Numerical Simulation of Gas Production and Reservoir Stability during CO2 Exchange in Natural Gas Hydrate Reservoir

Abstract

The prediction of gas productivity and reservoir stability of natural gas hydrate (NGH) reservoirs plays a vital role in the exploitation of NGH. In this study, we developed a THMC (thermal-hydrodynamic-mechanical-chemical) numerical model for the simulation of gas production behavior and the reservoir response. The model can describe the phase change, multiphase flow in porous media, heat transfer, and deformation behavior during the exploitation of NGH reservoirs. Two different production scenarios were employed for the simulation: depressurization and depressurization coupled with CO2 exchange. The simulation results suggested that the injection of CO2 promotes the dissociation of NGH between the injection well and the production well compared with depressurization only. The cumulative production of gas and water increased by 27.88% and 2.90%, respectively, based on 2000 days of production simulation. In addition, the subsidence of the NGH reservoir was lower in the CO2 exchange case compared with the single depressurization case for the same amount of cumulative gas production. The simulation results suggested that CO2 exchange in NGH reservoirs alleviates the issue of reservoir subsidence during production and maintains good reservoir stability. The results of this study can be used to provide guidance on field production from marine NGH reservoirs.

Numerical Simulation and Optimization of Well Parameters for Depressurization-Assisted CO2 Replacement Using a PSO Algorithm

“…23,24 Among them, the CMG-STARS model was adopted in this study, which can account for three phases (gas phase, liquid phase, and hydrate phase) and five mass components (CH 4 , CO 2 , water, CH 4 hydrate, and CO 2 hydrate) to simulate hydrate formation and dissociation. 25 The hydrate phase consisted of CO 2 hydrate and CH 4 hydrate, which were immobile solids. Considering the water and gas two-phase flow in porous media during the dissociation of hydrate, the mass conservation equations of CH 4 , CO 2 , water, and hydrate components can be represented as…”

“…Several numerical simulators have been developed for hydrate exploitation, and their reliability has been verified by international code comparison. , Among them, the CMG-STARS model was adopted in this study, which can account for three phases (gas phase, liquid phase, and hydrate phase) and five mass components (CH 4 , CO 2 , water, CH 4 hydrate, and CO 2 hydrate) to simulate hydrate formation and dissociation . The hydrate phase consisted of CO 2 hydrate and CH 4 hydrate, which were immobile solids.…”

Mechanical Properties of Gas Hydrate-Bearing Sediments Influenced by Multiple Factors: A Comprehensive Review of Triaxial Tests

“…With the same saturation, the increased OCR enhances the resistance of HBS to deformation, whose initial elasticity modulus increases with the OCR increasing, and related studies are shown in Table . The mechanisms of OCR effects on HBS are mainly reflected in 1) the increase of OCR breaks the cement structure of HBS, the hydrate attached to the surface of the particle is shed and fills the adjacent pores, making the density of HBS increase, so it affects the shearing strength of HBS; 2) the increase of OCR makes sediment particles arranged more tightly, and the shearing process can inhibit the sliding, rotation, and rearrangement behavior of particles significantly, which improves the initial elastic modulus and shearing strength of HBS, and prohibits the volume deformation.…”

Experimental Study on Permeability of Methane Hydrate Clayey Interbedded Sediments Considering Effective Stress and Hydrate Dissociation

“…Natural gas hydrate (NGH) is widely distributed across the world. NGH has advantages of large reserves and high energy density, and no toxic and harmful gases will be produced after combustion, which has attracted scientists from all over the world to pay great attention to this kind of energy. − …”