DOE, University of Tulsa embark on wax-deposition study

Jan. 22, 2001
A joint project between the US Department of Energy (DOE), the University of Tulsa, and 23 private companies will tackle the problem of wax accumulation in deepwater pipelines.
Tulsa University's instrumented flow loop will be used for paraffin-deposition tests with crude oil and natural gas mixtures for the US Department of Energy and 23 oil and gas companies.
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A joint project between the US Department of Energy (DOE), the University of Tulsa, and 23 private companies will tackle the problem of wax accumulation in deepwater pipelines.

DOE will provide $1.2 million in research funds from its Fossil Energy petroleum technology program. Tulsa University and industry partners will add another $2 million for the 3-year project, according to an announcement from DOE last month.

The research will use the University of Tulsa's instrumented flow loop in Tulsa.

Flow restrictions

Virtually all crude oils contain long-chained molecules of wax in proportions that can vary up to as much as 60% of the crude oil's weight. In refineries, the paraffin wax can be separated and sold as a commercial product.

But in a pipeline or a wellbore, especially where temperatures are cold as in the offshore waters of the Gulf of Mexico, the paraffin can deposit along the inside walls of the pipe, restricting its flow, increasing the strain on pumping equipment, or in the worst cases, shutting off production or causing a rupture in the pipe and accidental release into the environment.

Remediating pipeline blockages in water depths of about 400 m can cost $1 million/mile, said DOE.

The new University of Tulsa project will begin by enhancing computer models developed in previous DOE projects.

Earlier experiments conducted on the university's test-flow loop confirmed that a much broader collection of experimental data, including other oil samples, is necessary to develop more-accurate methods for predicting the complex processes of paraffin deposition.

Enhancing programs

Researchers will flow a variety of crude oils and oil-gas mixtures through the test loop to improve understanding of the physical properties of paraffin and the mechanisms that control its accumulation.

Using data from these experiments, computer programs developed in previous projects for predicting paraffin buildup will be enhanced and tested against actual field data from operating pipelines.

The university's instrumented flow loop could also be used to test and qualify subsea measurement sensors that are being developed to detect deposit thickness in flow lines and pipelines.

Better models and paraffin sensors could reduce or eliminate the need for costly duplicate pipelines that are required for round-trip pigging operations to remove paraffin from the pipeline walls.

Better computer models could also tell operators where to place safety valves to minimize the chances of failures because of paraffin fouling.

These and other improved methods of preventing and remediating paraffin accumulation could save billions of dollars per year in maintenance and repair costs, improving project economics of many marginal offshore Gulf of Mexico fields to where they could be produced.

Taxes and royalties from the additional production could significantly increase the $6 billion in annual federal revenue derived from these operations.