel adhesion forces were also investigated for different chemically modified steel surfaces.