Production of gas from tight naturally fractured reservoirs with active water

There are numerous examples of tight naturally fractured gas reservoirs wit h active water in the foothills of Alberta and north- eastern British Colum bia. Examples include the Pincher Creek field in Alberta and the Bucking Ho rse, Pocketknife, Sikanni and Grassy fields in British Columbia. Recovery f actor is typically low from this type of reservoir due to water production. The problem is frequently attributed to coning, but coning may actually pl ay a minor role. In fact, the gas/water contact in the fracture system may be relatively flat. Initial gas recovery comprises gas displaced from fract ures plus pressure depletion from the matrix. The amount of pressure deplet ion in the matrix is a function of structural relief above the original gas /water contact. Subsequent gas recovery is an imbibition process, which may be very slow. Laboratory work, conducted at the TIPM Laboratory on behalf of Husky, demonstrates that water will continue to imbibe into tight matrix rock submerged under water for months. This work implies that the best ope rating strategy may be to produce the wells at the highest rates possible u ntil water breakthrough, followed by a shut-in period of perhaps several ye ars to allow gas to re-accumulate.