Daqing Oilfield has conducted a polymer flood pilot with higher polymer concentration value of 2000mg/L, exploiting its high viscoelasticity to further increase micro-scale oil displacement efficiency. Previous simulation matches for the pilot show that because the simulator being adopted has no capability to simulate the process mechanism of polymer elasticity, the production performance could not be matched when the residual oil saturation value of polymer flood was same with that for water flood.
In order to achieve a good history matching for the pilot, we have modeled polymer elasticity process mechanism based on the laboratory study results as that polymer elasticity process could decrease residual oil saturation value below that for water flood, therefore increase relative permeability of oleic phase, and incorporated the polymer elasticity process model into a in-house simulator, developing a new simulator to have capability to simulate the process mechanism of polymer elasticity. We have also conducted a series of core flooding to measure the residual oil saturation for high concentration polymer flood, obtaining the input parameters for simulation in polymer elasticity process model. During simulation history matching, the relative permeability curve is modified according to the different residual oil saturation value at different polymer elasticity.
By means of these measures, the production performance for the polymer flood pilot has been matched very well, suggesting that: (1) the high concentration polymer flood could not only expand the sweep efficiency, but also increase the micro-scale oil displacement efficiency, (2) the newly developed simulator is suitable to simulate the process of polymer elasticity, (3) we provide a useful simulation history matching method for viscoelasticity polymer flood.