Hydraulic fracturing in shale with H2O, CO2 and N2

Xiang Li, Zijun Feng, Gang Han, Derek Elsworth, Chris Marone, Demian Saffer

Research output: Chapter in Book/Report/Conference proceedingConference contribution

27 Scopus citations


Slick-water fracturing is the most routine form of well stimulation in shales; however N2, LPG and CO2 have all been used as "exotic" stimulants in various hydrocarbon reservoirs. We explore the use of these gases as stimulants on Green River shale to compare the form and behavior of fractures in shale driven by different gas compositions and states and indexed by breakdown pressure and the resulting morphology of the fracture networks. Fracturing is completed on cylindrical samples containing a single blind axial borehole under simple triaxial conditions with confining pressure ranging from 10∼25MPa and axial stress ranging from 0-35MPa (σ1 > σ2 = σ3). Results show that: 1) under the same stress conditions, CO2 returns the highest breakdown pressure, followed by N2, and with H2O exhibiting the lowest breakdown pressure; 2) CO2 fracturing, compared to other fracturing fluids, creates nominally the most complex fracturing patterns as well as the coarsest fracture surface and with the greatest apparent local damage; 3) under conditions of constant injection rate, the CO2 pressure build-up record exhibits condensation between ∼5-7MPα and transits from gas to liquid through a mixed-phase region rather than directly to liquid as for H2O and N2 which do not; 4) there is a positive correlation between minimum principal stress and breakdown pressure for failure both by transverse fracturing (3axial) and by longitudinal fracturing (3radial) for each fracturing fluid with CO2 having the highest correlation coefficient/slope and lowest for H2O. We explain these results in terms of a mechanistic understanding of breakdown, and through correlations with the specific properties of the stimulating fluids.

Original languageEnglish (US)
Title of host publication49th US Rock Mechanics / Geomechanics Symposium 2015
PublisherAmerican Rock Mechanics Association (ARMA)
Number of pages8
ISBN (Electronic)9781510810518
StatePublished - 2015
Event49th US Rock Mechanics / Geomechanics Symposium - San Francisco, United States
Duration: Jun 29 2015Jul 1 2015

Publication series

Name49th US Rock Mechanics / Geomechanics Symposium 2015


Other49th US Rock Mechanics / Geomechanics Symposium
Country/TerritoryUnited States
CitySan Francisco

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Geochemistry and Petrology


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