A short-duration production test was undertaken at the Mallik site in Canada’s Mackenzie Delta in April
2007 as part of the JOGMEC/NRCan/Aurora Mallik 2007 Gas Hydrate Production Research Well Program.
Reservoir stimulation was achieved by depressurization of a concentrated gas hydrate interval between
1093 and 1105m (RKB). Geologic and porous media conditions of the production interval have been
quantified by geophysical studies undertaken in 2007 and geophysical and core studies undertaken by
previous international partnerships in 1998 and 2002. These investigations have documented that the
production interval consists of a sand-dominated succession with occasional silty sand interbeds. Gas
hydrate occurs mainly within the sediment pore spaces, with concentrations ranging between 50-90%.
Laboratory experiments conducted on reconstituted core samples have quantified the effects of pore water
salinity and porous media conditions on pressure-temperature stability, suggesting that the partition
between gas hydrate stability and instability should be considered as a phase boundary envelope or zone,
rather than a discrete threshold. Strength testing on natural core samples has documented the dramatic
changes in physical properties following gas hydrate dissociation, with sediments containing no hydrate
behaving as unconsolidated sands. While operational problems limited the duration of the production test, a
vigorous reservoir response to pressure draw down was observed with increasing gas flow during the
testing period. We interpret that pressure temperature (P-T) conditions within the test zone were close to
the gas hydrate phase equilibrium threshold, with dissociation initiated at 10 MPa bottomhole pressure
(BHP), approximately 1 MPa below in situ conditions. The observation of an increase in production rates at
approximately 8.2 MPa BHP may be consistent with the notion of an indistinct gas hydrate stability
threshold, with rates increasing as P-T conditions traverse the phase boundary envelope. Significant sand
inflow to the well during the test is interpreted to result from the loss of sediment strength during gas
hydrate dissociation, with the sediment behaving as a gasified slurry. The increase in gas production rates
during the final hours of the test may result from non-uniform gas hydrate dissociation and be affected by
accelerated dissociation along water filled natural fractures or fine-scale geologic heterogeneities. These
may initiate worm hole or high permeability conduits in association with sand production.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:BVAU.2429/2232 |
| Date | 07 1900 |
| Creators | Dallimore, Scott R., Wright, J. Frederick, Nixon, F. Mark, Kurihara, Masanori, Yamamoto, Koji, Fujii, Tetsuya, Fujii, Kasumi, Numasawa, Masaaki, Yasuda, Masato, Imasato, Yutaka |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | text |
| Rights | Dallimore, Scott R. |
Page generated in 0.0021 seconds