11244 Field Experience: Identification of the Potential Mechanism of Flow Assisted Corrosion Due to a Large Viscosity Contrast in Biphasic Flow of Heavy Crude Oil

Available for download

Product Number: 51300-11244-SG

ISBN: 2011 11244 CP

Author: Bernard J. Pesneau and Hugo Caceres Rosales

Publication Date: 2011

Member Price: $0.00

Non Member Price: $20.00

Price: $20.00

Qty:

Unexpected very fast line piercing was discovered in an onshore field producing heavy oil with low Gas Oil Ratio (GOR) in Africa. Corrosion started seven months after the first evidence of water production (29 mm/y) with the piercings affecting the lines at the 6 o’clock position. The carbon dioxide content of the associated gas (15%) was first suspected to be the major cause of corrosion despite of the existing mitigation program. Similar leaks continued to develop in other lines although the corrosion rates measured in the inhibited produced water with Electrical Resistance (ER) probes were low. Cut sections of the lines revealed local piercings with smooth shapes or grooves at 6 o’clock. Through continuous trial and error, it was discovered that the corrosion rate was accelerated by the unexpected high velocity of the free water as a result of the large viscosity contrast between the oil and water.

This paper describes the history of the field, the corrosion damage and the subsequent corrective measures adopted. This hypothesis of flow assisted corrosion due to high water flow rate occurring at the bottom of crude oil transportation pipes with the absence of a gas phase is proposed.

Key words: flow induced corrosion, Carbon dioxide, heavy crude oil, line bottom, six o’clock, mobility ratio.