Study on thermo-hydro-mechanical coupling effects of CO2 sequestration in deep saline aquifers based on an improved homogeneous model
WANG Xin
YANG Pengfei
LIANG Bing
SUN Weiji
XU Jun
WANG Fang
YANG Xinle
Abstract：Complex thermo-hydro-mechanical coupling issues are faced in deep saline aquifers.Existing studies have insufficiently considered the dynamic response of porosity and permeability changes in homogeneous models,and lack further corrections to the applicability of supercritical CO2 density and viscosity parameters under actual reservoir conditions.To make up for these deficiencies,this paper proposes an improved homogeneous model,adding dynamic porosity and permeability to the mathematical model,and combining the Peng-Robinson state equation with the Brokaw model to correct the density and viscosity characteristics of supercritical CO2 under different pressure and temperature conditions.A mathematical model for CO2 sequestration in deep saline aquifers is developed and validated based on the improved model.A mathematical model for CO2 storage in deep saline layers is constructed and verified based on the improved model,and the changing laws of reservoir pressure,temperature,CO2 saturation,porosity,permeability and displacement deformation are explored within a 15 years simulation period.The results indicate that the improved model accurately captures the pressure increase and thermal exchange effects caused by the injection of CO2.The pressure and temperature in the regions surrounding and above the injection well initially decrease and then increase over time.The CO2 saturation follows a gradient diffusion pattern,with the accumulation of CO2 at the caprock leading to a reduction in both porosity and permeability.The maximum vertical displacement of the reservoir is 0.283 m during the storage period,which is mainly due to the combined effects of the compaction effect caused by pressure and the shrinkage effect caused by temperature.The uplift caused by the compaction effect is greater than the settlement caused by the shrinkage effect,making the overall displacement appear as an uplift,which clarifies the coupling dominance of pressure and temperature on the vertical displacement of the reservoir.Compared with the traditional model,the improved model is closer to the multi-field coupling effect of the real reservoir.By introducing the dynamic porosity and permeability model,the nonlinear changes in pressure,changes in rock thermal stress,and changes in reservoir permeability during CO2 injection are more accurately reflected,which can provide theoretical support for improving the CO2 sequestration effect.
Keywords：deep saline aquifersCO2 storagedynamic porosity and permeabilitynumerical simulationcoupling effect
Publication Date：2025-03-30
Online Publishing Date：2025-08-15(First online date of this platform, not the publication date of the document)
Pages：14( 399-412 )