X-Stream: An Innovative Pipeline Solution to the Challenges of Extreme Water Depths

Abstract

In South America, the recent fields discovered in the pre-salt area are located more than 300km away from the coast, which makes exploring and especially the transportation of associated gas a major challenge in the coming years. Several issues are related to this problem: • distance to shore (more than 300 km) and ultra-deepwater (more than 2000 m); • vessel time and capacity (reduced number of boats/offshore units with capacity to install pipelines in deepwater); • increasing demand for these vessels worldwide; • flaring restrictions in accordance with Brazilian National Petroleum Agency (ANP). Deepwater pipelines have traditionally been built using very thick pipe walls, requiring large quantities of steel and special equipment for milling and pipe laying. This paper presents an innovative gas transportation concept for long distance in ultra-deep waters (X-Stream Pipeline Concept). A way to potentially reduce the required wall thickness of deep water pipelines by controlling in the differential pressure across the pipe wall (and thus allowing for a reduction in the pipeline wall thickness). This concept is also applicable in other deepwater exploratory frontiers, for instance: Gulf of Mexico and West Africa.

Deepwater pipelines – status, challenges and future trends

“…X-Stream is a novel pipeline concept developed by DNV, 20,21 with the objective of reducing the cost of deep water gas trunk lines within the current safety and integrity regime. The idea is to solve the collapse challenge by limiting and controlling the external over-pressure.…”

“…a rough cost comparison indicates a 20–30% cost reduction 20 (steel cost, transportation cost, welding costs) compared with a traditionally-designed gas trunk line of 200 km at 3000 m water depth.…”