Study On Experimental And Numerical Simulation Of Ferrofluid Flooding

Currently most of the oil fields in China have entered high water-cut stage and becomes more diffcult to further enhance oil recovery.The key issues mainly involve figuring out displacement fronts and enhancing sweep area.This article proposes a new flooding technology by the use of the ferrofluid as the displacing fluid in this background.The ferrofluids flow in the formation will change the original magnetic field and the displacement front position can be monitored by collecting the magnetic anomaly signal.Furthermore,the ferrofluid flooding direction can be controlled by the external magnetic field arranged based on the dymamic displacement condition to increase sweep area and enhance oil recovery.In terms of physical experiments,experimental devices are designed for the first time to study ferrofluid flooding in laboratory conditions;The single-phase ferrofluid pressure in a twodimensional plate influenced by a external magnetic field is measured.The magnetic force expression is valdiated by comparing the measurement results with the calculation results;Finally,the two-dimensional sand-filled model is applied to study the ferrofluid flooding process in heterogeneous and fractured porous media and the experimental results are compared with later numerical simulation results.In terms of numerical simulation,an improved magnetic field energy functional expression in consideration of ferrofluid magnetization process and different magnetic sources is proposed based on the Maxwell equations.Then the magnetic energy functional equations are discretized based on the finite element method and the corresponding calculation format is constructed to establish magnetic field numerical calculation method.Next,the expression of ferrofluid magnetic field force under the influence of external magnetic field is derived based on the the molecular current model and is substituted into the motion equation.A single-phase ferrofluid injection-production problem in heterogeneous and fractured porous media is analyzed based on finite element method and the algorithm is valdiated by comparing with analytical solution.Moreover,the two-phase ferrofluid flooding problem in both heterogeneity and fracture porous media at the laboratory scale is studied based on the finite volume method.And the displacement efficiency is compared with water flooding efficiency.The enhance oil recovery mechanisms of ferrofluid flooding in macroscale are analyzed and the numerical methods for simulate the ferrofluid flooding are formed.Finally,the magnetic field and seepage field are coupled together and based on the magnetic anomaly signal during the flooding process,the displacement front is monitored and the reservoir heterogeneity and fracture characteristics are analyzed.A set of integrated monitoring and enhance oil recovery technology based on ferrofluid flooding is proposed.The interference factors of oil displacement,such as magnetic field strength,magnetic properties of ferrofluid and the time of applying external magnetic field are studied.The research results show that ferrofluid can act as both a “tracer” to locate the displacement front and a controllable displacing fluid to improve sweep area in the flooding process and provides a new and potential technology for the further improvement of oil recovery for oil fields in China.