Effect of perforation shear on viscosity of polymer solution

¹ Oil Production Technology Institute, PetroChina Dagang Oilfield, Tianjin China
² Key Laboratory of Nano-chemistry, CNPC, Tianjin, China
³ The Fifth Oil Production Plant, PetroChina Dagang Oilfield, Tianjin, China
⁴ Exploration and Development Research Institute, Tuha Oilfield, CNPC, Xinjiang, China

Abstract

Polymer flooding is a tertiary oil recovery technology that is very suitable for the characteristics of China’s reservoirs. However, due to the fast flow rate of polymer solution in near-well zone, the shear effect of perforation blasthole and the compacted zone results in serious loss of polymer viscosity. In this paper, the polymer used in Dagang Oilfield is studied by simulation experiment through the shearing process of perforating holes, and the influence of different perforating parameters on polymer viscosity loss is analyzed, so as to provide theoretical basis for the optimization design of perforating technology in field test. The experimental results show that, the shear effect of perforation blasthole on polymer is not obvious, and the viscosity retention rate of polymer solution is greater than 96%. The size and shape of perforation blasthole have no effect on viscosity loss of polymer solution. The shear effect of compacted zone on polymer is obvious, and the viscosity retention rate of polymer solution is lower than 64% for the target block. The viscosity loss of polymer solution increases with flow rate at compacted zone, and the decrease of permeability can increase viscosity loss of polymer solution. The higher the polymer concentration is, the stronger the shear resistance is, while the higher the molecular weight is, the weaker the shear resistance is. It is suggested that perforation gun and perforation method with deep perforation depth and low compaction degree be chosen to reduce the flow rate at compacted zone and viscosity loss of polymer solution.