Understanding the Origin and Removal of Downhole Debris: Case Studies From the GOM

Abstract Potential damage to the formation and generation of destructive wellbore debris can occur during perforating operations with shaped charges. One type of damage is to the formation, which is related in part to the powdered metals and metal alloys incorporated into the metal casings that contain the explosive charges in controlled debris perforating systems. Upon discharge, gun debris, including casing-metal residue and reaction products from the perforating system, can also contribute significantly to the overall amount of destructive wellbore debris generated. In addition, the debris often includes metal fragments from the wellbore casing, formation sand and other minerals, cement, and drilling fluid remnants that eventually are ejected into the wellbore. All of these materials can promote costly mechanical failures, contribute to well control problems, and hamper onsite operations. Various factors influence the ultimate generation of destructive wellbore debris. These factors include gun type, fluid type, fluid density, bottom hole pressure and temperature, and the specific wellbore configuration and completion scenario employed. While previous authors have addressed formation damage issues or the impact resulting from the use of various casing metals, this work focused on the actual downhole debris generated and collected from the wellbore just after perforating the well, and relates these findings to the influencing factors. With the use of advanced downhole filtration and collecting techniques, downhole debris was collected from a series of deepwater projects in the GOM. Debris analysis coupled with well completion information has been studied. Results from the examination of downhole wellbore debris collected after perforating the well is presented and discussed. Improved wellbore integrity and reduced risk are obtained through proper management of perforation and wellbore cleaning practices.