The Impact of Permeability Heterogeneity on the Liquid Recovery from Gas Condensate Reservoir


In gas condensate reservoirs, when reservoir pressure drops below dew point pressure as production takes place at the surface, hydrocarbon liquids begin to form. The volume of the liquid formed in the reservoir increases as the reservoir pressure declines below dew point pressure. In most gas condensate reservoirs, the liquid saturation in the formation does not reach to the critical level for liquid flow to occur. Therefore, the liquid formed
as result of the pressure decline becomes trapped in the formation. The formation of the liquid in the reservoir causes the produced gas composition to change continuously leading to lower liquid recovery at the surface facilities. The formation permeability directly impacts the pressure in the reservoir and as consequence the amount of liquid that is trapped in a gas condensate reservoir. In this study, a gas condensate reservoir model was developed to investigate the impact of permeability and heterogeneity of the gas condensate reservoir on the liquid recovery. The constant compositional changes in the gas condensate reservoir require rigorous evaluation of the fluid system to determine the hydrocarbon recovery accurately.

A generic gas condensate reservoir model was constructed to simulate the liquid recovery and investigate the impact of permeability heterogeneity on the natural gas liquid recovery. Phase behavior model based on Peng-Robinson EoS equation of state (EoS) was developed by matching the results of a constant volume depletion (CVD) experiment obtained from a gas condensate reservoir in the Appalachian Basin. The phase behavior model was then incorporated into the reservoir model. The results of the investigation with the generic gas condensate reservoir model indicated that the permeability heterogeneity has a negative impact on the liquid recovery from a gas condensate reservoir.


Based on the analysis of the results obtained from this research study, the following conclusions can be made regarding the developed EoS model and the impact of the reservoir heterogeneity and properties on production from gas condensate.

  1.  An EoS fluid model was successfully developed and tuned via regression and was matched with the experimental data.
  2. The liquid recovery from a homogenous gas condensate reservoir is impacted by the permeability.
  3. Reservoir heterogeneity in a high-permeability gas condensate reservoir does not have significant impact on the liquid recovery.
  4. Reservoir heterogeneity in a low-permeability gas condensate reservoir negatively impacts the liquid recovery.
  5. As the severity of the reservoir heterogeneity (the number of layers with the reduced permeability) increases the liquid recovery decreases.
  6. The location of the reservoir heterogeneity (layers with the reduced permeability) does not have a significant impact on the liquid recovery reduction.