Water-Locking and Its Release Effects in Argillaceous Silt Hydrate-Bearing Sediments by NMR Technology

This is the authors' abstract. We don't add key points for this paper.

During natural gas hydrate production in the Shenhu area of the South China Sea, water released from hydrate dissociation coupled with formation water, may induce water-locking, which blocks gas flow pathways and restricts productivity. To elucidate the mechanisms and potential remediation strategies, this study employed low-field NMR to systematically investigate the spatiotemporal evolution of water-locking in argillaceous silt hydrate reservoirs at initial water saturations of 50%, 70%, 90%, and 100%, and evaluated three antiwaterblocking agents (fluorocarbon types I and II, and nonionic surfactant III). Results show that water-locking predominantly occurs in micropores (T2 < 10 ms, pore size < 1 μm), with intensity increasing exponentially with saturation through four stages (end-face, mid-end combined, wide-area, and full-domain water-locking) identifying 70% saturation as the critical range for the tested material. Agents I and II perform effectively at low to moderate saturations, but their efficacy is severely limited at saturations ≥90% and under fully saturated conditions. Displacement pressure synergistically enhances agent performance, yet pressure alone is insufficient. This study clarifies the evolution mechanisms and application boundaries of chemical remediation, offering theoretical guidance for water-locking prevention and efficient hydrate development in the South China Sea.