Proper Field Practices for Drill Collar Strings
Authors: Garrett W.R. , Wilson Gerald E. 
Published: December 2007

American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc.
This paper was prepared for the 49th Annual Fall Meeting of the Society of Petroleum Engineers of AIME, to be held in Houston, Texas, Oct. 6–9, 1974. 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 paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made. provided agreement to give proper credit is made. Discussion of this paper is invited. Three copies of any discussion should be sent to the Society of Petroleum Engineers office. Such discussions may be presented at the above meeting and, with the paper, may be considered for publication in one of the two SPE magazines.

Abstract
The selection of a properly engineered drill collar string can be a useful tool in achieving minimum cost drilling. A properly matched drill collar string serves many useful purposes in the drilling of a hole in the purposes in the drilling of a hole in the earth's formation. These functions are; to aid in the production of a trouble free usable hole, to provide weight on the bit in the amount as needed, to assist in obtaining maximum bit performance, to assist in obtaining and maintaining the desired direction of the drilled hole, and to insure prolonged drill pipe life and performance. pipe life and performance

Introduction
Proper field practice relative to drill collar strings begins with the engineered selection of the correct size of collars required for each hole size as dictated by the well program. Threaded connections and special features must be chosen which best meet the needs of the collar sizes and area in which the drilling is being done. Anticipated drilling bit weight will determine the number of drill collars for each drilling string. Properly engineered bottom hole assemblies such as reamers, stabilizers and vibration dampeners, should aleviate many hole and drilling problems that may be expected. Familiarization of rig crews with good practices and planned inspection of drill collars can keep collars in service for the maximum time with minimum danger of down hole failures.
The contents of this paper will treat the entire drill collar system with respect to selection, operating practice, care, maintenance and repair. Many good oil field periodicals deal with various aspects of drill collar selection, care and handling and are recommended as reference material if more detail is needed on a particular subject.

SELECTING THE DRILL COLLAR SIZE
The hole size and bit program will determine the best drill collar size selection. An over simplified approach on drill collar size is to select the largest outside diameter with the maximum permissible wall thickness that can be safely run in the hole. Several benefits will be derived. Fewer drill collars are needed for any required weight and consequently fewer drill collar connections are required. Less time is lost handling drill collars in trips. Factors governing good bit performance favor close fitting stiff members.