Abstract

Thermal recovery processes such as CSS (cyclic steam stimulation) and SAGD (steam-assisted gravity drainage) are affected and limited by reservoir geomechanics. This paper provides new thermal recovery screening criteria based on geomechanics. The purpose is to provide a means of screening prospective reservoirs to assess the practicality of using various steam injection recovery processes, and to assess their relative efficiencies in these reservoirs.

The choice of a thermal recovery process is based on the project economics, which are largely determined by the expected behaviour of the recovery process in the reservoir. Typically, geological hydraulic characteristics, such as the vertical permeability and the presence or absence of impediments to vertical flow, will be the deciding factors in the choice of the recovery process.

However, conventional reservoir characteristics are insufficient to determine the probable success of a recovery process. Reservoir geomechanics can have a significant and even dominant effect on the efficacy of recovery processes.

As a result, the same recovery process in reservoirs with identical conventional reservoir properties can have markedly different levels of success due to their differing geomechanical properties. Reservoir simulations and reserves evaluations should consider these differences, given the expected variance in performance in terms of production rates and ultimate recoveries.

Geomechanical screening provides an additional filter by which recovery processes can be assessed, and perhaps eliminated, based on their expected performance in any given reservoir. Furthermore, the valuation of the recoverable reserves of a reservoir is highly dependent on the expected efficiency of a recovery process, and if the geomechanical characteristics limit the efficiency of recovery processes, that should be known when assessing the value of the heavy oil or bitumen resource. This is essential for recovery process selection and operation.

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