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CORE 



William M. Koch 



When men began to delve into the earth for needed materials, it became 

 apparent that they required samples to guide their search. The ancient Egyptians 

 drilled into the rocks with tubular drills and secured short cores which aided 

 them in the construction of the pyramids. Many centuries ago, the Chinese, when 

 drilling water wells, performed a crude type of coring operation by driving 

 hollow bamboo poles into the earth and then examining materials packed in 

 the lower end. With the advent of the industrial revolution in the 19th century, 

 many new devices for drilling bore holes and for coring were invented. A 

 successful cable-tool coring device was patented in 1854; and in 1863 the first 

 rotary-coring tool was designed. 



In the early days of drilling for oil and gas, the cable-tool method was 

 used widely. By this method, a drilling bit, which could be likened to a star 

 drill, was pounded on the bottom of a bore hole to loosen the formation. When 

 sufficient cuttings were produced, a bailing device was used to remove them from 

 the bottom. The examination of these cuttings yielded information about the 

 penetrated formation. Later on a cable-tool core drill was developed which en- 

 cased a cylindrical core left by the drill. By raising the tool, a core catcher 

 broke and retained the cored section. Originally in the rotary-drilling method, 

 geologic information was obtained from the cuttings brought to the surface by 



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