Experimental Investigation on the Stability of Oil-Based Nitrogen Foam under Ultrahigh Pressure and Elevated Temperature

Abstract

Nitrogen flooding can effectively develop lowpermeability and tight reservoirs. However, because of the low viscosity and density of nitrogen, gas channeling easily occurs, resulting in low oil recovery. Oil-based nitrogen foam can be used to control gas channeling during nitrogen flooding, but the foam stability directly affects the application effect. In this paper, the performance of the foaming agent was optimized by compounding, and a stable oil-based nitrogen foam was successfully built, with a foam volume exceeding 400 mL and a half-life of liquid drainage exceeding 40 min. The foam stability under an ultrahigh pressure of 60 MPa and an elevated temperature of 80 °C were investigated by an ultrahigh pressure and ultrahigh temperature PVT system for the first time. The influence of base oil viscosity and interfacial tension on foam stability was examined. The experimental results showed that the foam stability improved when the pressure increased and worsened when the temperature rose. The foam stability was the best at 20 °C and 60 MPa, and the half-life of liquid drainage was nearly 4 h. The foam stability was the worst at 80 °C and 0.1 MPa, and the half-life was <1 min. The higher was the base oil viscosity, the better was the foam stability. Although the rise of pressure and temperature reduces the nitrogen−diesel interfacial tension, the interfacial tension is not the dominant factor affecting foam stability at elevated temperatures. This paper has a certain guiding significance for perfecting the stability mechanism of oil-based nitrogen foam under ultrahigh pressure and elevated temperature and better controlling gas channeling during nitrogen flooding in low-permeability and tight reservoirs.

Two-Dimensional Visual Analysis of Three-Phase Foam Flooding under Different Reservoir Conditions

“…This phenomenon occurred because after the internal pore throat of the model was plugged by TPF, the resistance of the subsequent injected fluid increased, which increased the model pressure. When the pressure reached the residual oil starting pressure, the remaining oil began to be displaced from the model, and the recovery factor was improved. − In summary, the TPF could plug and profile control of the pore throats by superimposing the effects of foam, particles, and gas. Therefore, the forward direction of the subsequent injected fluid was changed and the swept area of the fluid was increased.…”

Dynamic Features of Nonaqueous Foam in Fracture Systems

“…Their experimental results show that the stability of oil-based N 2 foam increases with the increase in pressure and decreases with the increase in temperature. 44 Oil-based foam exhibits excellent performance even under harsh experimental conditions.…”

“…In addition, they also investigated the performance of oil-based nitrogen foams under high-temperature and high-pressure conditions (80 °C and 60 MPa). Their experimental results show that the stability of oil-based N 2 foam increases with the increase in pressure and decreases with the increase in temperature . Oil-based foam exhibits excellent performance even under harsh experimental conditions.…”

Molecular dynamics simulation of the synergistic effect of a compound surfactant on the stability of CO2 oil‐based foam

“…The large electronegativity of the fluorine atom makes the bond energy of the carbon–fluorine bond large. Due to the protection of carbon–carbon bonds by fluorine atoms, fluorinated surfactants have high surface activity, stability, and chemical inertness and are hydrophobic and oleophobic 17–20 . Therefore, it is of great significance to study the influence of different surfactants on the stability of oil‐based foam.…”

“…Due to the protection of carbon-carbon bonds by fluorine atoms, fluorinated surfactants have high surface activity, stability, and chemical inertness and are hydrophobic and oleophobic. [17][18][19][20] Therefore, it is of great significance to study the influence of different surfactants on the stability of oil-based foam. In 1984, Raynolds et al studied an oil-based foam fracturing fluid with a fluorocarbon polymer as the foaming agent, which can achieve good stimulation.…”