Research On The Effects Of Microscopic Pore Structure Parameters On Oil Displacement Efficiency Of Polymer Flooding

With the increasing of water content of water flooding in oilfield, economic value of water flooding decreases year by year. As the tertiary oil recovery technology, polymer flooding can effectively enhance oil recovery. The oil reservoir is very complex porous structure, microscopic pore structure and parameters directly affect the polymer flooding efficiency. The research on the flow of polymer in reservoir in the microscopic pore scale is an important means to reveal the flow mechanism. Clear and definite the effects of microscope pore structure parameters on polymer flooding efficiency can provide a theoretical basis for polymer solution about how to adapt to all kinds of reservoir and how to improve displacement efficiency.In this paper, the method of establishing digital core is proposed on base of the distribution of pore throat radius frequency which is obtained by the pressing mercury experiment of the artificial core and the coordination number which is got by CT scan. The permeability of natural core is calculated using the digital core and compared with the real value, the correctness of construction of digital core is verified. The change of the different fluid flow in pore is determined using the principle of least resistance. Combined with similar principles of hydropower, seepage simulation of dynamic process of the water flooding and polymer flooding is achieved. The effects of viscoelasticity, inaccessible pore volume, and adsorption on the displacement efficiency of polymer are studied respectively. Consider the above several characteristics, the pore structure parameters are changed in order to study the impact of these parameters on the recovery of polymer flooding. Analyse the extent of influence by using the theory of grey correlation.The results showed that: Considering elastic properties of polymer solution, polymer flooding displacement efficiency increases, and with the increasing of elasticity, the displacement efficiency of polymer solution increases; Considering inaccessible pore volume, the value of polymer flooding displacement efficiency increases. Adsorption properties of polymer solution make the polymer flooding recovery lower, with the increasing of molecular weight and the concentration of polymer solution, the decreased value increased; With the increasing of pore throat radius, shape factor, the value of the recovery by polymer flooding increases; With the increasing of the coordination number, the chance of remaining oil formation decreases, the oil displacement efficiency of polymer flooding increases gradually; With the increasing of the pore throat ratio, the value of the recovery decreases; With the increasing of the ratio of hydrophilic throat, swept volume of polymer flooding gets bigger and oil displacement efficiency increase; The coordination number and throat radius of value has a greater influence on the increased value of recovery, and the influence degree of the coordination number is highest, shape factor and wettability also belongs to the important influence parameters but the influence degree of shape factor and wettability is smaller than coordination number and throat radius. The influence of pore throat ratio on polymer recovery is lowest.