Eventos Anais de eventos
COBEM 2021
26th International Congress of Mechanical Engineering
Interfacial rheology of cyclopentane hydrates
Submission Author:
Marina Bandeira , RJ
Co-Authors:
Marina Bandeira, Gustavo Alonso Barrientos Sandoval, Monica Naccache, Paulo Roberto de Souza Mendes, Adriana Teixeira, Leandro Valim
Presenter: Marina Bandeira
doi://10.26678/ABCM.COBEM2021.COB2021-0281
Abstract
Gas hydrates are crystalline solids physically resembling ice, but differing from ice in having small molecules (guests) trapped inside by the water hydrogen-bonds (hosts). The cavities formed by these structures are generally occupied by external molecules such as low molecular weight hydrocarbon gases. The stabilization of the gas hydrate structures occurs due to the presence of these small substances known as hydrate formers by means of the weak van der Waals force. Basically, hydrates are formed at low temperatures and moderate or high pressures. A classic example where these conditions are attained is in the offshore oil and gas drilling, production, and transportation processes. Therefore, hydrate substances can form within the flowlines causing a total block, resulting in catastrophic economic and safety problems. Hydrates formation occurs at the water-hydrocarbon interface, therefore, it is important to investigate the kinetics of hydrate systems directly at this region. One approach which permits conducting that investigation is through the interfacial rheology technique, then, the objective of the present work is to bring different insights about the hydrate film dynamics. Our experiments were conducted using cyclopentane as a guest molecule since this hydrocarbon forms hydrates under atmospheric pressure, and accessible temperatures. Moreover, it forms the crystalline structure II, which is the same found in production lines of the oil and gas industry. Oscillatory tests were performed to obtain the rheological response at the interface, using the commercial rheometer DHR-3 and the double wall ring geometry, which is placed at the interface between the water and hydrocarbon. To obtain an accurate temperature control of the system, a home-made brass base was employed in the tests. The results are depicted through the interfacial dynamic modulus G’ and G” for different oil phases, composed of primol and cyclopentane: (I) pure cyclopentane, (II) 90% cyclopentane and 10% primol, (III) 80% cyclopentane and 20% primol. The tests aim to evaluate the effect of adding primol on the kinetics of hydrate film formation. In all cases, hydrate formation is detected by a stochastic grow of the interfacial storage modulus (G’) with time. After that, G’ reaches a plateau meaning that a stable hydrate film was formed. The results show that increasing concentration of Primol oil hinders the aggregation of hydrates crystals, since the storage modulus decreases approximately one order of magnitude when the quantity of Primol is increased from 10% to 20%.
Keywords
Hydrates, Cyclopentane, Hydrate Formation, Interfacial rheology, Interface
