Justification of the boundary values of open porosity and gas permeability using data from flow studies for porous carbonate reservoirs

Abstract

This paper proposes a method for determining the boundary values of open porosity (K_{PO_GR}) and gas permeability (K_{PR_GR}) of porous-type carbonate reservoir rocks using the example of Tournaisian deposits of one of the oil fields of the Republic of Tatarstan. When justifying the boundary values, two databases on core studies are used: 1) on standard core studies (used mainly to calculate hydrocarbon (HC) reserves); 2) on special core studies (used for technological development projects). In the proposed method, the residual oil saturation factor is not a constant, but is taken from flow studies or calculated from core dependencies. When determining the lower limits of porosity and permeability from both databases, approximately the same boundary values were obtained: K_{PO_GR} = 0.11 fr. un., K_{PR_GR} = 2·10^–3 μm² and K_{PR_GR} = 1.7·10^–3 μm² , but they differ from the values, accepted by petrophysicists when calculating the reserves of considered deposit – K_{PO_GR} = 0.09 fr. un., K_{PR_GR} = 1·10^–3 μm² . Such a difference in determining the boundary porosity can significantly affect the calculation of hydrocarbon reserves, technological calculations and field development planning.