The Clyde oilfield lies within North Sea block 30/17b. First oil was produced from the field in March 1987.
Wells drilled during field appraisal indicated a potentially, highly corrosive downhole environment. Although high chromium content (Duplex) steels appeared to be the technically preferred completion material a decision was taken to use carbon steel tubulars.
Historical data has shown that carbon steel gives acceptable performance in the large majority of production wells. Failures have occurred but these have been highly specific and related to high fluid velocities and increasing watercuts. A "mixed" string completion employing carbon steel, 13 Cr and plastic coated tubing has been successful in controlling downhole corrosion in these few problem wells.
This paper reviews the downhole corrosion control strategy used on the field and shows how carbon steel may be used successfully in a severe downhole environment.