Development and Application of Slim-Hole Soluble Bridge Plugs in Fracturing Operations of Deformed Casing Wells

In the Sichuan Basin, deep shale gas reservoirs are characterized by greater burial depth (≥3500 m), higher formation temperatures (130–150 °C), and higher fracture pressures (120–130 MPa). During fracturing operations, frequent occurrences of casing diameter reduction prevent conventional bridge plugs from being effectively run downhole, anchored, and sealed, thus impacting normal fracturing operations. Therefore, structural design, material optimization, processing trials, and laboratory testing were conducted for small-diameter dissolvable bridge plugs. Field trials and applications were subsequently carried out in deep shale gas wells with casing deformation in regions such as Luzhou and western Chongqing. Research results indicate that: (1) The designed “helical” dissolvable metal seal structure achieves a maximum unilateral expansion of 27.15 mm, resolving the expansion-induced fracture problem inherent in conventional barrel-shaped seals. This meets the sealing requirements for isolating large annular gaps with small-diameter tools; (2) The combined anchoring structure featuring a “two-stage cone + segmented slip” design incorporates progressive embedding technology. This solves the insufficient expansion volume limitation of single-cone structures and fulfills small-diameter anchoring requirements in ultra-large annular environments; (3) Field applications demonstrate excellent plug running performance, reliable pressure-bearing sealing integrity, and rapid post-operation dissolution. This enables efficient stimulation in deep shale gas wells with casing deformations.