Figure 17-3. On-location core analysis equipment in well-logging unit. 



the treated mud sample and by comparison of the fluorescent particles to 

 samples of rig oils and greases. 



In determining oil in cuttings, it must be borne in mind that the fluorescence 

 of the cuttings may be mineral fluorescence. Calcite is the principle mineral 

 encountered that may cause interference. It is possible to distinguish easily 

 between mineral fluorescence and oil fluorescence by placing particles that fluor- 

 esce in a nonfluorescent solvent such as carbon tetrachloride and observe them 

 under the ultraviolet light. If fluorescent material is leached out of the fluores- 

 cent particles and the solvent becomes fluorescent, the indication is that oil is 

 in the particles. If, on the other hand, the fluorescence does not spread to the 

 solvent, the fluorescence is assumed to be due to the fluorescent minerals. 



As indicated above, the presence and relative amount of gas in the mud 

 and cuttings is determined by the hot-wire gas detector, which gives a meter 

 reading that is independent of the observer. However, in the present oil- 

 detecting methods, the judgment of the operator of the equipment is relied upon 

 to determine the presence and relative amounts of the shows of oil observed in 



360 



