TY - JOUR
T1 - Effect of hydration on fractures and permeabilities in Mancos, Eagleford, Barnette and Marcellus shale cores under compressive stress conditions
AU - Zhang, Shifeng
AU - Sheng, James J.
AU - Shen, Ziqi
N1 - Funding Information:
The work presented in this paper is supported by the Department of Energy under Award Number DE-FE0024311 .
Publisher Copyright:
© 2017 Elsevier B.V.
PY - 2017
Y1 - 2017
N2 - Hydration swelling was observed to generate microfractures at ambient conditions in some of earlier studies, thus the core permeability is increased. In this paper, to investigate if hydration swelling could induce fractures in shale cores under compressive stress, four shale cores (Mancos, Barnett, Marcellus and Eagleford) with various clay mineral contents and swelling properties were used. CT scan testing was used to observe fractures, and swelling strain testing was conducted to evaluate the hydration swelling properties. The permeabilities of shale cores before and after hydration were measured. In all of the four shale cores under 3000 psi isotropic confining pressure, hydration caused fractures to close rather than propagate. As a result, the permeabilities decreased significantly, up to two orders of magnitude, compared to intrinsic permeabilities in Mancos, Barnett, and Marcellus shales, and a large damage occurred in the Eagleford shale core. Clay mineral content was the main factor influencing the shale permeability damage due to hydration. When clay contents are higher than a certain percent (e.g., 15% in this paper), significant permeability damage was observed. 8% KCl solution could help recover more permeability damage than 4% KCl solution. As a result, during hydraulic fracturing, the salinity should be increased to mitigate the permeability damage caused by hydration.
AB - Hydration swelling was observed to generate microfractures at ambient conditions in some of earlier studies, thus the core permeability is increased. In this paper, to investigate if hydration swelling could induce fractures in shale cores under compressive stress, four shale cores (Mancos, Barnett, Marcellus and Eagleford) with various clay mineral contents and swelling properties were used. CT scan testing was used to observe fractures, and swelling strain testing was conducted to evaluate the hydration swelling properties. The permeabilities of shale cores before and after hydration were measured. In all of the four shale cores under 3000 psi isotropic confining pressure, hydration caused fractures to close rather than propagate. As a result, the permeabilities decreased significantly, up to two orders of magnitude, compared to intrinsic permeabilities in Mancos, Barnett, and Marcellus shales, and a large damage occurred in the Eagleford shale core. Clay mineral content was the main factor influencing the shale permeability damage due to hydration. When clay contents are higher than a certain percent (e.g., 15% in this paper), significant permeability damage was observed. 8% KCl solution could help recover more permeability damage than 4% KCl solution. As a result, during hydraulic fracturing, the salinity should be increased to mitigate the permeability damage caused by hydration.
KW - Hydrate-induced fractures
KW - Hydraulic fracturing
KW - Isotropic stress
KW - Permeability
KW - Shale hydration
UR - http://www.scopus.com/inward/record.url?scp=85030535333&partnerID=8YFLogxK
U2 - 10.1016/j.petrol.2017.06.043
DO - 10.1016/j.petrol.2017.06.043
M3 - Article
AN - SCOPUS:85030535333
VL - 156
SP - 917
EP - 926
JO - Journal of Petroleum Science and Engineering
JF - Journal of Petroleum Science and Engineering
SN - 0920-4105
ER -