Numerical Studies for the Characterization of Recoverable Resources from Methane Hydrate Deposits

Authors: George J. Moridis, Matthew T. Reagan, Suntichai Silpngarmlert, and Keni Zhang

Venue: 2008 AGU Fall Meeting, December 15-19, 2008 in San Francisco, California www.agu.org

Abstract: The amounts of hydrocarbon gases trapped in natural hydrate accumulations are enormous, leading to a recent interest in the evaluation of their potential as an energy source. Recent studies have provided strong indications that it is possible to produce large volumes of gas from natural hydrate deposits at high rates for long times from gas hydrate accumulations by means of depressurization-induced dissociation using conventional technology.

In this study we investigate by means of numerical simulation the gas production potential from Unit D, a Class 3 permafrost hydrate deposit at the Mount Elbert Site in North Slope, Alaska. Class 3 deposits are characterized by the absence of hydrate-free zones of mobile reservoir fluids. The hydrate-bearing formation in Unit D begins at a depth of 616 m, is about 11 m thick, is bounded by nearly impermeable shale layers, and has high porosity, permeability and hydrate saturation. Because of its proximity to the permafrost, its temperature is low, i.e., 2.3 – 2.6^o C.

The numerical simulation studies indicate that gas production using vertical wells is seriously inhibited by the low temperature and the limited thickness of the deposit, resulting in low production rates and very long times (several years) before production rates reach levels of commercial viability. Conversely, the use of appropriately placed horizontal wells leads to dramatic increases in gas production from this deposit, and appears to be the only practical alternative for viable gas production from this hydrate accumulation. The sensitivity of gas production to various properties and parameters was also analyzed. These parameters include the magnitude of the hydraulic properties (permeability and porosity), the anisotropy and heterogeneity in their spatial distribution; the heterogeneity in the distribution of the hydrate saturation, the effect of nonzero permeability is the shale boundaries, and operational parameters defining the production strategy.

Related NETL Project
This presentation is related to the NETL project G308, “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.

NETL Project Contacts
NETL – Richard Baker (richard.bakerl@netl.doe.gov" 304 285-4714)
Lawrence Berkeley National Laboratory. – George Mordis (GJMoridis@lbl.gov or 510 486-6709)