SPE and IADC Member
Helmerich and Payne International Drilling Co. has developed a data base of drill string failures experienced in the Anadarko Basin over a two year period. The analysis of this data has led to some operational changes in an effort to minimize drill string problems. This paper discusses the drill string failures experienced as well as the courses of action taken in an effort to reduce future failures.
Significant conclusions have been drawn from both the drill collar failures as well as the drill pipe failures. The drill collar failure analysis shows that a minimum bending stength ratio of 2.4 is recommended to avoid drill collar connection problems in the Anadarko Basin. Analysis of the drill pipe failures revealed that 43% of the failures occurred within the first 15 joints above the bottom hole assembly. As a result, H and P has increased the use of heavy walled drill pipe above the bottom hole assembly.
In October of 1984 H and P had a drill string failure that resulted in a fishing job, and ultimatley led to an expensive side tracking job. This prompted an effort to better understand the nature of our drill string failures, in hopes that some causes might be singled out and avoided in the future. Information concerning the nature and the circumstances surrounding our drill string failures was needed in order to conduct the study.
A "Drill String Failure Report" form (Figure 1.) was developed and distributed to the rig sites to gather information about future drill string failures. The form was designed to include information concerning the operating practices at the time of failure, as well as an actual description of the failure. It was decided that only drill string failures that resulted in operational problems (i.e. trip or fishing job) would be considered in this study. As the information was sent in from the rig sites after a drill string failure, it was put into a computer data base to facilitate analysis. This data base now contains information concerning over 35 drill collar failures and over 100 drill pipe failures.
The failures contained in this data base have occured while drilling for a number of different operators, using many different bottom hole assemblies, different hydraulics, different weights on the bit and different rotary RPM'S. Despite the varied circumstances surrounding the failures, there have been some common failure characteristics. This has led us to believe that there may be some general guide lines that can be used to help minimize drill string failures while drilling in the Anadarko Basin. Those common failure characteristics and general guide lines are discussed in this paper.
Perhaps the most obvious characteristic of our drill collar failures is that 97% of the failures occured at the box end of the drill collars (see Table 1.).