Abstract
To study the microscopic production mechanism of corner residual oil after polymer flooding, microscopic visualization oil displacement technology and COMSOL finite element numerical simulation methods were used. The influence of the viscosity and interfacial tension of the oil displacement system after polymer flooding on the movement mechanism of the corner residual oil was studied. The results show that by increasing the viscosity of the polymer, a portion of the microscopic remaining oil in the corner of the oil-wet property can be moved whereas that in the corner of the water-wet property cannot be moved at all. To move the microscopic remaining oil in the corners with water-wet properties after polymer flooding, the viscosity of the displacement fluid or the displacement speed must be increased by 100–1000 times. Decreasing the interfacial tension of the oil displacement system changed the wettability of the corner residual oil, thus increasing the wetting angle. When the interfacial tension level reached 10−2 mN/m, the degree of movement of the remaining oil in the corner reached a maximum. If the interfacial tension is reduced, the degree of production of the residual oil in the corner does not change significantly. The microscopic production mechanism of the corner residual oil after polymer flooding expands the scope of the displacement streamlines in the corner.
Highlights
The mechanism of polymer flooding involves adding a high-molecular-weight polymer to the injected water to increase the viscosity of the flooding phase, adjusting the water absorption profile, and increasing the swept volume of the flooding phase, thereby improving the ultimate recovery factor
Since polymer flooding in the Daqing Oilfield was put into industrial application in 1996, it has achieved remarkable technical and economic growth [1,2,3]
The tertiary oil recovery technology of the Daqing Oilfield has created a miracle in the history of world oilfield development with its large scale, high technical content, and good economic benefits [4,5,6,7]
Summary
The mechanism of polymer flooding involves adding a high-molecular-weight polymer to the injected water to increase the viscosity of the flooding phase, adjusting the water absorption profile, and increasing the swept volume of the flooding phase, thereby improving the ultimate recovery factor. Since polymer flooding in the Daqing Oilfield was put into industrial application in 1996, it has achieved remarkable technical and economic growth [1,2,3]. In 2002, the annual oil production from polymer flooding in the Daqing Oilfield exceeded 10 million tons. The tertiary oil recovery technology of the Daqing Oilfield has created a miracle in the history of world oilfield development with its large scale, high technical content, and good economic benefits [4,5,6,7]. Polymer flooding technology has become an important technical support to maintain the continuous high production and high water cut of the Daqing Oilfield and improve the oilfield development level in the later stage [8,9,10]. After injection into the oil layer, the polymer undergoes thermal degradation and further hydrolysis under high-temperature conditions, which destroys the stability of the polymer and greatly reduces its oil displacement effect [11,12,13]
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