PVT Analysis: Validity Checks and EOS Turning Techniques for Retrograde Condensate Reservoirs

Abstract

PVT analysis is pertinent to field-wide development and optimization. This is because we need to know the over-all behavior of the fluid from reservoir through production and process facilities, down to the refinery. Its emergence as a separate discipline has been supported by the development of modern computer software that utilize EOS models for simulating experiments and representing fluid phase behaviours. PVT simulations are carried out to determine operating conditions that will maximize the surface liquid content and extend the production plateau duration at the lowest possible cost. In such simulations, laboratory derived data are used to tune the EOS models and the results incorporated for reservoir simulation and studies. Obtaining a good match between EOS and laboratory data depends on data quality and for retrograde gas condensates; this can be very challenging due to their complicated phase behavior. Inadequate match results in computational errors and unrepresentative results when used in reservoir simulations and thus, jeopardize reservoir management decisions which are based on it. The major contributions of this paper are: first, a review of critical issues and success factors in PVT analysis and its associated challenges; second, methods for quality checking PVT data; and third, techniques for improving Lab-EOS match and their influence in PVT results.

Keywords: Gas condensate, PVT analysis, equations of state, tuning technique, validity checks