Numerical Modelling on Dynamic Adsorption of Viscoelastic Polymer in Near Wellbore Conditions by Population Balance Method

Abstract

Significant injectivity loss during polymer injection measured particularly in the near wellbore has been reported. This challengeable issue is identified as bridging polymer adsorption caused by the bridging of pore throats via macromolecular polymers previously stretched under elongational flow conditions occurring in the vicinity of the injection well. There has been no attempt to describe this phenomenon by numerical simulation model because the conventional Langmuir isotherm widely used in reservoir simulation is not able to contain this bridging-adsorption observed in complicated polymer flooding experiments. This study focuses on the development of numerical model for the bridging adsorption by implementing population balance theory and performs extensive simulation verifications with small core-scale reservoir rock. To reflect distinct flow condition to induce bridging adsorption, the rate of bridging adsorption is established by considering the relationship of expanded polymer under shear force and narrow pore size. To verify the feasibility of new model, simulation results are compared with experiment output reported in previous studies. The simulation results indicate that a considerable amount of bridged polymer can be generated in the low permeability cells only if the polymer solution is exposed to high shear velocity related with shear rate. This is in accordance with a number of previous experimental reports. In addition, the mechanism to induce permeability reduction is totally different from that of conventional Langmuir's isotherm which is widely incorporated in commercial simulators. With buildup of bridging-polymer, the adsorption model can enable the application of numerical simulation targeted at chemical EOR process to be wider.