The most obvious use for the caliper log in the oil industry is as a tool to 

 calculate the proper amount of cement necessary to fill up the annular space 

 between the casing and the open hole to a desired point. The actual amount of 

 cement necessary for a desired fill is often two or three times the amount one 

 would use from theoretical calculations. Figure 16-2 is an actual caliper log 

 of a well in Smith County, Texas. The hole was drilled with an 85/g-inch bit, with 

 5 14 -inch casing set on bottom. Theoretical fill-up is 22 sacks of cement per 100 

 feet of hole. For more than 1000 feet of section 220 sacks of cement is the 

 theoretical amount necessary to fill back to 9500 feet. The actual amount of 

 cement needed is 544.4 sacks, or more than twice the theoretical quantity. 



Another problem encountered in the successful completion of an oil well 

 is the location and reaming of tight spots in the hole, so that casing can be set 

 and successfully cemented without channeling and bridging. The value of a 

 caliper log in locating these zones has been demonstrated many times. 



Modern drilling practices presuppose the use of many scratchers, centralizers, 

 and guides welded to the casing to assist in obtaining a better cement job. All 

 these tools have proved extremely useful in obtaining better cementing jobs and 

 eliminating costly squeeze jobs, but they are useless unless properly positioned 

 in the hole with the aid of a caliper log. 



In plugging back with cement, plastics, or gravel packing, a knowledge of 

 hole size is invaluable. In remedial work of this kind, well records are usually 

 inaccurate or nonexistent, and it is only through an application of the knowledge 

 gained from a caliper log that a successful job may be performed. 



In the field of drill-stem testing, a knowledge of caving conditions has saved 

 oil operators an untold amount of money. Figure 16-3 is a caliper log of a well 

 in Smith County, Texas, where the operator wished to find a packer seat to drill- 

 stem test the Paluxey sand at 7140 feet. A glance at the log will show that, using 

 trial-and-error methods, the chances of successfully setting a packer are relatively 

 small. By applying the information to be gained from the use of a caliper log, the 

 proper point to set the packer and the proper size of packer are easily determined. 



Many other uses have been found for caliper logs. The successful completion 

 of a fishing job may depend on a knowledge of the size of the hole above the junk. 

 A log made after a fishing job is completed will provide the necessary data 

 successfully to resume drilling operations. 



A knowledge of hole size is essential in evaluating an acidizing job, picking 

 a zone to side-wall-core, evaluating the results of shooting with nitroglycerine, and 

 finding a proper zone to gun-perforate. The present caliper log has fulfilled all 

 these functions. 



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