Rheological Properties of Hydrate Slurry Formed from Mudflows in South China Sea

Abstract

Solid fluidization is a current promising method to explore hydrate resources. The rheological properties of hydrate slurry are significant to solid fluidization and prevent hydrate blockage during pipeline transportation. To determine the impact of hydrate on the rheological properties of mudflow, a rheological experiment was conducted on methane hydrate slurry formed from a mudflow, which was prepared with marine sediment sampled from South China Sea. It was found that both mudflow and hydrate slurry exhibited viscoelastic fluid properties. The existence of hydrate substantially increased the apparent viscosity of the mudflow, and when the hydrate formed at a rapid rate, the apparent viscosity rose rapidly. With different initial pressures, the amount of hydrate formed in mudflow was different. A larger water conversion rate would increase the viscosity of the hydrate slurry significantly. Meanwhile, a yield stress measurement was conducted by stress sweep after hydrate formation. When the water conversion fractions were 17.8%, 20.3%, and 21.2%, the yield stresses of the hydrate slurry were 57.8, 465.2, and over 10,000 Pa, respectively. In addition, a frequency test sweep was conducted, and the results showed that the existence of hydrate would significantly increase the elasticity of the slurry.

Experimental investigation on hydrate dissociation in near-wellbore region caused by invasion of drilling fluid: ultrasonic measurement and analysis

“…Natural gas hydrates are ice-like cage crystals composed of host water molecules and guest natural gas molecules (methane commonly consists more than 95%) under low temperature and high pressure conditions (Sloan 2003; Ye et al 2018;Liu et al 2021). In nature, gas hydrates are mainly buried in offshore sediments, and also diffused in a small amount in permafrost, the total global reserves amount to 2.1×10 16 m 3 (Zhang et al 2021;Gambelli 2021).…”

Effect of Methane Solubility on Hydrate Formation and Dissociation: Review and Perspectives

“…25,26 Many countries have formulated and implemented trial production of hydrate. 27,28 From 2007 to 2008, Japan and Canada conducted trial production of hydrate in the Mackenzie Delta area using a stepwise depressurization method. 29 It was inferred that in the initial stage of depressurization, the gas production rate increased rapidly due to the permeability increase, but then, the gas production rate decreased due to the permeability decrease.…”

“…There are three conventional NGH exploitation methods: depressurization, − thermal stimulation, , and inhibitor injection, − as well as the combined use of these three methods. − Among them, depressurization is considered the most economical and effective exploitation method. , Many countries have formulated and implemented trial production of hydrate. , From 2007 to 2008, Japan and Canada conducted trial production of hydrate in the Mackenzie Delta area using a stepwise depressurization method . It was inferred that in the initial stage of depressurization, the gas production rate increased rapidly due to the permeability increase, but then, the gas production rate decreased due to the permeability decrease .…”

Experimental Study on the Gas Permeability of Marine Sediments with Various Hydrate Saturations and Effective Stresses

“…On the one hand, it may cause sediment collapse, wellbore collapse, submarine landslides, and other geological disasters. , On the other hand, it may cause methane to leak into the ocean and atmosphere, which will destroy the marine ecosystems and exacerbate the greenhouse effect. , In addition, permeability can affect the distribution of hydrate in the reservoir and the methane flux to the ocean and atmosphere . Thus, the study of the permeability of hydrate-bearing sediments (HBSs) plays a crucial role in investigating hydrate reservoirs as a potential energy resource and evaluating the impact of hydrate decomposition on marine ecosystems and global climate change. , …”

“…27 Thus, the study of the permeability of hydrate-bearing sediments (HBSs) plays a crucial role in investigating hydrate reservoirs as a potential energy resource and evaluating the impact of hydrate decomposition on marine ecosystems and global climate change. 6,28 The permeability of porous media depends on the size, shape, and connectivity of the internal flow channels; that is, it is closely related to the pore structure. Therefore, the factors that make the flow channel structure more complex (including porosity, hydrate morphology, hydrate saturation, effective stress, etc.)…”