Modification of Vogel's IPR curve for saturated oil reservoirs

Vogel's inflow performance relationship relates the flowing well pressure to production rate for solution-gas drive reservoirs. Because two-phase flow exists, the graph of bottom-hole flowing pressures versus oil production rate results in a curved line. This trend accounts for the decrease in production as more gas comes out of the solution. Vogel assumes the initial reservoir pressure is the same as the bubble point pressure for the starting point of the IPR curve. This implies no gas has initially come out of the solution, i.e. the reservoir is at bubble point pressure. Saturated reservoirs, as studied in this paper, are initially undersaturated reservoirs with average reservoir pressure below the bubble point pressure. Traditionally, Vogel's inflow performance relationship has been applied to these reservoirs using the reservoir pressure as the starting point for the curve. However, due to the presence of gas at the reservoir pressure, this is not an accurate assumption. This paper modifies the Vogel IPR curve for use in wells within reservoirs that are below the bubble point pressure.