Speaker
Description
We study the in situ measured distributions of contact angles and curvatures within mm-size X-ray tomography images of rock samples from a producing
hydrocarbon carbonate reservoir imaged after wateflooding [1]. We analyse
their spatial correlation on a pore-by-pore basis using automated methods for
measuring contact angles [2], a new method for measuring curvatures, and by
performing pore network extraction using generalized network modeling [3]. The
automated methods allow us to study image volumes of diameter approximately
1.92 mm and 1.2 mm long, obtaining hundreds of thousands of values from a
dataset with 435 million voxels. We calculate the capillary pressure based on
the mode curvature value, and associate this value with a nearby throat, or
restriction, in the pore space.
We demonstrate the capability of our methods to distinguish different wetta-
bility states in the samples studied: water-wet, mixed-wet, and weakly oil-wet.
The contact angle is spatially correlated over approximately the scale of an av-
erage pore. There is a wide distribution of contact angles within single pores. A
range of local curvature is found with both positive and negative values. How-
ever, there is only a weak correlation between contact angle and curvature with
lower and negative values of the curvature associated with larger contact an-
gles (more oil-wet conditions). We observed a weak correlation between average
contact angle and pore size, with the larger pores tending to be more oil-wet.
Our analysis could potentially have large implications for pore-scale modeling
of multiphase flow, in which methods using local curvature measurements could be directly used to calculate capillary pressures for displacement.
References
[1] Alhammadi A. M., AlRatrout A., Singh K., Bijeljic B., and Blunt M. J. In situ characterization of mixed-wettability in a reservoir rock at subsurface conditions. Scientific Reports, 7:10753, 2017. https://doi.org/10.1038/s41598-017-10992-w.
[2] AlRatrout A., Raeini A. Q., Bijeljic B., and Blunt M. J.
Automatic measurement of contact angle in pore-space images. Advances in Water Resources, 109:158–169, 2017. https://doi.org/10.1016/j.advwatres.2017.07.018.
[3] Raeini A. Q., Bijeljic B., and Blunt M. J. Generalized network modeling: Network extraction as a coarse-scale discretization of the void space of porous media. Physical Review E, 96:013312, 2017. https://doi.org/10.1103/PhysRevE.96.013312.
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