Question

In secondary recovery, what is the exact numerical difference between the areal sweep efficiency and the vertical sweep efficiency when calculating the total displacement efficiency?

Accepted Answer

There is no exact numerical difference between areal sweep efficiency and vertical sweep efficiency because they are independent variables representing different spatial dimensions of a reservoir. Areal sweep efficiency measures the fraction of the horizontal reservoir area contacted by the injected fluid between the injection and production wells. Vertical sweep efficiency measures the fraction of the total vertical thickness of the reservoir contacted by the injected fluid. Total displacement efficiency, or recovery efficiency, is calculated as the product of three distinct factors: the microscopic displacement efficiency, the areal sweep efficiency, and the vertical sweep efficiency. Because these efficiencies are multiplied rather than subtracted, their numerical values are not defined by a fixed difference. For example, if a reservoir has an areal sweep of 0.8 and a vertical sweep of 0.5, their product contributes to the total recovery, but the difference between them remains 0.3 without possessing any inherent mathematical constraint or constant relationship.

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In secondary recovery, what is the exact numerical difference between the areal sweep efficiency and the vertical sweep efficiency when calculating the total displacement efficiency?