Print this pageProspecting for Gas Hydrate Accumulations using 2D and 3D Seismic Data, Milne Point, North Slope Alaska
The Milne Point gas hydrate prospect delineation study was
part of the U.S. Geological Survey (USGS) Alaska gas hydrate resource
characterization project in association with BP Exploration (Alaska) Inc. and
U.S. Department of Energy research that has helped answer questions about gas
hydrate distribution and reservoir properties. The interval below the base of
ice-bearing permafrost (IBPF) to just below the base of the gas hydrate
stability zone (GHSZ) was analyzed. Theoretical seismic modeling of stratigraphic and fluid boundaries, including shale to gas
hydrate reservoirs and shale to free gas reservoirs as well as transitional gas
hydrate to free gas reservoirs have been used to understand the acoustic
properties of these complex systems. Petrophysical
analysis
of known gas hydrates show saturations of 60-90% and porosities of
30-40%. Reservoir thickness and saturation were the primary variables used in
modeling acoustic attributes and calculating potential resource volumes.
Prospective “intra”-gas hydrate-bearing reservoirs below the IBPF and within the GHSZ and free gas-bearing reservoirs trapped below gas the GHSZ were delineated by seismic attributes. Fault-bounded intra-gas hydrate prospects were identified in areas that are structurally high, and that have acoustic properties corresponding to high concentrations of gas hydrate.
The historical log analysis work conducted by the USGS in this area combined
with knowledge gained from 3-D seismic attribute analysis
has helped us to
understand the geologic setting for these unconventional reservoirs. The Milne
Point area study has successfully delineated both intra-gas hydrate and sub-gas
hydrate free-gas prospects that are appropriate for potential production
testing operations.