154 Subsurface Geologic Methods 



The extensive and successful application of residues to petroleum 

 geology proves the value of residue studies, but few petroleum geologists 

 have published results. The Insoluble Residue Library of Midland, Texas, 

 is financed and operated by nineteen companies, which employ specialists 

 for residue examination or subscribe to a special service furnished by the 

 Midland Residue Research Laboratory. The Missouri Geological Survey 

 uses insoluble residues as a standard procedure for the correlation of 

 formations younger than Pennsylvanian. Its collection of residue samples 

 is probably the largest and the finest collection in the world. The state 

 geological surveys of Illinois, Kansas, Missouri, Oklahoma, and Texas and 

 the United States Geological Survey have utilized the study of residues as 

 a regular part of their programs for subsurface work. 



Plotting Residue Data and Descriptions 



Many methods of plotting residue data have been devised for indi- 

 vidual needs and purposes. Three will be discussed here. The writer 

 uses a method called the "constituent-percentage method," which is illus- 

 trated in figure 58. The data and description are plotted on a strip log 

 100 feet to the inch printed with a grid ruling. This scale allows the 

 comparison of residue logs with standard oil-well logs or sections. Other 

 intervals may be used according to the need and desire for detailed de- 

 scription. 



Column 2 shows the percentage of residue in relation to the original 

 sample, and column 3 shows the lithology. The percentage of each con- 

 stituent in reference to the total residue is plotted in column 4. Thus the 

 percentages of the constituents from a ten-percent residue of the original 

 sample will be shown in the same lateral space as the percentages from 

 a ninety-percent residue. Color and symbols with superscrips and over- 

 prints in ink over the colored background in column 4 describe and dis- 

 tinguish the constituents. The most specific information for correlation 

 work appears in this column. Lines representing the color of the cherts 

 are placed in column 7, the color being the same as the actual color of 

 the chert, except that white chert is designated by green. 



The percentage-percentage method is a second method of plotting. 

 By this method the percentage of each constituent is plotted in proportion 

 to its percentage of the original sample as shown in figure 59. Super- 

 scripts and overprints in ink and color similar to the first method are 

 used for differentiation of the constituents. An expanded scale is required 

 and percentages over 75 are eliminated. 



Residues from all types of samples may be plotted satisfactorily by 

 this method except rotary-tool samples having considerable cavings. The 

 caved material in rotary-tool samples hinders accurate judgment of the 

 percentage of any one constituent in relation to the indigenous portion 



