New Approaches for the Production of Hydrocarbons from Hydrate Bearing Sediments

Abstract

Abstract:The presence of natural gas hydrates at all active and passive continental margins has been proven. Their global occurrence as well as the fact that huge amounts of methane and other lighter hydrocarbons are stored in natural gas hydrates has led to the idea of using hydrate bearing sediments as an energy resource. However, natural gas hydrates remain stable as long as they are in mechanical, thermal and chemical equilibrium with their environment. Thus, for the production of gas from hydrate bearing sediments, at least one of these equilibrium states must be disturbed by depressurization, heating or addition of chemicals such as CO 2 . Depressurization, thermal or chemical stimulation may be used alone or in combination, but the idea of producing hydrocarbons from hydrate bearing sediments by CO 2 injection suggests the potential of an almost emission free use of this unconventional natural gas resource. However, up to now there are still open questions regarding all three production principles. Within the framework of the German national research project SUGAR the thermal stimulation method by use of in situ combustion was developed and tested on a pilot plant scale and the CH 4 -CO 2 swapping process in gas hydrates studied on a molecular level. Microscopy, confocal Raman spectroscopy and X-ray diffraction were used for in situ investigations of the CO 2 -hydrocarbon exchange process in gas hydrates and its driving forces. For the thermal stimulation a heat exchange reactor was designed and tested for the exothermal catalytic oxidation of methane. OPEN ACCESSEnergies 2011, 4 152 Furthermore, a large scale reservoir simulator was realized to synthesize hydrates in sediments under conditions similar to nature and to test the efficiency of the reactor. Thermocouples placed in the reservoir simulator with a total volume of 425 L collect data regarding the propagation of the heat front. In addition, CH 4 sensors are placed in the water saturated sediment to detect the distribution of CH 4 in the sample. These data are used for numerical simulations for up-scaling from laboratory to field conditions. This study presents the experimental set up of the large scale reservoir simulator and the reactor design. Preliminary results indicate that the catalytic oxidation of CH 4 operated as a temperature controlled, autothermal reaction in a countercurrent heat exchange reactor is a safe and promising tool for the thermal stimulation of hydrates. In addition, preliminary results from the laboratory studies on the CO 2 -hydrocarbon swapping process in simple and mixed gas hydrates are presented.

Are Laboratory-Formed Hydrate-Bearing Systems Analogous to Those in Nature?

“…Because methane solubility is low, hydrate formation from dissolved-phase methane in the laboratory is a slow and long-lasting process. 15,52,53 However, because it is assumed that this process forms the high hydrate concentrations in sands and coarse silts, 31,20 the method should be improved in order to provide information and data that are valuable for the interpretation of geophysical field and borehole measurements and the general understanding of this type of hydrate-bearing reservoirs. This formation process corresponds to scenario 1.…”

A cylindrical electrical resistivity tomography array for three-dimensional monitoring of hydrate formation and dissociation

“…Further details regarding LARS can be found in Schicks et al 2 Subsequent to the description of Schicks et al, 2 the pressure vessel was modified to include steel mesh-plates and porous filter plates at the fluid in-and outlets of the pressure vessel (Fig. 2).…”

“…Methane hydrate has been formed successfully from methane saturated saline water under simulated in situ conditions while temperature and pressure profiles have been recorded. Production tests, using thermal stimulation or pressure reduction for the dissociation of hydrates were successfully performed (e.g., Schicks et al 2,3 ). However, there was no way to image the spatial distribution of hydrate crystals a) mikep@gfz-potsdam.de during hydrate formation and dissociation, nor could the free methane gas phase released during hydrate dissociation be tracked.…”

Phase Equilibria of the CH4-CO2 Binary and the CH4-CO2-H2O Ternary Mixtures in the Presence of a CO2-Rich Liquid Phase

“…Amongst the processes under investigation, the storage of CO 2 in solid gas hydrates by replacing the CH 4 from natural accumulations seems to be very promising, since it helps to meet the global energy demand, while reducing net global carbon emissions. CH 4 production from gas hydrates coupled to CO 2 sequestration has been investigated 288.50 5.12-8.15 (10,10) [15] 293. 40 5.73-7.98 (13,13) 301.00 6.86-7.70 (6, 6) + Critical point [16] 274.…”