Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitr...Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitrogen(LN_(2))has been trialled in fields and is a waterless fracturing technique under intensive research these days.This study aimed to evaluate the cryogenic treatment efficacy of Karaganda coal samples as well as to understand the coal permeability evolution during the thawing period.X-ray fluorescent spectrometry(XRF)and microscope imaging identified the compositional and structural heterogeneities of coal specimens mined from different interlayers.Acoustic emission test,permeability measurement,and microscope imaging comparatively characterized the dry coal structure alteration before and after immersion into LN_(2).Cryogenic treatment slowed down the S-wave velocity through coal specimens,enhanced permeability by over 65%after temperature recovery as well as created new fractures,enlarged existing ones,and spalled coal particles.Dynamic permeability evolution against temperature rise during the thawing process has been successfully captured for the first time.Overall,the experimental measurements support that the LN_(2) cryogenic fracturing technique would be effective in stimulating coalbeds for CBM production in Karaganda Coal Basin.展开更多
基金support of the Collaborative Research Grant"Development of cryogenic fracturing technology for coalbed methane production in Karaganda Coal Basin,Kazakhstan" (Reference Number:021220CRP2022)by Nazarbayev University,Kazakhstanthe Open Fund of Engineering Research Center of Development and Management for Low to Ultra-Low Permeability Oil&Gas Reservoirs in West China,Ministry of Education,China。
文摘Karaganda Coal Basin bears the largest undeveloped reserve of coalbed methane(CBM)in Kazakhstan,which lacks water resources for implementing large-volume hydraulic fracturing.Cryogenic fracturing utilizing liquid nitrogen(LN_(2))has been trialled in fields and is a waterless fracturing technique under intensive research these days.This study aimed to evaluate the cryogenic treatment efficacy of Karaganda coal samples as well as to understand the coal permeability evolution during the thawing period.X-ray fluorescent spectrometry(XRF)and microscope imaging identified the compositional and structural heterogeneities of coal specimens mined from different interlayers.Acoustic emission test,permeability measurement,and microscope imaging comparatively characterized the dry coal structure alteration before and after immersion into LN_(2).Cryogenic treatment slowed down the S-wave velocity through coal specimens,enhanced permeability by over 65%after temperature recovery as well as created new fractures,enlarged existing ones,and spalled coal particles.Dynamic permeability evolution against temperature rise during the thawing process has been successfully captured for the first time.Overall,the experimental measurements support that the LN_(2) cryogenic fracturing technique would be effective in stimulating coalbeds for CBM production in Karaganda Coal Basin.
