Permeability of sediment cores from methane hydrate deposit in the Eastern Nankai Trough

Mechanical properties of hydrate-bearing turbidite reservoir in the first gas production test site of the Eastern Nankai Trough

“…Differential pressure was measured between the upper and lower boundaries of the sample for several constant values of pore fluid flow. The measured values were 1e100 mD for hydrate-bearing sandy sediments, two to three orders of magnitude higher than conventional estimates, such as those from nuclear magnetic response logging (Konno et al, 2015b). Our testing results, which were estimated using consolidation time, were compared with these flow test results and showed a good relationship.…”

“…Additionally, we observed that sandy sediments with and without hydrates have permeability values of tens of millidarcies, representing values before hydrate dissociation under in situ pressures. Konno et al (2015b) conducted a series of flow tests to determine the hydraulic conductivity of the LN2 core and the CH 4 purge LN2 core, which were both recovered in the same coring project. Differential pressure was measured between the upper and lower boundaries of the sample for several constant values of pore fluid flow.…”

“…There is no marked change in the weight percentage of smectite, and therefore might affect the bulk permeability of this reservoir. Konno et al (2015b) reported that the permeability decrease, after the pore fluid changed from sea water to distilled water during flooding tests, due to the swelling of smectite which is expanding clay. It suggested that the possibility of the permeability change of the sediments due to the variation of salinity, and it indicated that the potential of the smectite content as one of the parameter for the permeability of a reservoir.…”

Characterizing electrical properties and permeability changes of hydrate bearing sediments using ERT data

“…Because the sediment's pore space in our experiments is completely water saturated at all times throughout hydrate formation and hydrates are formed from methane dissolved in the pore water, we assume to mimic the formation of natural, marine gas hydrates. Recent studies (Konno et al 2015;Santamarina et al 2015) carried out on natural sediment cores obtained from a methane hydrate reservoir in the Eastern Nankai Trough indicated from permeability and velocity measurements that natural, marine hydrates form and accumulate in the centre of the pores, justifying the assumption made by eq. (9).…”

Bulk sediment mineralogy of gas hydrate reservoir at the East Nankai offshore production test site

“…The formation and dissociation of gas hydrates are exceedingly sensitive to temperature and pressure conditions (e.g., Max et al, 2006), and therefore a database of sediment mineralogy allows us to create a more realistic gas-hydrate reservoir model. Effective permeability (e.g., Konno et al, 2015) and geomechanical behaviors (e.g., Yoneda et al, 2015) of the sediments are also likely dependent on the mineralogical variation along with grain size and porosity.…”