Study On The Numerical Simulation Of Crosslinked Polymer Flooding

Currently, polymer flooding is a widely used EOR method. The class I and II reservoirs whose development conditions are good have successively carried out polymer flooding, and in many oilfields, polymer flooding has been completed, entering the water cut rising period. After polymer flooding, the reservoir heterogeneity becomes more serious, which causes polymer flooding not suitable to further enhance oil recovery. Additionally, because of the poor ability of temperature and salt resistance as well as the shortcomings of large consumption of the ordinary polymer, polymer flooding cannot be used for class III reservoir to improve oil recovery. In order to further enhance oil recovery after polymer flooding, and to expand the polymer flooding technology application range, reduce the polymer injection amount, improve economic returns, in recent years a new technology of oil displacement and profile control with crosslinked polymer is proposed.Based on the study of oil displacement and profile control mechanism with crosslinked polymer, a three-dimensional two-phase (oleic, aqueous) five components (oil, water, polymer, crosslinked polymer, crosslinker) mathematical model for crosslinkd polymer flooding is established. The model takes many physical-chemical phenomena of the crosslinked polymer system into consideration, such as viscosity, adsorption and retention, permeability reduction, inaccessible pore volumes, molecular diffusion and kinetics of crosslinking reaction for each component, and it mainly studies the mathematical model description of the kinetics of crosslinking reaction.For solving the model, firstly we adopt the normal IMPES method, namely the implicit pressure, explicit saturation and concentration method. Then it proposes a more efficient and more stable Douglas difference scheme which using the step-by-step reduced-order idea reached the purpose of accurately and efficiently solving the model. At the same time, it compares the solution efficiency of different algorithms. For convenient application, a crosslinked polymer flooding numerical simulation software was developed.In this paper, based on a heterogeneous model with five-point well type, it contrasts the crosslinked polymer flooding numerical simulation software and the commercial simulation software CMG through the sensitive research results of water flooding, polymer flooding and crosslinked polymer flooding, which shows that the proposed crosslinked polymer flooding model is correct, and verifies the reliability of the crosslinked polymer flooding numerical simulation software.Based on the above research results, selecting an actual oilfield block, we made the crosslinked polymer flooding parameters optimization study from both single and multiple aspects using the crosslinked polymer flooding numerical simulation software. The conclusions of the study are of great significance for the displacement mechanism study and pilot scheme design of crosslinked polymer flooding.