In 1997, one of the Wytch Farm production pipelines failed from internal corrosion. After repair, the pipeline was returned to service but failed again.
Results of a high-resolution magnetic flux leakage (MFL) intelligent-pig inspection of the pipeline in late 1996 showed internal corrosion along the length of the pipeline, totaling 281 defects.
The frequency of defects increased towards the gathering station, particularly downstream of Well Site X (Fig. 2). The defects were believed to be restricted mainly to pipe body defects, with only limited indications of corrosion within the girth welds.
In June 1997, two failures occurred, one at the upstream end of the line close to Well Site K and one on the downstream end of the line within the boundary of the gathering station.
Pitting corrosion at the girth welds caused the failures. Small diameter (about 10 mm) pits were found to be entirely in the weld. The intelligent pig inspection had given no indication of the presence of these features.
Type:
Uncontrolled Discharge
Field:
Conventional
Stage:
Production
Region:
Site:
Wytch Farm Oilfield
Company:
BP