Gas-driven tensile fracturing in shallow marine sediments

Daigle, Hugh; Cook, Ann E.; Fang, Yi; Bihani, Abhishek; Song, Wen; Flemings, P. B.

doi:10.1002/essoar.10503987.1

Cited by 4 publications

(10 citation statements)

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“…Our estimate of Poisson's ratio at the top of the doming zone is 0.44, which is a reasonable value for shallow submarine sediments (Hamilton, 1979; Reynolds, 1997). The corresponding effective stress ratio

\frac{σ_{h}^{'}}{σ_{v}^{'}}

of 0.78 is reasonable for this sub‐seafloor depth (Daigle et al., 2020) and would be typical of mudrocks that can act as effective sealing units (Casey et al., 2015).…”

Section: Discussionmentioning

confidence: 73%

“…First, we use Poisson's ratio

v

to estimate

σ_{h}

, based on the assumption of linear elasticity and uniaxial strain (e.g., Daigle et al., 2020; Eaton, 1969) (Equation 2):

σ_{h}^{'} = \frac{v}{1 - v} σ_{v}^{'} .

σ_{v}^{'}

and

σ_{h}^{'}

are the effective vertical and horizontal stresses, respectively–i.e.,

σ_{v}^{'} = σ_{v} - P_{f}

and

σ_{h}^{'} = σ_{h} - P_{f}

, where P f is pore fluid pressure, which we here assume to be hydrostatic.…”

Section: Discussionmentioning

confidence: 99%

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Upward‐Doming Zones of Gas Hydrate and Free Gas at the Bases of Gas Chimneys, New Zealand's Hikurangi Margin

et al. 2021

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Focused gas migration through the gas hydrate stability zone in vertical gas conduits is a global phenomenon. The process can lead to concentrated gas hydrate formation and seafloor gas seepage, which influences seafloor biodiversity and ocean biogeochemistry. However, much is unknown about how gas and gas hydrate co‐exist within and around gas conduits. We present seismic imaging of the gas hydrate system beneath a four‐way closure anticlinal ridge at New Zealand's southern Hikurangi subduction margin. Gas has accumulated beneath the base of gas hydrate stability to a thickness of up to ∼240 m, which has ultimately led to hydraulic fracturing and propagation of a vertical gas conduit to the seafloor. Despite the existence of an array of normal faults beneath the ridge, these structures are not exploited as long‐range gas flow conduits. Directly beneath the conduit, and extending upward from the regional base of gas hydrate stability, is a broad zone characterized by both negative‐ and positive‐polarity reflections. We interpret this zone as a volume of sediment hosting both gas hydrate and free gas, that developed due to partial gas trapping beneath a mass transport deposit. Similar highly reflective zones have been identified at the bases of other gas conduits, but they are not intrinsic to all gas conduits through gas hydrate systems. We suggest that pronounced intervening sealing units within the gas hydrate stability zone determine whether or not they form.

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\frac{σ_{h}^{'}}{σ_{v}^{'}}

of 0.78 is reasonable for this sub‐seafloor depth (Daigle et al., 2020) and would be typical of mudrocks that can act as effective sealing units (Casey et al., 2015).…”

Section: Discussionmentioning

confidence: 73%

“…First, we use Poisson's ratio

v

to estimate

σ_{h}

, based on the assumption of linear elasticity and uniaxial strain (e.g., Daigle et al., 2020; Eaton, 1969) (Equation 2):

σ_{h}^{'} = \frac{v}{1 - v} σ_{v}^{'} .

σ_{v}^{'}

and

σ_{h}^{'}

are the effective vertical and horizontal stresses, respectively–i.e.,

σ_{v}^{'} = σ_{v} - P_{f}

and

σ_{h}^{'} = σ_{h} - P_{f}

, where P f is pore fluid pressure, which we here assume to be hydrostatic.…”

Section: Discussionmentioning

confidence: 99%

Upward‐Doming Zones of Gas Hydrate and Free Gas at the Bases of Gas Chimneys, New Zealand's Hikurangi Margin

et al. 2021

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“…Then, we adjust the value of this parameter after referring the results of physical simulation experiments about the fracturing of hydrate-bearing sediments. 41 − 43 where A is the fracture aperture and H is the thickness of the grid cells near the fractures in the model.…”

Section: Gas Production Strategy and Numerical Modelmentioning

confidence: 99%

“…Its values are calculated by the cube’s law first, which is mainly obtained by the geometric characteristics of fractures. Then, we adjust the value of this parameter after referring the results of physical simulation experiments about the fracturing of hydrate-bearing sediments. − where A is the fracture aperture and H is the thickness of the grid cells near the fractures in the model.…”

Section: Gas Production Strategy and Numerical Modelmentioning

confidence: 99%

Numerical Evaluation of Gas Hydrate Production Performance of the Depressurization and Backfilling with an In Situ Supplemental Heat Method

Zhang

et al. 2021

ACS Omega

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The depressurization and backfilling with an in situ supplemental heat method had been proposed to enhance the gas production of methane hydrate reservoir. This novel method is evaluated by a numerical simulator based on the finite volume method in this work. Based on the typical marine low-permeability hydrate-bearing sediments (HBS), a reservoir model with gas fracturing and CaO powder injection is constructed. The simulation results show that the stimulated fractures could effectively enhance the pressure drop effect. Moreover, the CaO injection could provide in situ heat simultaneously. Based on the sensitivity analysis of the equivalent permeability of fractures and the mass of CaO injection, it is found that a threshold fracture permeability exists for the increasing of gas production. The gas production increases with the equivalent permeability only when the permeability is smaller than the threshold value. Meanwhile, the more CaO are injected into reservoir, the larger volume of gas production. In general, this work theoretically quantifies the potential value of the depressurization and backfilling with an in situ supplemental heat method for marine gas hydrate recovery.

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“…Considering the physical forms and geological settings of these gas hydrate occurrences, You et al (2019) categorized into them into five types, which include Type-1: low-concentration hydrate in clay-domain sediments, Type-2: fracture-filling hydrate at nonvent sites, Type-3: enriched hydrate at bottom of GHSZ (BGHSZ) in clay-domain sediments, Type-4: concentrated hydrate at vent sites, and Type-5: concentrated hydrate in sands. The formation of these types of hydrates depends on the gas source (Kida et al, 2015), the stability conditions determined by temperature, pressure, and salinity (Sloan and Koh, 2007;Torres et al, 2002;Dugarov et al, 2019), reservoir property (Liu and Flemings, 2011; Daigle and Dugan, 2011) and fluid migration mechanism (Daigle et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

Joint control of pressure and gas hydrate stability zone on hydrate occurrences

Deng

Kuang

Jiang

et al. 2022

Preprint

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Most fracture-filling hydrates are discovered in the clay-domain sediments shallower than 200 meters below seafloor, while pore-filling hydrates were found in deeper sediments except for shallow sands worldwide. The controlling mechanisms for the occurrences of different types of hydrates are universally unrecognized. In this study, the ubiquitous hydrate reservoirs recovered in the northern South China Sea are categorized into three types based on the depth of hydrate-bearing sediments and hydrate morphology, including 1) fracture-filling hydrates in shallow clay sediments, 2) shallow fracture-filling hydrates and associated hydrates in coarse grained sediments, and 3) pore-filling hydrates in deeper clay-domain sediments. By analyzing the in-situ pressures, a critical depth range (CDR) is found where capillary pressure almost equals to the sum of the minimum principal stress and tensile strength, and hydrate types are determined by the coupling relationship between the depth of bottom of gas hydrate stability zone (BGHSZ) and the depth of CDR. Above CDR where the capillary pressure is greater, gas first migrates by inducing fractures, and a BGHSZ shallower than CDR must be matched to produce fracture-filing hydrates. Below CDR where capillary pressure is basically less than fracturing pressure, gas prefers migrating between pores. If BGHSZ is deeper than CDR at the same time, pore-filling hydrates are forming below CDR. The formation of hydrate further reduces the permeability of sediments, blocking fluids to migrate into the sediments above CDR. This study reveals the controlling mechanisms of hydrate occurrences, and provide scientific implications for hydrate research worldwide.

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Gas-driven tensile fracturing in shallow marine sediments

Cited by 4 publications

References 0 publications

Upward‐Doming Zones of Gas Hydrate and Free Gas at the Bases of Gas Chimneys, New Zealand's Hikurangi Margin

Upward‐Doming Zones of Gas Hydrate and Free Gas at the Bases of Gas Chimneys, New Zealand's Hikurangi Margin

Numerical Evaluation of Gas Hydrate Production Performance of the Depressurization and Backfilling with an In Situ Supplemental Heat Method

Joint control of pressure and gas hydrate stability zone on hydrate occurrences

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