Development and Evaluation of a High-Permeability Sealing Fluid for Open-Hole Sections of Horizontal Wells in Shallow Deepwater Formations

High-permeability channels in open-hole horizontal wells in shallow deepwater hydrate reservoirs are vulnerable to instability and plugging caused by hydrate dissociation, fines migration, and hydrate reformation. This study developed a composite sealing fluid integrating cementation strengthening, acid-containing microcapsules for proposed dissolution-assisted flow modification, and kinetic inhibition of hydrate formation. Laboratory experiments characterized temperature, pressure, and flow effects on dissociation. At 2.5 MPa, increasing temperature from −1 to 4 °C increased cumulative gas release over 600 min from 2305 to 24,452 mL, highlighting the need to preserve structural support during dissociation. Proppants and four inorganic binders were screened, and acid-containing microcapsules and a methacrylamide–N-vinylpyrrolidone–N-vinylcaprolactam terpolymer inhibitor were prepared. Glass-microsphere cement provided 1.95 D permeability at 0 °C and 11.7 MPa compressive strength. In separate dissolution tests, nominal 12% HCl dissolved 55.4% of seabed mud and 0.8% of quartz, providing a rationale for selective dissolution of susceptible mineral components. At 0.5 wt% and a reported subcooling of 7.2 °C, the inhibitor gave an induction time of 1813 min. The composite fluid remained pumpable for at least 90 min at 4 °C. The composite had a reported compressive strength of 13.5 MPa and retained 97.8% of its initial permeability during 4 h of laboratory flooding. Outlet particle concentration decreased from 390 mg·L−1 at 1 h to 146 mg·L−1 at 4 h. These preliminary results are limited by the 4 h flooding duration, incomplete formulation records, and unavailable replicate-level data. The proposed reconstruction mechanism, long-term reservoir performance, and field applicability remain unverified.