SOUE News Issue 3

The 16th Jenkin Lecture: Oil Production: from Nitroglycerine to Fibre-optics

Paul Martins (Pembroke 1972-5) - report by David Witt

After reading Engineering Science at Pembroke, 1972-5, Paul worked as a Civil Engineer for three years, and then did a PhD in soil mechanics at Imperial College. With this behind him he went to work for BP, at first doing research on the fracturing of underground rock formations to increase the flow of oil from them, and then putting the research into practice in North Sea oil and gas fields. The techniques that were developed proved very effective, and apart from boosting production, won for Paul and his colleague Tim Harper the 1992 MacRobert award, the Royal Academy of Engineering's premier award for engineering innovation.

Paul described the new fracturing technique in his lecture. It is to pump into the well, at extremely high pressures (e.g. 1000 bar, 100 MPa, at the surface), a slurry composed of a viscous polymer gel and ceramic granules. The fluid pressure opens up cracks in the rock, and the granules lodge in these cracks and stop them closing when the pressure is removed. The cracks can be 50-100 m high and, though very narrow, can extend hundreds of metres radially from the well. They can thus increase by up to 10,000 times the area of rock surface from which oil can flow into the well.

Success did not come at once. At first the industry was sceptical, and drillers reluctant to cooperate. Much larger volumes of gel were needed than had been expected, and they realised that for maximum benefit the wells had to pass perpendicularly through the oil-bearing strata, which meant they had to be drilled S-shaped if they were to tap strata at some horizontal distance from the drilling platform [how to do this is yet another remarkable development, but not part of Paul's lecture]. Experiments on a well could cost millions, and there was a risk of destroying the well altogether. Eventually they were able to increase the flow from a well by up to a factor of seven compared with an unfractured one. This meant they could exploit a field with many fewer wells, thus saving enormous sums of money.

Paul then went on to talk about current developments in well technology. Wells are now drilled in water 1000 m or more deep, and can go down more than 2000 m into the seabed underneath. Since the hire of a drill-ship can cost $250,000 a day, it is clearly important to make the most of each well. Various "down-hole" sensors have and are being developed to tell the engineers what is going on there. Since the temperature at these depths can reach 150°C, the development of sensors that can operate with complete reliability is something of a challenge. Fibre-optic technology is coming in useful here, for instance to measure temperature and three-phase flows, and pick up the seismic signals used to determine the geological surroundings.

[We were very distressed to hear in August 2004 that Paul Martins had died in a swimming accident while on holiday with his family in Devon. Our deep sympathies are with his wife Charlotte and their children. His death is also of course a great loss to his colleagues in the oil industry.]

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