Delivering Value for Tracking Coiled-Tubing Failure Statistics

Abstract

Abstract The concept of tracking coiled tubing (CT) failure statistics for use in developing performance indicators is not new. It has been covered extensively as the subject of previous abstracts. Tracking relies on an established process for reporting and investigation of pipe-related failures allowing the collection of data from CT operations of a leading service provider, which has global representation. The primary aim of the process is the identification of the immediate cause of the failure and, more importantly, the failure mechanism for the incident. Only with a good understanding of prevailing trends, if any, can remedial action addressing the root cause(s) of the problem be enacted. This is particularly important for an organization with more than 200 CT units and more than 750 CT strings in service over a wide geographic landscape. In an environment of high CT activity, which has been the experience of the last two years, the value of this process cannot be overstated. The value to overall CT operations is demonstrated in two examples in which the identified failure trends became the focus of separate service delivery improvement initiatives. The first issue resulted in a change in the organization's policy for reel storage and maintenance, while the second caused a modification in the CT unit controls to properly address the root cause. An in-depth discussion of the issues and their mitigation is the subject of this paper. The most recent paper on this subject presented information covering the period 1995 to 2000. This paper provides updated information on these CT performance indicators, presenting material from activities during the five-year period 2001 to 2005. The evolution of pipe failure trends is covered and contrasted against the changes that have taken place in the CT industry as a whole over the last decade. Introduction Since 1995, a leading CT service provider in conjunction with their pipe supplier has adopted a CT pipe failure analysis program. The main objective of the program is to determine the cause of tubing failures and prevent or reduce similar failures in the future. The scheme involves collection of the failed tubing samples from the local site, which are then visually inspected by experts at a central processing location. All operational circumstances, including treatment history and fatigue monitoring results are also reviewed. Based on an initial evaluation, metallurgical failure analyses (chemical analysis, microstructural analysis, mechanical properties testing, etc.) are then performed by a qualified third-party laboratory. The laboratory work determines whether tubing limits were exceeded or if failure was due to material inconsistency, bias or seam weld problems, etc. All failure analyses are performed based on established guidelines. This complete process is covered thoroughly by Adrichem 1 in an earlier paper. Following each failure analysis, a comprehensive report is prepared summarizing the results, including recommendations for corrective actions. The failure mechanism and the root cause of each failure are categorized based on pre-defined failure codes given in Table 1 (Appendix). Failure mechanism is defined as that which caused the final failure or breakdown, rendering the CT string unserviceable. Not be confused with the cause of failure, defined as the initial condition that triggers the CT string to eventually fail. These results become important in explaining the nature of the pipe failure, particularly when it occurs during a critical, high profile operation. The true value of the program, however, is in the collective data as it provides statistical insight for tubing failures over a period of time and becomes the basis for directing future improvement efforts. This process of utilizing failure statistics has been adopted successfully over the past decade and continues to drive improvement initiatives in the manner CT pipe activities are managed.