Thermal Decomposition Effects on Perforating Performance and Safety

Abstract

AbstractExplosive thermal stability is an important topic for oilfield perforating operations and impacts perforating system performance and safety. Explosives have time dependent temperature limits which can lead to thermal decomposition when exceeded and, under some circumstances, can result in performance losses and safety hazards. Explosive thermal stability information is currently provided by perforating system manufacturers through time versus temperature plots. While these plots have proved useful for many years, this review of current industry thermal stability data and practices aims to highlight a need for improvement and expanded testing representative of the energetic materials as used in actual well environments.More specifically, this review discusses the potential economic impact on well performance and operational safety when thermal stability limits are exceeded. When using currently available time versus temperature plots, operators sometimes must select lower performing explosives which are thermally stable at higher temperatures especially for high temperature well environments. As a result, operators risk optimal well inflow performance with significant economic impact. Furthermore, exceeding the time dependent temperature limits can lead to thermal decomposition. Off-gassing from thermal decomposition can trap pressure inside of gun carriers creating safety hazards during misruns. This review includes a reference to a known occurrence where overexposure to temperature led to thermal runaway and a surface explosion of a recovered perforating system.Additionally, this review discusses shortcomings in thermal stability test methods and related API recommended practices. Current methods assessing thermal stability, including vacuum thermal stability, ampule, and ODTX (One Dimensional Time to Explosion) tests tend to use unrealistic test conditions. The API recommended practices do not directly assess thermal decomposition which is important in developing safe practices for recovered perforating systems which may have been exposed to temperatures exceeding thermal stability limits.This review concludes with recommendations for future work to better understand thermal stability in oilfield explosives. More suitable thermal stability tests which evaluate oilfield explosives in well environment conditions will lead to improved safety recommendations and has the potential for significant economic impact on well productivity through enhanced understanding of the time dependent temperature limits. Finally, this paper draws on the urgent requirements of the Operator community, the experience of the manufacturing community and the advanced technical support of a US National Laboratory to provide a concise review and recommendations which can then be promulgated through the API, as a major step in enhancing safety and ultimately well performance.