Sandwich Pipe for Long Distance Pipelines: Flow Assurance and Costs

The low oil prices have produced severe impact on the offshore industry slowing down new projects. The projects to become economically feasible shall incorporate innovative solutions for subsea equipment. In this context, the use of sandwich pipes for deepwater scenarios can be a useful alternative to conventional long distance pipelines. Sandwich pipe is a new concept composed of two concentric steel pipes separated by and bonded to a cement annulus that provides a combination of high structural strength with thermal insulation. For ultra deepwater scenarios, related to water depths beyond 1,500 m, the single wall steel pipe requires very thick wall and high insulation capacity. In this work, structural configurations for single wall pipe (SW), pipe-in-pipe (PIP) and sandwich pipe (SP) are designed for several deepwater scenarios. Collapse and buckling propagation are considered to overcome the high pressure environment while flow assurance is considered to overcome the low temperature. Simulations on flow assurance and cost evaluation will provide the basis for the comparative studies and recommendation about the appropriate scenarios for sandwich pipe applications. Flow assurance was simulated with OLGA software for the considered scenarios to avoid solid deposition. The costs related to each pipeline technology are finally compared for the established scenarios, and the sandwich pipe was considered to be a promising technology when high collapse strength and good thermal insulation are required.