An Investigation of Sustained Casing Pressure Occurring on the NCS

Abstract

Reports from the Gulf of Mexico (GoM) show that thousands of wells exhibit sustained casing pressure (SCP), however the extent of this phenomena and its driving factors have yet to be studied in detail on the Norwegian Continental Shelf (NCS). The central questions investigated and discussed are the occurrence of SCP, the specific factors that increase the likelihood of SCP and if SCP increases the likelihood of incidents or accidents during normal operations or permanent plugging and abandonment. The Petroleum Safety Authority does not require SCP to be reported on the NCS, but rather a general “Well Integrity Status”. No previously identified research has investigated the full extent of SCP issues on the NCS. SCP is believed to be a significant issue on the NCS as indicated by findings from the GoM and through dialog with operators and review of the World Offshore Accident Database (WOAD) the author hopes to shed light on the topic. A survey and substantial document review has been performed to form the basis for analysis and further work, but the availability and willingness and time constrain by data owners to share well data and integrity information has been a limiting factor. It is apparent that SCP does occur on the NCS and is linked to overburden zones with flow potential and compaction induced well damage, however due to annulus inaccessibility there is significant uncertainty especially concerning subsea wells and the potential environmental risk.