Feeling the pressure

Researchers at the Norwegian University of Science and Technology have developed a technique that uses pressure pulses to locate blockages in oil pipelines on the ocean floor.

One key problem in oil exploration is wax deposits that can form a plug when oil sent from a platform cools as it passes through pipelines.

Currently, the oil industry shuts the pipe down and sends a robot through it to locate the obstruction. The robots sometimes get stuck when they encounter an obstruction that is too impenetrable, so the operator then has to reverse the pressure in the pipe to free it. This can be a costly cut into production time.

Prof Jon Steinar Gudmundsson came up with the pressure-pulse method after he observed the shutdown of a geothermal well in Iceland.

‘When a well like this is closed with the help of a pressure valve, a pressure wave is created. I realised that this pulse could be used for something constructive,’ he said.

The method is based on a seismic principle and is similar to an echo sounder – a pressure pulse is sent out and the return signal is measured.

‘The principle is the same as what we call a “water hammer” – that’s the bang you hear in a washing machine or a dishwasher when the flow of water to the machine is shut off quickly,’ added Gudmundsson.

The reflected waves from the sound pulses can be measured, then used to create a map of the inside of the pipeline, showing where the pipe narrows and where the deposits are so thick that they plug the pipe. The information helps operators choose the best possible method for clearing the pipe.

Gudmundsson’s idea needs no new equipment as it uses the existing pressure valve and sensors to measure pressure.