Prospecting for
Gas
Hydrate Accumulations Using 2-D and 3-D Seismic Data, Milne Point, North Slope Alaska
Tanya Inks1, Timothy Collett2, David Taylor3, Warren Agena2, Myung Lee2,
and Robert Hunter4
1 IS Interpretation Services, Inc, Denver, CO
2 U.S. Geological Survey, Denver, CO
3 U.S. Geological Survey, Lakewood, CO
4 SRC Energy Services, Inc, Anchorage, AK
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.