TY - GEN
T1 - Experimental Study of CO2 Fracturing Behaviour in Ultralow Permeability Formations
AU - Zhang, C. P.
AU - Ma, Z. Y.
AU - Ranjith, P. G.
N1 - Funding Information:
Partial content of this paper was presented at an international journal on Engineering Fracture Mechanics. The authors were supported by the China Postdoctoral Science Foundation (No. 2020M673142), the Chongqing Science and Technology Bureau Foundation (No. cstc2020jcyj-bshX0072, No. cstc2020jcyj-zdxmX0023), the Chongqing Human Resources and Social Security Bureau Foundation (No. cx2019100) and the Fundamental Research Funds for the Central Universities (No. 2019CDXYZH0020).
Publisher Copyright:
© 2021 ARMA, American Rock Mechanics Association
PY - 2021
Y1 - 2021
N2 - CO2 fracturing with many unique advantages has been successfully used as an alternative to water-based fracturing in unconventional gas production. However, the great difference of fracturing behaviours between water and CO2 fracturing for different gas reservoirs is still scarcely studied. The intention of this study is to investigate the fracturing mechanism and to compare the fracture geometry characters between water and CO2 fracturing, and a series of fracturing tests on sedimentary rocks was therefore conducted. Experimental results show that breakdown pressure of CO2 fracturing is much lower than that of water fracturing for siltstone samples, and the difference of breakdown pressure between water and CO2 fracturing for shale samples with much lower permeability is much greater. The much higher breakdown pressure for shale samples than siltstone samples indicates that high pore pressure within rock matrix due to the strong penetration ability can greatly decrease the breakdown pressure. CO2 fracturing creates more loose particles and discrete blocks acting like proppants, and fracture aperture of CO2 fracturing is 2-5 times that of water fracturing. Multi-parallel fractures and bigger discrete blocks contribute to the low fracture compressibility, and the secondary shear fractures along the weak bedding planes in shale samples greatly increase the complexity of the fracture network.
AB - CO2 fracturing with many unique advantages has been successfully used as an alternative to water-based fracturing in unconventional gas production. However, the great difference of fracturing behaviours between water and CO2 fracturing for different gas reservoirs is still scarcely studied. The intention of this study is to investigate the fracturing mechanism and to compare the fracture geometry characters between water and CO2 fracturing, and a series of fracturing tests on sedimentary rocks was therefore conducted. Experimental results show that breakdown pressure of CO2 fracturing is much lower than that of water fracturing for siltstone samples, and the difference of breakdown pressure between water and CO2 fracturing for shale samples with much lower permeability is much greater. The much higher breakdown pressure for shale samples than siltstone samples indicates that high pore pressure within rock matrix due to the strong penetration ability can greatly decrease the breakdown pressure. CO2 fracturing creates more loose particles and discrete blocks acting like proppants, and fracture aperture of CO2 fracturing is 2-5 times that of water fracturing. Multi-parallel fractures and bigger discrete blocks contribute to the low fracture compressibility, and the secondary shear fractures along the weak bedding planes in shale samples greatly increase the complexity of the fracture network.
UR - http://www.scopus.com/inward/record.url?scp=85123382260&partnerID=8YFLogxK
M3 - Conference contribution
AN - SCOPUS:85123382260
T3 - 55th U.S. Rock Mechanics / Geomechanics Symposium 2021
BT - 55th U.S. Rock Mechanics / Geomechanics Symposium 2021
PB - American Rock Mechanics Association (ARMA)
T2 - 55th U.S. Rock Mechanics / Geomechanics Symposium 2021
Y2 - 18 June 2021 through 25 June 2021
ER -