Journally Speaking: Europe seismic survey

Austrian oil and gas company OMV AG earlier this year concluded what it calls Europe’s largest onshore 3D seismic survey, which covered 1,500 sq km from northeast of Vienna to Weinviertel, Lower Austria, and southwest of the Danube.

“This 3D seismic campaign has enabled OMV to generate data of around 700 terabytes,” said Johann Pleininger, OMV deputy chairman and executive board member responsible for upstream. “A total of around 250 people were involved in the project. Together, they put in more than 500,000 working hours, all without a single incident. Safety is the top priority within OMV.”

Measurements probed the geologic subsurface to depths of 6,000 m, providing data that is being processed as OMV looks for natural gas reservoirs. Results from the processing are expected in 2020, OMV said.

Seismic acquisition was limited to winter months in consideration of farmers’ needs to move about freely for sowing and harvesting. The actual survey acquisition spanned 9 months.

Seismic contractor DMT Group set up 140,000 geophone stations using 2 million geophones total. The nodal system was paired with slip-sweep technology, OMV said. Wien Energie of Austria was a partner with OMV in the survey.

Logistics planning

During the seismic acquisition, seismic vibrators produced waves that were reflected off geologic boundaries. The survey measured up to 1,200 vibration points daily compared with earlier seismic projects that measured only 150 vibration points daily, OMV said.

With the slip-sweep method, 12 pulse-generator vehicles, called vibrotrucks, sent soundwave-like oscillations into the ground at set intervals of time and space. The vibrations were reflected at a depth by rock formations and then captured by geophones at the earth’s surface.

The vibrotrucks transmitted vibrations into the underground with a 65-sec time shift, DMT said. The survey also involved the use of wireless measuring stations.

Rudiger Misiek, DMT project manager, explained that the seismic acquisition had to be scheduled to avoid breeding and nesting season in April as well as to avoid disrupting farm activities.

“Nature left us extremely little time for the investigation,” he said.

The seismic acquisition in areas of the Vienna basin was done during December 2017 through March 2018 and then again during October 2018 through this past March.

The use of wireless seismic stations enables seismic acquisition across large areas in an environmentally friendly manner, he said, adding that the data quality was excellent.

“In the past, we had to lay cables across the entire landscape for such surveys,” Misiek said. “This means an encroachment on nature and the environment.”

Misiek said it was the first time DMT combined slip-sweep technology with wireless seismic technology in Europe.

“The concession areas [in Europe] are generally too small,” for this combination, he said.

OMV-CGG collaborate

Separately, OMV has renewed a contract with French seismic company CGG to operate a dedicated center in Vienna. The center gives OMV direct onsite access to CGG’s subsurface imaging and reservoir characterization expertise.

CGG and OMV have worked together since the center opened in 1979. Geoscientists in Vienna provide OMV with support from CGG’s latest technologies, experts, and computing capacity available from CGG’s Paris and London hubs.

CGG Chief Executive Officer Sophie Zurquiyah said, “The OMV center is the longest-running of the 11 dedicated centers CGG operates for clients worldwide.”

She said the strategic partnership develops new technologies and workflows. Advances in seismic technology improve industry’s ability to explore for oil and gas, to develop fields more effectively and safely, and to monitor production.