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Interpretation Module in Interactive Petrophysics 
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Joined: Mon Jul 09, 2012 3:31 pm
Posts: 18
Post Interpretation Module in Interactive Petrophysics
Dear members,

Based on SLB Log Interpretation Chart Book, porosity from Neutron is all in apparent limestone porosity which is used in crossplots for Lithology and Porosity Determination. Would you mind telling me whether it is necessary or not to convert Neutron porosity from Limestone matrix to Sandstone matrix (Zone of interest dominated by SS) in IP interpretation module particularly Clay Volume and Porosity and Water Saturation Analysis?

Does it mean that I have to use NPHI or NPHIC in apparent limestone porosity although I am working on SS reservoirs? (Crossplot Analysis will be carried out to identy lithology; however, their is no core data for core-log calibration)

I just wonder the way we select clay volume for further analysis. Asquith stated that the minimum values will be used (if we calculate it from different logs). Could you please explain me if the results from IP is the following?

Code:
Well : ...
Date Run : 7/19/2012 6:40:14 PM

Curve     Units      Nulls   Fail Disc   Top            Bottom      Net           Min         Max        Mean       Median     Mode      Std Dev   

VCL        Dec        0        0           1930.000    2000.000    70.500     0.000      0.696      0.222      0.238      0.259      0.135     
VCLAV    Dec        0        0           1930.000    2000.000    70.500     0.102      0.798      0.480      0.513      0.583      0.147     
VCLGR    Dec        0        0           1930.000    2000.000    70.500     0.000      1.000      0.624      0.730      N/A         0.277     
VCLND    Dec        0        0           1930.000    2000.000    70.500     0.004      0.925      0.478      0.491      0.523      0.218     
VCLR      Dec        0        0           1930.000    2000.000    70.500     0.000      0.993      0.339      0.277      0.306      0.254 


(Please kindly refer to the attached picture of curve statistics)

Kindly regards,

Milky Way


Attachments:
File comment: Curve Statistics
Curve Stat.PNG
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Sat Aug 11, 2012 10:58 pm

Joined: Tue Apr 05, 2011 8:38 am
Posts: 80
Post Re: Interpretation Module in Interactive Petrophysics
You can use the NPHI recorded in limestone units as it is, without converting to sandstone units. IP uses the NPHI log to do neutron/density crossplot as well as compute the crossplot porosity.
However, you have the option to choose which porosity you want to use in your interpretation. In the porosity module, there is an option to choose the method of porosity determination that you wish to use. You even have the option of using an external porosity, like porosity from other sources e.g. thermal decay neutron log, core porosity etc.
You can use the NPHIC, if you have already corrected for borehole and environmental corrections. I believe the IP software has an option to choose the neutron/density crossplot either with or without environmental corrections. I am not sure about this, since I am using an old version of IP software (for quicklook interpretation for operational purposes), as our corporate software is now Geolog.

To avoid overestimating the clay volume, it is usually advisable to choose the minimum clay volume from different methods of computation. I would advise you to use the clay volume from neutron and density logs, unless you are in a gas reservoir. If you have gas, you need to make gas correction on both density and neutron logs before computing the Vclay. The clay volume from Gamma Ray log tends to be more pessimistic, especially if you use the linear equation.

The IP results you sent me are statistical analyses of the different methods of Vclay computation. They are giving the results in terms of Net Sand, Minimum Vclay, Maximum Vclay, Mean Value, Median, etc.
I suggest you read the help file in IP for the explanations of these terms.
Here again, IP gives you an option to choose the Vclay that you wish to use in your interpretation, either Vcl(average) from all methods or from a particular method, like from GR or Neutron/Density, etc.

Regards,

Ko Ko Kyi


Sun Aug 12, 2012 1:57 am

Joined: Mon Jul 09, 2012 3:31 pm
Posts: 18
Post Re: Interpretation Module in Interactive Petrophysics
Dear Ko Ko Kyi,

Thank you so much for quick response and help.

Kindly regards,

Milky Way


Sun Aug 12, 2012 2:44 am

Joined: Tue Apr 05, 2011 8:38 am
Posts: 80
Post Re: Interpretation Module in Interactive Petrophysics
Dear Milky Way,

You are most welcome.

Ko Ko Kyi


Sun Aug 12, 2012 5:45 am
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