Key Factors and Changing Rules of Foam Stability in Gas Well Field.

In the process of natural gas production using foam to lift liquid, there exists obvious difference in the requirements of foam stability between wellbores and gathering & transportation systems. To ensure the effect foam dewatering of gas wells and highly efficient defoaming and gas-water separation on surface, it is meaningful to investigate the influencing factors of foam stability comprehensively. In this paper, a tight gas block in China which adopted foam for liquid lifting was taken as an example. It was researched that the key influencing factors and changing rules of foam stability through static and dynamic experiments on foam stability, chemical defoaming experimets and field tests. The results showed that the concentration of foaming agent used in the field, namely UT-11C, had the most significant effect on the foam stability followed by the salinity, temperature and PH value. Foam stability was also can be improved with higher pressure. Results of chemical defoaming experiments showed that even under the optimal defoaming concentration, mamely 1%, it also took about 20 minutes to completely eliminate the foam. Combined with the laboratory results and the statistical analysis of the water production in field, the optimal injection amount of foaming agent was calculated, which makes the dosage reducing by 40%. And the effective was validated by field test. This work not only ensures the high production of gas wells, but also takes the economy into account, having a strong guidance for the production of natural gas fields. [ABSTRACT FROM AUTHOR]