Energy Policy Act of 2005 (Ultra-deepwater and Unconventional Resources Program)
Application Of Natural Gas Composition To Modeling Communication Within And Filling Of Large Tight-Gas-Sand
Reservoirs, Rocky Mountains
Colorado School of Mines (CSM), Golden, CO 80401
University of Oklahoma, Norman, OK 73019
U.S. Geological Survey, Denver, CO 80225
University of Manchester, Manchester, ENGLAND M139PL
The large tight-gas-sand reservoirs of the Rocky Mountains comprise a major natural gas resource in the United States. While it is clear that these reservoirs fill from the bottom up, not
from a top seal downward as do conventional reservoirs, the process(es) by which gas migrates into these reservoirs is unknown. Possible mechanisms are that: (a) gas diffuses upward through
a series of moderately permeable seals, (b) gas forces its way upward by fracturing intermediate seals, or (c) gas migrates up conduits such as faults or fracture systems and then diffuses laterally.
Each model has implications for predicting the top of gas within fields and the distribution of fields within a sedimentary basin and for estimating the scale of the natural gas resource with sedimentary basins. We also do not know the extent to which gas can circulate within a field or the extent to which circulation is restricted by stratigraphic or structural barriers.
We propose to use the composition of natural gas samples from several major tight-gas fields in Wyoming, Colorado and Utah, to test possible mechanisms for gas migration into the tight-gas sand reservoirs and communication within such reservoirs. We will integrate data on bulk hydrocarbon composition, the isotopic composition of hydrocarbon gases and CO2 and the noble and radiogenic gases from these gas fields with experiments to determine the composition of gas entering the reservoir from source rocks and gas migration computer models. If this research is successful, we will have identified new tools and models that can be used by natural gas resource companies to enhance their development of these fields and to discover new fields. This research may also lay the groundwork for geophysical approaches to the direct detection of natural gas tight-gas-sand reservoirs.
Principal Investigator: Dr. Nicholas B. Harris