A numerical model to evaluate formation properties through pressure-transient analysis with alternate polymer flooding

A numerical pressure transient analysis method of composite model with alternate polymer flooding is presented, which is demonstrated by field test data provided by China National Petroleum Corporation. Polymer concentration distribution and viscosity distribution are obtained on the basis of polymer rheological model, considering shear effect, convection, diffusion, inaccessible pore volume and permeability reduction of polymer. Pressure analysis mathematical model is established by considering wellbore storage effect and skin effect. Type curves are then developed from mathematical model which have seven sections and parameter sensitivity is analyzed, among which the transient sections of low-concentration and high-concentration hydrolyzed polyacrylamides (HPAM) solution, high-concentration HPAM solution and crude oil show obvious concave shape on pressure derivative curve due to different viscosities of three zones. Formation parameters and viscosity distribution of polymer solution can be calculated by type-curve matching. The polymer flooding field tests prove that the three-zone composite model can reasonably calculate formation parameters in onshore oilfield with alternate polymer flooding, which demonstrate the application potential of the analysis method. © The Author(s) 2019.