Gas Condensate Well Deliverability: Integrated Laboratory-Simulation-Field Study

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractIt is well known that the deliverability of gas condensate wells can be impaired by the formation of a condensate bank once the bottomhole pressure drops below the dew-point. There have been many excellent laboratory studies on gascondensate relative permeability that describe this phenomenon, but there are few integrated laboratorysimulation-field studies that compare systematic predictions to field performance.We present extensive experimental relative permeability data sets on some sandstone reservoirs. These data span the k rg /k ro and capillary number parameter space. We discuss the experimental procedures, and the design of fluid systems that mimic reservoir fluids, but at lower temperatures. Next we demonstrate various steps involved in our approach by modeling a gas condensate well with field production history. Here we first measured relative permeability data on core samples from the reservoir and fit them to capillary number dependent relative permeability models. Then, we performed detailed single well compositional modeling with realistic geology and boundary conditions. Finally, we compared the predictions to actual production data, and found that the match was quite good. The productivity reduction was found to be in the range of 80%, the majority of which occurred in the initial phases of production. Our ability to reasonably predict the well performance has given us confidence that our approach, including measuring only the relevant portion of the relative permeability curves and using synthetic fluids, may be sufficient.

Deliverability Modeling of West Siberia Gas-Condensate Wells

“…Numerous studies [6][7][8][9][10][11][12] point out that if the capillary number exceeds the value of 10 -4 the effective gas and condensate relative permeability starts to increase. This effect is commonly known as the Velocity Stripping or Velocity Depending Relative Permeability (VDRP) effect.…”

“…Different methods using the live reservoir or synthetic fluid were reported and discussed in the literature [9][10][11][12][13][14][15][16][17] . The most comprehensive experimental procedure would be using the original reservoir fluid at conditions that can be expected near the wellbore.…”

“…Several studies indicated that such simplified experimental approach is sufficient to reasonably predict gas-condensate blockage effect for a well performance. For example an integrated lab-simulation-field study for five gas-condensate sandstone reservoirs was provided in [9][10][11] . It is concluded that the pseudo steady-state experiments with synthetic (3-component) fluids are qualified to predict the condensate banking issues reasonably well.…”