The Flow Field Simulation And Experimental Study Of Polymer Flooding Helical Static Mixer

Currently, Enhanced Oil Recovery(EOR) technology has been widely used in various domestic oilfields. Polymer injection displacement method has become the main oil way of EOR because of its high oil recovery. Polymer inj ection displacement means injecting the polyacrylamide(PAM) liquor and water after mixing in the static mixer into the bottom of the well to exploit oil. Oil displacement efficiency of this process depends on the viscosity of the polymer, the higher the viscosity, the higher the oil displacement efficiency. Because of the strong shearing to the polymer, conventional static mixer will make higher viscosity loss rate, resulting in displacement efficiency decrease, thereby affecting the oil production. Based on the mixing mechanism and PAM solution viscosity analysis of the static mixer, this paper identified factors that influence solution viscosity changes, including static mixer structure(unit rotation) and structure parameters(unit pitch, unit spacing), the initial flow velocity of the fluid. On this basis, the paper optimized these three aspects by computational fluid dynamics simulations, gave two structure-improved low shear static mixer. The optimization was proved by experiments, which means the viscosity loss was controlled. The details of this paper are as follows:First analyzed the mixing mechanism of static mixer, obtained the pressure distribution and velocity distribution of the fluid in the static mixer. Then the paper elaborated common polymer solution viscosity model, established PAM solution viscosity model according to it’s own characteristics based on the Carreau equation, and identified that start viscosity loss control optimization from the static mixer structure, structural parameters and initial velocity.Then by means of computational fluid dynamics simulation, using advanced CFX software, the paper compared the performance of conventional static mixer and the new spiral static mixer, simulation results show that the latter is better performance. On this basis, the paper expanded spiral static mixer optimization. The effect of static mixing structure parameters and initial velocity of fluid mixing uniformity and its entrance pressure was studied, the effect relationship was derived. The static mixer structure parameters were preliminarily optimized according to the simulation results.Using PAM solution viscosity model, the influence of static mixer structure parameters and initial velocity of fluid on the outlet fluid viscosity was analyzed respectively by simulation. The effect relationship was derived and the structure parameters were further optimized based on the simulation results. On the basis of the two optimization results, the structure of spiral static mixer was improved, two different types of static mixer unit were designed, and the mixing of them was simulated. Simulation results indicate that fluids were mixed uniformly through the two static mixer, and the viscosity of the mixture at the outlet of the latter was higher than the former, which means that the second structure is better.Finally, set up experimental device, to verify the viscosity loss control effect of the optimized spiral static mixer. The results show that two optimized static mixer viscosity loss values are lower than the conventional static mixer in ensuring the mixing uniform. The viscosity loss of the two agreed well with the simulation results, which verified the correctness of the theory and simulation analysis to some extent.