Abstract
This paper offers a new correlation to construct inflow performance relationship (IPR) for vertical oil well operated under solution gas drive with bottomhole pressure below the bubble poinr pressure. In this case an area with liberated free gas is created in the near-wellbore part of the reservoir. For this case a new functional equation (correlation) for IPR curve in the form of power law is suggested based on the analytical derivation and using pseudopressure function approach. In contrast to the other studies where a parametric IPR equation (usually in the polynomial form) with subsequent selection of coefficients (e.g. Vogel's methodology) was a priory used the new correlation is consistent with the fact of similarity between the oil wells IPR curves built in dimensionless coordinates. In particular case the IPR correlation considered is approximately close to the Vogel's IPR curve which allows using it as Vogel's simple alternative. A modification of the method is suggested. This modification corrects IPR curve behavior in the case of the presence of a transition zone where oil mobility decrease for the pressure values closed to the bubble-point pressure. The paper introduces the justification of the n exponent suggested by Fetkovich IPR and shows how application of new IPR correlation eliminates the contradictions associated with variation range of this parameter. Relations are also proposed to predict the future form of IPR curve and future values of the absolute open flow rate. Based on the large set of numerical calculations the expected values of exponent n for new IPR curve are presented thus they can be applied in the case studies when the experimental data are not available.
