CHAPTER 10 

 GRAPHIC REPRESENTATIONS 



L. W. LeROY 



Carefully selected and drafted illustrations of any report permit 

 minimization of the text material and enable the reader to obtain a more 

 concise understanding of the subject treated. Concepts and interpreta- 

 tions should be displayed graphically whenever possible. Each drawing 

 should be adequately captioned and correlated with the text. 



Well Logs 



Data to be included on final well logs are governed by company 

 policy. Some logs contain all information relating to the well, whereas 

 others may contain only the minimum facts. Well-log scales vary consider- 

 ably (1 inch = 50 feet, 1 inch = 100 feet, 1 inch = 200 feet) and are de- 

 termined by the amount of detail to be shown. Logs are commonly pre- 

 pared on standard commercial strips (1 inch = 100 feet (fig. 430). 



Log headings should include the following information: name of 

 well and company; location (state, county, area, section, township, and 

 range) ; elevation (ground, derrick floor) ; date well corrimenced, com- 

 pleted, or abandoned; total depth; type of drilling equipment; casing 

 record, and by whom logged. The graphic log should include the lithologic 

 column with lithology represented by graphic symbols (fig. 431), colers 

 (pi. 11), or a combination of both; formation description (abbreviated) ; 

 cored intervals; the position of oil and gas shows (symbols) ; core dips 

 and fractured phases; casing points (depth, size, and cement data) ; 

 formational and age boundaries; mineralogic and paleontologic data; 

 marker beds; tested intervals, including a brief summary of results; per- 

 forated and plugged intervals; points of loss of circulation or fluid en- 

 trance; hole deviation; mud and temperature data; drilling progress 

 (day, week, month) ; and points of mechanical trouble and bit changes. 



Electric-, radioactive- and drill-time-log profiles should be added 

 whenever possible, and the condition of the mud at the time these survey 

 runs were made should also be given. 



Plotted lithic data obtained from ditch cuttings frequently do not 

 correspond exactly with other logging data (electric, drill-time, etc.), 

 consequently reinterpretations and adjustments are required. 



Some subsurface geologists prefer plotting lithology on a percentage 

 basis, if the penetrated section is not well-known. Straight lithic calls are 

 common practice after formational units have been adequately established. 



Colors symbolizing various lithologies are widely used although the 

 color pattern varies among companies. Generally, yellow indicates sand; 

 blue, limestone; and hues of such colors as green, red, gray, and tan, 

 represent shales. Advantages in the use of color symbols are rapid plotting 



