Joseph Asks PERM:
In Drainage Capillary pressure measurements using porous plate, how will you ensure that there is enough/good capillary contact between the core plug sample and porous plate?
In most cases labs uses the 2 electrode core holder. And i have heard that if the phase angle of impedance measured across the electrode is small enough then it could be assumed that there is good contact between the plate and sample. What is the theoretical basis for this?
Plus are there any other ways to ensure that capillary contact is achieved? Especially when you don’t have ISSM and is just restricted to electrical measurements?
Dr. Sergey Kyruchkov from PERM Answers:
As I understand, you are asking on how to check the capillary contact (that it is good), not on the methods of achieving it.
No contact means there are (non-conducting) gaps between the core and the plate/electrode.
This gap acts as a capacitor. So, the equivalent circuit becomes consecutively connected capacitor (contributes to imaginary part of impedance) and resistor (contributes to real part of impedance). The smaller the contribution of the capacitor to impedance – the smaller the phase angle of the total impedance. This is the theoretical basis for the mentioned criterion.
This criterion has to be used with cation, as the impedance of the core itself can contain imaginary part. Frequency dependence of the phase angle can provide information allowing to separate the two.