Eliminating Human Error During Coiled Tubing Operations

Abstract

Summary In the last decade, several successful initiatives have been introduced to mitigate the risk of coiled tubing pipe failure while performing interventions in oil and gas wells. Through the use of reasonably accurate computer modeling, the industry has seen a marked reduction in the number of pipe failures associated with material fatigue caused by the constant plastic deformation occuring during pipe-tripping operations. Similarly, the judicious practice of employing off-line pipe-quality inspection tools, as well as the availability of real-time monitoring of pipe geometry through a variety of devices has contributed to a more predictable and more favorable pipe performance. A study of root causes for coiled tubing (CT) pipe failures during a 5-year period indicates that a substantial percentage of incidents were attributed to human error. This type of incident involves the application of excessive overpull, resulting in pipe necking or complete parting of the pipe because of tensile failure. Similarly, too much snubbing force will cause pipe buckling and compressive failure. Both have the undesirable result of a damaged CT string (at best) or a compromised well control security (at worst). Using a properly trained and fully competent crew can minimize such events. However, the arduous and stress-filled nature of live-well CT operations will limit the elimination of this human element. This paper presents an effective means for eliminating the possibility of human error becoming a factor in conditions that could result in a pipe failure during normal CT operations. Through the incorporation of a specialized system in the coiled tubing unit controls, a safety device is put in place to provide a shutdown feature when specific job-designed setpoints are exceeded. This paper provides a discussion of the features and capabilities of such a system. It cites details of recent experiences demonstrating the benefits with use of the device in actual CT interventions. Introduction In the last decade, the oil and gas industry has witnessed continued technology innovations in conjunction with CT use. Primary drivers for this development include tougher wellbore conditions and more complex intervention objectives. The impact of operating failures (OF) during execution of these high-technology CT interventions becomes more critical. These OFs can be the direct result of equipment failure, procedural inadequacy, product incompatibility, failure in the service organization, and human error. Seldom can the root cause be attributed to a single factor, and is often a combination of these mechanisms. Overall systems improvement and better service quality (SQ) can only be obtained through an investigation of all failures associated with CT well interventions. Failure of CT strings continues to be a recurring issue whenever the subject of OFs is discussed. Based on a study of operating data, a common root cause is human error, although other contributing factors are also in play. To mitigate the human error element contributing to an undesirable outcome, a specialized control system has been incorporated in the coiled tubing units of a major service provider. Statistics gathered during a 5-year period, from 2001 to 2005, is presented to determine if this has been effective in reducing the number of OFs attributed to this causation profile.