Hamzah from Ryerson University Asks PERM:
I would like some guidance with respect to the selection of core dimensions for a laboratory polymer flooding experiment. Throughout my literature review, I have not come across justification for the core dimensions selection. Any assistance regarding this matter would be much appreciated.
Dr. Jonathan Bryan from PERM Answers:
Thank you very much for your question! The reason that there isn’t much documentation on the selection of core dimensions is really because the selection of core dimensions is decided by many different things:
If you are using native state core and you want to study vertical permeability, then you have the option of running either full diameter core or something smaller like a 1.5″ diameter core plug stack. But if you want horizontal core taken from vertical full diameter core, then in general you don’t have a choice but to run on smaller diameter core stacks. So when running tests on native state core, you are very much constrained by the material available to you.
If you are making your own sand packs, then of course you have more options. In this case, the design of core dimensions will be affected by what is the objective of your test. If you want to study the microscopic sweep efficiency of polymer compared to water, this is generally accomplished by running tests in linear systems (i.e. small diameter cores with length >> diameter). But if you are looking more at polymer sweep efficiency improvements in more of a 3D sense or in a heterogeneous system, or a system with lots of water fingering and bypassing oil, then it may be more instructive to look at the polymer response in a larger diameter system. The big difference is that, in a small diameter core, if the polymer plugs off just a few of the water channels, this can lead to a big improvement in overall sweep efficiency in the core, but this effect may not be as prominent in a larger diameter system. So the choice of core size is dependent on the question you are trying to answer.
Finally, all of this discussion has been focused around understanding the choice of core diameter. For looking at the rationale for various core lengths, this is affected by several other design parameters. First, if you want to study effective permeability to water vs. polymer, for example, then the system needs to be linear so that you can apply a 1D form of Darcy’s Law. So length has to generally be much greater than diameter. The choice of core length is also a constraint of your experimental technique – shorter cores lead to smaller pore volumes, and this has potential issues in terms of accuracy of your measurement. Conversely, longer cores lead to larger pore volumes, meaning that the test takes longer to complete. So your choice of core length will also be affected by the simple operational constraints of your test – your sampling frequency and how long you want the test to run.
Hopefully this helps, and sorry that the answer is not more quantitative!
Dr. Jonathan Bryan