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Crude oil and the problem of wax deposition on pipeline systems during transportation: A review

Crude oil, the world’s major source of energy, is obtained from the earth as a Newtonian fluid and needs to be transported to refineries for further processing. Pipeline transport has proven to be the most efficient, environmental-friendly and cost effective of all modes of crude oil transportation from subsea production sites. However the formation and deposition of waxes (mainly paraffinic and asphaltenic components) along pipelines remains one of the greatest flow assurance problem in the petroleum industry. This is aided by attainment of wax appearance temperature (WAT), the crude’s hydrocarbon contents and rheological properties, and the production conditions amongst others. The deposited waxes clog the pipeline, reduces the flow diameter, converts the behavior of the fluid from Newtonian to non-Newtonian, decreases throughput, causes more work on pumps and other process equipment, increases energy consumption, and ultimately raises the cost of production thereby decreasing profits. It also leads to several downtimes and in extreme cases can cause permanent shut down of facilities. Several studies have been done to understand the nature of crude oil waxes and the various techniques for solving this problem. This paper takes a critical look at crude oil and reviews the current state of research into the causative factors, deposition mechanisms and remediation methods including the thermal, mechanical, biological and chemical techniques. At the end there is a conclusion and further research on the use of biological techniques (microorganisms) has been advised herein.