Effects of Oil Viscosity and the Solution Gas–Oil Ratio on Foamy Oil Flow in Solution Gas Drive

Abstract

The anomalously high recovery of solution gas drive in some heavy oil reservoirs has been associated with foamy oil. The effects of external factors such as temperature, permeability, and the pressure depletion rate on foamy oil flow have been studied sufficiently, but few studies are available on the effect of heavy oil itself. In order to investigate the effect of oil viscosity and the solution gas–oil ratio on foamy oil, 11 tests of solution gas drive through a sandpack were carried out in this work. The results show that a typical foamy oil solution gas drive exists in three stages, which are the oil phase expansion stage, the foamy oil flow stage, and the oil–gas two-phase flow stage. As the oil viscosity decreases, the foamy oil flow stage shortens, resulting in reduced recovery of this stage significantly. In the experiment with an oil viscosity of 200 mPa·s, foamy oil flow was not observed. A lower limit of oil viscosity should exist for steady flow of foamy oil, which is considered to be approximately 600 mPa·s according to the experimental results. As the solution gas–oil ratio increases, the oil recovery first increases and then decreases. Foamy oil flow could be observed clearly when the solution gas–oil ratio was between 10 and 26 Sm 3 /m 3 , which indicates that there is an optimal range of solution gas–oil ratios for foamy oil solution gas drive. The test with a solution gas–oil ratio of 35 Sm 3 /m 3 showed that oil–gas two-phase flow followed the oil phase expansion stage as a result of the production of a quantity of gas, which illustrates that excess solution gas is unbeneficial to foamy oil flow on the contrary. The investigation revealed that oil viscosity and the solution gas–oil ratio are essential for foamy oil flow, which provides theoretical support for foamy oil production.

Stability Analysis of Anionic-CO2-Soluble Surfactant Di-(2-ethylhexyl) Sodium Sulfosuccinate-Assisted Oily Foam Based on Statistical Analysis of Bubble Dynamic Characteristics

“…Regarding the stability of oily foam, previous studies have indicated that it is primarily assessed through measurements of foam half-life (the time it takes for a foam’s volume to reduce to half of its initial volume after formation) and maximum foam volume. − Factors such as bubble radius, bubble morphology, foam comprehensive index, and others have not been explored. Therefore, there is a need for a comprehensive evaluation method.…”

“…The principle of enhancing heavy crude oil recovery with oily foam is akin to gas dissolution drive. 7 It involves gas dissolving into crude oil, leading to volume expansion, reduced density, improved flow, increased relative permeability, and elevated reservoir pressure. These factors collectively enhance heavy crude oil recovery by improving flow and mobility, making it easier to extract the oil from the reservoirs.…”

“…These bubbles grow and expand, rapidly driving the crude oil toward the wellbore. The principle of enhancing heavy crude oil recovery with oily foam is akin to gas dissolution drive . It involves gas dissolving into crude oil, leading to volume expansion, reduced density, improved flow, increased relative permeability, and elevated reservoir pressure.…”