The geomechanics of Shenhua carbon dioxide capture and storage(CCS) demonstration project in Ordos Basin,China

Carbon dioxide(CO2) capture and storage(CCS) is considered widely as one of promising options for CO2emissions reduction,especially for those countries with coal-dominant energy mix like China.Injecting and storing a huge volume of CO2in deep formations are likely to cause a series of geomechanical issues,including ground surface uplift,damage of caprock integrity,and fault reactivation.The Shenhua CCS demonstration project in Ordos Basin,China,is the first and the largest full-chain saline aquifer storage project of CO2in Asia.The injection started in 2010 and ended in 2015.during which totally 0.3 million tonnes(Mt) CO2was injected.The project is unique in which CO2was injected into 18 sandstone formations simultaneously and the overlying coal seams will be mined after the injection stopped in 2015.Hence,intense geomechanical studies and monitoring works have been conducted in recent years,including possible damage resulting from the temperature difference between injected CO2and formations,injection induced stress and deformation change,potential failure mode and safety factor,interaction between coal mining and CO2geological storage,determination of injection pressure limit,and surface monitoring by the interferometric synthetic aperture radar(InSAR) technology.In this paper,we first described the background and its geological conditions of the Shenhua CCS demonstration project.Then,we gave an introduction to the coupled thermo-hydro-mechano-chemical(THMC) processes in CO2geological storage,and mapped the key geomechanical issues into the THMC processes accordingly.Next,we proposed a generalized geomechanical research flowchart for CO2geological storage projects.After that,we addressed and discussed some typical geomechanical issues,including design of injection pressure limit.CO2injection induced near-field damage,and interaction between CO2geological storage and coal mining,in the Shenhua CCS demonstration project.Finally,we concluded some insights to this CCS project.

Carbon sequestration potential of the Habanero reservoir when carbon dioxide is used as the heat exchange fluid

The use of sequestered carbon dioxide(CO) as the heat exchange fluid in enhanced geothermal system(EGS) has significant potential to increase their productivity, contribute further to reducing carbon emissions and increase the economic viability of geothermal power generation. Coupled COsequestration and geothermal energy production from hot dry rock(HDR) EGS were first proposed 15 years ago but have yet to be practically implemented. This paper reviews some of the issues in assessing these systems with particular focus on the power generation and COsequestration capacity. The Habanero geothermal field in the Cooper Basin of South Australia is assessed for its potential COstorage capacity if supercritical COis used as the working fluid for heat extraction. The analysis suggests that the major COsequestration mechanisms are the storage in the fracture-stimulation damaged zone followed by diffusion into the pores within the rock matrix. The assessment indicates that 5% of working fluid loss commonly suggested as the storage capacity might be an over-estimate of the long-term COsequestration capacity of EGS in which supercritical COis used as the circulation fluid.

Geomechanical modeling of CO2 geological storage:A review

This paper focuses on the progress in geomechanical modeling associated with carbon dioxide(CO2)geological storage.The detailed review of some geomechanical aspects,including numerical methods,stress analysis,ground deformation,fault reactivation,induced seismicity and crack propagation,is presented.It is indicated that although all the processes involved are not fully understood,integration of all available data,such as ground survey,geological conditions,microseismicity and ground level deformation,has led to many new insights into the rock mechanical response to CO2injection.The review also shows that in geomechanical modeling,continuum modeling methods are predominant compared with discontinuum methods.It is recommended to develop continuum-discontinuum numerical methods since they are more convenient for geomechanical modeling of CO2geological storage,especially for fracture propagation simulation.The Mohr-Coulomb criterion is widely used in prediction of rock mass mechanical behavior.It would be better to use a criterion considering the effect of the intermediate principal stress on rock mechanical behavior,especially for the stability analysis of deeply seated rock engineering.Some challenges related to geomechanical modeling of CO2geological storage are also discussed.