Well-Integrity Issues Offshore Norway
- Birgit Vignes (Petroleum Safety Authority) | Bernt Sigve Aadnoy (U. of Stavanger)
- Document ID
- Society of Petroleum Engineers
- IADC/SPE Drilling Conference, 4-6 March, Orlando, Florida, USA
- Publication Date
- Document Type
- Conference Paper
- 2008. IADC/SPE Drilling Conference
- 6.1.5 Human Resources, Competence and Training, 1.6 Drilling Operations, 3 Production and Well Operations, 1.6.11 Plugging and Abandonment, 4.5 Offshore Facilities and Subsea Systems, 1.14.1 Casing Design, 5.4 Enhanced Recovery, 2 Well Completion, 1.7.5 Well Control, 2.2.2 Perforating, 5.4.2 Gas Injection Methods, 3.1.6 Gas Lift, 4.2.3 Materials and Corrosion, 1.14 Casing and Cementing
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A number of serious well failures in recent years led to investigations of well integrity issues. The Petroleum Safety Authority Norway (PSA) performed a "pilot well integrity survey" based on supervisory audits and requested input from 7 operating companies, 12 pre-selected offshore facilities and 406 wells. The wells were a representative selection of production and injection wells with variation both in age and development categories.
The pilot project indicates that 18% of the wells in the survey have integrity failure, issue or uncertainties and 7 % of these are shut in because of well integrity issues. The selection of wells and the companies indicate that the statistics is representative.
The well incidents in the past and the results of "pilot well integrity survey" revealed that the industry needs to increase focus on the barrier philosophy. Control of barrier status is an important SHE factor to avoid major incidents caused by e.g. unintentional leaks and well control situations. Knowledge of well integrity status at all times enables the companies to take the right actions in a proactive manner and thereby prevent incidents.
The paper presents the results and the conclusions from the pilot survey. In addition a number of technical well failures will be presented, identifying critical elements such as corrosion, leaks and operational factors. In particular, the understanding of barrier regulations, standards and implementation was found inadequate.
A number of well incidents had been reported to the PSA with significant impact and potential for serious accidents (several companies - various well categories). This were typically aging effects or design, unclear understanding of barriers, weaknesses in well design and planning processes, insufficient validation of premises and other reasons.
PSA experienced shortcomings in the industry's handling of well related non-conformities, management of change, well conversion and lack of recognition of the entire well barrier envelope. In addition "safety critical equipment and elements?? were not included in the companies' maintenance system.
Information from the employees and union representatives indicated varied comprehension of well barriers, lack of overview, including variable approaches for corrective actions. Examples are difficulties for key personnel to get access to essential well-data when well control situations occurred. There were differences in the way the well barrier concept was implemented
There were examples of insufficient systematic control of the technical capability of entire "barrier envelopes?? and limited standardization according to the NORSOK D-010 recommendations for well barriers. Examples comprise design capabilities exceeded in operation, excessive exposure time with aims for increased oil recovery, and non-technical "benchmarking?? and missing continuity from design through operation and maintenance.
Furthermore; there were examples of insufficient transfer of critical information during license acquisitions, change of operator ship and a general need for improved "hand-over??-documents for operations.
In order to get a better picture of the well integrity status on the Norwegian Continental Shelf (NCS), PSA initiated a "pilot project??, based on "spot checks?? of selected production- and injection-wells from some of the operating companies. All of the companies involved were positive to the pilot well integrity survey.
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