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Geology/Well site identification of reservior fluid with oil based mud during drilling


Dear Sir,

Good Day,

How do we identify reservior fluid fro oil based mud as both of them will show fluorescence under UV light. What is the well site method of differentiate them.

Thanks and regards


Dear Rahul,

I have responded similar question and forwarding you the answer I have given few months ago.

Please Do Rate it it.



Dear Ali Mohammad,

Thanks for sending me this question.

It is common that  oil is mixed with water based mud to increase the lubrication for ease of drilling and better rate of penetration and also to decrease the Clay  swallowing effect when in contact with water while drilling which causes problems and some time it packed the well bore.
Some time oil is the only medium which is being used for drilling. When OBM is being used for drilling first thing you have to do to keep a fresh oil sample in the logging unit and keep it safe in the fluoroscope in a china dish as a visual reference . Usually the fluorescence of lighter oil is white, creamy and bluish white.

If the oil is being used as a major component instead of water then cuttings need to be washed by diesel or other agents that can remove or decrease the oil from cuttings. In that case all agents including diesel  need to be  collected and keep safe as a visual reference in UV Box.

Keep in mind that oil in the mud system is being biodegraded due to mixing of water and exposure  in which all the lighter components of oil washing away and the color of oil fluorescence start becoming golden, yellow and brown. Your eyes will automatically train after examining  several samples and any change of nature of the fluorescence, usually few new spots of bluish white or cream color fluorescence in the background of yellow or brown fluorescence  will be a new anomaly  and then you have to pick and eliminate those grains from other sample and watch them their shows again and if required add few drops of Tri Choloro Ethan and compare their nature of fluorescence with bulk of the sample.


1) get all component of drilling fluids and keep them in UV Box
2) train your eyes visualizing in UV Box with oil from drilling mud
3) Different type of fluorescence need to be picked and separated  and examine.

Hope, this answer helps.

If happy RATE it generously.



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Syed Tariq Hasany


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