Optimization of Polymer-surfactant Flooding Parameters in Maling Jurassic Low Permeability Reservoir

The low-permeability Jurassic reservoir in Changqing Maling has been in the middle and high water cut stage after long-term development of water injection. In order to improve development efficiency and further explore a new way to enhance oil recovery of the reservoir, a significant development test and a polymer-surfactant flooding study were carried out in the Maling Beisan area in 2011. Compared with other polymer-surfactant flooding reservoir of PetroChina, Jurassic reservoir in Beisan area had relatively low permeability and high salinity of formation water and injected water, which puts forward higher requirements on the injectivity and salt resistance of the binary system. At the same time, the viscosity of the formation crude oil was low, and the viscosity of the polymer required to achieve the optimum fluidity ratio was relatively low, which is an important advantage of implementing the binary flooding in the reservoir. In this paper, hydrophobic associating polymer and betaine surfactant were selected through laboratory experiments. According to the experimental data, numerical simulation technology was used to analyze and optimize the influence factors, including injection speed, injection-production ratio, slug size, slug polymer, and surfactant concentration. Finally, the development index of binary flooding was predicted. The results show that the optimized polymer-surface system had good injectivity and high formation compatibility. Through on-site differential control measurement of injection and production, the recovery was enhanced significantly. This study had guiding significance for the production of polymer-surface flooding in the similar reservoirs.