Impact of supercritical CO2 on mechanical properties of burnt shale in overlying strata of gasification combustion zone
LI Huaizhan
TANG Chao
GUO Guangli
LI Wei
ZHA Jianfeng
CAO Jingchun
HUANG Wengang
YUAN Yafei
Abstract：The influence of supercritical CO2 on the mechanical properties of burnt surrounding rock in the gasification combustion zone is a key parameter for evaluating the risk of CO2 leak-age in UCG-CCS.Given the current lack of research on the mechanical tests of burnt surround-ing rock under the influence of supercritical CO2 infiltration,this study is carried out by levera-ging a self-developed supercritical CO2 saturation pressurization device.Through Brazilian splitting tests and uniaxial compression tests,the changes in the tensile strength,uniaxial compressive strength and fracture failure characteristics of shale under different gasification temperatures,supercritical CO2 soaking pressures and supercritical CO2 soaking times were studied.The results show that the mass of burnt shale decreases,and with the extent of mass reduction increases with the rise in temperature.The tensile strength and uniaxial compressive strength of burnt shale exhibit a stepwise decline.After supercritical CO2 soaking,the quality of burnt shale specimens increases.Supercritical CO2 weakens the tensile strength,compres-sive strength and elastic modulus of burnt shale.Supercritical CO2 soaking weakens the tensile strength and uniaxial compressive strength significantly.As the soaking pressure increased,the tensile strength of burnt shale gradually decreases,but the reduction rate becomes smaller.Both the compressive strength and elastic modulus also decline gradually.As the soaking time increases,the tensile strength and compressive strength of the burnt shale rock specimens ex-hibit a gradual decline.As the gasification temperature,supercritical CO2 soaking pressure and soaking time increases,the primary cracks of burnt shale rock samples slowly expand,and the secondary cracks begin to emerge.In this study,we meticulously construct fitting functions that correlate the tensile strength of shale with temperature,soaking pressure,and soaking time,as well as for compressive strength in relation to the same variables,are meticulously constructed.These outcomes offer profound theoretical and practical insights for the site selec-tion,design,and widespread application of UCG-CCS projects.
Keywords：underground coal gasificationsupercritical CO2 storageburnt shalegasification combustion zonemechanical property
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( 385-398 )