Core Descriptions 



It is usually desirable to describe cores in more detail than space on the 

 log permits. For this reason it is advisable to make a special plot on a larger 

 scale at the bottom of the strip. This large-scale plot should bear a descriptive 

 heading, and depth designations at the edge of the log must be changed to cor- 

 respond to actual depths. 



When the procedure given above is followed, the detailed core descriptions 

 should be plotted first on the large scale. Then this description should be sum- 

 marized to the extent that it can be plotted at regular scale (1 inch = 100 feet) 

 in the proper position on the strip. The small-scale plot is necessary when the 

 log is used for correlation with other logs. An example of this presentation of 

 core descriptions is shown in Figure 3-6. 



Engineering Data 



Unless engineeering data have a specific lithologic connotation, they should 

 not be plotted on the face of the lithologic log. Lithologic and stratigraphic 

 descriptions and designations require all the space on the log, and extraneous 

 data are introduced only at the sacrifice of space needed for the more pertinent 

 information. An attempt to show both geologic and engineering information is 

 bound to result in an inadequate presentation of both. 



Some microscopists plot the results of engineering operations at the ap- 

 propriate depths on the back side of the strip. While this method results in a 

 presentation rather awkward to use, it does have the advantage of placing such 

 information as drill-stem tests, lost circulation, and cementing jobs, where it 

 can be appraised with direct reference to the lithologic log. 



Preservation of the Colored Strip 



The time required to examine the samples and complete a log of a well 

 will range from a few days to as long as two weeks. The log is often the sole 

 record of this work, and a simple calculation will demonstrate that its worth 

 may be several hundred dollars. Obviously, the small amount of time required 

 to protect it from deterioration with repeated use is insignificant compared to 

 the time that has gone into its construction. 



The inked white portion of the strip will withstand much use without serious 

 deterioration. The color column, on the contrary, is damaged by handling and 

 exposure to sunlight or moisture. The dry indelible colors tend to rub off or 

 smear, and even a small amount of water changes the pencil colors to brilliant 

 dyes, thus ruining the meticulous color work of the microscopist. 



The color column may be preserved as follows: 



The materials needed are (1) a good-quality artist's flat-bristle brush, i/g 

 inch wide; (2) synthetic transparent lacquer, which can be obtained from craft 



48 



