A Study on the Electrical Characteristics of Fractured Gas Hydrate Reservoirs Based on Digital Rock Technology

Abstract The electrical characteristics of fractured gas hydrate reservoirs were investigated through the diffusion-limited aggregation model, digital rock technology, and the finite element method. The results show that the fracture and gas hydrate have a significant effect on the electrical characteristics of rock partially saturated with gas hydrate, where the matrix pore and fracture mixed gas hydrate form a dual-porosity system. Due to the fracture and gas hydrate effect, the electrical characteristics of fractured gas hydrate reservoirs cannot be described well by traditional Archie equations. The resistivity index vs. water saturation curve of fractured gas hydrate reservoirs shows a nonlinear relationship for different gas hydrate pore habits (pore-filling, cementing, and grain-coating types), and this curve consists of two parts with different gas hydrate saturation exponents for pore-filling and cementing gas hydrate and presents a curve without a fixed water saturation exponent for grain-coating gas hydrate. Fractured gas hydrate reservoirs with different fracture apertures, different gas hydrate pore habits, and saturation features will lead to macroscopic electrical anisotropy. The results of theoretical analysis and numerical simulation show that the electrical anisotropy coefficient of fractured gas hydrate reservoirs is a function of gas hydrate saturation. The function curve consists of three segments with the turning point for pore-filling and cementing gas hydrate, and this curve can be divided into two parts through the turning point. The findings of this study can help for a better understanding of the electrical characteristics of fractured gas hydrate reservoirs, which have great significance for the exploration and development of gas hydrate resources.

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

Frontiers in Earth Science ◽

10.3389/feart.2021.641606 ◽

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.

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Consolidation of gas hydrate-bearing sediments with hydrate dissociation

E3S Web of Conferences ◽

10.1051/e3sconf/202020511007 ◽

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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Enhanced CH4-CO2 Hydrate Swapping in the Presence of Low Dosage Methanol

Energies ◽

10.3390/en13205238 ◽

2020 ◽

Vol 13 (20) ◽

pp. 5238 ◽

Cited By ~ 1

Author(s):

Jyoti Shanker Pandey ◽

Charilaos Karantonidis ◽

Adam Paul Karcz ◽

Nicolas von Solms

Keyword(s):

Gas Hydrate ◽

Methane Hydrate ◽

Water Saturation ◽

Co2 Storage ◽

Residual Water ◽

Methane Recovery ◽

Initial Water ◽

Hydrate Film ◽

Hydrate Reservoirs ◽

Low Dosage

CO2-rich gas injection into natural gas hydrate reservoirs is proposed as a carbon-neutral, novel technique to store CO2 while simultaneously producing CH4 gas from methane hydrate deposits without disturbing geological settings. This method is limited by the mass transport barrier created by hydrate film formation at the liquid–gas interface. The very low gas diffusivity through hydrate film formed at this interface causes low CO2 availability at the gas–hydrate interface, thus lowering the recovery and replacement efficiency during CH4-CO2 exchange. In a first-of-its-kind study, we have demonstrate the successful application of low dosage methanol to enhance gas storage and recovery and compare it with water and other surface-active kinetic promoters including SDS and L-methionine. Our study shows 40–80% CH4 recovery, 83–93% CO2 storage and 3–10% CH4-CO2 replacement efficiency in the presence of 5 wt% methanol, and further improvement in the swapping process due to a change in temperature from 1–4 °C is observed. We also discuss the influence of initial water saturation (30–66%), hydrate morphology (grain-coating and pore-filling) and hydrate surface area on the CH4-CO2 hydrate swapping. Very distinctive behavior in methane recovery caused by initial water saturation (above and below Swi = 0.35) and hydrate morphology is also discussed. Improved CO2 storage and methane recovery in the presence of methanol is attributed to its dual role as anti-agglomerate and thermodynamic driving force enhancer between CH4-CO2 hydrate phase boundaries when methanol is used at a low concentration (5 wt%). The findings of this study can be useful in exploring the usage of low dosage, bio-friendly, anti-agglomerate and hydrate inhibition compounds in improving CH4 recovery and storing CO2 in hydrate reservoirs without disturbing geological formation. To the best of the authors’ knowledge, this is the first experimental study to explore the novel application of an anti-agglomerate and hydrate inhibitor in low dosage to address the CO2 hydrate mass transfer barrier created at the gas–liquid interface to enhance CH4-CO2 hydrate exchange. Our study also highlights the importance of prior information about methane hydrate reservoirs, such as residual water saturation, degree of hydrate saturation and hydrate morphology, before applying the CH4-CO2 hydrate swapping technique.

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Multiphase Flow Behavior of Layered Methane Hydrate Reservoir Induced by Gas Production

Geofluids ◽

10.1155/2017/7851031 ◽

2017 ◽

Vol 2017 ◽

pp. 1-15 ◽

Cited By ~ 15

Author(s):

Yilong Yuan ◽

Tianfu Xu ◽

Xin Xin ◽

Yingli Xia

Keyword(s):

Multiphase Flow ◽

Gas Hydrate ◽

Methane Hydrate ◽

Nankai Trough ◽

Flow Behavior ◽

Gas Production ◽

Production Performance ◽

Heterogeneous Structure ◽

Hydrate Saturation ◽

Hydrate Reservoirs

Gas hydrates are expected to be a potential energy resource with extensive distribution in the permafrost and in deep ocean sediments. The marine gas hydrate drilling explorations at the Eastern Nankai Trough of Japan revealed the variable distribution of hydrate deposits. Gas hydrate reservoirs are composed of alternating beds of sand and clay, with various conditions of permeability, porosity, and hydrate saturation. This study looks into the multiphase flow behaviors of layered methane hydrate reservoirs induced by gas production. Firstly, a history matching model by incorporating the available geological data at the test site of the Eastern Nankai Trough, which considers the layered heterogeneous structure of hydrate saturation, permeability, and porosity simultaneously, was constructed to investigate the production characteristics from layered hydrate reservoirs. Based on the validated model, the effects of the placement of production interval on production performance were investigated. The modeling results indicate that the dissociation zone is strongly affected by the vertical reservoir’s heterogeneous structure and shows a unique dissociation front. The beneficial production interval scheme should consider the reservoir conditions with high permeability and high hydrate saturation. Consequently, the identification of the favorable hydrate deposits is significantly important to realize commercial production in the future.

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GAS HYDRATE SATURATION ESTIMATED FROM ACOUSTIC IMPEDANCE IN THE ANDAMAN SEA, INDIA

Marine Geology & Quaternary Geology ◽

10.3724/sp.j.1140.2013.02163 ◽

2014 ◽

Vol 33 (2) ◽

pp. 163-168

Author(s):

Xiujuan WANG ◽

Jiliang WANG ◽

Wei LI ◽

Nittala Satyavani ◽

Kalachand Sain

Keyword(s):

Gas Hydrate ◽

Acoustic Impedance ◽

Andaman Sea ◽

Hydrate Saturation

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

Energies ◽

10.3390/en14040804 ◽

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%.

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