Continuous Coring for Oil and Gas
Authors: Bobo Roy A. 
Published: December 2007

This paper was prepared for the 40th Annual California Regional Meeting of the Society of Petroleum Engineers of AIME, to be held in San Francisco, Calif., Nov. 6–7, 1969. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgment of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.

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The concentric drill string method of obtaining continuous core and chip specimen, heretofore used in mineral industry for exploration purposes, can be carried out from the surface to great depths in oil and gas wells. This method may be used to greatly enhance the means for evaluating formations as they are traversed by the drill bit.

Introduction

In recent years, the direction of industry has been focused on development of new and better ways of sinking a hole in the earth. Under particular consideration are the hydraulic automated particular consideration are the hydraulic automated drilling rig, the retractor rig, explosive drilling, erosion drilling, and pellet drilling. While engaged in spending vast sums of money in these plausible pursuits, some of the old standard methods that were pursuits, some of the old standard methods that were developed for the prime purpose of evaluating the formations understandably were not advanced, while others, such as the logging instruments now do an amazing job. While significant developments are being attempted elsewhere in the drilling field, one new drilling means that lends itself ideally to continuous recovery of substantially unaltered formation specimens has been developed for use in shallow minerals exploration. It will be shown herein that this system can be employed for continuous coring and/or core sampling (chipping) to depths of 10,000' and below for ready use in ascertaining the oil and gas bearing potential of the formations as they are traversed. potential of the formations as they are traversed. The recovery is fast, relatively inexpensive, and accomplished with a minimum of flushing of the fluids in the pore spaces. The system is known by the trade name "Con-Cor" and is a product of the Walker-Neer Manufacturing Company of Wichita Fall, Texas. The prime advantage of chipping over coring is that bits can be used with conventional rock bit cutters and rock bit bearings. For this reason, it is possible to obtain the same bit loading as would be possible for the same size of hole in conventional drilling. The marked superiority of rock bits as contrasted with core bits has made core chipping the more popular of the two methods. This is particularly so since geologists have found the chipped particularly so since geologists have found the chipped samples of sufficient size for ore analysis.