Rheological Model and Transition Velocity Equation of a Polymer Solution in a Partial Pressure Tool

Abstract

In order to solve the problem of the low production degree of oil layers caused by an excessively large permeability difference between layers during polymer flooding, we propose partial pressure injection technology using a partial pressure tool. The partial pressure tool controls the injection pressure of a polymer solution through a throttling effect to improve the oil displacement effect in high- and low-permeability reservoirs. In order to analyze the influence of the partial pressure tool on the rheological property of the polymer solution, a physical model of the tool is established, the rheological equation of the polymer solution in the partial pressure tool is established according to force balance analysis, the transition velocity equation for the polymer solution is established based on the concept of stability factor, and the influence of varying the structural parameters of the partial pressure tool on the rheological property of the polymer solution is analyzed. The results show that the pressure drop of the polymer solution increases with the decrease of the front groove angle of the partial pressure tool (from 60° to 30°), reaching a maximum of 1.77 MPa at a front groove angle of 30°. Additionally, the pressure drop of the polymer solution increases with the decrease of the outer cylinder radius (from 25 to 24 mm), reaching a maximum of 1.32 MPa at a radius of 24 mm. However, the apparent viscosity of the polymer solution before and after flowing through the partial pressure tool does not change for any of the studied parameters. These research results are of great significance to research on partial pressure injection technology and enhanced oil recovery.

Experimental and numerical simulation study on the flow characteristics and optimization of structural parameters of displacement agent in partial pressure tools

“…This is because of the influence of the shape of the flow channel, which produces jet flow at the minimum flow channel. When the fluid enters the expanded area of the flow channel, the flow channel loses its function of restricting flow due to the inertia of the fluid, and a certain degree of free flow develops, resulting in the change of flow direction . As the polymer solution flows in a variable cross section, it is a process of contraction before expansion and changes periodically, so the velocity and streamline of the polymer solution in the partial pressure tool change periodically.…”

“…When the fluid enters the expanded area of the flow channel, the flow channel loses its function of restricting flow due to the inertia of the fluid, and a certain degree of free flow develops, resulting in the change of flow direction. 38,[55][56][57] As the polymer solution flows in a variable cross section, it is a process of contraction before expansion and changes periodically, so the velocity and streamline of the polymer solution in the partial pressure tool change periodically. Figures 11 and 12 show the pressure nephogram and pressure change curve of the polymer solution in the partial pressure tool when the flow rate is 10 m 3 /d.…”

“…Using the principle of the labyrinth seal, a partial pressure tool with a throttling groove structure was developed. Figure shows a three‐dimensional structure diagram of the partial pressure tool.…”

“…In order to study the flow characteristics of the polymer solution in specific tools, the RNG k‐ε model was used in the numerical simulation. This model is a semi‐empirical formula, which is mainly based on turbulence kinetic energy and diffusivity.…”

Effect of a Partial Pressure Tool on Improving the Heterogeneous Oil Recovery and Polymer Solution Microstructure

“…Corresponding research has been carried out in order to study the effectiveness of the partial pressure tool in enhancing oil recovery. Huang et al established the physical model of the partial pressure tool and the rheological equation of the polymer solution in the tool using force balance analysis and then analyzed the influence of the partial pressure tool structural parameters on the rheological properties of the polymer solution . Huang et al studied the flow characteristics of the polymer solution in the partial pressure tool by finite element analysis and verified the results of the numerical simulation through laboratory experiments.…”