Definition - What does Effective Permeability mean?
Effective Permeability is the ability to advantageously transmit a particular fluid when there are other immiscible fluids in a reservoir. It is affected by the relative saturations of fluids and nature of the reservoir. It is a function of rock wetting characteristics, geometry of rock pores and fluid saturation. It is assumed normally that the effective permeability is same for all fluids present in a rock at 100% saturation. On the contrary, absolute permeability is the measurement of permeability while single phase or fluid is present in the rock.
Petropedia explains Effective Permeability
Effective Permeability is considered less than absolute permeability because the size of holes available for the flow of first fluid to be reduced due to the presence of the second fluid. It is measured as zero if there is no flow of fluid. Effective Permeability of oil is sometimes used at irreducible water saturation to normalize the relative permeability instead of absolute permeability. When using the permeability data, it essential to determine if effective permeability or absolute permeability is to be used for normalizing. The permeability data is used in almost all the calculations of reservoir engineering which involve the movements of various fluids together.