Binu Asks PERM:
I am planning to conduct a core flood experiment using a restored core of 7 cm length, 3 cm diameter, 14% porosity and liquid permeability of 50 mD. The PV of the core is 15 ml.
Kindly tell me how to set the injection rate in ml/hr. Is there any rule of thumb for fixing injection rate?
Dr. Jonathan Bryan from PERM Answers:
Thank you for your email. There is no fixed answer to this, but there are a few rules of thumb that we like to follow in our lab:
1) Frontal velocity – you want to calculate the frontal velocity (Q/cross-sectional area) as being on the order of 30 cm/day or less. If you flow too fast, it is not representative of reservoir flux values.
2) Pressure gradient – within the reservoir, especially in radial flooding configurations, the pressure drop per meter of reservoir is not that high. In fact, far from the injector, pressure gradients may be on the order of 40 – 100 kPa/m. You can look at this for your specific application by considering maximum injection pressure for a given well, and the distance between wells in the field. If you run your core flood under pressure gradients that are much higher than what you can sustain in the field, then once again the results may be difficult to extrapolate to field conditions.
3) Finally, for your small system (pore volume = 15 cm³) one other constraint that you may be faced with is the size of your production samples. If you want to track things like oil recovery or producing water cut vs. PV injected, you want samples that are small enough to give you some resolution on these trends. How large or small of a sample can you take? And how many pore volumes will you want to inject? This practical limitation may be of high importance to you as well, for knowing how long you need to run a test and if you need to man the equipment 24 hrs a day or just for shorter time periods. So the choice of injection rate may be limited by this constraint as well.