Defoaming Characteristics of Crude Oil Foams Containing CO₂

Abstract

After gas-channeling happening in CO₂ flooding, the content of CO₂ in the produced fluid will increase gradually, which may cause a more serious crude oil foaming problem and harm the operation of separators. At present, little research has been done on crude oil foams, and the defoaming internals are often selected and installed according to experience. In this paper, the collapse characteristics of crude oil foams and the influence of defoaming net on it are studied. CO₂ saturated crude oil is made by a pressure piston vessel and then sprayed through a tube into a graduated cylinder to produce foam and the collapse process of foam is recorded. The process of crude oil flowing through the defoaming net is simulated by moving the defoaming net through the foam at a certain speed. The effects of function time of net, mesh number, thread diameter, and number of layers are studied. The experimental results show that the process of collapsing is composed of three stages: foam drainage, foam drainage with coalescence of bubbles, and coalescence of bubbles. The best function time is 51 s after the end of spraying, and it shows that defoaming net has a better effect on the foam with less liquid in the second stage. Defoaming effect is better when there are more layers of net, the collapsing time of foam is shorten by 14.6% with the using of 4 layers of net. It is found that the net with bigger mesh number has a much better defoaming effect than the net with smaller mesh number. The material of net and thread diameter also have some influence on defoaming effect.