The methane hydrate formation and the resource estimate resulting from free gas migration in seeping seafloor hydrate stability zone

2009 ◽  
Vol 36 (4-5) ◽  
pp. 277-288 ◽  
Author(s):  
Jinan Guan ◽  
Deqing Liang ◽  
Nengyou Wu ◽  
Shuanshi Fan
Keyword(s):  
Methane Hydrate ◽  
Hydrate Formation ◽  
Gas Migration ◽  
Stability Zone ◽  
Free Gas ◽  
Hydrate Stability

scholarly journals Numerical Modeling of Gas Migration and Hydrate Formation in Heterogeneous Marine Sediments

2019 ◽  
Vol 7 (10) ◽  
pp. 348 ◽  
Author(s):  
Keqi Bei ◽  
Tianfu Xu ◽  
Songhua Shang ◽  
Zilin Wei ◽  
Yilong Yuan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Hydrate Formation ◽  
Stable Region ◽  
Gas Migration ◽  
Stability Zone ◽  
Shenhu Area ◽  
China Sea ◽  
Porosity And Permeability ◽  
Hydrate Stability

The formation of marine gas hydrates is controlled by gas migration and accumulation from lower sediments and by the conditions of the hydrate stability zone. Permeability and porosity are important factors to evaluate the gas migration capacity and reservoir sealing capacity, and to determine the distribution of hydrates in the stable region. Based on currently available geological data from field measurements in the Shenhu area of Baiyun Sag in the northern South China Sea, numerical simulations were conducted to estimate the influence of heterogeneities in porosity and permeability on the processes of hydrate formation and accumulation. The simulation results show that: (1) The heterogeneity of the hydrate stability zone will affect the methane migration within it and influence the formation and accumulation of hydrates. This is one of the reasons for the formation of heterogeneous hydrates. (2) When the reservoir is layered heterogeneously, stratified differences in gas lateral migration and hydrate formation will occur in the sediment, and the horizontal distribution range of the hydrate in a high porosity and permeability reservoir is wider. (3) To determine the dominant enrichment area of hydrate in a reservoir, we should consider both vertical and lateral conditions of the sedimentary layer, and the spatial coupling configuration relationships among the hydrate stability region, reservoir space and gas migration and drainage conditions should be considered comprehensively. The results are helpful to further understand the rules of hydrate accumulation in the Shenhu area on the northern slope of the South China Sea, and provide some references for future hydrate exploration and the estimation of reserves.

Methane hydrate saturations at the Southern Hikurangi margin (New Zealand) estimated from seismic and rock physics inversion

2020 ◽  
Author(s):  
Francesco Turco ◽  
Andrew Gorman ◽  
Gareth Crutchley ◽  
Leonardo Azevedo ◽  
Dario Grana ◽  
...  
Keyword(s):  
New Zealand ◽  
Gas Hydrate ◽  
Methane Hydrate ◽  
Waveform Inversion ◽  
Hydrate Formation ◽  
Rock Physics ◽  
Stability Zone ◽  
Hydrate Saturation ◽  
Physics Model ◽  
Hydrate Stability

<p>Geophysical data indicate that the Hikurangi subduction margin on New Zealand’s East Coast contains a large gas hydrate province. Gas hydrates are widespread in shallow sediments across the margin, and locally intense fluid seepage associated with methane hydrate is observed in several areas. Glendhu and Honeycomb ridges lie at the toe of the Hikurangi deformation wedge at depths ranging from 2100 to 2800 m. These two parallel four-way closure systems host concentrated methane hydrate deposits. The control on hydrate formation at these ridges is governed by steeply dipping permeable strata and fractures, which allow methane to flow upwards into the gas hydrate stability zone. Hydrate recycling at the base of the hydrate stability zone may contribute to the accumulation of highly concentrated hydrate in porous layers.<br>To improve the characterisation of the hydrate systems at Glendhu and Honeycomb ridges, we estimate hydrate saturation and porosity of the concentrated hydrate deposits. We first estimate elastic properties (density, compressional and shear-wave velocities) of the gas hydrate stability zone through full-waveform inversion and <span>iterative geostatistical seismic amplitude versus angle (AVA) inversion</span>. We then perform a petrophysical inversion based on a rock physics model to predict gas hydrate saturation and porosity of the hydrate bearing sediments along the two ridges.<br>Our results indicate that the high seismic amplitudes correspond to the top interface of highly concentrated hydrate deposit, with peak saturations around 35%. Because of the resolution of the seismic data we assume that the estimated properties are averaged over layers of 10 to 20 meters thickness. These saturation values are in agreement with studies conducted in other areas of concentrated hydrate accumulations in similar geologic settings.</p>

scholarly journals Crustal fingering facilitates free-gas methane migration through the hydrate stability zone

2020 ◽  
Vol 117 (50) ◽  
pp. 31660-31664
Author(s):  
Xiaojing Fu ◽  
Joaquin Jimenez-Martinez ◽  
Thanh Phong Nguyen ◽  
J. William Carey ◽  
Hari Viswanathan ◽  
...  
Keyword(s):  
Hydrate Formation ◽  
Elevated Pressure ◽  
Water Mixture ◽  
Gas Migration ◽  
Stability Zone ◽  
Critical Gap ◽  
Methane Seepage ◽  
Field Evidence ◽  
Hydrate Bearing Sediments ◽  
Hydrate Stability

Widespread seafloor methane venting has been reported in many regions of the world oceans in the past decade. Identifying and quantifying where and how much methane is being released into the ocean remains a major challenge and a critical gap in assessing the global carbon budget and predicting future climate [C. Ruppel, J. D. Kessler. Rev. Geophys. 55, 126–168 (2017)]. Methane hydrate (CH4⋅5.75H2O) is an ice-like solid that forms from methane–water mixture under elevated-pressure and low-temperature conditions typical of the deep marine settings (>600-m depth), often referred to as the hydrate stability zone (HSZ). Wide-ranging field evidence indicates that methane seepage often coexists with hydrate-bearing sediments within the HSZ, suggesting that hydrate formation may play an important role during the gas-migration process. At a depth that is too shallow for hydrate formation, existing theories suggest that gas migration occurs via capillary invasion and/or initiation and propagation of fractures (Fig. 1). Within the HSZ, however, a theoretical mechanism that addresses the way in which hydrate formation participates in the gas-percolation process is missing. Here, we study, experimentally and computationally, the mechanics of gas percolation under hydrate-forming conditions. We uncover a phenomenon—crustal fingering—and demonstrate how it may control methane-gas migration in ocean sediments within the HSZ.

scholarly journals Methane Hydrate Formation in Thick Sandstones by Free Gas Flow

2018 ◽  
Vol 123 (6) ◽  
pp. 4582-4600 ◽  
Author(s):  
Kehua You ◽  
Peter B. Flemings
Keyword(s):  
Methane Hydrate ◽  
Gas Flow ◽  
Hydrate Formation ◽  
Free Gas

scholarly journals Thermal State of the Blake Ridge Gas Hydrate Stability Zone (GHSZ)—Insights on Gas Hydrate Dynamics from a New Multi-Phase Numerical Model

Energies ◽  
2019 ◽  
Vol 12 (17) ◽  
pp. 3403 ◽  
Author(s):  
Burwicz ◽  
Rüpke
Keyword(s):  
Numerical Model ◽  
Gas Hydrate ◽  
Methane Flux ◽  
Stability Zone ◽  
Free Gas ◽  
Blake Ridge ◽  
Geochemical Profiles ◽  
Multi Phase ◽  
Hydrate Stability

Marine sediments of the Blake Ridge province exhibit clearly defined geophysical indications for the presence of gas hydrates and a free gas phase. Despite being one of the world’s best-studied gas hydrate provinces and having been drilled during Ocean Drilling Program (ODP) Leg 164, discrepancies between previous model predictions and reported chemical profiles as well as hydrate concentrations result in uncertainty regarding methane sources and a possible co-existence between hydrates and free gas near the base of the gas hydrate stability zone (GHSZ). Here, by using a new multi-phase finite element (FE) numerical model, we investigate different scenarios of gas hydrate formation from both single and mixed methane sources (in-situ biogenic formation and a deep methane flux). Moreover, we explore the evolution of the GHSZ base for the past 10 Myr using reconstructed sedimentation rates and non-steady-state P-T solutions. We conclude that (1) the present-day base of the GHSZ predicted by our model is located at the depth of ~450 mbsf, thereby resolving a previously reported inconsistency between the location of the BSR at ODP Site 997 and the theoretical base of the GHSZ in the Blake Ridge region, (2) a single in-situ methane source results in a good fit between the simulated and measured geochemical profiles including the anaerobic oxidation of methane (AOM) zone, and (3) previously suggested 4 vol.%–7 vol.% gas hydrate concentrations would require a deep methane flux of ~170 mM (corresponds to the mass of methane flux of 1.6 × 10−11 kg s−1 m−2) in addition to methane generated in-situ by organic carbon (POC) degradation at the cost of deteriorating the fit between observed and modelled geochemical profiles.

Fluid dynamics at the base of hydrate-bearing sediments at the Vestnesa Ridge inferred from 5 years of high-resolution 4D seismic surveying

2020 ◽  
Author(s):  
Malin Waage ◽  
Stefan Bünz ◽  
Kate Waghorn ◽  
Sunny Singhorha ◽  
Pavel Serov
Keyword(s):  
High Resolution ◽  
Gas Hydrate ◽  
Seismic Data ◽  
Time Lapse ◽  
Stability Zone ◽  
Seismic Surveys ◽  
Free Gas ◽  
4D Seismic ◽  
Hydrate Bearing Sediments ◽  
Hydrate Stability

<p>The transition from gas hydrate to gas-bearing sediments at the base of the hydrate stability zone (BHSZ) is commonly identified on seismic data as a bottom-simulating reflection (BSR). At this boundary, phase transitions driven by thermal effects, pressure alternations, and gas and water flux exist. Sedimentation, erosion, subsidence, uplift, variations in bottom water temperature or heat flow cause changes in marine gas hydrate stability leading to expansion or reduction of gas hydrate accumulations and associated free gas accumulations. Pressure build-up in gas accumulations trapped beneath the hydrate layer may eventually lead to fracturing of hydrate-bearing sediments that enables advection of fluids into the hydrate layer and potentially seabed seepage. Depletion of gas along zones of weakness creates hydraulic gradients in the free gas zone where gas is forced to migrate along the lower hydrate boundary towards these weakness zones. However, due to lack of “real time” data, the magnitude and timescales of processes at the gas hydrate – gas contact zone remains largely unknown. Here we show results of high resolution 4D seismic surveys at a prominent Arctic gas hydrate accumulation – Vestnesa ridge - capturing dynamics of the gas hydrate and free gas accumulations over 5 years. The 4D time-lapse seismic method has the potential to identify and monitor fluid movement in the subsurface over certain time intervals. Although conventional 4D seismic has a long history of application to monitor fluid changes in petroleum reservoirs, high-resolution seismic data (20-300 Hz) as a tool for 4D fluid monitoring of natural geological processes has been recently identified.<br><br>Our 4D data set consists of four high-resolution P-Cable 3D seismic surveys acquired between 2012 and 2017 in the eastern segment of Vestnesa Ridge. Vestnesa Ridge has an active fluid and gas hydrate system in a contourite drift setting near the Knipovich Ridge offshore W-Svalbard. Large gas flares, ~800 m tall rise from seafloor pockmarks (~700 m diameter) at the ridge axis. Beneath the pockmarks, gas chimneys pierce the hydrate stability zone, and a strong, widespread BSR occurs at depth of 160-180 m bsf. 4D seismic datasets reveal changes in subsurface fluid distribution near the BHSZ on Vestnesa Ridge. In particular, the amplitude along the BSR reflection appears to change across surveys. Disappearance of bright reflections suggest that gas-rich fluids have escaped the free gas zone and possibly migrated into the hydrate stability zone and contributed to a gas hydrate accumulation, or alternatively, migrated laterally along the BSR. Appearance of bright reflection might also indicate lateral migration, ongoing microbial or thermogenic gas supply or be related to other phase transitions. We document that faults, chimneys and lithology constrain these anomalies imposing yet another control on vertical and lateral gas migration and accumulation. These time-lapse differences suggest that (1) we can resolve fluid changes on a year-year timescale in this natural seepage system using high-resolution P-Cable data and (2) that fluids accumulate at, migrate to and migrate from the BHSZ over the same time scale.</p>

The replacement of methane hydrate in the reservoir by injection into the liquid carbon dioxide

2017 ◽  
Vol 12 (2) ◽  
pp. 206-213 ◽  
Author(s):  
O.F. Shepelkevich
Keyword(s):  
Carbon Dioxide ◽  
Methane Hydrate ◽  
Hydrate Formation ◽  
Liquid Carbon ◽  
Liquid Carbon Dioxide ◽  
Free Gas ◽  
Methane Gas ◽  
Hydrate Reservoir ◽  
Piston Displacement ◽  
Hydrate Saturation

The paper deals with the process of injecting liquid carbon dioxide into a hydrate reservoir. It is shown that the process of methane replacement in a hydrate reservoir by injecting liquid carbon dioxide into it can consist of the following steps: piston displacement of free gas from the pores; replacement of methane with liquid carbon dioxide, its dissolution and leaching from the formation; completion of hydrate formation and leaching of the remaining methane gas from the hydrate reservoir. We have presented the distributions of pressure, density, hydrate saturation and temperature at different times.

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