Dear Members,
We've recently completed an entire set of relative permeability measurements as part of our SCAL studies program. we've carried out the following studies:
- Unsteady state on both native and restored state plugs
- Steady State on native plugs (composite of 4 plugs)
- Centrifuge on native state plugs
Problem statement/ Issues:
we did the quality check on the measurements based on all the production/ injection and pressure data being provided by the lab. There were no issues which we can find as far as the measurements were concerned. But the issues which were troubling for us were the measured end point permeability values:
- Effective oil permeability values (our rocks are multi darcys) were in the range of 30 - 50% of the air permeability values even for initial water saturation as low as 2-5%. This was bit inscrutable as to how the presence of such small water fraction can drop the permeability values drastically.
- Even for the centrifuge experiments, same behaviour has been observed with effective oil permeability.
- We even measured the specific oil permeability (100% oil) on the cleaned core plugs (same plugs on which above mentioned experiments have been carried out) and they came in the range of 80 - 90% of the air permeability values which was encouraging and perhaps eliminates the concern over fluid being the issue.
Please share your thoughts, observations and experience if there is anything we're missing or needs to be investigated as we can't physically accept this low values because we've been producing the field from more than 3 years and initial well test permeabilities (which were measured at the start of the field and which basically represents effective oil permeability at initial Sw) were mostly in-line with log permeability values.
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Manjit Singh
Reservoir Eng
Cairn India Pty. Ltd.
Gurgaon
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