Effect of Dynamic Surface Activity of Surfactant on Performance of Foam for Gas Well Deliquification

Abstract

Abstract As gas well flow rate decreases, liquid loading occurs in the wellbore and reduces the gas productions. Among various artificial lift methods for liquid removal, foam is one of most economic and widely used method. Foam process in gas deliquification is different from foam applications in drilling fluid and fracturing fluid. The foam for gas well deliquification is generated by gas flow in the tubing. The liquid is accumulated in the thin film of foam and plateau border area, which reduces the overall density of the fluid and unload liquid at lower gas flow rate. In this foaming process, a dynamic diffusion of surfactant to the interface is involved. Dynamic surface and elastic properties of foam are very important parameter to success in foam deliquification. We hereby studied the dynamic surface properties of the foaming surfactant by maximum bubble pressure tensiometer at high flow rate/frequency. The different molecular structures of surfactants were studied and compared. The dynamic surface activity is correlated well to performance of liquid unloading with foam column test method, while equilibrium surface activity obtained by Wilhelmy plate tensiometer is not correlated. Surfactant concentration can be also optimized by evaluation of its dynamic surface activity. For the foam evaluation test method, blender test is also widely used to in the industry to evaluate foam in gas well deliquification. It was found that the two foam generation test methods gave different results when they were compared with the performance of different foamers. The blender foam test is more static, and is not simulated well to the real foam generating process in the gas well. Hence, dynamic surface activity of surfactant by maximum bubble pressure tensiometer gives a high throughput screening parameter to predict performance of different foamers for liquid deliquification.