ABSTRACT

Wax deposition is a major concern in most offshore projects. Mostly, it is possible to manage this problem during a project design phase just by defining a required thermal insulation. However this solution is suitable only for relatively short pipelines; for the longer ones – ranging over 80 km, or 50 miles – the thermal insulation is not enough to solve the problem and, in practical terms, it is not possible to avoid wax build-up. This type of project will probably require other measures, such as pigging and chemicals. To select and implement a solution for this case one needs to know severity of the deposition.

The models that describe the wax deposition process in pipes may require tuning of the diffusion and shear terms for the field application. This paper describes a case study performed to support the design of a long pipeline to transport waxy oil through a distance more than 90 miles from a deepwater field located offshore Brazil. The wax deposition data were obtained at Tulsa University Paraffin Deposition Projects (TUPDP) facilities. A total of eight paraffin deposition tests were conducted for different liquid flow rates and shear stresses at different oil and coolant temperatures. The measured data were compared with computational simulations using both OLGA and WAXPRO, software developed by TUPDP. OLGA and WAXPRO are tuned using the flow loop data, thereby, lowering the uncertainty in predictions and increasing the project reliability.

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