Determination of Bedding Plane (8) 



Since dip is measured downward from a horizontal plane, it is convenient 

 to use the electrode reaching the bedding plane at the highest point as the zero 

 electrode, which in this case is electrode III. Electrode I has a recorded azimuth 

 of 234 degrees and the sonde is not spinning; therefore electrode III must be 

 on azimuth 114 degrees. On the curves, electrode I reached the bedding plane 10 

 inches below III, and elecrode II 6 inches below III. It is necessary to convert 

 these vertical differences to angles within the well bore. 



Figure 25-12 illustrates the geometrical basis for the formula: Tan a 

 equals depth difference divided by hole radius times 1.732. This may be very 

 conveniently solved by slide rule, but tables eventually may be compiled for 

 this purpose. The angles determined are entered on the form above the depth 

 differences. We now have two apparent dips in the well bore, and the true dip 

 is to be determined. 



Placing the stereogram previously begun on the stereo-net, we mark the 

 zero electrode (III) at azimuth 114 degrees, (fig. 25-11). This point is re- 



Tan, a 



_ Depth difference 



Hole rad. x 1.732 

 Figure 25-12. Geometrical relations of dipmeter points on bedding plane in borehole. 



545 



