Hydrate-bearing Sediments Research Articles

Influence of CO2 injection rate and memory water on depressurization-assisted replacement in natural gas hydrates and the implications for effective CO2 sequestration and CH4 exploitation

This study was conducted to investigate the influence of CO2 injection rate and memory water on guest exchange and hydrate reformation behavior in CH4 hydrate-bearing sediment, using a one-dimensional (1-D) reactor to optimize depressurization-assisted replacement. Increasing the CO2 injection rate facilitated the rapid sweeping of CH4 into the pore space of the hydrate-bearing sediment, inducing immediate hydrate reformation and preventing CH4 re-enclathration in the middle region of the 1-D reactor. Despite dissociating 50 % of the initial CH4 hydrate for depressurization-assisted replacement, the replacement efficiency converged at around 70 % due to drastically reformed gas hydrates hindering mass transfer. Introducing time intervals between depressurization and replacement to reduce the residual memory effect of water led to delayed hydrate reformation, altering the longitudinal distribution of replacement efficiency in the 1-D reactor. An increase in replacement efficiency toward the outlet was seen, suggesting that improved CO2 propagation in the hydrate-bearing sediment resulted in a higher CO2 concentration in the vapor phase at the point of hydrate reformation, in turn enhancing CO2 storage efficiency in the newly formed hydrates. These experimental results highlight the importance of CO2 injection rates and time intervals in determining the hydrate reformation behaviors of hydrate-bearing sediments and optimizing the efficiency of depressurization-assisted replacement.

Significance of well placement and degree of hydrate reserve recovery for synergistic CH4 recovery and CO2 storage in marine heterogeneous hydrate-bearing sediments

The synergistic CH4 recovery and CO2 storage in marine natural gas hydrate reservoirs presents an emerging strategic solution for energy and environment challenges, yet the efficiency requires innovative engineering designs to enhance. In this study, a water-saturated CH4 hydrate-bearing sediment (HBS, V = 22 L, T = 284 K, and P = 11.2 MPa) was synthesized to investigate the pilot-scale combined processes of CH4 recovery by depressurization followed by CO2 storage through CO2/N2 injection. The synthesized HBS exhibited vertical heterogeneity with higher hydrate saturation observed in the upper sediment and a decreasing saturation trend in the lower sediment. The effect of well placement designs on CH4 recovery and hydrate restoration by mixed CH4/CO2/N2 hydrate (Mix-H) formation was investigated, considering two scenarios: upper well for recovery while lower well for injection (URLI), and lower well for recovery while upper well for injection (LRUI). Additionally, the impact of the degree of hydrate reserve recovery (100% and 80% hydrate dissociated) on subsequent Mix-H formation was also studied. Results indicate that the URLI setting achieves a higher CH4 recovery ratio and rate during depressurization compared to the LRUI setting which encounters low-T shielding. The T variation between upper and lower sediment highlights the influence of heterogeneity on fluid behaviors. Halting the CH4 recovery after 80% hydrate dissociation results in a halved recovery time and water production. During later CO2/N2 injection and Mix-H formation process, the LRUI setting achieves a 13–54% higher Mix-H saturation and a 33–56% higher CO2 hydrate encapsulation than the URLI setting. Moreover, 80% dissociation proves more favorable for Mix-H formation achieving nearly twice higher final amount than 100% hydrate dissociation. However, it results in a lower CO2 encapsulation. This study provides insights into the trade-off between CH4 recovery and CO2 storage efficiency, emphasizing the need for optimized well placement and controlled hydrate extraction.

Gas flow in frozen hydrate-bearing sediments exposed to compression and high-pressure gradients: Experimental modeling

Changes in temperature and pressure patterns in gas- and hydrate-saturated permafrost caused by natural geodynamic processes or human impacts can lead to the active flow of gas through unfrozen zones, and its explosive emission is often accompanied by crater formation. Gas flow and accumulation in the shallow permafrost can be explained by the conditions of gas pressure equal to or exceeding the overburden pressure and high-pressure gradients. For the first time, filtration tests were conducted on ice- and hydrate-saturated rocks under uniaxial compression at various negative temperatures using a developed methodology. The modeling of gas flow in a mixture of ice-saturated sand and 25 % montmorillonite at gas pressure gradients within 2 MPa, shows that gas flow can start at warm negative temperatures near the thaw point. Pore hydrate formation in frozen sand heated to positive temperatures and frozen back led to a linear decrease in gas permeability by up to eight times. However, the behavior of gas permeability during hydrate dissociation is nonlinear as it increased within a few hours after the onset of dissociation, but then decreased exponentially in the following 24 h.

Analysis of near-well hydraulic fracture propagation behavior in inhomogeneous deep-sea hydrate-bearing-sediments

The hydrate reservoirs exhibit significant inhomogeneity due to the presence of various hydrate types, potentially impacting the effectiveness of hydraulic fracturing. The investigation of the relationship between hydraulic fracture extension patterns and pure hydrate blocks for varying conditions is highly valuable. The extended finite element method (XFEM) is applied to reveal the influence mechanism of hydrate heterogeneity on fracture propagation law. First, compared with the results of the fracturing experiments in hydrate-bearing clayey silt sediments, the accuracy of the method is verified. Subsequently, a model for fracturing near-well in deep-sea inhomogeneous hydrate-bearing-sediments is established, containing sedimentary matrix and pure hydrate blocks. The effects of disseminated hydrate saturation, injection rate, horizontal stress difference and the distribution location of pure hydrate blocks on the fracture extension path are investigated. Due to the pure hydrate is much more brittle, most hydraulic fractures, once encountered with it, choose to bypass. If the fracture is unable to bypass the pure hydrate block, the fracture appears to arrest and penetrate. The seafloor sediment matrix is characterized by its loose nature, and a continuous increase in the injection rate may result in the competing development of the fractures in both length and width directions.

Integrated test system for interfacial strength and morphology of multi-type hydrate-bearing sediments.

Predicting the strength parameters of multi-type sediments containing hydrates is the basis and precondition for the safe and efficient development of natural gas hydrates. However, studies on the shear mechanical behavior and morphology of multi-type hydrate-bearing sediments (HBS) are still insufficient. Herein, this study presents an integrated test system that can be used to measure the interfacial strength and morphology of multi-type sediments containing hydrates. This device integrates specimen preparation, shear test, morphology observation, and data analysis, which is helpful to comprehensively evaluate interfacial strength, roughness, and morphology. The propagation and development characteristics of microfractures of HBS during shearing can be obtained, which is favorable for identifying the damage and failure modes. Preliminary validation experiments have been conducted on massive pure hydrate, hydrate-sediment interface, and homogenous HBS to verify the applicability of the device for multi-type HBS. The device and corresponding analysis method are expected to support the evaluation of interfacial strength and morphology, thereby promoting a deeper understanding of hydrate-sediment interactions and failure mechanisms of hydrate reservoirs.

3D DEM investigation on macro-meso mechanical responses of gas hydrate-bearing sediments in process of unloading confining pressure

Well drilling, gas production, and reservoir stimulation can disrupt stress states of gas hydrate-bearing sediments (GHBSs) surrounding wellbores, potentially inducing wellbore instability due to confining pressure unloading. Therefore, it is very important to know about the macro-meso mechanical responses of GHBSs under an unloading confining pressure path (UCPP). Herein, a discrete element method (DEM) was used to perform triaxial tests on three-dimensional numerical GHBSs under the UCPP and a conventional drained path (CDP) to bridge the knowledge gap. Results show that GHBSs under the UCPP are more prone to failure and dilatation than under the CDP, due to the reduced bearing capacity of contact force chains, relatively unstable particle assembly, and rapid cementation breakage development. Additionally, the stress path has little effect on the cohesion and friction angle of GHBSs. Furthermore, under the UCPP, the failure and dilatation risk of GHBSs are positively correlated with unloading confining pressure rate, inversely related to hydrate saturation and initial effective confining pressure. The grey relational analysis illustrates that compared to hydrate saturation and initial effective confining pressure, the unloading confining pressure rate minimally affects the unloading confining pressure effect. These findings can serve for experimental studies and field applications (e.g., optimizing drilling mud density, sand production rate, and fracturing fluid flowback rate) concerning the unloading confining pressure responses of GHBSs.

Subsidence Characteristics of Hydrate-Bearing Sediments during Depressurization: Insights from Experimental and Discrete Element Method Simulations

Subsidence Characteristics of Hydrate-Bearing Sediments during Depressurization: Insights from Experimental and Discrete Element Method Simulations

Insight into the depressurization-assisted flue gas replacement behavior with the artificial hydrate-bearing clay-silt sediment containing organic matter

The existence of organic matters in naturally hydrate-bearing sediments would notably impact the CH4 extraction from reservoirs via CO2 swapping. In this work, the depressurization-assisted flue gas replacement was explored with artificial hydrate-bearing clay-silt sediments containing organic matter. The effect of organic matter type and content, depressurization moment and amplitude was systematically investigated. The results showed that the replacement was promoted at 5.0 wt% sulfonated lignin (SL) before depressurization, while it was inhibited at a lower SL content and this inhibition was weakened after depressurization. The CH4 replacement ratio and CO2 sequestration ratio increased as the fulvic acid (FA) content increased. For the organic matter-contained systems, the earlier depressurization moment was conducted, the higher CH4 recovery was obtained. The CH4 replacement ratio increased with the increase of depressurization amplitude, which reached 71.48 % in the 3.0 wt% FA system at the depressurization amplitude of 3.0 MPa. Aspen simulation revealed that the energy consumption was mainly caused by compression, there exist an optimum injection pressure of flue gas for the energy return on investment. The findings provide useful information for the depressurization-assisted flue gas replacement and would contribute to the actual NGH exploitation in the future.

Experimental study of mechanical properties of deep-sea hydrate-bearing sediments under multi-field coupling conditions

To ensure the long-term safety of hydrate-bearing sediments (HBSs) in the deep sea, it is necessary to conduct a comprehensive study of the mechanical properties of HBSs, which is closely related to the safe extraction of natural gas hydrates (NGH). In this study, a HBSs preparation method was proposed preparing HBSs artificially to meet the test requirement. A series of triaxial shear tests were carried out by the self-developed HBSs multi-field coupling intelligent triaxial test device to analyze the effects of different hydrate saturation and NaCl concentration on the mechanical properties of HBSs. The results show that HBSs have elastic-plastic properties under multi-field coupling conditions, and the stress-strain curves show a strain-hardening trend. Hydrate saturation affects the shear strength of hydrate-bearing sediment critically. When the hydrate saturation is Sh>35 %, the cohesion and internal friction angle is directly proportional to the hydrate saturation. When the NaCl concentration is low, the cohesion of HBSs is more affected by the NaCl concentration, and the shear strength and yield strength are proportional to NaCl concentration. When NaCl concentration is high, the internal friction angle of HBSs is more affected by NaCl concentration and the shear strength is inversely proportional to NaCl concentration. Under the condition of multi-field coupling, the influence of each factor on the mechanical properties of HBSs has an upper limit, which is not a purely linear relationship.

Inversion of gas hydrate saturation and solid frame permeability in a gas hydrate-bearing sediment by Stoneley wave attenuation

Natural gas hydrate is a potential novel energy resource that is widely distributed globally. Acoustic logging can effectively provide information on the surrounding reservoir and plays an important guiding role in gas hydrate exploration and development. Natural gas hydrate-bearing sediments are composed of a solid frame with natural gas hydrates and water-filled pores. The borehole mode wave characteristics of two-phase porous media cannot be used to evaluate the parameters of such a multiphase porous medium. We explore factors that influence the monopole Stoneley wave in a borehole embedded in a multiphase porous medium containing two solids and one fluid and analyze the influence of each factor on monopole Stoneley wave attenuation systematically. The sensitivity analysis results indicate that the Stoneley wave attenuation is highly sensitive to solid frame permeability and gas hydrate saturation. Building upon this foundation, a method to invert for gas hydrate saturation and solid frame permeability is first developed using Stoneley wave attenuation. Synthetic logging data are used to demonstrate the feasibility of this method for inverting for gas hydrate-bearing sediment properties. Even in the presence of considerable noise added to the receiver signal arrays, the inversion method is stable, and reliably evaluates gas hydrate saturation and solid frame permeability.

Dissociation Behavior of Methane Hydrate Inside Different Saturation Sediments in a Sustained Depressurization Process

Summary Methane hydrate is one of the important energy storage sources, naturally distributed in marine porous sediments. However, the dissociation behavior of hydrate inside different saturation sediments during sustained depressurization remains unclear. In this study, methane hydrate-bearing sediments were synthesized using initial water saturations varying between 9.5% and 56.9% and subsequently dissociated at a gas exhaust rate of 0.77 Ls/min. The results indicate that the dissociation of hydrates is closely related to the initial hydrate distribution until the sediments get iced when the sediment pressure declines below 2.5 MPa. Due to the exothermic reaction of ice formation, the dissociation of hydrates after icing accelerates significantly, and its limiting factor becomes the gas exhaust rate. In addition, both production and monitoring pipes were used in this study to evaluate the possible plugging within the sediments, and the plugging zone within the sediments can be located by examining the thermodynamic correlation between pressure and temperature responses. It was found that all experimental cases with high saturations (47.4% and more initial water) easily induce plugging between sediments and production/monitoring pipes, with the maximum pressure gap reaching up to 2.5 MPa. These findings may aid in ensuring the safety and efficiency of the hydrate exploitation process in the future.

Properties and Model of Pore-Scale Methane Displacing Water in Hydrate-Bearing Sediments

The flow characteristics of methane and water in sedimentary layers are important factors that affect the beneficial exploitation of marine hydrates. To study the influencing factors of methane drive-off water processes in porous media, we constructed nonhomogeneous geometric models using MATLAB 2020a random distribution functions. We developed a mathematical model of gas–water two-phase flow based on the Navier–Stokes equation. The gas-driven water processes in porous media were described using the level-set method and solved through the finite element method. We investigated the effects of the nonhomogeneous structure of pore media, wettability, and repulsion rate on gas-driven water channeling. The nonhomogeneity of the pore medium is the most critical factor influencing the flow. The size of the throat within the hydrophilic environment determines the level of difficulty of gas-driven water flow. In regions with a high concentration of narrow passages, the formation of extensive air-locked areas is more likely, leading to a decrease in the efficiency of the flow channel. In the gas–water drive process, water saturation changes over time according to a negative exponential function relationship. The more hydrophilic the pore medium, the more difficult the gas-phase drive becomes, and this correlation is particularly noticeable at higher drive rates. The significant pressure differentials caused by the high drive-off velocities lead to quicker methane breakthroughs. Instantaneous flow rates at narrow throats can be up to two orders of magnitude higher than average. Additionally, there is a susceptibility to vortex flow in the area where the throat connects to the orifice. The results of this study can enhance our understanding of gas–water two-phase flow in porous media and help commercialize the exploitation of clean energy in the deep ocean.

Theoretical investigation of threshold pressure gradient in hydrate-bearing clayey-silty sediments under combined stress and local thermal stimulation conditions

Due to the characteristics of smaller grain size and higher clay mineral content, the threshold pressure gradient (TPG) exists in multi-phase flow within hydrate-bearing clayey-silty sediments (HBCSS), which significantly affects the gas production from hydrate reservoirs. However, multi-phase flow through HBCSS relates to thermal-hydrological-mechanical coupling, leading to the understanding of TPG in HBCSS with complex pore structures and hydrate distribution is unclear. In this study, a theoretical TPG model of HBCSS is developed by considering the combined influences of effective stress, temperature increase, pore structures, hydrate saturation and its growth patterns. The proposed TPG model has been thoroughly validated using available experimental data. Moreover, the parameter sensitivity analysis is conducted based on this derived model, revealing a positive correlation between TPG and both effective stress and temperature increase. While TPG generally increases with higher hydrate saturation when other parameters are held constant, the relationship between TPG and hydrate saturation is non-monotonic. This observation suggests that TPG is impacted not only by hydrate saturation but also by other factors, including hydrate growth patterns and pore structures. The findings of this study establish a theoretical foundation for characterizing the nonlinear flow behavior during hydrate exploitation.

Experimental study of permeability characteristics of fracture-hosted hydrate-bearing clay sediments under triaxial shear

Reservoir permeability during the hydrate exploitation process is closely related to gas production. Fractures influence hydrate distribution and the evolution of reservoir permeability. Moreover, shear during exploitation can disturb the structure of sediments. Therefore, studying permeability and its evolution under shear in fracture-hosted hydrate-bearing sediments is significant for hydrate exploitation projects in the South China Sea. In this paper, standard sand and montmorillonite were mixed, and three different fracture angles were created to simulate sediment fracture. Consolidation, shear, and permeability measurements were employed to investigate mechanical and permeability properties. The results showed that the permeability of fracture-hosted hydrate-bearing sediments decreased and then increased with increasing hydrate saturation, both before and after consolidation. The compressibility of sediments played an important role in the permeability damage rate caused by consolidation and normalized permeability at the breaking point. Furthermore, fractures caused an undesired double peak and the disappearance of the permeability breaking point hysteresis relative to the stress breaking point. However, these effects were mitigated by increasing saturation. Lastly, the analysis of permeability sensitivity coefficients revealed that permeability was most sensitive to strain in the early shear stages. This study can guide methane hydrate exploitation in the South China Sea.

Upward migration of the shallow gas enhances the production behavior from the vertical heterogeneous hydrate-bearing marine sediments

Low gas production rates and insufficient gas yield hinder the large-scale production from natural gas hydrates; a joint production of gas hydrate and its underlying shallow gas is expected to address this limitation. This study focuses on the interaction between heterogeneous hydrate reservoirs and the upward migration of the shallow gas. The results indicated a 38.4 % increase in production efficiency with the assistance of the shallow gas. Specially, the melt water generated from extensive hydrate decomposition could potentially induce a lateral migration of the shallow gas at the interfacial zones of the heterogeneous reservoirs. Further investigation revealed that a lower production pressure would help the release of the shallow gas as well as the hydrate decomposition, thereby contributing to a 64.55 % shorter t90. A faster depressurization rate could facilitate the temperature recovery by intensifying the lateral movement of the shallow gas in the junction layer. Consequently, a proper control of the upward channeling of the shallow gas was suggested in the field test for a successive and secure gas production. Our results could be of help in elucidating the interlayer interference mechanisms and the selection of the depressurization strategy for a better recovery efficiency from the multi-gas source reservoirs.

P-wave velocity evolution and interpretation of seepage mechanisms during CO2 hydrate formation in quartz sands: Perspective of hydrate pore habits

The hydrate-based CO2 storage (HBCS) is a promising technology for controlling CO2 emissions. A comprehensive understanding of the hydrate pore habits and seepage mechanism of hydrate-bearing sediments (HBSs) could provide a theoretical basis for HBCS. In the study, the hydrate occurrence characteristics, water migration and P-wave velocity response during hydrate formation in quartz sands are investigated. In addition, a new theoretical equation that relates P-wave velocity to permeability is presented. The digital core of porous media containing hydrate is also established, and the seepage characteristics during hydrate formation are revealed by numerical simulation. The results show that hydrates are preferentially generated in large pores and initially appear in a non-cementing pore-filling pattern, while an annular flow path for water is formed in quartz sands during hydrate formation. The hydrate morphology is changed from a pore-filling pattern to a patchy pattern at a critical hydrate saturation of around 3–7% for quartz sands with various particle diameters. The formation sites and spatial heterogeneity of hydrates can be depicted by the evolution pattern of streamlines. The results of the experiments indicate that the new semiempirical model is effective for estimating the permeability from the P-wave velocity of HBSs. These findings offer significant theoretical and practical insights for HBCS in porous media.

Application of time domain reflectometry to triaxial shear tests on hydrate-bearing sediments

Various triaxial shearing apparatus are used to quantify mechanical properties of hydrate-bearing sediments which are basically required to the assessment of risks posed by dissociation of natural gas hydrates. However, the key factor, hydrate saturation, has not been well measured during triaxial shearing tests. This study aims to show how a time domain reflectometry (TDR) method nondestructively measures hydrate saturation for triaxial shear tests on hydrate-bearing sands. Hydrate saturation is determined based on the difference of volumetric water contents measured by using a flexible TDR probe with two rods after calibration. The results suggest that values of hydrate saturation acquired by the TDR method are accurate, and the flexible TDR probe can monitor the kinetic process of hydrate formation and avoid any reinforcement effects on triaxial shearing properties of test specimens.

Fundamental insights into multistep depressurization of CH4/CO2 hydrates in the presence of N2 or air

Exploitation of natural gas hydrates provides an alternative way to address energy crisis. Dilute CO2 gas (13–30mol%CO2 with remaining N2/Air) injection into CH4 hydrates for hydrate swapping (SW) allows cheaper and more practical CH4 recovery and in-situ CO2 sequestration. However, the roles of N2/Air in dilute CO2 gas during exploitation remain unknown. It is unclear whether depressurization should be coupled after SW and continued below CH4 hydrate stability pressure. This work employed multistep depressurization (MD) to dissociate the mixed hydrates formed after SW from 86.5 to 97.9 bar at 0.7–1.2 °C in bulk-water and sandpack with CH4 hydrate saturation of 4.1–25.3 %. Effects of N2/Air on exploitation were investigated by examining hydrate morphologies and gas compositions. Morphological results in bulk-water indicated higher N2 fraction in 20mol%CO2/N2 triggered more CO2-rich hydrate reformation and CH4-rich hydrate dissociation. Exploitation results in sandpack indicated 13mol%CO2/N2 produced the highest CH4 swapping percent (46.6 %) and CO2 hydrate sequestration percent (29.1 %). Air exerted weaker promoting effects on exploitation compared with equivalent N2. The promotion of N2/Air on exploitation was dominated by dilute CO2 gas injection altering mixed hydrate equilibrium which varied with time-dependent gaseous compositions during MD. l-methionine of 3000 ppm had stronger promoting effects on CO2 sequestration in sandpack than bulk-water depending on mass transfer and water availability. Ceasing points (13.9–31.4 bar) suggested MD could be continued below CH4/above CO2 hydrate stability pressures and before water production. For the first time, this study provided insights into the roles of N2/Air to determine injection gas types and depressurization schemes for efficient and safe hydrate exploitation in gas-rich hydrate-bearing sediment.

A granular thermodynamic constitutive model considering THMC coupling effect for hydrate-bearing sediment

The interaction among mechanical, hydraulic, and temperature fields plays a crucial role in determining gas production efficiency and reservoir mechanical response. Considering particle rearrangement and cementation degradation effect, this study establishes a thermodynamic model that couples thermal, hydraulic, mechanical, and chemical fields (THMC) for hydrate-bearing sediments. For the proposed model, the mechanical field incorporates pore pressure and cementation terms, the hydraulic field considers the porosity, volumetric strain, and thermal driving effect, and the thermal field couples heat conduction, heat convection, and energy dissipation from hydrate dissociation. Furthermore, gas/liquid seepage rate and temperature conservation equation are not introduced as assumptions but are inferred from thermodynamic identities. Numerical simulations are conducted to investigate the physical significance of the three coupling elements and the mechanism of crucial parameters influencing gas production efficiency and reservoir mechanical response. The proposed model is simulated and validated at varying hydrate saturation levels and depressurization pressures. The modeling outcomes indicate that the theoretical model can accurately anticipate mechanical responses, gas production efficiency, and temperature variations during the hydrate consolidation and dissociation process.

The geomechanical response of the Gulf of Mexico Green Canyon 955 reservoir to gas hydrate dissociation: A model based on sediment properties with and without gas hydrate

Gas hydrate is commonly found concentrated in sand- and silt-rich reservoirs and these are thought to have great potential as an energy resource. To evaluate this potential, it is critical to understand their in-situ stress state and their behavior during production. We explore the geomechanical behavior of sandy silt sediments from a hydrate reservoir at Green Canyon GC 955, deep-water Gulf of Mexico without hydrate and compare these results to previous work on the same sandy silty sediments with hydrate present. Previous results from hydrate-bearing sediments at GC 955 using intact specimens show that the ratio of lateral to axial effective stress under uniaxial strain (K0) is strongly time-dependent and over long timescales approaches 1 (isostatic stress state). New results from sediments without hydrate using reconstituted specimens reveal that K0 is 0.51 and independent of time and stress. The reservoir without hydrate is approximately three times more compressible than with hydrate. In addition, we find that hydrate-free sediments have a normalized creep rate of Cα/Cc of about 0.028 at all stress levels, whereas hydrate bearing sediments exhibit a decrease in Cα/Cc with stress. We use these observations to present a new geomechanical model that describes how stress and porosity evolve during production of the hydrate reservoir. The key insight in our proposed model is that the sediment skeleton and gas hydrate phases share any applied external load in proportion to their relative stiffnesses. The model results predict that hydrate-bearing sediments are stiffer than gas hydrate-free sediments and that K0 reduces dramatically after gas hydrate dissociation, as is observed. At GC 955, a 5 MPa depressurization is needed to cause gas hydrate dissociation. This change in pore pressure increases the vertical and horizontal effective stresses from 3.8 to 8.8 MPa and 3.8–4.4 MPa, respectively. The dramatic vertical effective stress increase will cause significant compaction (7%) and perturb stresses near the wellbore. These experimental observations and the load-sharing model presented have the potential to underpin a new generation of hydrate reservoir simulation models, which may drive more effective production approaches.