Abstract
A giant mature light oil field under miscible WAG injection is a potential candidate for foam application to control gas mobility and reduce field gas – oil ratio (GOR). We conducted a feasibility study which comprised live oil corefloods at reservoir conditions and compositional numerical simulation coupled with a foam formulation. The objectives of this study were to identify critical variables and potential detrimental factors for the process implementation; and evaluate the GOR decrease due to foam application.
This feasibility study comprises an evaluation of the effect of foam on a field scale through numerical simulation, and the study of foam creation under reservoir conditions through coreflood experiments. We used a compositional simulator with an empirical foam implementation to predict the effect of foam in a mechanistic sector model of a high production area of the field. Simulation results show that foam is able to reduce field GOR by reducing the mobility of injected gas in high permeability layers. It became clear that the incremental oil production is strongly dependent on gas production limits; thus, foam application has to be coupled with overall field optimization.
Due to challenging field conditions for foam application, we performed an extended laboratory study. Static mixing experiments allowed surfactant compatibility limits in mixtures of formation and injection brines to be defined. In addition, a series of corefloods showed that foam can be successfully generated with a commercial alpha-olefin-sulfonate surfactant under reservoir pressure and temperature in presence of live reservoir oil, rich hydrocarbon gas and injection brine.
To our knowledge this is the first published feasibility study of foam application in a mature miscible WAG project including compositional simulation and live oil corefloods with rich hydrocarbon gas injection under reservoir conditions.
