A new method for productivity calculation of perforated wells in gas condensate reservoirs

Flow in perforated regions has been the subject of numerous investigations in the past 60 years. These studies have mainly concentrated on proposing practical tools for the productivity estimation of perforated wells. The skin factor proposed can be applied in an equivalent (one dimensional radial) open-hole system replicating the flow around the actual complex three dimensional flow geometry of the perforated region. However, the majority of these studies concentrate on single-phase flow conditions. In gas condensate systems at relatively low interfacial tension (IFT) values, phase change and dependency of relative permeability on velocity and interfacial tension add significant complexity to proposing such an efficient and much needed tool for practical applications.

This work is aimed at the development of a practical and convenient method for defining an effective wellbore radius of an equivalent open-hole system, replicating flow around a perforated well in gas condensate reservoirs. The new method is based on the physics of the flow and applicable for both single-phase non-Darcy and two-phase gas condensate flow systems. Since the mechanical perforation skin formulations available in the literature are not accurate for highly anisotropic formations, a new more efficient skin formulation is introduced for such applications. In these exercises the finite-element based simulator developed by Jamiolahmady et al. (2007) was used to generate the large bank of data required to confirm the integrity of the proposed practical approach for productivity calculation of perforated wells in gas condensate reservoirs.