scholarly journals Stability Analysis of Near-Wellbore Reservoirs Considering the Damage of Hydrate-Bearing Sediments

2019 ◽  
Vol 7 (4) ◽  
pp. 102 ◽  
Author(s):  
Zhang ◽  
Xia ◽  
Xu ◽  
Han
Keyword(s):  
Gas Hydrate ◽  
Structural Damage ◽  
Coupled Model ◽  
Damage Variable ◽  
Field Coupling ◽  
Mechanical Field ◽  
Hydrate Saturation ◽  
Key Issues ◽  
The Stability ◽  
Hydrate Bearing Sediments

The stability of hydrate-bearing near-wellbore reservoirs is one of the key issues in gas hydrate exploitation. In most previous investigations, the damage evolution process of the sediment structure and its effect on near-wellbore reservoir stability have been neglected. Therefore, the damage variable is introduced into a multi-field coupled model based on continuous damage theory and multi-field coupling theory. A thermo-hydro-mechanical-chemical (THMC) multi-field coupling mathematical model considering damage of hydrate-bearing sediments is established. The effects of damage of hydrate-bearing sediments on the thermal field, seepage field, and mechanical field are considered. Finally, the distributions of hydrate saturation, pore pressure, damage variable, and effective stress of a near-wellbore reservoir in gas hydrate exploitation by depressurization are calculated, and the stability of a hydrate-bearing near-wellbore reservoir is analyzed using the model. Through calculation and analysis, it is found that structural damage of hydrate-bearing sediments has an adverse effect on the stability of hydrate-bearing near-wellbore reservoirs. The closer to the wellbore, the worse the reservoir stability, and the near-wellbore reservoir stability is the worst in the direction of minimum horizontal ground stress.

Experimental Techniques for Mechanical Properties of Gas Hydrate-Bearing Sediments

2013 ◽  
Vol 275-277 ◽  
pp. 316-321 ◽  
Author(s):  
Jian Zhang ◽  
Yu Guang Ye ◽  
Chang Ling Liu ◽  
Zhong Ming Sun ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Gas Hydrate ◽  
Experimental Techniques ◽  
Marine Geology ◽  
Natural Gas Hydrate ◽  
Hydrate Saturation ◽  
Basic Parameters ◽  
National Patent ◽  
The Stability ◽  
Hydrate Bearing Sediments

The mechanical properties of gas hydrate-bearing sediments are important basic parameters during natural gas hydrate drilling and exploitation. It’s very hard to get and preserve the actual gas hydrate specimens for the measurements of these characteristics. Experimental techniques for mechanical properties of gas hydrate-bearing sediments are essential and unique because of the special high pressure and low temperature conditions for the stability of gas hydrate. Qingdao Institute of Marine Geology has developed an experimental equipment (Chinese National patent No. ZL 2010 2 0253067.3) to study the variation of mechanical properties along with gas hydrate saturation in different sediments. The combination, configuration and advantages of the equipment, as well as some preliminary experimental results were introduced in this article.

scholarly journals Wave Propagation Characteristics in Gas Hydrate-Bearing Sediments and Estimation of Hydrate Saturation

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 804
Author(s):  
Lin Liu ◽  
Xiumei Zhang ◽  
Xiuming Wang
Keyword(s):  
Gas Hydrate ◽  
Clay Content ◽  
Clean Energy ◽  
Compressional Wave ◽  
Physical Parameters ◽  
Well Log ◽  
Log Data ◽  
Phase Velocities ◽  
Hydrate Saturation ◽  
Hydrate Bearing Sediments

Natural gas hydrate is a new clean energy source in the 21st century, which has become a research point of the exploration and development technology. Acoustic well logs are one of the most important assets in gas hydrate studies. In this paper, an improved Carcione–Leclaire model is proposed by introducing the expressions of frame bulk modulus, shear modulus and friction coefficient between solid phases. On this basis, the sensitivities of the velocities and attenuations of the first kind of compressional (P1) and shear (S1) waves to relevant physical parameters are explored. In particular, we perform numerical modeling to investigate the effects of frequency, gas hydrate saturation and clay on the phase velocities and attenuations of the above five waves. The analyses demonstrate that, the velocities and attenuations of P1 and S1 are more sensitive to gas hydrate saturation than other parameters. The larger the gas hydrate saturation, the more reliable P1 velocity. Besides, the attenuations of P1 and S1 are more sensitive than velocity to gas hydrate saturation. Further, P1 and S1 are almost nondispersive while their phase velocities increase with the increase of gas hydrate saturation. The second compressional (P2) and shear (S2) waves and the third kind of compressional wave (P3) are dispersive in the seismic band, and the attenuations of them are significant. Moreover, in the case of clay in the solid grain frame, gas hydrate-bearing sediments exhibit lower P1 and S1 velocities. Clay decreases the attenuation of P1, and the attenuations of S1, P2, S2 and P3 exhibit little effect on clay content. We compared the velocity of P1 predicted by the model with the well log data from the Ocean Drilling Program (ODP) Leg 164 Site 995B to verify the applicability of the model. The results of the model agree well with the well log data. Finally, we estimate the hydrate layer at ODP Leg 204 Site 1247B is about 100–130 m below the seafloor, the saturation is between 0–27%, and the average saturation is 7.2%.

New Predictive Model for Relative Permeability of Deformable Gas Hydrate-Bearing Sediments

2020 ◽  
Author(s):  
Gang Lei ◽  
Qinzhuo Liao ◽  
Patil Shirish
Keyword(s):  
Relative Permeability ◽  
Gas Hydrate ◽  
Water Phase ◽  
Flow In Porous Media ◽  
World Population ◽  
Water Mixture ◽  
Gas Saturation ◽  
Hydrate Saturation ◽  
Stress Dependent ◽  
Hydrate Bearing Sediments

<p>Global energy demand is expected to grow significantly as the world population and the standard of living increase in the coming decades. As a potential source of energy, gas hydrate, which is a crystalline compound of gas-water mixture formed in stable of high pressure and low temperature, has been intensively investigated in the past few decades. In this work, a new analytical model is derived to study the effect of hydrate saturation on stress-dependent relative permeability behavior of hydrate-bearing sediments. The proposed relative permeability model solves the steady-state Navier-Stokes equations for gas-water two-phase flow in porous media with hydrates. It considers water saturation, hydrate saturation, viscosity ratio and hydrate-growth pattern, and is adequately validated with the experimental results in existing literatures. The model demonstrates that gas-water relative permeability in wall coating hydrates (WC hydrates) is larger than that in pore filling hydrates (PF hydrates). For WC hydrates, water phase relative permeability monotonically decreases as gas saturation increases. However, for PF hydrates, water phase relative permeability firstly increases and then decreases with the increase of gas saturation, which can be explained by the “lubricative” effect of the gas phase that exists between the water phase and hydrates. This work constitutes a comprehensive investigation of stress-dependent relative permeability in deformable hydrate-bearing sediments, which is a key issue for sustainable gas production. It not only provides theoretical foundations for quantifying relative permeability in hydrate-bearing sediments, but also can be used to estimate pore-scale parameters and rock lithology of gas hydrate-bearing sediments using inverse modeling.</p>

Experimental Study on Dynamic Elastic Properties of Gas Hydrate Bearing Sediments

2012 ◽  
Vol 446-449 ◽  
pp. 1396-1399
Author(s):  
Ling Dong Li ◽  
Yuan Fang Cheng ◽  
Xiao Jie Sun
Keyword(s):  
Elastic Properties ◽  
Gas Hydrates ◽  
Gas Hydrate ◽  
Hot Spot ◽  
Confining Pressure ◽  
Measuring System ◽  
Fundamental Parameters ◽  
Hydrate Saturation ◽  
Hydrate Bearing Sediments

As a kind of emerging energy with massive reserves, natural gas hydrates are becoming the hot spot of global research. The elastic properties of gas hydrate bearing sediments (HBS) are the fundamental parameters for gas hydrates exploration and resource evaluations. As the original coring in HBS is difficult and expensive, experimental method is important to study the problem. An acoustic wave in-situ measuring system for HBS was developed. Using the in-situ method, hydrate bearing rock samples of different hydrate saturation were synthesized, of which the supersonic wave measurement was carried out under different confining pressure. According to the elasticity theory, the dynamic elastic parameters were obtained using the measured ultrasonic wave velocity. The results show that compressional and shear waves increase with the confining pressure and hydrate saturation increasing, and so the dynamic elastic modulus is.

scholarly journals The Acoustic Properties of Sandy and Clayey Hydrate-Bearing Sediments

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1825
Author(s):  
Xiao-Hui Wang ◽  
Qiang Xu ◽  
Ya-Nan He ◽  
Yun-Fei Wang ◽  
Yi-Fei Sun ◽  
...  
Keyword(s):  
Wave Velocity ◽  
Gas Hydrate ◽  
Acoustic Properties ◽  
P Wave ◽  
S Wave ◽  
Hydrate Saturation ◽  
New Apparatus ◽  
Sandy Sediments ◽  
Hydrate Bearing Sediments ◽  
And Control

Natural gas hydrates samples are rare and difficult to store and transport at in situ pressure and temperature conditions, resulting in difficulty to characterize natural hydrate-bearing sediments and to identify hydrate accumulation position and saturation at the field scale. A new apparatus was designed to study the acoustic properties of seafloor recovered cores with and without hydrate. To protect the natural frames of recovered cores and control hydrate distribution, the addition of water into cores was performed by injecting water vapor. The results show that hydrate saturation and types of host sediments are the two most important factors that govern the elastic properties of hydrate-bearing sediments. When gas hydrate saturation adds approximately to 5–25%, the corresponding P-wave velocity (Vp) increases from 1.94 to 3.93 km/s and S-wave velocity (Vs) increases from 1.14 to 2.23 km/s for sandy specimens; Vp and Vs for clayey samples are 1.72–2.13 km/s and 1.10–1.32 km/s, respectively. The acoustic properties of sandy sediments can be significantly changed by the formation/dissociation of gas hydrate, while these only minorly change for clayey specimens.

Numerical Simulations of Drilling Mud Invasion into the Marine Gas Hydrate-Bearing Sediments

2011 ◽  
Vol 366 ◽  
pp. 378-387 ◽  
Author(s):  
Fu Long Ning ◽  
Yi Bing Yu ◽  
Guo Sheng Jiang ◽  
Xiang Wu ◽  
Ke Ni Zhang ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Gas Hydrate ◽  
Wellbore Stability ◽  
Drilling Mud ◽  
Hydrate Dissociation ◽  
Hydrate Saturation ◽  
Drilling Condition ◽  
Hydrate Bearing Sediments ◽  
Invasion Behavior ◽  
Hydrate Stability

When drilling through the oceanic gas hydrate-bearing sediments, the water-based mud under overbalanced drilling condition will invade into the borehole sediments. The invasion behavior can influence the hydrate stability, wellbore stability and well logging evaluation. In this work, we performed the numerical simulations to study the effects of density (i.e., corresponding pressure), temperature and salinity of mud on the mud invasion and hydrate stability around borehole. The results show that the mud invasion will promote greatly the hydrate dissociation near wellbore sediments if the temperature of mud is higher than that of hydrate stability. Under certain conditions, the higher mud density, temperature and salinity, the greater degree of mud invasion and heat transfer, and the more hydrate dissociation. The gas produced from hydrate dissociation can reform hydrates again in the sediments, and even the hydrate saturation is higher than that in situ sediments due to the displacing effect of the mud invasion, which forms a high-saturation hydrate girdle band around the borehole.

scholarly journals Rock Physics Model and Seismic Dispersion and Attenuation in Gas Hydrate-Bearing Sediments

2021 ◽  
Vol 9 ◽  
Author(s):  
Zhiqi Guo ◽  
Xueying Wang ◽  
Jian Jiao ◽  
Haifeng Chen
Keyword(s):  
Gas Hydrate ◽  
Rock Physics ◽  
P Wave ◽  
Pore Filling ◽  
P Wave Velocity ◽  
Hydrate Saturation ◽  
Physics Model ◽  
Rock Physics Model ◽  
Hydrate Bearing Sediments ◽  
Dispersion And Attenuation

A rock physics model was established to calculate the P-wave velocity dispersion and attenuation caused by the squirt flow of fluids in gas hydrate-bearing sediments. The critical hydrate saturation parameter was introduced to describe different ways of hydrate concentration, including the mode of pore filling and the co-existence mode of pore filling and particle cementation. Rock physical modeling results indicate that the P-wave velocity is insensitive to the increase in gas hydrate saturation for the mode of pore filling, while it increases rapidly with increasing gas hydrate saturation for the co-existence mode of pore filling and particle cementation. Meanwhile, seismic modeling results show that both the PP and mode-converted PS reflections are insensitive to the gas hydrate saturation that is lower than the critical value, while they tend to change obviously for the hydrate saturation that is higher than the critical value. These can be interpreted that only when gas hydrate begins to be part of solid matrix at high gas hydrate saturation, it represents observable impact on elastic properties of the gas hydrate-bearing sediments. Synthetic seismograms are calculated for a 2D heterogeneous model where the gas hydrate saturation varies vertically and layer thickness of the gas hydrate-bearing sediment varies laterally. Modeling results show that larger thickness of the gas hydrate-bearing layer generally corresponds to stronger reflection amplitudes from the bottom simulating reflector.

scholarly journals Consolidation of gas hydrate-bearing sediments with hydrate dissociation

2020 ◽  
Vol 205 ◽  
pp. 11007
Author(s):  
Maria De La Fuente ◽  
Jean Vaunat ◽  
Hector Marín-Moreno
Keyword(s):  
Effective Stress ◽  
Gas Hydrate ◽  
Hydrate Dissociation ◽  
Economic Production ◽  
Mechanical Formulation ◽  
Sediment Consolidation ◽  
Hydrate Saturation ◽  
Sediment Deformation ◽  
Hydrate Bearing Sediments ◽  
Hydrate Reservoirs

Quantifying sediment deformation induced by depressurization of gas hydrate reservoirs and hydrate dissociation is crucial for the safe and economic production of natural gas from hydrates, and for understanding hydrate-related natural geological risks. This study uses our recently developed fully-coupled Thermo-Hydro-Mechanical formulation for gas hydrate-bearing geological systems implemented in the 3D Code_Bright simulator. First, the model formulation is briefly presented. Then, the model is applied to reproduce published experimental consolidation tests performed on hydrate-bearing pressure-core sediments recovered from the Krishna–Godavari Basin (offshore of India) during the India National Gas Hydrate Project Expedition 02 (NGHP02). The numerical simulation reproduces the tests in which the sediment is loaded and unloaded prior and after hydrate dissociates via depressurization at constant effective stress. Our results successfully capture sediment collapse when hydrate dissociates at a mean effective stress above that of the host sediment consolidation curve. The mechanical constitutive model Hydrate-CASM also allows reproducing the experimentally observed changes in sediment swelling index with changes in hydrate saturation.

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