The Role of Bacteria in Under-Deposit Corrosion In Oil and Gas Facilities: a Review of Mechanisms, Test Methods and Corrosion Inhibition

摘要

Under-deposit corrosion (UDC) represents a threat to pipeline integrity. This phenomenon has been appointed as responsible for localised corrosion damage in both laboratory testing as well as in root cause analysis of critical pipeline failures. UDC causes localised corrosion to form beneath the deposits which occur due to chemical and physical differences between the bare and deposited-steel surfaces and, in case of fully deposited surfaces, as a result of the conditions under the deposits. Typically, horizontal or inclined sections of pipelines where the flow velocity is under its minimum limit tend to accumulate (usually at 6 o'clock position) corrosion products and scales of the line leading to deep penetration of the metal surface. Under-deposit corrosion can frequently take place in sub-sea injection, transmission and well-fluid pipelines. However, it can also occur in cooling water systems with scales and foulants. Solid particles can promote corrosion in two ways: 1) adsorption of inhibitors onto deposits reducing inhibitors availability and thus leading to inadequate inhibition beneath the deposits, and 2) producing corrosion-erosion at high low velocities by either eroding the metal wall or removing layers of corrosion products and filming inhibitors.