Jetting Running Tools and Wellhead Systems Development Opportunities Based in Pre-Salt Lessons Learned

Abstract

Abstract The execution of six different jetting operations in Santos pre-salt basin serves as field proof for methodology in conductor casing design and brings up new problems that need to be addressed for complete success both in the jetting operation and in the construction of the second section of the well. Several jetting operations were executed in three different pre-salt fields of the Santos Basin, using the most recent guidelines in Petrobras conductor casing design. As the six wells had very similar drilling scope – they all had jetted conductor casing and surface casing cemented up to mudline–which made possible to sort out similar patterns and difficulties in jetting performance, cement operations and housing installation. The observations indicated good overall performance during the jetting operation, but all jetting operations needed BHA weight slack off in addition to casing weight, also known as compression jetting. Another running tool resource that could be used in high difficulty jetting operations is called pre-drilling, which means disconnecting the jetting tool mandrel, drilling ahead to weaken the soil and reconnecting to resume jetting, in order to achieve the final depth, was planned as possibility in every well design, but was not deemed necessary during the execution. Surface casing section, with extensions up to 1300 m, had good overall performance in drilling. Open hole caliper was estimated using tracer pills and pressure monitoring while pumping high density fluid prior to pulling the drill string out of the hole. Surface casings cement jobs were all successful in filling the whole annular with cement up to the wellhead, a critical point to future well integrity. In some wells, when disconnecting the cement job running tool, a difficulty in identifying the neutral point in the wellhead caused an excess slack off and, consequently, a downward movement in conductor casing was observed, needing to pick up weight again and wait on cement for final disconnection. Jetting operations identified the need for development of running tools that are able to apply additional weight without risk of disconnection during the jetting; to be able to disconnect, drill ahead, reconnect and resume the jetting; to be able to visually identify the neutral point in the wellhead; and, finally, to be able to lock the High Pressure Housing into position without additional slack off besides the surface casing weight. Successful jetting operations in Santos Basin opened possibilities for further performance enhancement in well drilling, that will only be totally fulfilled with respective technology development. This work points out some of the development opportunities in jetting running tools and in wellhead systems that could bring more reliability to jetting operations and guarantee both performance and well foundation integrity.