Popularization and application of the capillary foam deliquification technology in horizontal wells with low pressures and low liquid flow rates: A case study on middle–shallow gas reservoirs in the Western Sichuan depression

Abstract

The application effect of the foam deliquification technology in horizontal wells is poor because the foaming agent fails to reach the target location. In view of this, the adaptability of the capillary foam deliquification technology in the Western Sichuan Gas Field in the Sichuan Basin was analyzed from the aspects of gas flow rate, liquid flow rate and casing program of gas wells, and the design of injection depth and the selection of capillary size, tool string parameters (the maximum length and the minimum counterweight) and foam deliquification parameters (foaming agent type selection, ground injection concentration and rate) were optimized. Then, a standardized capillary operation process was developed. Finally, a field application test was carried out. And the following research results were obtained. First, the capillary foam deliquification technology has a popularization potential in the horizontal wells of middle–shallow depth, low pressure and low liquid flow rate, but it is not suitable for the wells with too low gas flow rate, too high liquid flow rate or too high condensate content. Second, the well deviation angle at the injection depth shall be between 70° and 80°, the selection of capillary size shall satisfy the requirement for tension strength by the well depth, the foam deliquification parameters shall be optimized based on the specific well conditions and the liquid loading characteristics, and the capillary operation shall comply with the standardized process. Third, by the end of July 2017, the capillary foam deliquification technology had been successfully applied in 9 horizontal wells in the Western Sichuan Gas Field with a cumulative gas increment of 295 × 104 m3. Fourth, 4 supporting technologies of the capillary foam deliquification are formed, including capillary sticking prevention, integrated agent injection and pressure measurement, combined cleaning and deliquification and capillary wellhead suspension. In conclusion, the capillary foam deliquification technology provides a technological support for the deliquification and production stabilization of horizontal wells with middle–shallow depth, low pressures and low liquid flow rates in the Western Sichuan Depression, and also provides technological reference for the deliquification of horizontal wells in the similar type of gas reservoirs.