ABSTRACT:

Hydrocarbon transportation in pipelines is affected by low temperature-driven problems like hydrate and wax deposition. Such problems may have an impact which is measured in millions of USD, when remedial actions are required on pipelines, especially in offshore production. While a considerable effort has been spent so far to predict such problems with a reasonable degree of success, there is still a need for restriction monitoring on a real-time basis. In principle, such target could be achieved by using high-tech solutions, like, e.g., fiber-optic sensor technologies, that are difficult to implement in an existing pipeline. In this frame, a low-cost, retro-fitting analysis tool would be welcome in many instances. A very simple and cheap technique is proposed in this paper that makes use of both measured and calculated pressure and temperature drop generated using a simplified multiphase flow model to be run online with the wax deposition map generation tool. A peculiarity of the model is the treatment of fluid transport in non-newtonian conditions, since if the oil temperature drop down the cloud point, wax nucleation and crystallization causes the oil to reach a non newtonian behaviour. The proposed tool generates, for a given network and a given fluid composition, the following information:

  • Occurrence of deposition;

  • Position and extent of the deposition region;

  • Flowing section reduction along the deposition region;

  • Amount of wax deposited.

requiring as inputs standard production data:

  • Well production;

  • Pressure drops;

  • Temperature profiles.

Validation of the multiphase model and example of the application of map generation tool are reported within the text

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