Abstract: Three Dimensional Groundwater Flow Modeling
of the Ferron
Sandstone, Central Utah
ANNA, L.O., C.C. FAUNT, F.A. D'AGNESE, and M. E. HENRY, U.S. Geological Survey, Lakewood, CO
Large quantities of water are produced from coalbeds within the
Ferron Sandstone as part of coalbed methane production. The
groundwater flux, flow patterns, and water chemistry in the Ferron
Sandstone and adjacent units respond to increased water drainage
from the coals. Modeling
can address the complex interaction
between the regional groundwater flow system, the local flow system
in the cleated (fractured) coal, and faults. Objectives are to
describe the local groundwater flow system in a “typical”
coalbed using a discrete fracture network (DFN) method, describe
the regional groundwater flow system in the Ferron Sandstone and
contiguous units utilizing GIS and MODFLOWP, quantify potential
water yields of a “typical” coalbed, and identify the
effects of dewatering the main coal as a result of gas
production.
Preliminary DFN modeling
shows that block-scale permeability
calculations of the coal's cleat network can be used to
determine a bulk permeability for a specific direction. This
determination quantifies the degree of anisotropy of the network
which will be included in the regional-scale flow model
representing a coalbed layer.
A 3-D digital representation of the Ferron Sandstone and contiguous units has been developed for the regional groundwater flow system. This 3-D model describes the geometry and permeability patterns of units controlling groundwater flow. The digital model is used to assess potential water yields and the effects of dewatering through pumping simulations. Hydrochemical data are used to help identify the effects of dewatering. As a result, the study will help assess the effects of coalbed methane production on the groundwater flow system.
AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah