On the Relation of Porosity and Permeability in Low Porosity and Low Permeability Rock

The view about the higher porosity with the higher permeability has guided high porosity and high permeability reservoir production operations,but in the low porosity and low permeability reservoirs,there often appears the phenomenon contrary to this view,the capacity difference is very large in almost the same porosity reservoir.Experiment data from 250 rock samples indicate that permeability is not obviously controlled by the total porosity in the low porosity and low permeability rock,traditional porosity-permeability calculation method is no longer applicable.In the low porosity and low permeability rock,permeability is mainly controlled by pore structure,the pore with different pore sizes has different contribution to the permeability,the pore sizes and the corresponded proportion in the pores control the permeability value together.On this basis,the nuclear magnetic resonance logging is used to depict the pore size ranges,then the interval porosity is used to calculate the permeability.This method not only improves the permeability calculation accuracy in the low porosity and permeability reservoir but also develops the traditional formula,it can effectively guide the productivity evaluation of low porosity and low permeability reservoirs in the future.