Nitrogen foam technology for removing soft plugging in gas wells and its application

In the middle and later stages of gas well production, "soft plugging" issue that commonly occurs in the production string has become a key challenge restricting productivity. This kind of plugging is mainly formed by the deposition of a mixture of condensate oil, oil sludge sand, and residual foaming agents under low flow rate conditions. To address this problem, the concept of "soft plugging" is proposed, and its formation mechanism is revealed. And then, the main dynamic production behavior and hazards after plugging are identified, providing an important basis for recognizing such gas wells. Based on the low density and high sand-carrying capacity of nitrogen foam fluid, a "foam density - flow rate" cooperative control model is established. By optimizing the flushing parameters, a balance is achieved between the sand-carrying efficiency of nitrogen foam and reservoir protection. Field tests in 8 wells (6 shale gas wells and 2 tight sandstone gas wells) demonstrates a 100% success rate in removing plugging, the gas production of single well is increased by 3.3 times, and the validity exceeds 90 days. Research indicates that nitrogen foam flushing technology can provide an economical and efficient solution for the stable production of gas wells in the middle and later stages, with significant potential for broad application.