Perspective on the oil-dominated gas hydrate plugging conceptual picture as applied to transient Shut-In/Restart

Journal Article · 25 May 2022 · Fuel

DOI: https://doi.org/10.1016/j.fuel.2022.124606 · OSTI ID:1984245

Pickarts, Marshall A. ^[1]; Ravichandran, Sriram ^[2]; Ismail, Nur Aminatulmimi ^[2]; Stoner, Hannah M. ^[2]; Delgado-Linares, Jose ^[2]; Sloan, E. Dendy ^[2]; Koh, Carolyn A. ^[2]

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1. Colorado School of Mines, Golden, CO (United States); Colorado School of Mines
2. Colorado School of Mines, Golden, CO (United States)

Gas hydrate formation is rarely an issue during continuous production conditions. Unplanned and/or extended shut-downs comprise the majority of scenarios where overlapping concern and uncertainty for gas hydrate blockages exist. To date, most experimental studies and theoretical analysis of gas hydrate formation derive from the steady-state conceptual picture. Yet, significant distinctions induced by phase separation and prolonged cooling suggest an altered conceptual picture is required for transient shut-in/restart operations. To address this outstanding issue, this work presents a conceptual picture for the base case of a non-surface active hydrocarbon undergoing cold restart without enacted mitigation efforts. First, phase separation upon shut-in leads to the localization of gas hydrate ingredients due to fluids density differences and pipeline inclination. Cooling to the seafloor temperature, then, induces gas hydrate film formation at the hydrocarbon interface and maximizes subcooling, resulting in rapid and confined gas hydrate growth occurring upon restart. Furthermore, this ultimately leads to plugging dominated by the deposition of porous, low conversion gas hydrate masses. Direct visual observations and results from Raman spectroscopy, hydrate contact angle and film growth, micromechanical force apparatus, rocking cell, and flow loop studies support the mechanisms outlined within each step. Similar to the influence provided by the original Colorado School of Mines steady-state conceptual picture that was introduced about 15 years ago, this transient counterpart builds a foundation that could inspire new directions of hydrate research and analysis in areas where uncertainty abounds.

• Research Organization: Colorado School of Mines, Golden, CO (United States)
• Sponsoring Organization: USDOE
• Grant/Contract Number: FE0031578
• OSTI ID: 1984245
• Journal Information: Fuel, Journal Name: Fuel Vol. 324; ISSN 0016-2361
• Publisher: ElsevierCopyright Statement
• Country of Publication: United States
• Language: English