Journal of Natural Gas Science and Engineering
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Knowledge of the dynamic responses of hydrate-bearing sediments under small strain conditions is a fundamental issue in terms of evaluating the stability of gas hydrate-bearing layers under natural forces, such as eustatic sea level and earthquakes as well as artificial activities for example gas production from hydrate reservoirs. However, this issue has not yet been fully understood. In this study, a customized hydrate resonance column was utilized to measure the dynamic response of tetrahydrofuran hydrate-bearing sediments with different conditions. The results show that the shear modulus increases exponentially with increases in the confining pressure or decreases in the shear strain, while the damping ratios decrease exponentially under identical conditions. Under the same confining pressure, the shear modulus and damping ratio increases as hydrate saturation rises. The stress sensitivity index (b) of shear modulus decreases monotonically with an increase in hydrate saturation. The shear modulus is negatively correlated with porosity when the tetrahydrofuran (THF) hydrate is predominantly pore-filling type, and the damping ratio and sensitivity index b are positively correlated with porosity. However, when the hydrate is mainly load-bearing type, the shear modulus and damping are both related positively with porosity. This is because the total amount of hydrate in specimens with identical hydrate saturation increases with higher porosity, while the sensitivity index b is negatively related to porosity. The hydrate formed in pores leads to a normal increase in the shear modulus and an abnormal increase in the damping, due to trace amounts of residual water between the surface of the hydrate and the particles. This study provides a basis for the comprehensive understanding of the dynamic responses of hydrate-bearing sediments under small strains. It is of great significance for seismic or sonic well logging evaluations on gas hydrate saturation and its dissociation degree in hydrate reservoirs.
Natural gas hydrate is a crystalline ice-like compound that is formed by host water molecules and guest gas molecules (such as CH4 and C2H6) under conditions of low temperature and high pressure, which often occurs in permafrost and the deep ocean sediments (Boswell, 2009; Collett et al., 2015; Sloan, 2003). As a potential new energy source for the 21st century, it has attracted worldwide attention because of its abundance, clean, and low-carbon characteristics (Boswell and Collett, 2011; Makogon et al., 2007). Field trails concerning the production of gas hydrate have been performed in Mackenzie; the North Slope of Alaska; Nankai Trough; Shenhu Sea Area, and the South China Sea, among others. (Konno et al., 2017; Li et al., 2018; Myshakin et al., 2016). And, current studies have suggested that borehole instability, reservoir sand production, formation subsidence, gas leakage, and even geological hazards are easily induced by natural gas production from the hydrate deposits, which is expected to seriously restrict safe and economic hydrate exploitation (Cheng et al., 2019; Liu et al., 2019a; Li et al., 2010; Smith et al., 2013; Sun et al., 2018; Wang et al., 2018). The main cause of these problems is that mechanical properties of hydrate-bearing sediments become weak during gas production process.
Seismic wave, well logging, and drilling cores have been used to study the mechanical properties of hydrate reservoirs. For example, The wave velocity and attenuation were acquired by seismic inversion has been used to calculate elastic modulus and damping (Guerin and Goldberg, 2002; Li et al., 2014); the wave velocity and density are obtained via logging in order to calculate mechanical parameters such as Poisson's ratio, Young's modulus, and the shear modulus (Dickens et al., 1997; Liu et al., 2018; Lu and McMechan, 2004). Hydrate cores are usually obtained using special samplers that include a system that preserves both pressure and/or temperature, and the mechanical properties of the hydrate reservoirs can therefore be evaluated through triaxial tests (Yoneda et al., 2015, 2017). However, its usage in mechanical study is limited because of the technical difficulties and the high cost of field tests.
In the laboratory, direct shear, triaxial and elastic wave tests (mainly including ultrasonic measurement, bender element, and the resonant column test) are the main methods used for mechanical measurement of hydrate-bearing sediments. The direct shear and triaxial tests are generally chosen for measurement under large strain conditions. Many researchers used these tests to obtain the stress-strain curves, mechanical strength, Poisson's ratio, the cohesion and internal friction angle of hydrate-bearing sediments, then the effects of temperature, pore characteristics, hydrate saturation, stress, and the loading mode of stress on the mechanical properties and responses of hydrate-bearing sediments are discussed. (Dong et al., 2019; Hyodo et al., 2013; Liu et al., 2017, 2018; Madhusudhan et al., 2019). However, the tested specimens are usually destroyed, and the obtained results are not convenient for use in comparative analysis or under identical conditions. In the elastic wave measurement tests, wave velocity and attenuation are mainly obtained through wave signals, which can be used to calculate shear modulus, damping, and Poisson's ratio (Liu et al., 2019b; Winters et al., 2007; Yun et al., 2005). High frequency (approximately 0.25–1MHz) acoustic waves are usually used in traditional ultrasonic measurement, but the accuracy of the results is easily affected by hydrate content and distribution. Bender element testing is easy to produce the near-field effect and overshoot phenomenon in the test, resulting in insufficient accuracy of measurement results (Jovičić et al., 1996; Sanchez-Salinero et al., 1986). While the resonant column test can be applied to accurately measure the acoustic parameters of hydrate bearing-sediments and to study their dynamic characteristics under conditions of small strains without damaging the sample, using a test frequency of between 10Hz and 1kHz. A few researchers have studied the relationship between dynamic characteristics and hydrate saturation, confining pressure, or the features of particles within the sediments (Priest et al., 2005, 2006, 2009; Sultaniya et al., 2015). However, the porosity of the sediment, which varies in the fields, also tremendously affects its dynamic characteristics. And the range of hydrate saturation in laboratory tests should be matched with that of in situ hydrate reservoir to make the research results applicable.
Here we investigated the dynamic response of tetrahydrofuran (THF) hydrate-bearing sediments with different porosities and hydrate saturations under various confining pressures and shear strains by employing a customed resonance column. The shear modulus (shear wave velocity) and damping ratio (attenuation coefficient) was calculated. The influence of hydrate saturation (Sh), porosity (Φ), hydrate content (Ch), confining pressures (σ) and shear strains (γ) on these dynamic parameters were analyzed. This research will provide useful information for a full understanding of the dynamic response of hydrate-bearing sediments, which can be used for the accurate interpretation of seismic and sonic well logging.
Device design and experimental materials
A customed resonance column, which is a modified version of the fixed-free Stokoe Resonance Column Device (Stokoe et al., 1999), is equipped with a water-cooled jacket and a high-pressure chamber for hydrate formation. Pressures of 0–60MPa and temperatures between −40°C and room temperature can be achieved using this system. The system is constructed from five main components: a sample cooling system (cold water jacket and coolant), a sample confining pressure loading system (high pressure
Response of shear modulus with confining pressure
Fig. 2(a–e) demonstrates that the shear modulus of the five groups of specimens with different hydrate saturations all increased exponentially as the confining pressure was increased. For hydrate saturation in the range of 0%–55% and under the same confining pressure, the shear modulus of specimens with the same hydrate saturation was found to decrease as porosity increased, and the increment of shear modulus under the same porosity interval (5%) was found to gradually decrease. While, for the
Shear modulus (shear wave velocity) and hydrate distribution
Fig. 8 summarizes the trend curve for the relationship between hydrate saturation and shear wave velocity (Vs) in four structural types of hydrate-bearing sediments (I: Contact cement; II: Grain-coating; III: Pore filling; IV: Load bearing), obtained from Dvorkin's prediction formula (Dvorkin et al., 2003; Mavko and Mukerji, 1998) and verified through experiments (Helgerud et al., 1999; Jakobsen et al., 2000). The trend curve for the relationship between hydrate saturation and the shear wave
A series of resonance column tests of THF hydrate-bearing sediments with different porosities and hydrate saturations under various confining pressures and shear strains were conducted to investigate the dynamic response of those sediments, and the results are as follows:
the shear modulus increases exponentially and the damping ratio decreases exponentially as the confining stress is increased. While the shear modulus decreases exponentially and the damping ratio increases exponentially with a
CRediT authorship contribution statement
Dongdong Wang: Investigation, Formal analysis, Writing - original draft. Zhichao Liu: Methodology. Fulong Ning: Conceptualization, Writing - review & editing. Wei Hu: Validation. Li Peng: Formal analysis. Gaowei Hu: Validation, Resources. Zhun Zhang: Software. Qiang Luo: Investigation. Xiaodong Li: Data curation. Xiaofeng Dou: Visualization. Lele Liu: Resources. Yanlong Li: Supervision. Changling Liu: Project administration, Funding acquisition.
This work was supported by Qingdao National Laboratory for Marine Science and Technology Open Fund (QNLM2016ORP0203, QNLM2016ORP0207), the National Key Research and Development Program of China (2018YFE0126400, 2017YFC0307600), the National Natural Science Foundation of China (51274177), China Geological Survey Project (DD20190231, DD20190232), and Fundamental Research Funds for the National University, China University of Geosciences, Wuhan (1810491T05).
- W. Cheng
A porothermoelastic wellbore stability model for riserless drilling through gas hydrate-bearing sediments in the Shenhu area of the South China sea
J. Nat. Gas Sci. Eng.
- J.-f. Li
The first offshore natural gas hydrate production test in South China Sea
- Z. Liu et al.
An easy and efficient way to evaluate mechanical properties of gas hydrate-bearing sediments: the direct shear test
J. Petrol. Sci. Eng.
- Y. Makogon et al.
Natural gas-hydrates — a potential energy source for the 21st Century
J. Petrol. Sci. Eng.
- E. Myshakin et al.
Numerical simulations of depressurization-induced gas production from gas hydrates using 3-D heterogeneous models of L-Pad, Prudhoe Bay Unit, North Slope Alaska
J. Nat. Gas Sci. Eng.
- J. Santamarina
Hydro-bio-geomechanical properties of hydrate-bearing sediments from Nankai Trough
Mar. Petrol. Geol.
- D. Smith et al.
Sea level rise and submarine mass failures on open continental margins
Quat. Sci. Rev.
- J. Sun
Wellbore stability analysis during drilling through marine gas hydrate-bearing sediments in Shenhu area: a case study
J. Petrol. Sci. Eng.
- Y. Wang et al.
Pilot-scale experimental evaluation of gas recovery from methane hydrate using cycling-depressurization scheme
- W.J. Winters et al.
Methane gas hydrate effect on sediment acoustic and strength properties
J. Petrol. Sci. Eng.
Mechanical behavior of hydrate-bearing pressure-core sediments visualized under triaxial compression
Mar. Petrol. Geol.
Pressure-core-based reservoir characterization for geomechanics: insights from gas hydrate drilling during 2012–2013 at the eastern Nankai Trough
Mar. Petrol. Geol.
Measured acoustic wave velocities of R11 (CCl3F) hydrate samples with and without sand as a function of hydrate concentration
J. Geophys. Res.
Long-wavelength propagation in composite elastic media. I. Spherical inclusions
J. Acoust. Soc. Am.
Is gas hydrate energy within reach?
Current perspectives on gas hydrate resources
Energy Environ. Sci.
Flexural excitation in a standard torsional-resonant column
Can. Geotech. J.
Interparticle contact behavior and wave propagation
J. Geotech. Eng.
Microstructural evolution of gas hydrates in sedimentary matrices observed with synchrotron X-ray computed tomographic microscopy
Geochem. Geophy. Geosyst.
Methane hydrates in nature—current knowledge and challenges
J. Chem. Eng. Data
The effects of disseminated methane hydrate on the dynamic stiffness and damping of a sand
Hydrate morphology: physical properties of sands with patchy hydrate saturation
J. Geophys. Res.: Solid Earth
Direct measurement of in situ methane quantities in a large gas-hydrate reservoir
Strength estimation for hydrate-bearing sediments based on triaxial shearing tests
J. Petrol. Sci. Eng.
Modulus and Damping of Soils by the Resonant-Column Method, Dynamic Geotechnical Testing
Introduct. Phys. Propert. Elast. Mod.
Sonic waveform attenuation in gas hydrate-bearing sediments from the Mallik 2L-38 research well, Mackenzie Delta, Canada
J. Geophys. Res.
Elastic‐wave velocity in marine sediments with gas hydrates: effective medium modeling
Geophys. Res. Lett.
Observation of gas hydrate distribution in sediment pore space
Chin. J. Geophys.
Acoustic properties of gas hydrate-bearing consolidated sediments and experimental testing of elastic velocity models
J. Geophys. Res.
Assessment of sustainable expanded glass granules for enhancing shallow soil stabilization and dynamic behaviour of clay through resonant column tests
2023, Engineering Science and Technology, an International Journal
In geotechnical engineering applications such as artificial slope fills, backfill for retaining walls and embankments are required to be as light as possible, yet more durable and provide drainage. Recently, the use of waste materials in stabilization applications is preferred due to both a more sustainable environment and economic advantages. In this study, expanded glass granules, used in lightweight and stabilization material such as autoclaved aerated concrete, were mixed with clay at various ratios (by mass 1 – 2% and by volume 2.5 – 5 – 7.5 – 10 – 15%) and their dynamic properties such as initial shear modulus, damping ratio and modulus reduction were investigated under various effective pressures comparatively using resonant column/torsional shear test (RCTS). Considering the shear modulus results of the mixtures by mass (1–2%) and by volume (2.5–5 − 7.5%), it is observed that low and medium shear strain amplitude (0.001–0.05%) were observed to be higher in the range of up to 40% and 10% compared to the reference sample. In addition, it was calculated that the density of the mixed specimens (2.5–5 − 7.5%) with high shear modulus were up to 6.2% lower than the reference sample. The study concludes that the use of expanded glass granules (by mass 1–2%, by volume 2.5, 5%) is experimentally satisfactory for shallow soil stabilization in geotechnical applications where the presented boundary conditions are valid.
Mechanical properties of polycrystalline tetrahydrofuran hydrates as analogs for massive natural gas hydrates
2021, Journal of Natural Gas Science and Engineering
Citation Excerpt :
Mechanical tests using natural gas hydrate-simulated specimens that can be handled under milder conditions are important as a model experiment to elucidate the failure behavior and conditions of bulk natural gas hydrates with various morphologies. Because of the milder conditions used for hydrate formation and easier crystal growth controllability, clathrate hydrates of tetrahydrofuran (THF) have been used widely as analogs of natural gas hydrates in laboratory experiments to assess the mechanical and thermal properties of hydrate-bearing sediments, hydrate-bearing pattern modeling, and assessment of inhibition effects of chemicals on hydrate crystal growth in natural gas flow lines (e.g. Cortes et al., 2009; Huang and Fan, 2005; Larsen et al., 1998; Muraoka and Nagashima, 2014; Wang et al., 2020; Yun et al., 2007). Clathrate hydrates of THF (C4H8O), which is a water-soluble cyclic ether, forms sII clathrate hydrate frameworks incorporating THF molecules as guest molecules.
For experiments simulating marine sediments that include massive hydrate crystals for geotechnical stability assessment and for development of hydrate recovery techniques for such natural gas hydrate deposits, mechanical properties of massive natural gas hydrate crystals must be assessed as important factors affecting geotechnical stability for submarine hydrate deposits. This report describes mechanical properties of polycrystalline tetrahydrofuran hydrates of two types as analogs for massive natural gas hydrates. All tetrahydrofuran hydrate specimens exhibited brittle failure under uniaxial compression, similarly to reported massive natural gas hydrates. The uniaxial compressive strength of transparent massive hydrate specimens solidified by cooling aqueous tetrahydrofuran solution with small subcooling was 2.8–4.3MPa. Its elastic modulus was approximately 800–1300MPa. The strengths of cloudy massive hydrate specimens prepared from a slurry in which fine hydrate crystals were dispersed at higher subcooling were 5.3–5.7MPa. The specimens’ elastic moduli were approximately 400MPa. Comparison with the reported mechanical properties of massive natural gas hydrates showed that the strengths of tetrahydrofuran hydrate specimens have good agreement with the strengths of natural ones, significantly higher similarity to natural specimens was found for transparent specimens. Regarding the elastic modulus, cloudy specimens showed higher similarity to the natural specimens. The transparent specimens showed elastic modulus values that were a maximum 4.6 times higher than the natural ones.
The effect of particle size and hydrate status on dynamic mechanical properties of hydrate-bearing sediments
2022, Energy Science and Engineering
Review on the Test Methods and Devices for Mechanical Properties of Hydrate-Bearing Sediments
2022, Sustainability (Switzerland)
Optimisation of measuring system construction in the context of high flow variability
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103447
The article presents the concept of construction of natural gas measuring systems with high variability of gas flow through a metering station. The considerations are based on the analysis of the flow rate range of gas meters available on the European market, performance analysis of real measuring systems located in gas stations as well as on laboratory tests of gas meters. Studies were carried out and errors of turbine and rotary gas meter readings below their measuring ranges were presented. A concept of optimum construction of measuring systems utilised at stations with high gas flow variability was presented. A block diagram of the autonomous control of measuring strings was presented together with a microcontroller algorithm developed by the authors to support a system to control valves of the measuring strings.
Experimental investigation on anisotropic characteristics of marine shale in Northwestern Hunan, China
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103421
The anisotropic characteristics is obviously performed for the marine shale in Northwestern Hunan, China, it's closely related to the developed bedding existing in shale formation layers. While the investigations of the shales' anisotropic behaviors under the different bedding angles are still lacking on comprehensive understanding in this region. In order to understand shales' anisotropic behaviors considering its bedding angle, in this paper, the mechanical properties and failure modes of the marine shales, as well as shales' fragments fractal behaviors were researched based on the elastic strain energy in the shales' failure process. The results show that, the elastic energy release and storage in the failure process of shale are depended on bedding angles, it decides the shales' failure modes, which including piercing blast failure, penetrating shear-slip failure, sliding failure, sliding-shear failure and tensile failure. The findings also indicate that under the different bedding angles, the correlations between the uniaxial compressive strength (UCS), elastic strain energy, and the elastic modulus can be established. Further, via fractal statistics, the relationship between fractal dimensions of the shales' fragments and elastic strain energy has also been obtained. Finally, a novel evaluation scheme was proposed to define the shale's anisotropy grade based on the elastic strain energy. This investigation is significant for the hydraulic fracturing performing design related with the anisotropy characteristics of the marine shale theory.
Exergy comparison of single-shaft and multiple-paralleled compressor schemes in offshore processing of CO2-Rich natural gas
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103390
Deepwater oil and associated gas productions resort to floating rigs operating at continuously decreasing gas-loads during the last three quarters of the field campaign. As centrifugal compressors are sized at maximum loads, anti-surge recycles are used making operation inefficient in terms of power consumption and emissions per oil barrel produced. Smaller paralleled compressors and variable-speed drivers are investigated at peak and partial gas-loads and compared to traditional anti-surge recycle designs in terms of exergy efficiency, investment, footprint and emissions. Oversized compressors with anti-surge recycles result in almost constant power consumption along process lifespan, regardless the gas-load, increasing fuel and CO2 intensities as gas-load decreases and attaining exergy efficiencies of 49% and 83% at 25% and 100% gas-loads, respectively. On the other hand, with variable-speed drivers and smaller paralleled compressors, power consumption becomes proportional to gas-load with exergy efficiencies always between 80% and 88%, and attaining 11% and 39% less power consumptions at 100% and 25% gas-loads. Moreover, CO2 intensity and investment are, respectively 34% and 3% less than in traditional layouts with oversized compressors. These savings resulted from eliminating a gas turbine thanks to lower power demand when no anti-surge recycles are used.
Pore structure characteristics and hydrocarbon generation potential of middle Jurassic lacustrine source rocks in the Yuka depression, Qaidam Basin, NW China: Implications from petrographic and organic geochemical analyses
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103481
The Yuka depression is one of the most important energy production bases in the Qaindam Basin. Although shales in the 7th member of the Dameigou Formation (J2d7) are key members of Middle Jurassic Petroleum System, organic geochemistry and petrography of different rock facies have not been fully analyzed. In this study we evaluate hydrocarbon generation potential of the J2d7 by applying integrated petrographic, geochemical and mineralogical analyses. In addition, pore structure is characterized using field emission scanning electron microscopy (SEM), CO2 and N2 physisorption. Results indicate that mudstone, carbonaceous-mudstone and siltstone have total organic carbon (TOC) values of 2.64%, 5.61% and 0.48%, respectively, as well as variations in the hydrogen index (HI). Kerogen types are mainly Type Ⅲ, with maturity varying from marginally mature to mature. Notably, excess methane adsorption capacities were higher in the carbonaceous-mudstone sample (4.66cm3/g) than in the mudstone sample (1.78cm3/g). Primary minerals in the mudstone were quartz and clay; kaolinite, illite and illite/smectite (I/S) were the dominant clay minerals. Clay minerals and TOC content, as well as positive correlations between illite, I/S and mesopore SSA, were factors controlling pore structure development; in contrast, kaolinite contents were negatively correlated with SSA. Liptinite is the dominant maceral composition and a high content of C29 regular sterane in the carbonaceous-mudstones suggests primary higher-plant input, associated with a low gammacerane index (0.28–0.32) and a high pristane/phytane (Pr/Ph) ratio (3.02–3.96). Petrographic and geochemical results indicate an alternating depositional environment across suboxic semi-saline to oxic fresh water changes. Higher-plants were predominant and a small quantity of algae were preserved through in-situ accumulation and migration during shale development; an oxic water column with carbonaceous-mudstone was also present. Although organic matter was marginally mature to mature, the abundance of liptinite (average of 63%) was derived from higher-plants, possibly being the primary materials producing gaseous hydrocarbons.
Concentration of unconventional methane resources using microporous membranes: Process assessment and scale-up
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103420
Unconventional methane resources are usually diluted in air, which prevents their use as feedstock in chemical or thermal processes. Some of them (e.g. coal mine ventilation air or diluted landfill biogas) are emitted directly to the atmosphere without harnessing, increasing the contribution of methane to global warming. Gas permeation membranes offer an alternative for the concentration of these methane resources, increasing considerably their harnessing possibilities. Microporous materials, such as carbon molecular sieve, zeolite or metal organic frameworks, have emerged as alternative to polymeric materials for the preparation of these membranes.
The present work is based on simulations of the separation of methane and nitrogen mixtures, using SAPO-34 and carbon molecular sieve membranes. Mass transfer has been modelled in two scales: the membrane material (modelled using the Maxwell-Stefan multicomponent surface diffusion model) and the membrane module (based on the plug flow model). A sensitivity analysis of the influence of the main operating variables on the membrane performance has revealed that the most important ones are transmembrane pressure difference, methane feed concentration and membrane loading. It has been found that SAPO-34 membranes are more suited to concentrate methane in lean mixtures, while the carbon membrane perform better with rich mixtures.
The membrane process has been scaled-up for a feed gas flow rate of 1000m3/h n.t.p. with target methane recovery of 70% for two cases: lean (1%) and rich (50%) methane feed mixtures.
Prediction of the driving force for a cup pig based on the distribution of contact stress
Journal of Natural Gas Science and Engineering, Volume 81, 2020, Article 103415
To Predict the driving force of a cup pig has significant meaning in ensuring the success of its pigging operation. The pigging process of the cup pig with a specific structure under different conditions (with different friction coefficients and interferences) was simulated based on the 3D finite element method (FEM), and the equations of contact stress on cups were studied with the method of nonlinear regression. Additionally, a prediction model of the driving force for cup pig was first established based on the integral form of the contact stress equations. The results indicate that the contact stress equations present two different forms before and after a critical interference which is proved to be related to the cup lip percentage. Besides, the friction coefficient has almost no effect on the distribution of the contact stress while it affects the magnitude of it significantly. The quantitative effect of friction coefficient on the magnitude of contact stress was described by the correction equation which perfects the prediction model, and the extent of the effect is related to the interference. According to the modeling approach introduced in this paper, the driving force of the cup pigs with arbitrary structure forms can also be predicted.
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