Innovation and incidents

Two incidents which were well publicised at the time were the gas blow-out at the very first well drilled and the much more serious blow-out on 2 December 1968 while drilling the production wells in the Marlin field. In the latter incident, an unexpected surge of drilling mud occurred and despite all the measures taken by the drillers to control it, after about an hour mud began to break out from the sea bottom and within minutes the sea was boiling angrily. The most immediate fear was that the gas would ignite and cause a fire which would engulf the platform and then be extremely difficult to extinguish. Urgent radio consultations with Esso in Sale, Melbourne and Sydney followed and it was decided that it was a job for 'Red' Adair. He arrived from Houston within 48 hours.

After consultations with Esso executives it was decided that the blow-out could probably be staunched from the platform, using a huge amount of mud and associated equipment. This took until just before Christmas to assemble, when the weather deteriorated and 80 km per hour winds whipped up 3 metre seas. The weather finally cleared on New Year's Eve. At 8 pm the pumps were started and around midnight the Marlin 7 blowout was sealed.

Adair, about to return to Houston told reporters, 'To me, this was one of the biggest technical jobs we've ever had, in assembling so much equipment and getting it rigged in the short order of time that we did. We have so many people who deserve a lot of credit ... not just me.' It had cost Esso and BHP $5 million, but it saved the best gas field in the Strait. The following account of innovative technology may seem something of an anti-climax after these dramatic events but collectively they are really more significant in the long run.

Hyperbaric welding

Hyperbaric welding is welding carried out at pressures substantially above atmospheric pressure, such as in a habitat on the sea bed. An example of this was the underwater 'tie-in' when the two sections of the Halibut-Marlin pipeline which were laid in opposite directions, met in February 1970. Choctaw, a unique twin hulled 22,000 tonne semi-submersible vessel lowered the habitat on guidelines to the sea bed 67 metres below the surface, so that it enclosed the pipe ends. A team of five diver-welders were then 'saturated' to a pressure of 700 kilopascals in a compression chamber aboard Choctaw, and moved between surface and habitat and back in a pressurised diving bell. Working in pairs, the diver welders aligned the ends of the pipe, using specialised hydraulic equipment in the habitat. They cut and cleaned the pipe ends to about 450 mm apart. Then an exactly measured 'pup' joint of pipe was lowered from Choctaw into the gap. Two high quality butt welds completed the job.

The welders used, for the first time in Australia, a tungsten inert-gas process. The welds were then X-rayed and coated with epoxy resin for corrosion protection. Although Ocean Systems Inc. USA designed and commissioned the habitat, Eglo Engineering built it at Williamstown, Victoria and most of the equipment was manufactured or obtained in Australia.

DRA

DRA or drag reducing agent is a long-chain polymer that was first used in the Trans-Alaska pipeline to reduce the resistance to the flow of oil and therefore the size of the pumps and the cost of pumping. The way it operates is still a matter of scientific interest but its effect is to make the oil more 'slippery'. It is introduced into the crude oil in tiny quantities at the pipeline inlets and disappears without trace.

Australian Academy of Technological Sciences and Engineering