The presence of black solids in oil and gas pipelines can lead to major flow assurance issues as solids build up over time within a production application. This paper describes two real-case studies used to identify the dominant mechanisms involved during black solids formation in production applications.
A systematic field-based audit was used as a key tool in identifying the source of oxygen (O2) into the production applications. This approach considers field operational parameters, corrosion side-stream monitoring data and in-situ generated data to identify the source of integrity and scaling issues in the system and developing a tailor-made chemical solution.
In the first case study, black solids were noticed in the vapour recovery unit (VRU) after several years of operations, whilst in the second one, calcium carbonate and iron (II) oxide were predominantly found to induce black solids due to the oxygen ingress from one of the produced water tanks. In both scenarios, the key component affecting the production process was caused by corrosion mechanisms, whose kinetics became too fast and uncontrollable in the presence of oxygen.
The outcome of this systematic approach identified O2 ingression as the root of the problem and enabled the design of a fit-for-purpose chemical management program to prevent further black solids formation in the system.