Development of a Thermodynamic Model and Reservoir Simulator for the CH CH4, CO , CO2,and CH,CH4-CO -CO2 Gas Hydrate System

摘要

An equation of state (EOS) software module was developedrnfor CHrnCH4, CO , CO2, and CH , CH4-CO -CO2 mixed hydrates by usingrnVanderWall-Platteeuw model. The model is based on classicalrnthermodynamics and is used to predict the thermodynamicrnbehavior of gas hydrates including pressure and temperature atrnwhich gas hydrates form. A numerical scheme was developedrnfor solving Lw-V-H and I-V-H equilibrium conditions forrnbulk hydrate formation from pure water and gas. The modelrnwas further extended to determine hydrate equilibriumrnconditions in the presence of salt. The results calculated fromrnthe model were in close agreement with the experimental datarnreported in literature. One of the contributions of this work isrnthat the proposed model can predict hydrate dissociationrnpressures at temperatures above 285 K more accurately thanrnany of the existing available modules. The new EOS has beenrnimplemented in the multiphase flow simulator STOMP-COrnCO2rndeveloped at PNNL for simulating geological storage ofrncarbon dioxide. Simple reservoir simulations were performedrnwith the new module to examine decomposition of methanernhydrate and formation of COrnCO2-hydrate as a new means ofrnnatural gas production from gas hydrate reservoirs.