OSLO, Norway – Petroleum Safety Authority (PSA) Norway has issued its findings concerning a hydrocarbon leak last June on the Oseberg A platform in the Norwegian North Sea.
PSA says it has identified serious breaches of Norwegian regulations, and has notified operator Statoil of an order.
Wells on the Oseberg field center began to produce sand around 2000. They are tested with the test separator to identify the acceptable rate of flow for sand production, and sand is accordingly produced into the system during well testing.
PSA says the test manifold’s blowdown line is unfavorably configured with regard to sand production, because its connection to the manifold means that sand can accumulate in the line.
Also, a 90° bend positioned directly downstream from the line’s orifice plate causes sand transported in the gas stream to hit the outer wall of the bend at a very high speed. This led to a hole being eroded in connection with the pressure blowdown on June 17.
PSA concludes that no adequate review of the plant had been conducted to verify that it could handle sand production. Its investigation identified nonconformities related to:
- Overpressure protection of the test manifold
- Risk assessment in using the equalizing and blowdown system for gas injection
- Work processes for operating the wells and process plant
- The inspection program
- The design for dealing with sand production.
Critical work processes for operating the Oseberg field center are inadequate, PSA claims. Several of these activities have continued for a number of years without the work processes being risk assessed, updated, or prepared.
Statoil is therefore ordered to perform a review, risk assessment, and update of work processes for operation of the wells and process plant on the Oseberg field center. Deadline for compliance is March 31.