Hightech in the Deep Sea
At temperatures below 80 °C, crude oil changes in a way that can lead to problems. The paraffin in the oil compresses to form wax. In addition, the long-chained hydrate molecules, compounds containing water, turn into knotted, fluff-like structures. The situation becomes especially critical when the wax and hydrates meet and become a sticky mass. The flow of oil gets bogged down, resulting in expensive downtimes for the extracting company. The oil bubbling up from a freshly tapped well will initially be between 100 °C and 130 °C. But even in well-insulated pipelines, the temperature will fall significantly sooner or later.
Pipe-in-pipe with heating
The solution is the pipe-in-pipe process with electrical trace heating, also known as ETH-PIP. In this system, the pipeline carrying the oil is covered in heating strips that are supplied with electricity via feed-in points. This keeps the oil in the pipeline at a sufficiently high temperature, preventing it from clogging. From an economic standpoint, the system helps keep the process flowing. Additional protection against lower temperatures is provided by two layers of insulation around the heating strips made from highly insulating polymers. This forms a second pipe surrounding the pipeline that actually transports the oil – this is where the name “pipe-in-pipe” comes from.
Stress on the cables
The pipelines are first wrapped before being laid. A single spool can measure up to 80 meters across and have up to eight kilometers of pipeline. The tensile force and the curvature puts great stress upon the heating tapes, meaning that the heating cables have to be robustly designed. A maximum of four heating tapes arranged in a spiral around the inner pipe also help to reduce the high tensile and bending forces.
Semiconductors are the key
This considerable increase in efficiency in the pipe-in-pipe procedure is made possible by new technology. A special semiconductor layer surrounding the copper wire protects against the corona effect. This allows a voltage of up to 5,000 volts to be applied. With just a single feed-in point, it is possible to create heating circuits up to 20 kilometers in length. It becomes clear how much money the extracting company can save when you think about the costs for a single feed-in point. “Deep Sea Star”, the product developed by BARTEC in cooperation with big-name partners, has been available since 2013.
Going deeper underground
Whilst stocks just below sea level have been almost fully exploited, there are massive reserves hidden below 800 meters. Heated pipe-in- pipe systems are needed to retrieve these. There is also price pressure on the extractors. The fracking process, in which oil is won from the rock using pressure and chemicals, is becoming increasingly common in the USA and allows new oil reserves to be accessed more economically. Manufacturing costs need to be kept to a minimum in order to stay competitive on the global market. The newly developed and highly efficient pipe-in-pipe procedure could help make crude oil extraction more cost-effective.