Study On Microscopic Experimental Image Processing Methods And Displacement Mechanism Of Polymer Flooding

As China’s oil consumption increases yearly, requirements from enhancing oil recovery are increasingly higher. With the extensive application of polymer flooding, grasping the microscopic polymer flooding process and researching the mechanism of polymer flooding from a more detailed perspective has become a possibly effective way to further improve the recovery of polymer flooding. 2-D microscopic visualization experiments can intuitively observe microscopic fluid flow within the microscopic pore space and, relatively accurately, evaluate the effect of displacement by means of image processing.During the experiments, several kinds of etch models with different coordination numbers and pore-throat ratios are designed, in order to observe the effect of different pore-throat structure on polymer microscopic displacement mechanism. And, for reflecting the enhanced oil recovery mechanism of polymer flooding, each polymer experiment is contrasted with water flooding experiments.Extract the medial axis of the pore space by combining thinning algorithm and watershed algorithm. So that, the topology structure of the space can be relatively integrallty reserved and the medial axis can get better centering effect. When measure the radius of the space, it can be interfered by the noise of the space edge and the deviation of centering effect of the medial axis. The noise can be filtered by means of wavelet packet de-noising and the location of the bottle neck can be relatively accurate. During the segmentation of pore & space, nodes and necks can be used to find the center and edge of pores respectively. The space out of pore serves as throat.For the segmented pore space, we can count for coordination number, radius, area, water saturation and pore-throat ratio of different pores or throats via the breadth-first algorithm. On this basis, we define three indicators: microscopic sweep efficiency, displacement efficiency and microscopic recovery, for the evaluation of microscopic flooding effect.By contract the experiments of water flooding and polymer flooding we can find that, with the viscosifying mechanism and the lowering permeability mechanism, polymer can dramatically enhance the sweep efficiency of the water and eventually increase recovery efficiency of the polymer flooding. Although polymer can enhance the displacement efficiency of sweeping phase, its effect is limited. As the pore-throat rate increases, the effect of lowering the effective permeability of water, with the trapping of polymer, will be much more marked. As a result, the sweeping efficiency of the water phase can be enhanced. Also, the sweeping efficiency of the polymer flooding will be enhanced, as the increase of coordination numbers of pores. Accordingly, it enhances the microscopic recovery efficiency of the polymer flooding. For the different parts of the model, the rate of descent of the remaining oil saturation can be much faster and the saturation of residual oil can be much lower, if the part is much closer to the injection end. In the polymer flooding experiments, the rate of descent of remaining oil saturation is much faster and its descend range is much bigger, comparing to the water flooding. The saturation of remaining oil in the corner of the model can reach a much lower status in the polymer flooding experiments.