A foam drainage technology used in gathering pipelines under complex topographical conditions

Liquid loading tends to happen easily in the gas gathering pipelines of gas fields. To solve this problem, the foam drainage technology which is commonly used in the wellbore is creatively applied to gathering pipelines. In this paper, the effects of foam drainage technology in hilly pipelines were explored by means of loop test, high-speed camera and data analysis. It is shown that there are two effects, i.e., drainage effect and drag reduction effect. Then, the influences of inlet condition, pipeline undulation angle and foaming agent concentration on the drainage and drag reduction effects were analyzed. It is indicated from test that compared with wellbores, the foaming degree of foam in pipelines will be influenced by the smaller undulation slope of pipelines. In this case, the foam quality is in the foam dispersion area or the foam interference area. However, the prerequisite to guarantee the effectiveness of the foam drainage technology in hilly pipelines is to drive the foam fluid into the stable foam zone. The drainage effect and drag reduction effect are better when it is in the working conditions with low liquid holdup, large dip angle pipeline and foaming agent concentration higher than the critical micelle concentration. It is suggested to change the original filling method on site, improve the injection rate of foaming agent, and take advantage of the effective means to improve the foam quality of fluids in hilly pipelines.