Compositional simulations of producing oil-gas ratio behaviour in low permeable gas condensate reservoir

Abstract

Gas condensate flow behaviour below the dew point in low permeable formations can make accurate fluid sampling a difficult challenge. The objective of this study was to investigate the producing oil-gas ratio behaviour in the infinite-acting period for a low permeable gas condensate reservoir. Compositional isothermal flow simulations were performed using a single-layer, radial and two-dimensional, gas condensate reservoir model with low permeability. The main finding in this thesis was that during a drawdown for long producing times, the producing oil-gas ratio quickly stabilized below the initial oil-gas ratio and remained almost constant throughout the infinite-acting period. The stabilization level of the producing oil-gas ratio depended on the producing rate. No previous work on the observations in this thesis has been found. A sensitivity study using two other sets of gas-oil relative permeability curves was performed, but no significant change in the producing oil-gas ratio behaviour was observed. The conclusion is that a recombined oil and gas PVT-sample from a low permeable gas condensate field could be inaccurate if the stabilized level of the producing oil-gas ratio is different from the initial oil-gas ratio.