Electronic Thermometer/Pressure Gauge for Deep Earth Drills

• EXTREME PARAMETER: Precision of Pressure Measurement in Wide Range under Extremely Rough Conditions
• ACTIVITY AREA: Measurement
• INDUSTRY SECTOR: Chemistry
• CLIENT: NAFTA a.s.
• YEAR: 2002
• PROJECT LEADER: Ing. Július Kovács

The information that NAFTA a.s. company was searching for a supplier of a special measurement device was delivered to us by pure coincidence. They were in need of a data logger for monitoring of deep earth drills allowing them to maintain natural gas reservoirs. To tell the truth, this was sort of a joke – hardly anybody would go into this deal. Just quote the basic requirements and every engineer would say: run away! Here they are: temperature measurement in the range from 20 to 150°C. So far so good, neither the iron casing nor the silicon semiconductors would melt, only the processor will be sweating a little. Pressure measurement in the range from 0 to 400 Bar? Well, it´s starting to be interesting now. But once they said the accuracy of the pressure readout has to be of 0,025%, the smiles were wiped off our faces. And this accuracy is required within the whole pressure and temperature ranges! And there also has to be a built-in battery inside (you can find no electric wall socket 2km below the ground level). Everybody knows batteries hate high temperatures. And finally, we should not forget the fact that the whole device has to be a cylindrical rod 4cm in diameter.

So let´s sum it all up. We have to build a computer with an extremely precise measurement module and put it into a pipe with an outside diameter of 4cm, including the battery. The whole device should withstand temperatures of up to 150°C and a pressure of 400kg per every square centimeter while flawlessly measuring and recording temperatures and pressures with the required accuracy continuously for several days.

We started to think about this idea more from a sole interest than from a real intention to accept such a challenge. The only positive thing was that we would not have to compete with anybody

– nobody would attempt to deliver a product of this kind. Even the very first information regarding the possible pressure sensors was frustrating. We contacted 8 world leading companies in the pressure sensors market and ended up with 8 negative responses. A sensor like that simply doesn´t exist. But when we finally succeeded in finding a company (through a trade fair) that was able to deliver the desired part, everything was decided. We are going to work on the project. We submitted our offer, agreed upon terms and signed the contract.

Maybe we were lucky not to have realized quite well what lay ahead of us. The project ended successfully and several units were produced. These proved themselves well in the client´s use. We also obtained a certificate that the device can be used in an explosive environment. In fact, it is constantly working in a gigantic flammable gas reservoir.

And what is the memory I like the most? The first tests of the device and its calibration in the test room. When the device was placed into a sealed oil chamber and the temperature and pressure started to rise. All the way up to 150°C and 400Bar! Our body temperature and blood pressure were rising just the same way. Naturally, everything was designed and calculated properly, but those pointers on the measurement devices looked scary. Even the very first tests were successful – both from the device durability and also from the required accuracy viewpoint.

We confirmed the saying: where one sees a difficulty, another one sees an opportunity.

Technical information about the project