EOSHYDR: A TOUGH2 Module for CH4-Hydrate Release and Flow in theSubsurface

• Main Authors: Moridis, George, Apps, John, Pruess, Karsten, Myer, Larry
• Language: unknown
• Published: 2008
• Subjects: 03 NATURAL GAS; 58 GEOSCIENCES; DEPRESSURIZATION; DISSOCIATION; GAS HYDRATES; HEAT FLUX; HEAT TRANSFER; HYDRATES; KINETICS; METHANE; NATURAL GAS HYDRATE DEPOSITS; PERMAFROST; SEDIMENTS; SIMULATORS; SOLUBILITY; STIMULATION; THERMODYNAMICS; WATER; Ice; Methane hydrate; permafrost
• Online Access: http://www.osti.gov/servlets/purl/876206; https://www.osti.gov/biblio/876206

EOSHYDR is a new module for the TOUGH2 general-purpose simulator for multi-component, multiphase fluid and heat flow and transport in the subsurface. EOSHYDR is designed to model the non-isothermal CH{sub 4} release, phase behavior and flow under the conditions of the comrilon methane hydrate deposits (i.e., in the permafrost and in deep ocean sediments) by solving the coupled equations of mass and heat balance. As with all other members of the TOUGH2 family of codes, EOSHYDR can handle multidimensional flow domains and cartesian, cylindrical or irregular grids, as well as porous and fractured media. EOSHYDR extends the thermophysical description of water to temperatures as low as -30 C. Both an equilibrium and a kinetic model of hydrate formation or dissociation are included. Two new solid phases are introduced, one for the CH{sub 4}-hydrate and the other for ice. Under equilibrium conditions, water and methane, as well as heat, are the main components. In the kinetic model, the solid hydrate is introduced as the fourth component. The mass components are partitioned among the gas, liquid and the two solid phases. The thermodynamic phase equilibrium in EOSHYDR is described by the P-T-X diagram of the H{sub 2}O-CH{sub 4}system. Phase changes and the corresponding heat transfers are fully described. The effect of salt in pore waters on CH{sub 4} solubility and on the growth and decomposition of gas hydrates is also taken into account. Results are presented for three test problems designed to explore different mechanisms and strategies for production from CH{sub 4}-hydrate reservoirs. These tests include thermal stimulation and depressurization under both permafrost and suboceanic conditions. The results of the tests tend to indicate that CH{sub 4} production from CH{sub 4}-hydrates is technically feasible and has significant potential. Both depressurization and thermal stimulation seem to be capable of producing substantial amounts of CH{sub 4} gas.