Technology of annular channeling plugging under pressure for low-temperature shallow gas wells

The use of conventional cement-based plugging agents in plugging channeling in annular space often leads to issues such as plugging failure, difficulty in solidification in low-temperature shallow layers and inter-well channeling. To address these challenges, the technique of annular space channeling plugging under pressure including the procedure of dredging, plugging and sealing was proposed. Initially, the gas emission volume was determined through a drainage method to assess the leakage risk of combustible gas in the Xujiahe formation. For situations close to the combustible risk level, a gas-tight and anti-channeling solid-phase discrete cement slurry system was employed for sealing, while for situations below the combustible risk level, a micro-expansion and low-friction cement slurry system was employed for sealing. Subsequently, a nanoscale preflush displacement fluid with enhanced core imbibition efficiency was used to dredge the Penglaizhen formation and shallow layers. Then, a high-strength gel was injected to shape a 2-meter-thick gas-proof isolation wall to temporarily block the interlayer gas channel. Finally, an ultrafine crystal whisker expanding cement slurry was employed to stabilize the gas channel, complemented by a high-strength oil-soluble resin cementing fluid to seal and solidify the channeling pathways. Field tests in three wells in the Sumatou block indicate that, after successful sealing of the Xujiahe formation, the injection of nanoscale silica dioxide preflush displacement fluid into the Penglaizhen formation and upper shallow layers reduces the injection pressure in the Penglaizhen formation by 2 MPa to 3 MPa. After treatment, the annular pressure dropped from 1.6 MPa to 0.0 MPa, effectively resolving the annular space pressure bearing issue in the three wells. This technology can serve as a technical reference for annular space treatment under pressure in similar wells.