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Title: Experimental investigation of injection-induced fracturing during supercritical CO 2 sequestration

Leakage risk assessment is an inevitable procedure in permanent sequestration and storage of CO 2 in deep saline aquifers and depleted oil and gas reservoirs, where the integrity of caprock is most critical. Here, low porosity and low permeability concrete cubes were employed as caprock analogs to investigate the supercritical CO 2 injection-induced fracturing processes under true tri-axial stress conditions. A systematic experimental procedure, consisting of active acoustic emission measurement, pressure decay, injection pressure and temperature monitoring, fracture coloring, and gas fracturing, is formulated to qualitatively and quantitatively characterize the injection-induced fracturing processes and fracture morphology. Occurrence of injection-induced fracturing can be directly identified from peaks of borehole pressure profiles as well as sharp drops on temperature profiles due to CO 2 expansion, but generally there was no fracture propagation plateau appearing for the 20 cm rock cubes with zero pore pressure. Acoustic wave signatures, including both waveform change and arrival time delay, can effectively capture the extension of induced fractures inside the opaque rock. Initiation and propagation of supercritical CO 2 injection-induced fractures are highly dominated by the tri-axial stresses, following the general trend of continuum mechanics at high stress levels with large stress difference. As the stress difference decreases,more » induced fractures branch off in relatively arbitrary directions. For these supercritical CO 2 injection-induced fracturing experiments, poroelastic mechanics model makes a decent fit with the measured breakdown pressure of the caprock analogs. Findings in this study are valuable for risk analysis and operation optimization of geological CO 2 sequestration and storage as well as for CO 2 fracturing design and implementation in shale and tight reservoirs.« less
 [1] ;  [1] ;  [2] ;  [3] ;  [1] ;  [1] ;  [1]
  1. Colorado School of Mines, Golden, CO (United States). Petroleum Engineering Dept.
  2. China Univ. of Petroleum, Beijing (China). College of Petroleum Engineering
  3. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States). Earth Science Division
Publication Date:
Grant/Contract Number:
AC02-05CH11231; FE0023305
Accepted Manuscript
Journal Name:
International Journal of Greenhouse Gas Control
Additional Journal Information:
Journal Volume: 63; Journal Issue: C; Related Information: © 2017 Elsevier Ltd; Journal ID: ISSN 1750-5836
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); National Energy Technology Lab. (NETL), Pittsburgh, PA, and Morgantown, WV (United States)
Sponsoring Org:
USDOE Office of Fossil Energy (FE); Energi Simulation, Calgary, AB (Canada)
Country of Publication:
United States
42 ENGINEERING; 54 ENVIRONMENTAL SCIENCES; CO2 sequestration and storage; Supercritical CO2; Fracturing; Geomechanics; True tri-axial stress; Caprock
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1459451