Formation Of Solid Hydrates Research Articles

Deep ocean bubble transport model coupled with multiple hydrate behavior characteristics

AbstractSubmarine gas seepage is a widely observed process. In this study, a unified mechanistic model of bubble transport both inside and outside the gas hydrate stability zone (GHSZ) was developed. Multiple hydrate‐related behaviors were considered, including hydrate nucleation, hydrate film lateral spread, hydrate shell dynamic growth, hydrate dissolution and decomposition, and collapse and fracture deformation of hydrate‐coated bubbles. Using the proposed model, a series of simulation studies about bubble dissolution and rising fate were conducted. The results indicate that the formation of solid hydrates in the deep‐sea environment can provide a fairly effective barrier for the dissolution and shrinkage of bubbles, and the deeper the initial release water depth, the smaller the critical size of the bubble required for arriving at the water surface. Furthermore, the majority of gases released from the seafloor would be absorbed by the shallow oceanic layer, but larger bubbles could still pass through the water column to the atmosphere.

Hydrate Plugging and Flow Remediation during CO2 Injection in Sediments

Successful geological sequestration of carbon depends strongly on reservoir seal integrity and storage capacity, including CO2 injection efficiency. Formation of solid hydrates in the near-wellbore area during CO2 injection can cause permeability impairment and, eventually, injectivity loss. In this study, flow remediation in hydrate-plugged sandstone was assessed as function of hydrate morphology and saturation. CO2 and CH4 hydrates formed consistently at elevated pressures and low temperatures, reflecting gas-invaded zones containing residual brine near the injection well. Flow remediation by methanol injection benefited from miscibility with water; the methanol solution contacted and dissociated CO2 hydrates via liquid water channels. Injection of N2 gas did not result in flow remediation of non-porous CO2 and CH4 hydrates, likely due to insufficient gas permeability. In contrast, N2 as a thermodynamic inhibitor dissociated porous CH4 hydrates at lower hydrate saturations (<0.48 frac.). Core-scale thermal stimulation proved to be the most efficient remediation method for near-zero permeability conditions. However, once thermal stimulation ended and pure CO2 injection recommenced at hydrate-forming conditions, secondary hydrate formation occurred aggressively due to the memory effect. Field-specific remediation methods must be included in the well design to avoid key operational challenges during carbon injection and storage.

Solid and liquid phase equilibria and solid-hydrate formation in binary mixtures of water with amines

Solid and liquid phase equilibria and solid-hydrate formation in binary mixtures of water with amines

Solid and liquid phase equilibria and solid-hydrate formation in binary mixtures of water with amines

Solid and liquid phase diagrams have been constructed for water+triethylamine, or+N, N-dimethylformamide (DMF) or+N, N-dimethlacetamide (DMA). Solid-hydrates form with the empirical formulae N(C2H5)3.3H2O, DMF.3H2O, DMF.2H2O, DMA.3H2O and (DMA)2.3H2O. All are congruently melting except the first which melts incongruently. The solid-hydrate formation is attributed to hydrogen bond. The results are compared with the references.

(Solid + liquid) phase equilibria and solid-hydrate formation in water + methyl, + ethyl, + isopropyl, and + tertiary butyl alcohols

(Solid + liquid) phase diagrams have been obtained from time-temperature melting curves for water + methyl, + ethyl, + isopropyl, and + tertiary butyl alcohols. Incongruently melting hydrates form in all four systems. In addition, water + t-butyl alcohol has a congruently melting compound. Correlations between inflexions found in the water-rich compositions of the (solid + liquid) equilibrium lines and the size of the alkyl groups of the alcohols are noted, and a possible interpretation is given.