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Pressure transient response for a small DST

By Kamran Imam posted 06-18-2013 03:41 AM

  
Hi All,
I am analyzing DST data for an exploratory well. The drawdown was for ~31hrs and the buid up was ~8hrs. The data is mostly masked by spherical flow behavior mainly due to limited perfs. I am getting a downward trend towards the end of the BU test. Geologically we understand that there is neither an active aquifer (no significant water production from bottom perfs) nor a fault or anything like that. My understanding is that we started the BU test before the initial DD transient hit the boundaries. As a result I am seeing a pressure support in my PTA but this pressure support is not due to aquifer but due to HC body which, in fact, is an extension of my reservoir.
Is this a correct hypothesis? Is this a common occurrence in small DSTs?

I would really appreciate if anyone could help me with this.

Thanks a lot!
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Comments

Vigen Ghazarian
06-20-2013 04:29 AM

Kamran,
Based on the information you have supplied, the roll-over is not necessarily indication of pressure support. Such a roll-over could be related to partial penetration effects and/or increasing mobility thickness away from the wellbore (i.e. KH/U).
The drawdown pressure derivative (depending on the data quality) might provide further insight into the presence/lack of pressure support hypothesis. Under such a scenario, both the drawdown and pressure build up derivatives should roll downward....
Cheers
Vigen