Rheological study of methane gas hydrates in the presence of micron-sized sand particles

Abstract

Natural gas hydrates, intricate crystalline structures formed by water molecules and small gas molecules, have emerged as a significant and globally impactful clean energy resource. However, their commercial exploitation faces challenges, particularly operational disruptions caused by sand-related blockages. Understanding the rheological properties of hydrate slurry, especially in the presence of micron-sized sand particles, is imperative for ensuring the flow assurance of subsea hydrate exploitation. This study extensively investigates the rheological properties of sand-containing hydrate slurries. The findings reveal that these slurries exhibit non-Newtonian fluid characteristics, including yield stress, thixotropy, and shear-thinning behavior. Solid-like elastic features are observed in sand-containing hydrate slurries before yielding, transitioning to viscous behavior after yielding. Even with a minimal amount of sand, both static yield stress and yield strain experience substantial changes, correlating with the increase in sand concentration. The research conclusively establishes the thixotropic nature of sand–hydrate slurries, where the viscosity decay rate is directly influenced by the shear rate. These insights aim to contribute comprehensively to the development of effective flow assurance strategies, ensuring the safe and stable operation of subsea hydrate exploitation.