320 Subsurface Geologic Methods 



make possible the correlation of zones of like permeability in a reservoir. 

 The possibility of gas or water channeling can be minimized by using the 

 permeability data for selective shooting, plugging, acidizing, or packer 

 setting. 



Core analysis is a highly specialized phase of petroleum-reservoir 

 engineering. The technique and procedures employed in analyzing cores 

 vary with the formation and type of core samples being tested. These 

 techniques may be considered somewhat mechanical, but the interpretation 

 of core data requires experience. There are many core analysts but few 

 qualified core-data interpreters. The use of one set of rules without com- 

 mon sense or judgment usually results in bad predictions on the part of 

 the interpreter. An attempt has been made to point out the factors beyond 

 the control of the interpreter, and due consideration should be given by 

 the oil operators for these extenuating factors. 



The practical value of core analysis to the petroleum industry is 

 evidenced by its ever-increasing use in the exploration and exploitation 

 of gas and oil reservoirs. The cost of this specialized service is small in 

 comparison to the present-day cost of drilling a well. To core a well 

 without analyzing the cores is as obsolete as drilling the well without 

 making an electric-log survey. 



Sometimes hundreds of thousands of dollars are spent in order to 

 core but a small fraction of the total depth of the well. Merely smelling, 

 tasting, and blowing through these cores can not tell how much oil or 

 gas is present and how much can be recovered. Such predictions are the 

 work of the qualified core analyst. 



Acknowledgments 



Appreciation is expressed for the encouragement, valuable criticisms, 

 and suggestions made by the writer's associates, Robert Caran, C. E. 

 Gordon, R. C. Kenney, S. H. Caran, and E. C. Lamon. 



All of the well data presented in this paper were taken from the files 

 of Core-Engineers and represent information from actual analyses; the 

 company and well names were withheld because it was felt that these wells 

 were selected merely as examples, and the data were not intended to be 

 used for correlation or exploratory work. 



FLUOROANALYSIS IN PETROLEUM EXPLORATION 

 JACK DE MENT 



Luminescence is the emission of light by matter under the influence 

 of energy; such a light emission violates the laws of thermal radiation. 

 Two types of luminescence are generally recognized: one, called "fluo- 

 rescence," lasts only as long as the matter is under the influence of the 

 exciting energy; the other, called "phosphorescence," persists after the 

 exciting energy has ceased to influence the matter. The fluorescence cor- 



