The composite method of rock permeability have always been applied in the calculation of oil reserves

complication of oilfield development plan

numerical simulation of reservoirs and other reservoir engineering research

which mainly include the permeability compositon of vertically different stratigraphic horizons and the permeability composition of different permeable zones along filtrational directions.Based on Darcy's law and combined with established filtration pattern

two composite formulas of permeability have been derived from mathematic calculation.The composite formula of permeability in vertically different stratigraphic horizons corresponds to that in historical literature

but the composite formula in different permeable zone is more different from the forefathers' formula.Based on the examination of actual data

calculated error of new formula is about 0.28%-5.35%

which is basically within permissible error range.