Institute of Petroleum Engineering

Project: Characterization of 3-phase flow and Water Alternating Gas (WAG) Injection

“Three-phase flow occurs in many processes of great practical importance to reservoir engineering including in WAG (water alternating gas) and SWAG (simultaneous water and gas injection) processes. In such situations, accurate determination of relative permeability values to water, oil, and gas is crucial for prediction of the reservoir performance and estimation of oil recovery under these processes. Unfortunately, compared with two-phase relative permeabilities, measured three-phase relative permeability data are rare and prone to error. This results in considerable uncertainty in determining ultimate oil recovery for processes involving three-phase flow. This lack of measured three-phase relative permeability data is mainly due to significant difficulties in obtaining accurate three-phase laboratory data. Many models and correlations have been proposed for obtaining three-phase relative permeability values from two-phase ones, and some are available in commercial simulators. These are generally not based on sound physical understanding of three-phase flow and have been shown to be incapable of producing representative three-phase relative permeability data. This is, in particular, true for conditions involving mixed wettability, low-IFT and low oil saturations. Hysteresis and cyclic changes involved in the WAG and SWAG processes only add to the difficulties of the already complex problem of three-phase flow and its relative permeability determination.

At Heriot-Watt University we have been studying the physics of three-phase flow with particular attention to the WAG and SWAG processes since December 1997. In our well-equipped research laboratories we have high-pressure core facilities that have been used to carry out multiphase core flood experiments and measure fluid saturation profile within the core using x-ray techniques for many years.  We also have sophisticated high-pressure micromodel rigs that we have used over the past two decades to study the pore level mechanisms involved in multiphase flow including the depressurisation of waterflooded reservoirs and the WAG and SWAG processes accurately.  Immiscible and near miscible WAG and SWAG injection studies have been carried out successfully using models of different wettability.  Many pertinent flow parameters including the effects of trapped gas saturation and film flow and corner filament flow of oil and water have been observed, analysed and used to gather the pore scale physics for input to network modelling.”

WAG, 25K