Hydromechanical Properties of Gas Hydrate‐Bearing Fine Sediments From In Situ Testing

Abstract

The hydromechanical properties of gas hydrate‐bearing sediment are key in assessing offshore geohazards and the resource potential of gas hydrates. For sandy materials, such properties were proved highly dependent on hydrate content (Sh) as well as on their distribution and morphology. Owing to difficulties in testing gas hydrate‐bearing clayey sediments, the impact of hydrates on the behavior of such materials remains poorly understood. Hence, to provide insight into the characterization of clayey sediments containing hydrate, this study relies on a unique database of in situ acoustic, piezocone, and pore pressure dissipation measurements collected in a high gas flux system offshore Nigeria. Compressional wave velocity measurements were used as means of both detecting and quantifying gas hydrate in marine sediments. The analysis of piezocone data in normalized soil classification charts suggested that contrary to hydrate‐bearing sands, the behavior of gas hydrate‐bearing clays tends to be contractive. Correlations of acoustic and geotechnical data have shown that the stiffness and strength tend to increase with increasing Sh. However, several sediment intervals sharing the same Sh have revealed different features of mechanical behavior; suggesting that stiffness and strength of gas hydrate‐bearing clays are influenced by the distribution/morphology of gas hydrate. Pore pressure dissipation data confirmed the contractive behavior of gas hydrate‐bearing clays and showed that at low hydrate content, the hydraulic diffusivity (Ch) decreases when Sh increases. However, for Sh exceeding 20%, it was shown that an increase of Ch with Sh could be linked to the presence of fractures in the hydrate‐sediment system.

Shallow Gas Hydrate Accumulations at a Nigerian Deepwater Pockmark—Quantities and Dynamics

“…In Pockmark A, gas hydrates are widely distributed in a sediment body down to a depth of 34 mbsf at maximum (Sultan et al, 2014;Taleb et al, 2018Taleb et al, , 2020Wei et al, 2015). Gas hydrates with gas-filled macropores in shallow sediments of the "Rough Patch 1" (Sultan et al, 2014) point to their rapid formation from gaseous methane (e.g., Bohrmann et al, 1998;Torres et al, 2004).…”

Introduction to Special Issue on Gas Hydrate in Porous Media: Linking Laboratory and Field‐Scale Phenomena

“…The Special Section also includes a rare field study that uses in situ measurements to constrain hydraulic, geomechanical, and other properties of fine‐grained sediments in a rapid gas flux setting in the Gulf of Guinea (Taleb et al, ). The in situ data imply that seafloor hydrate‐bearing clays are in a contractive state, which contrasts with the dilative state of coarser‐grained HBS and also the findings of Yun et al () for a range of sediments that includes clays.…”

“…The in situ data imply that seafloor hydrate‐bearing clays are in a contractive state, which contrasts with the dilative state of coarser‐grained HBS and also the findings of Yun et al () for a range of sediments that includes clays. The Taleb et al () study also infers the relative hydraulic diffusivity of hydrate‐bearing clay sediments by measuring pore water dissipation. Increased hydrate saturation leads to the expected decrease in hydraulic diffusivity, but the relationship does not persist beyond 20% saturation.…”

“…Pressure coring will continue to become more routine and reliable over the next decade, and more tools and approaches will be adopted to image and interrogate pressure cores. Field methods for measuring HBS physical properties from conventional ships (Taleb et al, ) are likely to continue evolving alongside techniques to directly constrain HBS geotechnical properties using borehole instrumentation. The synergy between reservoir models and HBS property studies will likely continue and should yield increasingly refined models for potential production from high‐saturation deposits, particularly in well‐studied deep water marine gas hydrate provinces.…”

“…Fine-grained particles that are mixed with coarser sediments can be mobilized under certain conditions and are also considered a component of pore fill in some cases. (2018) On the importance of advective versus diffusive transport in controlling the distribution of methane hydrate in heterogeneous marine sediments Lei and Santamarina (2018) Laboratory strategies for hydrate formation in fine-grained sediments (also fines) You and Flemings (2018) Methane hydrate formation in thick sandstones by free gas flow Effect of gas flow rate on hydrate formation within the hydrate stability zone Meyer, Flemings, DiCarlo, You, et al (2018) Experimental investigation of gas flow and hydrate formation within the hydrate stability zone Sahoo et al (2018) Presence and consequences of coexisting methane gas with hydrate under two phase water-hydrate stability conditions Almenningen et al (2018) Upscaled anisotropic methane hydrate critical state model for turbidite hydrate-bearing sediments at East Nankai Trough Ge et al (2018) Laboratory investigation into the formation and dissociation process of gas hydrate by low-field nuclear magnetic resonance technique Role of fines Han et al (2018) Depressurization-induced fines migration in sediments containing methane hydrate: X-Ray computed tomography imaging experiments Hyodo et al (2017) Influence of fines content on the mechanical behavior of methane hydrate-bearing sediments Jang et al (2018) Impact of pore fluid chemistry on fine-grained sediment fabric and compressibility Taleb et al (2018) Hydromechanical properties of gas hydrate-bearing fine sediments from in situ testing Geomechanical and hydraulic properties Spangenberg et al (2018) A quick look method to assess the dependencies of rock physical sediment properties on the saturation with pore-filling hydrate Madhusudhan et al (2019) The effects of hydrate on the strength and stiffness of some sands Kossel et al (2018) The dependence of water permeability in quartz sand on gas hydrate saturation in the pore space Gil et al (2019) Numerical analysis of dissociation behavior at critical gas hydrate saturation using depressurization method Cook and Waite (2018) Archie's saturation exponent for natural gas hydrate in coarse-grained reservoirs Zhou et al (2018) Upscaled anisotropic methane hydrate critical state model for turbidite hydrate-bearing sediments at East Nankai Trough Coupled numerical modeling Sánchez et al (2018) Coupled numerical modeling of gas hydrate-bearing sediments: From laboratory to field-scale analyses Kim et al (2018) Methane production from marine gas hydrate deposits in Korea: Thermal-hydraulic-mechanical simulation on production wellbore stabilit...…”