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Title: Acoustic emission characterization of microcracking in laboratory-scale hydraulic fracturing tests

Understanding microcracking near coalesced fracture generation is critically important for hydrocarbon and geothermal reservoir characterization as well as damage evaluation in civil engineering structures. Dense and sometimes random microcracking near coalesced fracture formation alters the mechanical properties of the nearby virgin material. Individual microcrack characterization is also significant in quantifying the material changes near the fracture faces (i.e. damage). Acoustic emission (AE) monitoring and analysis provide unique information regarding the microcracking process temporally, and information concerning the source characterization of individual microcracks can be extracted. In this context, laboratory hydraulic fracture tests were carried out while monitoring the AEs from several piezoelectric transducers. In-depth post-processing of the AE event data was performed for the purpose of understanding the individual source mechanisms. Several source characterization techniques including moment tensor inversion, event parametric analysis, and volumetric deformation analysis were adopted. Post-test fracture characterization through coring, slicing and micro-computed tomographic imaging was performed to determine the coalesced fracture location and structure. Distinct differences in fracture characteristics were found spatially in relation to the openhole injection interval. Individual microcrack AE analysis showed substantial energy reduction emanating spatially from the injection interval. Lastly, it was quantitatively observed that the recorded AE signals provided sufficient informationmore » to generalize the damage radiating spatially away from the injection wellbore.« less
Authors:
ORCiD logo [1] ;  [2] ;  [3] ;  [3] ;  [4]
  1. Colorado School of Mines, Golden, CO (United States). Dept. of Civil & Environmental Engineering; New England Research, Inc., White River Junction, VT (United States); Halliburton, Houston, TX (United States)
  2. Colorado School of Mines, Golden, CO (United States). Dept. of Civil & Environmental Engineering
  3. Halliburton, Houston, TX (United States)
  4. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Publication Date:
Report Number(s):
LA-UR-17-30661
Journal ID: ISSN 1674-7755
Grant/Contract Number:
AC52-06NA25396; FE0002760
Type:
Accepted Manuscript
Journal Name:
Journal of Rock Mechanics and Geotechnical Engineering
Additional Journal Information:
Journal Name: Journal of Rock Mechanics and Geotechnical Engineering; Journal ID: ISSN 1674-7755
Publisher:
Chinese Society for Rock Mechanics and Engineering - Elsevier
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Laboratory Directed Research and Development (LDRD) Program
Country of Publication:
United States
Language:
English
Subject:
42 ENGINEERING; 58 GEOSCIENCES; acoustic emission (AE); microcracking; hydraulic fracturing; laboratory-scale testing; moment tensor analysis; fracture coalescence; computed tomography (CT) imaging
OSTI Identifier:
1454998