It is well known that the permeability of porous media represents a first order control on fluid flow in hydrocarbon reservoirs and that the magnitude of the permeability often depends on the rock volume under consideration. Core plug permeability does not necessarily equal whole core permeability and permeability from core may not necessarily reflect well test permeability. Each of these disparate data sources measures permeability at a particular scale. For the purposes of reservoir modelling, the permeability systems characterizing a giant offshore oil field have been broadly categorized as either matrix permeability or excess permeability. Matrix permeability further subdivides into two categories based on the abundance and type of microporosity. Excess permeability subdivides into three sub-categories depending whether it is the result of depositional processes emplacing anomalously high permeability storm beds (HKS or high permeability streaks), diagenetic processes creating dissolution enhancement of permeability, or fractures. Although not all these permeability systems are active in any reservoir interval, each reservoir interval possesses at least two if not three of these systems. The multi-scale nature of permeability arises because of 1) differences in the spatial extent of these permeability systems and 2) permeability contrasts between the systems.
Several techniques have been developed and will be explored in this paper that attempt to account for the influence of multi-scale permeability systems on reservoir performance behaviour. In what might be the simplest case, the mixture of permeability systems includes only matrix permeability without significant microporosity and excess permeability resulting from HKS. In this case, matrix permeability was modelled independently of excess permeability creating significant short-range permeability contrasts that better predicted reservoir pressures and water movement in the reservoir during history-matching. In another case with the same type of matrix permeability, the excess permeability represents the contributions from a mixture of fractures and HKS. In this case, matrix permeability was also modelled independently of excess permeability. Estimates of the relative contributions of HKS and fractures to excess permeability were tested as a history-matching parameter. Ultimately, this approach to characterizing permeability attempts to capture some of the rudimentary aspects of a dual permeability model without incurring the associated computational expense.