Summary
Wax and hydrates deposition is a major concern for hydrocarbon transport in pipelines, production tubing, and other pipes in cold environments. Traditionally, chemical, mechanical, and thermal methods are used to mitigate the deposition at the expense of production interruption, complex maintenance, costs, and environmental hazards, and many of these methods are not feasible in deep water environments.
This paper studies the potential of nanopaint-aided electromagnetic pigging. This process has potentially low production impact, simple maintenance, low energy cost, and no chemical expense or hazards. The electromagnetic pig contains an induction coil that emits an alternating magnetic field. The alternating magnetic field induces heat in the nanopaint coating (i.e., coating with embedded paramagnetic nanoparticles) on the pipeline’s inner wall and in the pipeline wall itself. The heat then melts and peels off the wax and hydrates adhering to the pipeline, allowing the hydrocarbon to carry them away. Without loss of generality, we focus on wax remediation in this paper.
We analyze the heating effectiveness and efficiency of electromagnetic pigging. The heating effectiveness is measured by the maximum pigging speed that allows deposit removal. The heating efficiency is measured by the ratio of the heat received by the wax over the total emitted electromagnetic energy, which we define as the pig induction factor (PIF).
An axisymmetric transient model is built to study the heat transfer without considering phase change. Based on our numerical model, we compare the PIF for different coil designs, different hydrocarbon flow rates, and different pig traveling speeds. We reevaluate the maximum pig speed defined by the static pig model from our previous work and found the electromagnetic pigging system is much more effective than previously estimated, while we confirm that a solenoid with larger radius allows higher pig speed. We find that faster pig speed generally improves the efficiency but decreases effectiveness and that shorter solenoids with larger radius have higher efficiency. The hydrocarbon flow rate does not impact the heating process if the wax is thicker than the threshold wax thickness. Based on the simulation results, the field application is discussed.
