Evaluating Cathodic Protection on a Steel Catenary Riser Connected to a Platform and a Wet Christmas Tree

摘要

In general, it was observed that maintaining the riser electrically connected to the platform has the advantage of guaranteeing the protection of the riser in the majority of cases. The only exception is shown in Figure 4, where the platform was maintained at ~ -0,800 V_(Ag/AgCl) with low coating efficiency. It must be noted, however, that for higher coating efficiency, it was confirmed that the platform is protected by the galvanic anodes, requiring little or no IC. This fact should be taken into consideration in the design of the galvanic CP system. Electrical isolation between the riser and platform was shown to be advantageous at the start of the system operation, when the coating efficiency is high. In this case, the loss of current of the platform is avoided (Figure 2). Ideally, the potential maintained on the platform should be dynamically adjusted so that the potential on the electrically connected, isolated riser is as close as possible, guaranteeing that there is no loss of current and optimizing the system (in accordance with the case shown in Figure 4). It was also observed that the removal of the well piping, representing an increase of 5 A in the current available for the rest of the system, brought no significant variations in the platform and riser potentials. This indicates that an increase in the number of available galvanic anodes should not greatly modify the potential distribution close to the platform.