CP System for Trenchless CO2 Pipeline Crossing in Perforated HDPE Casing

Abstract Cathodic protection of a trenchless crossing is often challenging due to the depth of the horizontal directional drilled (HDD) pipeline, the various soil conditions along the trajectory and the technical limitations for installing anode ground beds. In this case study a pipeline is carrying carbon dioxide (CO2) captured from the petrochemical harbor of Rotterdam to a depleted offshore gas field in the North Sea. The HDD runs underneath the entrance of the harbor having a total span of 629 m (2063 ft). A perforated high-density polyethylene (HDPE) was pre-drilled for allowing curving of the carrier pipeline due to geotechnical obstructions along the routing. A cathodic protection system was designed based on computational modeling to insure that effective protection of the CO2 pipeline inside the HDPE casing is achieved. The cathodic protection system consists of a new impressed current system installed at the entry point of the HDD and an existing sacrificial anode system on the subsea pipeline connected to the gas field. Various scenarios were simulated to optimize the diameter and special arrangement of the holes in the HDPE, and the location of the anode ground bed for adequate protection while minimizing interference on third party pipelines and cables in the congested area.