Miscellaneous Subsurface Methods 591 



A few surveys have been oriented on sucker rods inside 2^-inch up- 

 set tubing to shallow depths in producing wells. A small- diameter, 

 multiple-shot survey instrument in a steel barrel was used. These surveys, 

 on which readings at 10-foot intervals to depths of 50 to 100 feet were 

 taken, were run to determine the position of the tubing in the well. Since 

 the inside diameter of large casing provides ample room for the tubing to 

 move, the exact position of the tubing is unknown unless surveyed. It is 

 not impossible for the tubing to deviate as much as 18 inches from vertical 

 in the upper 50 feet of casing. This misalignment results in severe wear 

 on the polish rod and difficulty with stuffing boxes. A plot and section of 

 the course of the tubing (fig. 305) gives the operator adequate infor- 

 mation for adjusting the level of the pump slab being poured, or for 

 shimming the pump base so that the polish rod may be correctly aligned. 

 This type of oriented survey may be made when the well is down and the 

 sucker rods have been removed from the tubing. 



Most drilling companies find it false economy to save the small 

 amount of time and expense involved in making a directional survey of 

 each well drilled because of the advantages gained by having such a 

 record. 



ORIENTED CORES 

 KIRK CARLSTEN 



Core orientation is a method by which a sample cut by an oil-well 

 coring bit can be removed from the well bore so that it may be oriented 

 in space in the same position that it occupied in the formation from which 

 it was taken. Presuming that the core contains bedding planes, the dip 

 and strike of the formation can be measured. The importance of taking 

 oriented cores in drilling wildcat wells is obvious. The dip and strike of 

 the new structures encountered are necessarily of vital concern to the sub- 

 surface geologist. Other methods are used for ascertaining this geologic 

 information, but actual cores of the formation itself are the best evidence 

 available. 



The Eastman Oil Well Survey Company offers a service for and con- 

 structs specialized equipment capable of obtaining oriented cores cut by 

 either conventional core barrels or by retractable wire-line coring equip- 

 ment. 



The equipment for one method applicable to conventional core bar- 

 rels is illustrated in A of figure 306. When a core is cut, it is scratched at 

 one point on its circumference by a scriber attached to the inner-core bar- 

 rel. The inner barrel is prevented from rotating by the friction of the 

 core catcher against the core, as well as the scriber, which is imbedded in 

 the core. Thus, the outer barrel containing the diamond cutter cuts the 

 formation, and the core is forced up into the inner barrel. It can be seen 

 from A of figure 306 that a shaft extending from the top of the inner bar- 



