TY - JOUR
T1 - Determination of NMR T2 cut-off for clay bound water in shales
T2 - A case study of Carynginia Formation, Perth Basin, Western Australia
AU - Testamanti, M. Nadia
AU - Rezaee, Reza
N1 - Publisher Copyright:
© 2016 Elsevier B.V.
PY - 2017
Y1 - 2017
N2 - Low-field Nuclear Magnetic Resonance (NMR) has proved to be a valuable tool for the petrophysical characterization of conventional reservoirs, but its effective application to unconventional reservoirs is still under research. Pore structure characterization of shales is particularly challenging due to the complexity of the pore network and the small size of pores. Using low-field NMR, we performed transverse relaxation (T2) experiments on samples from the Perth Basin, Western Australia. The samples were initially saturated with KCl brine to obtain the total NMR porosity and T2distribution, then centrifuged and finally oven-dried at increasing temperatures. T2spectra were also acquired after centrifuging and heating the samples. Our results indicate that most of the transverse relaxation occurs below 3 ms in saturated samples and that a conventional centrifuge cannot remove water from the smaller pores, making the commonly accepted clay bound water cut-off unsuitable for shales. Furthermore, the results from NMR experiments performed on the oven-dried shale samples suggest that the water content remains relatively constant after heating them above 65 °C. The calculated T2cut-off for clay bound water is between 0.22 and 0.26 ms for the samples studied. The methodology presented in this paper can be replicated in other formations to find a suitable T2value for clay bound water, which can be a good indication of potentially producible porosity and can also be used for permeability estimation.
AB - Low-field Nuclear Magnetic Resonance (NMR) has proved to be a valuable tool for the petrophysical characterization of conventional reservoirs, but its effective application to unconventional reservoirs is still under research. Pore structure characterization of shales is particularly challenging due to the complexity of the pore network and the small size of pores. Using low-field NMR, we performed transverse relaxation (T2) experiments on samples from the Perth Basin, Western Australia. The samples were initially saturated with KCl brine to obtain the total NMR porosity and T2distribution, then centrifuged and finally oven-dried at increasing temperatures. T2spectra were also acquired after centrifuging and heating the samples. Our results indicate that most of the transverse relaxation occurs below 3 ms in saturated samples and that a conventional centrifuge cannot remove water from the smaller pores, making the commonly accepted clay bound water cut-off unsuitable for shales. Furthermore, the results from NMR experiments performed on the oven-dried shale samples suggest that the water content remains relatively constant after heating them above 65 °C. The calculated T2cut-off for clay bound water is between 0.22 and 0.26 ms for the samples studied. The methodology presented in this paper can be replicated in other formations to find a suitable T2value for clay bound water, which can be a good indication of potentially producible porosity and can also be used for permeability estimation.
KW - Clay bound water
KW - Nuclear magnetic resonance
KW - Pore structure
KW - Shale reservoir
KW - Tcut-off
UR - http://www.scopus.com/inward/record.url?scp=85028238525&partnerID=8YFLogxK
U2 - 10.1016/j.petrol.2016.10.066
DO - 10.1016/j.petrol.2016.10.066
M3 - Article
AN - SCOPUS:85028238525
SN - 0920-4105
VL - 149
SP - 497
EP - 503
JO - Journal of Petroleum Science and Engineering
JF - Journal of Petroleum Science and Engineering
ER -