Abstract

The conventional, non-compositional, tubing hydraulics programs are inadequate for accurately predicting the flowing pressure gradient in high rate gas condensate wells. These programs do not directly account for the pressure losses caused by liquid (hydrocarbon and /or water) condensation in the well bore. To improve the accuracy of predicting wellbore pressure gradients, Mobil developed a compositional tubing hydraulics program. The program incorporates an energy balance, together with a mechanistic fluid flow model to determine the pressure gradients, in conjunction with phase equilibrium calculations to chart the pressure and temperature profiles along the tubing string.

The new compositional program is being used for gas deliverability studies by Mobil. The conventional (non-compositional) tubing hydraulics programs resulted in overly optimistic gas deliverability predictions, particularly during the later stages of depletion when liquid condensation in the wellbore is prevalent. For high rate gas wells, this inaccuracy can be significant. A comparison of wellbore pressure gradients and gas deliverability predicitons using the two programs is included in the paper.