Sensitivity Analysis of Gas Production from Class 2 and Class 3 Hydrate Deposits (OTC 19554)

Authors: Matthew T. Reagan (speaker), George J. Moridis, and Keni Zhang

Venue: 2008 Offshore Technology Conference, Houston, Texas, May 5-8, 2008 ( http://www.spe.org and http://www.smenet.org [external sites] )

Abstract: Recent studies indicated that it is possible to produce large volumes of gas from oceanic Class 2 and Class 3 hydrate deposits at high rates and for long periods by depressurization-induced dissociation. Previous computational work has examined how production from Class 2 and Class 3 deposits is affected by production methodology, well design, initial hydrate saturation, and the temperature of the deposit. This study investigated the effect of (1) porosity and permeability, (2) capillary pressure, (3) well spacing, (4) anisotropy in formation properties, (5) permeability of the confining layers, (6) pore compressibility, and (7) salinity of the aqueous phase within the reservoir.

The results of this study indicate that lower permeability, larger well spacing, lower salt (inhibitor) concentration, higher compressibility, and higher capillary pressure have a significant negative impact on gas production from Class 2 and Class 3 hydrate deposits. Water salinity and anisotropy properties of the porous-media have a weak to mild effect on production rates. Increasing permeability of the overburden leads to a drastic reduction in gas production, because of reduced depressurization (brought about by the higher permeability of the boundary), and loss of the gas accumulated at the top of the reservoir during depressurization into the overburden.

Related NETL Project:
This presentation is related to the NETL project G308-01, “Numerical Studies for the Characterization of Recoverable Resources from Methane Hydrate Deposits.” The objective of this project is to develop a reservoir model that simulates the behavior of hydrate-bearing geologic systems and evaluates appropriate hydrate production strategies for both permafrost and marine environments, including thermal stimulation, depressurization and dissociation induced and/or enhanced by inhibitors (such as brines and alcohols). This research will enhance natural gas hydrate research and development activities by bringing new numerical simulation capabilities and laboratory measurements to bear on the difficult problems of characterization and gas recovery of methane hydrate deposits.

Project Contacts
NETL – Richard Baker (Richard.Baker@netl.doe.gov or 304-285-4714)
LBNL – George Moridia (GJMoridis@lbl.gov or 510-486-4414)