Proof of concept for gas hydrate production using the depressurization technique, as established by the JOGMEC/NRCan/Aurora Mallik 2007-2008 Gas Hydrate Production Research Well Program

Scientific and engineering studies advanced through the JOGMEC/NRCan/Aurora Mallik 2007-2008 Gas Hydrate Production Research Well Program have successfully established proof of concept that sustained gas production can be achieved by simple depressurization of a gas hydrate reservoir using conventional oil-and-gas drilling, completion, and production methods. This paper reviews the scientific findings that substantiate this claim. These include 1) establishment of a petroleum-system model for the emplacement of a gas hydrate field by migration along vertical faults of thermogenic methane sourced from deeper sedimentary strata, with subsequent trapping as gas hydrate within a regionally extensive structural anticline; 2) quantification of the detailed physical properties (geological, geophysical, geomechanical) of gas hydrate reservoir sands and enclosing sediments; 3) construction and safe operation of a production well using conventional oilfield drilling and completion technologies; and 4) 6 days of continuous gas production by reservoir depressurization, with sustained gas- and water-flow rates averaging about 2000 and 10 m3/d respectively, and peak gas-flow rates in the range of 3500-4000 m3/d . Modestly increasing trends in the gas rate were apparent throughout the stage 2 and stage 3 production periods. Numerical reservoir simulations of the observed short-term gas- and water-production rates at Mallik have been undertaken with some success. We conclude, however, that before field-scale production can be realized there is a need for an improved understanding of the long-term production responses of the Mallik reservoir, which might reasonably be achieved through a future production test of between 6 and 12 months duration.