George Asks PERM:
I read a paper you co-authored with Taqa, SCA2015-020, and I wonder if you have any experience with running NMR logs on Montney cores post-Dean Stark cleaning. I found your conclusion interesting that there was a material amount of water left in the core after the Dean Stark cleaning process and I liked the use of NMR to quantify that. My opinion is most folks assume the Dean Stark process removes all the water.
Dr. Jonathan Bryan from PERM Answers:
Yes, for sure in very low permeability rocks and shales, Dean-Stark is insufficient for removing all the water. When pore sizes are incredibly small, capillary forces are so high that it is difficult for even boiling to work for removal of water.
We commonly run NMR on post-DS cores when we do shale analyses, and then when we measure gas expansion porosity, this is the effective open space of the rock. The total porosity is the residual water + open space that Dean-Stark accessed. Now that residual water is trapped even from boiling, so it is porosity but essentially closed. We think that it should be reported as part of the porosity, but it doesn’t contribute to flow, so some people neglect it. The only thing is that, if you want to compare to other instruments (e.g. density logs) those are also total porosity indicators, not just the effective porosity.
Dr. Jonathan Bryan
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