Gas hydrate layers

Uddin et al. (2008b) conducted several depressurization simulations for the Mallik 5L-38 well. Their results showed that the Mallik gas hydrate layer with its underlying aquifer could yield significant amounts of gas originating entirely from gas hydrates, the volumes of which increased with the production rate. However, large amounts of water were also produced. Sensitivity studies indicated that the methane release from the hydrate accumulations increased with the decomposition surface area, the initial hydrate stability field (P-T conditions), and the thermal conductivity of the formation. Methane production appears to be less sensitive to the specific heat of the rock and of the gas hydrate. 

Area Gas hydrate layer Origin of gas Average TOC (in situ methane production) Geological setting Fluid flow... 

Transport properties of hydrated PFSA membranes strongly depend on nanophase-segregated morphology, water content, and state of water. In an operational fuel cell, these characteristics are indirectly determined by the humidity level of the reactant streams and Faradaic current densities generated in electrodes, as well as the transport properhes of catalyst layers, gas diffusion layers, and flow... 

FIGURE 2.8 Schematic diagram showing structure II is built up of layers of 512 cavities alternating with layers of 51264 and 512 cavities. (Reproduced from Udachin, K., Ripmeester, J.A., in Proc. Fifth Int. Conf. on Gas Hydrates, Trondheim, Norway, June 13-16, Paper 2024 (2005). With permission.)... 

Andreassen (1995) used the amplitude versus offset (AVO) technique to determine the phases at the BSR interface. The classical AVO technique, as stated by Ostrander (1984), measures the angle-dependent P-wave ratio amplitude (reflected to incident). Andreassen and coworkers determined that usually gas is just below the hydrate layer. 

Class 1—hydrate layer underlain by two-phase zone of mobile gas and water... 

Most economical for dissociation by depressurization is the subpermafrost reservoir in which hydrates overly a free gas, with impermeable boundaries both at the top of the hydrate layer, and at the bottom of the free gas layer. 

The storage of methane as hydrates offers a potentially vast natural gas resource. As to the question of how much hydrate there is right now, there is no definitive answer. However, the worldwide amount of carbon bound in gas hydrates has been estimated to total twice the amount of carbon to be found in all known fossil fuels originally on Earth. Additionally, conventional gas resources appear to be trapped beneath methane hydrate layers in ocean sediments.22... 

Finally, gas hydrates were prepared using our gas-pressure equipment. The cooled mixtures were filled into a pressure cell layer by layer at -10°C. To form methane hydrate from these porous media the pressure cells were mounted onto the gas pressure rig at a constant temperature of 3°C. After 25 minutes of temperature equilibration and ongoing melting of the ice phase, 10 MPa of methane gas pressure was applied. The progress of the transformation from water into hydrate was followed by the observed pressure drop in the cells, continually recorded in a computer. Methane gas was refilled manually whenever the pressure had fallen below 9.6 MPa. 

The structure of a CH4 hydrate layer from ice was argued by Moudrakovski et al. and L. A. Stem et al. A polemic is given answering the publication by Moudrakovski (Letter, Hydrate layers on ice particles and superheated ice A NMR microimaging study in J. Phys. Chem. 1999, 103, 4969) by L. A. Stem et al The experimental conditions in both groups are completely different for the formation of CH4 hydrate from ice and CH4 gas, i.e. under high pressure (27-33 MPa) by Stern et al and at lower pressures (5.7-11.9 MPa) by Moudrakovski s NMR microimaging experiments. 

Fig. 14.11 Hydrate fabrics typical for shallow gas hydrate specimens (A, C and D) sediment-hydrate interlayering (A), pure dense hydrate layer (C), and highly porous bubble-shaped framework (D) B Field-electron scanning micrograph of hydrate surrounded by bubble-shaped ice.

Haeckel, M., Suess, E., Wallmann, K., and Rickert, D., 2004. Rising methane gas bubbles form massive hydrate layers at the seafloor Geochimica et Cosmo-chimica Acta, 68 4335-4345. 

Optimum parameters for a successful accomplishment of the EOR process are defined in [239]. First, they can be realized in reservoirs consisting of sandstones, sands, carbonates or mixtures of these materials with a layer thickness of under 25 m and permeability of over 20 mD, containing crude oil with a viscosity of <60 mPa s. In this case, a formulation containing, along with alkali, 20 - 30 g/1 salts, ethoxysulphates and alkyl sulfonates, used for injection at a temperature below 80 °C. The authors are optimistic about the wide commercial use of EOR, since oil will remain the main energy source up to the second half of the 21 century. Surfactants can also be used to recover oil containing gas for the purpose of gas hydrate formation control [240]. 

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