Modeling and Simulation; Subsea Stepout and Tieback

Abstract

Recovery of subsea resources located at great distances from shore at great depth often envision some processing of the recovered product on the sea floor prior to transportation to a floating or onshore facility. Processing and transportation efforts require that energy be transported at the required rate and controlled to facilitate stable operation. In sea floor processing facilities, energy consumers can be expected to be deployed down hole at primary pumping/compression and booster pumping/compression stations on the sea floor as well as being located along the length of the tie-back (pipeline) to the onshore receiving facility. Electrical supply is likely to consist of a subsea transmission line running (step-out) alongside the tie-back and being periodically tapped along the length as required to deliver power to booster pumping/compression stations. The length of the transmission line, various global loading scenarios, and varying loading at specific receiving points is a challenge for maintaining power quality and stability at each receiving point, where energy/power is drawn to supply loads. ABS has built preliminary models of subsea pipeline tiebacks and electrical step outs. Engineers have performed simulations of energization of the step out, and have studied step-out electrical transients. Future work will focus on the study of steady state and slow dynamic pipeline flow, power system characteristics and the interaction between the hydraulic and electrical systems refining the models to include more of the hydraulic characteristics and electrical characteristics of the coupled systems to increase the fidelity of the simulation.