Petroleum Reservoir Characterisation for Fluid with Yield Stress Using Finite Element Analyses

Abstract

Abstract Flow behaviour of Newtonian fluids in different discrete fracture geometry orientations has been studied by several researchers. Not all reservoir fluids can flow easily with its inherent energy, and producing such fluids can be very difficult. Some forces, for example yield stress, greater than a threshold value need to be exceeded to achieve flow of these fluids. The flow channel can either be through interconnected pore spaces or discrete fractures. Because of variation observed in geometry of real fracture systems in naturally fractured reservoir, NFR, flow computation of these fluids in fractured media is full of difficulty. This paper reports the flow behaviour of Bingham plastic and Herschel-Bulkley fluids in discrete fractures oriented at θ = 0°, θ = 20° and θ = −20° represented on a 1m dimensioned fractured block using finite element analyses. Each fracture orientation has its associated pressure gradients which result in flow of fluids. Our approach is the discrete fracture network (DFN) where fluid flow into the wellbore is only through fractures, which are surrounded by an impermeable rock matrix. Flow through fractures in naturally fractured petroleum reservoir has been observed to contribute to overall production of fluid from the reservoir through the wellbore to the surface. The results obtained from similar orientations of discrete fracture geometry for Bingham plastic and Herschel-Bulkley fluids are compared to results obtained for power law and Carreau models by Fakinlede et al. (2011). Results comparison is later extended to Newtonian fluids. The flow of yield stress fluid has applications in the in-situ recovery of bitumen from oilsands reservoir since the bitumen will not flow unless the yield stress is exceeded.