Liquid limit as a predictor of mudrock permeability

Casey, Brendan J.; Germaine, John T.; Flemings, Peter B.; Reece, Julia S.; Gao, B.; Betts, W.

doi:10.1016/j.marpetgeo.2013.04.008

Cited by 29 publications

(14 citation statements)

References 21 publications

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“…274739). We added 0.5 wt % smectite‐rich clay from the Gulf of Mexico in the Eugene Island protraction area (Casey et al, ) to accelerate hydrate nucleation (Riestenberg et al, ). We stirred the dry sediment mixture with a whisk to assure a reasonably homogeneous clay distribution within the sample and packed the sample using slow, dry pluviation (Germaine & Germaine, ).…”

Section: Methodsmentioning

confidence: 99%

Experimental Investigation of Gas Flow and Hydrate Formation Within the Hydrate Stability Zone

et al. 2018

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We form methane hydrate by injecting methane gas into a brine‐saturated, coarse‐grained sample under hydrate‐stable thermodynamic conditions. Hydrate forms to a saturation of 11%, which is much lower than that predicted assuming three‐phase (gas‐hydrate‐brine) thermodynamic equilibrium (67%). During hydrate formation, there are temporary flow blockages. We interpret that a hydrate skin forms a physical barrier at the gas‐brine interface. The skin fails periodically when the pressure differential exceeds the skin strength. Once the skin is present, further hydrate formation is limited by the rate that methane can diffuse through the solid skin. This process produces distinct thermodynamic states on either side of the skin that allows gas to flow through the sample. This study illuminates how gas can be transported through the hydrate stability zone and thus provides a mechanism for the formation of concentrated hydrate deposits in sand reservoirs. It also illustrates that models that assume local equilibrium at the core‐scale and larger may not capture the fundamental behaviors of these gas flow and hydrate formation processes.

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Section: Methodsmentioning

confidence: 99%

Experimental Investigation of Gas Flow and Hydrate Formation Within the Hydrate Stability Zone

et al. 2018

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“…This modification to the packing procedure helped maintain more homogeneous sample porosity. The samples consisted of clean, silica sand (362‐μm median grain size) mixed with 0.5 wt % smectite‐rich clay (Casey et al, ). The clay was added to accelerate hydrate nucleation (Riestenberg et al, ).…”

Section: Methodsmentioning

confidence: 99%

Effect of Gas Flow Rate on Hydrate Formation Within the Hydrate Stability Zone

2018

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We form methane hydrate in brine‐saturated, coarse‐grained samples, under hydrate‐stable conditions, by injecting methane vapor at various flow rates. Decreasing the flow rate results in higher hydrate saturation, lower brine saturation, a smaller affected volume, and larger average pressure differentials across the sample. We interpret that the longer execution times at lower flow rates allow for additional methane transport and hydrate formation at the hydrate‐brine interface. As a result, the hydrate skin is thicker at lower flow rates and thus is capable of sustaining larger pressure differentials. In several experiments, we stop brine flow and supply methane gas to the sample for an additional 800 hrs. During this period, hydrate continues to form, pressure differentials develop, and the bulk density changes within the affected volume. We interpret that there is gas present in the sample that is disconnected from the gas source. Hydrate forms around the disconnected gas due to methane transport through the skin that surrounds it, causing the internal gas pressure to decline and leading to inward collapse and net volume decrease. This lowers the brine pressure and creates a differential pressure across the sample that induces gas flow. This study indicates that lower gas flow rates through the hydrate stability zone can produce very high saturations of hydrate but require a larger differential pressure to sustain flow. Ultimately, this process is an alternative mechanism for sustained upward gas flow and hydrate formation far above the base of the hydrate stability zone.

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“…This is also supported by the measured liquid limit of 40.3%, which indicates that the sediment is of low permeability of the order of 10 À16 m 2 (Casey et al, 2013). À An effective confining stress of 2 MPa was applied to the sediment in the core holder.…”

Section: Discussionmentioning

confidence: 60%