Simulation of Transient Heat Transfer of Sandwich Pipes With Active Electrical Heating

Sandwich pipes consisting of two concentric metal pipes with insulation material in the annulus have been developed to meet challenging mechanical and thermal requirements of deep and ultra deepwater oil and gas production. Passive thermal insulation is designed to meet flow assurance requirements under steady-state production conditions, but is unlikely to meet more severe conditions during transient events such as warm-up and cool-down. In this work, we present the analysis of transient heat transfer in the sandwich pipelines with active electrical heating. The mathematical model governing the heat conduction in the composite pipeline and the energy transport in the produced fluid is solved by using finite difference methods. As unplanned cool-down of the pipelines is most critical to safe and economical operation of pipelines in deep and ultra deep water conditions, it is presented here numerical results of computational simulation of cool-down for three sandwich pipeline configurations under typical production conditions. The analyses show that the sandwich pipe with active heating is a viable solution to meet severe flow assurance requirements of ultra deepwater oil production even under unplanned and prolonged cool-down conditions.