Wax Deposition

Flow Assurance

wax depositCrude oil is a mixture of hydrocarbons like paraffins, naphthenes, aromatics, and others. The solubility of high molecular weight paraffins drops with decreasing temperature. If there are more of these paraffins than can be dissolved, they are deposited as wax.

Temperature drops after production, once the crude oil leaves the reservoir and travels through transportation pipelines. Over time the wax forms  deposits that can build up within the pipeline.

The wax deposition thickness depends on the composition of oil, temperature, velocity of fluid, and pressure.

In the worst case scenario, wax will completely plug the flow, causing significant production and economic loss.

Objectives:

  • Develop a model for simulating the effects of thermal insulation, production rate, and well geometry on temperature profile in the production string.
  • Develop a model for predicting wax deposition and growth in the production string.
  • Combine both models to predict wax deposition profile along the production string.

A dynamic flow loop was set up to simulate wax deposition in production string under different production scenarios.

Conclusions:

  • The fluid flow model can be used to predict wellbore temperature profile in different production conditions.
  • If flow rate increases, deposition thickness decreases; if wall temperature increases, deposition thickness decreases.
  • The wax deposition model can predict model oil wax deposition thickness.

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