What hides beneath the surface of the Earth? This is a question the OMV geophysicists strive to answer every day. Literally. They explore the innards of the Earth using seismic measurements. And in an ideal scenario they also come across oil and gas. As is currently the case in Weinviertel, on OMV’s largest seismic campaign in Austria.
Slowly and sedately the three impulse generating vehicles roll across the fields, one after another. They stop every few meters and send waves into the ground below, more precisely they send up to 90 vibrations per second. Since the start of the year, a 151-strong team and a total of 68 vehicles have been deployed in Weinviertel, Lower Austria, to search for natural gas deposits below the ground. To achieve this they survey more than 600 square kilometers – from the Slovakian border to the Donaustadt district of Vienna. An undertaking that takes many weeks. By the end of March the vehicles of the seismic crew will have clocked up a mighty 250,000 kilometers.
A seismic study of the size we are conducting here in Marchfeld is highly complex and takes several weeks. It is deliberately undertaken in the winter months so that we don’t harm the vegetation in the fields.
The fact that this year’s winter was extremely cold and dry had another positive consequence: “We were lucky that the ground had completely frozen through over time due to the cold winter. This meant that the vehicles didn’t permanently sink so much and we weren’t up to our ears in slush and sludge”, grins geophysicist Bernhard Novotny, who has headed up quite a few seismic campaigns in his career at OMV.
Like a 3D ultrasound image of the Earth
A small convoy of impulse generating vehicles is ambling through the survey area. On a principle similar to a doctor’s ultrasound, artificially generated vibrations produce waves every ten to twenty meters, penetrating the subsurface to depths of 6,000 meters. When these waves hit the layer boundaries of various rock formations, they are reflected to the surface.
This also explains the geophones one can see lying in the fields. There are over 720,000 of them spread across Marchfeld. These geophones register the sound waves reflected by the rock layers and the data is recorded right where the geophones are laid out.
It’s really something special to stand here in Marchfeld and watch the seismic progressing – after all, this is the foundation stone for drilling for natural gas in a couple of years’ time.
And yet quite a few more steps and numerous calculations are required before the geoscientists actually have a clear, three-dimensional picture of the rock strata. “Once the seismic measurements are completed, the huge amounts of data are processed and analyzed with high-performance computers”, explains Herwig Peresson. This alone can take up to a year, but it’s worth it. After all, when the team finds new deposits they will provide us with energy for decades to come.