In this section
@article{MacAllister:2019:10.1029/2019JB017829,
author = {MacAllister, DJ and Graham, MT and Vinogradov, J and Butler, AP and Jackson, M},
doi = {10.1029/2019JB017829},
journal = {Journal of Geophysical Research. Solid Earth},
pages = {7918--7933},
title = {Characterising the self-potential response to concentration gradients in heterogeneous sub-surface environments},
url = {http://dx.doi.org/10.1029/2019JB017829},
volume = {124},
year = {2019}
}
TY - JOUR
AB - Selfpotential (SP) measurements can be used to characterise and monitor, in realtime, fluid movement and behaviour in the subsurface. The electrochemical exclusiondiffusion (EED) potential, one component of SP, arises when concentration gradients exist in porous media. Such concentration gradients are of concern in coastal and contaminated aquifers, and oil and gas reservoirs. It is essential that estimates of EED potential are made prior to conducting SP investigations in complex environments with heterogeneous geology and salinity contrasts, such as the UK Chalk coastal aquifer. Here, we report repeatable laboratory estimates of the EED potential of chalk and marls using natural groundwater (GW), seawater (SW), deionised (DI) water and 5 M NaCl. In all cases the EED potential of chalk was positive (using a GW/SW concentration gradient the EED potential was c.14 to 22 mV), with an increased deviation from the diffusion limit at the higher salinity contrast. Despite the relatively small pore size of chalk (c.1 μm), it is dominated by the diffusion potential and has a low exclusionefficiency, even at large salinity contrasts. Marl samples have a higher exclusionefficiency which is of sufficient magnitude to reverse the polarity of the EED potential (using a GW/SW concentration gradient the EED potential was c.7 to 12 mV) with respect to the chalk samples. Despite the complexity of the natural samples used, the method produced repeatable results. We also show that first order estimates of the exclusionefficiency can be made using SP logs, supporting the parameterisation of the model reported in Graham et al. (2018), and that derived values for marls are consistent with the laboratory experiments, while values derived for hardgrounds based on field data indicate a similarly high exclusionefficiency. While this method shows promise in the absence of laboratory measurements, more rigorous estimates should be made where possible and can be conducted following
AU - MacAllister,DJ
AU - Graham,MT
AU - Vinogradov,J
AU - Butler,AP
AU - Jackson,M
DO - 10.1029/2019JB017829
EP - 7933
PY - 2019///
SN - 2169-9356
SP - 7918
TI - Characterising the self-potential response to concentration gradients in heterogeneous sub-surface environments
T2 - Journal of Geophysical Research. Solid Earth
UR - http://dx.doi.org/10.1029/2019JB017829
UR - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JB017829
UR - http://hdl.handle.net/10044/1/72209
VL - 124
ER -