Am working on discriminatio of minerals/lithologies, am using this "if volume of shale is less than 6 then 7 else 16 end" for basic log calculations in well logging software, but am getting just sand and shale discrimination, please is there a way of getting more lithology discrimination using a more complex logic statement and any other means to discriminate lithology or minerals, from well logging data
Hello Okechukwu.
Please let us know what do you have in your well logging dataset to perform a logical test?
Regarding to predefined standards yo can use sonic, Gamma and Neutron logs to make a "joint lithology discrimination".
Here I put some clues for you.
http://infohost.nmt.edu/~petro/faculty/Engler370/fmev-chap12-soniclog.pdf
Hi Okechukwu, I think your approach may be a bit cumbersome. If you rely on software alone, you may run into some trouble as they basically give you a box approach where most times you have no idea what you are doing. If you do have raw data i would suggest you use spectral gamma ray data with U, Th and K to correlate with density log and neutron log. In my experience, using density, sonic, neutron and gamma in cross-plots could be very useful, note the density of minerals and try to note them on density log etc or cross plot with gamma to link density to lithology etc. The lithology part can be a bit tricky depending on the amount of detail required if you don't have core or cuttings data to compare wit but a little background detail of your well environment should help as with logs, you can't hope to be 100%. Basically, you need to stop looking at the software and do some background reading, the software gives you results but how you interpret those results depends on the strength of your knowledge.
Okey, A combination of core analysis (XRD- mineralogy) with spectra gamma log, can be of help.
Okey, When I look at a well log, I do not use a "if" statement ... I tend to use an "and" statement. I consider log data like pointers, and many often seem to be pointing in random (= sometimes wrong) directions. Making an interpretation involves taking all those pointers, and forming a coherent pattern. By using an "if" statement, you run the risk of excluding data, whereas using an "and" statement, you are forced to find out why the pointer is in that direction, and seeing that it also fits into the pattern. But the pointers you have are more than the log data - think of geologists reports, seismic analysis, lithology logs, driller's data, offset wells, cores, etc. In all of this, no data should be excluded. So, "if" GR > 45, it doesn't mean de-facto that it is shaley. "if" dT = 67 it is probably salt, but can also be ...... ?? Using this approach opens up solutions to very complex lithologies, but don't expect a computer to give you the answer.
Density and sonic log (dt values are important lithology disrimination if dt 55 lithology is sandstone .If Density is 2.3 g/cc lithology is sandstones density is 2.6 g/cc lithology is shale. Also SEM_EDS analysis is very important mineral disriminations.
Thank you Ubani Chikwendu, Dinfa Vincent Barshep, Herald Bolt and Aynur Buyukutku for all your answers and contributions, I have been well enlightened.
I was able to use IP with more understanding from your contributions to solve my challenge
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