Multiphase Compositional Well Flow Modelling: The Case of Injecting in Low Pressure Reservoirs

Abstract

Summary A steady-state compositional flow model has been developed for simulating the injection of condensed steam together with non-condensable gases (NCGs). All fluids are originated from a high enthalpy subsurface source, and after the recuperation of their energy in a geothermal power plant they must be reinjected back into the earth for controlling the emissions of greenhouse and toxic gases. For high content of NCGs in the initial geothermal fluid and reinjection of the totality of the fluids, the dissolution of the gas into the liquid phase is partial and a two-phase mixture must be injected. Targeting a low pressure (depleted) reservoir for the injection can result in a liquid column inside the well which is far for the surface in a depth of several hundreds of meters. The model considers a prototype well completion which overcomes these restrictions by injecting separately the water and the NCGs, and by mixing the two phases in a certain depth while ensuring the downward flow of the mixture.