plots the coordinates. Figure 18-5 illustrates a type of form on which drilling- 

 time data may be tabulated. 



Determination of the time factor from the chart, using the engineer's 

 scale, is made by placing the scale parallel with the long dimension of the chart 

 and at the left of the base line from which the slanting stroke is made. The 

 zero of the scale is then placed at the top side of the depth stroke and the 

 position of the top side of the succeeding depth stroke noted on the scale. The 

 observer can read the scale to the nearest quarter of a division or fifteen seconds 

 of time, and this reading is the time factor for the foot being measured. Because 

 of the type of coordinate paper recommended for plotting the log, it will facili- 

 tate recording and plotting these time factors if decimals instead of fractions 

 are used, as in Figure 18-5. 



No difficulty will be encountered in reading and tabulating the time 

 where there have been no interruptions in drilling. If drilling has been stopped 

 at other than at the completion of an even foot, as at 6021-6022 feet in Plate 18-1, 

 the time out must be subtracted from the total time to indicate only the net 

 time consumed in the drilling of the foot. The position of the 6022-foot stroke 

 on the scale is shifted to the top of the bottom horizontal line, indicating the end 

 of the time out. The position on the scale of the top side of the top horizontal 

 time-out line will be the net total time required in the drilling of this foot. If 

 more than one interruption has been made in the drilling of one foot, this 

 process is repeated for each pair of horizontal lines indicating interruptions. 

 All interruptions should be recorded on the tabulation, as in Figure 18-5, and 

 by conventional symbols shown on the plotted log, as in Figure 18-6, to prevent 

 false interpretations. Care should be given to the pens so that they are in exact 

 horizontal registry in respect to each other at the top of each chart; otherwise, 

 errors in calculating time-out intervals may be made. 



After the chart has been prepared with the proper depths indicated, any 

 instructed person may make the time determinations and plot the log. Office 

 clerical assistance is used often by geologists supervising the work on several 

 wells being drilled at the same time. When this is done, it is imperative that 

 the original charts be received with the correct depth designations shown. 



Plotting the log starts with the tabulation of data as in Figure 18-5. The 

 selection of the time scale is important and has been discussed and illustrated 

 in previous papers by the writer. The log strip found to be most satisfactory for 

 interpretative work consists of coordinate paper with twenty divisions per inch 

 and cut six to eight inches in width. The heading at the top should show the 

 name and location of the well, datum elevations, and the vertical scale used. The 

 name of the observer or plotter may be useful for the record. Referring to 

 Figure 18-6, the depths are given at the left edge of the log at intervals of 10, 

 25, 50, or 100 feet as determined by the vertical scale used. The time scale is 

 shown across the top of the log in terms of minutes per foot. 



384 



