Reservoir behavior during boundary-dominated two-phase flow

In this work we determined the overall in situ composition path during depletion of different fluid types in the reservoir including gas condensates, volatile oil, and black oil reservoirs. A "tie-line relationship" concept was introduced to describe the overall compositional changes in the reservoir. The tie-line relationship can be used to determine the accuracy with which the fluid phase properties can be estimated from constant composition expansion experiments.;The applicability of laboratory experiments like the constant composition expansion and constant volume depletion to model reservoir performance was investigated. We developed alternative procedures that are more applicable to determine the average pressure-saturation relation for the entire depletion history of the reservoir. A single-cell simulator was developed to model the average reservoir performance and was tested with the results from a full compositional simulator. The results obtained from the single-cell simulator gave accurate prediction of the average reservoir performance where other laboratory procedures failed.;The pressure and saturation profiles in the reservoir were determined by developing the necessary equations and using the pressure-saturation relation from the single-cell simulator. The application of this method lead to the confirmation of the non-uniqueness of pressure-saturation relation throughout the reservoir and the saturation dependence on location.