Simulation of the effect of hydrate adhesion properties on flow safety in solid fluidization exploitation

Abstract

During the solid fluidization exploitation of marine natural gas hydrates, the hydrate particles and cuttings produced via excavation and crushing are transported by the drilling mud. The potential flow safety issues arising during the transport process, such as the blockage of pipelines and equipment, have attracted considerable attention. This study aims to investigate the impact of hydrate adhesion features, including agglomeration, cohesion, and deposition, on the flow transport processes in solid fluidization exploitation and to provide a reference for the design and application of multiphase hydrate slurry transport in solid fluidization exploitation. We established a numerical simulation model that considers the hydrate adhesion properties using the coupled computational fluid dynamics and discrete element method (CFD-DEM) for the multiphase mixed transport in solid fluidization exploitation. An appropriate model to simulate the adhesion force of the hydrate particles and the corresponding parameter values were obtained. The conclusions obtained are as follows. Under the same operating conditions, a stationary bed is more likely to form in the transport process due to the hydrate adhesion forces; adhesion forces can increase the critical deposition velocity of the mixture of hydrate particles and cuttings. Hydrate adhesion lowers the height of the solid-phase moving bed, while the agglomeration and cohesion of particles can intensify the aggregation and deposition of hydrate debris and cuttings at the bottom of the pipe. These particles tend to form a deposit bed rather than a moving bed, which reduces the effective flow area of the pipeline and increases the risk of blockage.

Keywords

Solid fluidization exploitation / Critical flow velocity / Height of the moving bed / Adhesion properties / CFD-DEM

Acknowledgment

This study was supported by the National Natural Science Foundation of China under the projects “Characteristics of argillaceous-silt natural gas hydrate reservoirs in the South China Sea and the gas-liquid-solid multiphase heat and mass transfer mechanisms” (U19B2005) and “Study on the decomposition mechanism and transportation rules of natural has hydrate slurry in the solid fluidization exploitation of combustible ice” (51874323).

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