Reservoir Temperature

[LOST]

Dear Engineers,
I have a question:
how can we obtain a certain reservoir temperature?
I mean if we have MDT data, Well Test data and petrophysic log data?
which is more accurate?

Thanks

[kochichiro]

I just love this temperature talks. Ok, temperature provided by well logs in general less than undisturbed reservoir temperature, especially for old logging tools. It caused due to cooling of wellbore zone by drilling mud.
I don’t work much with MDT tools so can’t say much about them.
For me most reliable temperature is one from the production well test. To get it you must use temperature recordings during pressure build-up. Just plot the temperature vs Horner time on semi-log scale and interpolate the semi-log line to intersect with temperature axis. Here you would receive undisturbed reservoir temperature.
Remember that temperature curve is following pressure curve trend, so pressure models would be the same for temperature.
To get done this process easier you can load temperature listings to Saphir just like pressures, when program asks for oil formation factor, viscosity and compressibility just enter random crap like 1, 1, 1. Than model response with appreciate model. In results listings Pi would be your undisturbed temperature.
You must follow this procedure because any liquid production cause increase in wellbore temperature. Dry gas production cause decrease in wellbore temperature due to gas cooling effect.
Using the same logic I can assume that MDT tool would provide, during build-up, temperature measurement close to initial reservoir temperature. Because production rates and times during MDT are low.

[vinomarky]

kochichiro is correct

Another way of thinking about it is to realize that instead of a pressure transient which is created by a delta pressure, we are creating a temperature transient by circulating cooler fluid downhole. The math is almost exactly the same (hence why Horner plots & DST analysis software work just fine).

So, if someone asked which wellbore pressure measurement was most representative of reservoir pressure, you'd understand if the answer was along the lines of whichever was after the most shutin period and/or a Horner extrapolation - similarly for temperature it is that which has had longest period of undisturbed temperature and/or a Horner extrapolation.