Modelagem termodinâmica do equilíbrio de fases de hidratos de gás a altas pressões

Abstract

Thermodynamic modeling of hydrates at high pressures (in this work are considered high pressures those ones that can liquefy the hydrate former gas) helps the oil and gas industry to understand the events in oilfield production, especially those with high pressures and/or low temperatures, such as the Brazilian Pre-salt. Thoseconditions are favorable to the formation of hydrates, which are compounds formed by the occlusion of gas or liquid of low molecular mass within a crystalline structure of water molecules. The formation and crowding of hydrates may cause an obstruction in oil and gas transport lines, making the process less efficient and compromising the operational safety. This work presents a thermodynamic modeling of phase equilibrium of carbon’s dioxide and ethane hydrates, to predict, above all, the region in which is seen the coexistence of three phases in equilibrium, liquid water, hydrate and a hydrate’s former condensed (LW-H-LG), under a pressure above the upper quadruple point(Q2), conditions that can be observed during the production of petroleum, such as in Brazilian Pre-salt reserves. To predict the phenomena of phase equilibria, the CPA (Cubic Plus Association) equation of state was used to model the fluid phases (LW-LG) and the van der Waals and Platteeuw model was used to model the hydrate phase(H).