Selecting the seismic data acquisition system that’s best for the job at hand doesn’t necessarily entail an either-or decision.
This was aptly demonstrated via a 3-D program implemented in the Po Valley in northern Italy.
The seismic survey was conducted under the aegis of Eni S.p.A.
The Po Valley is a major geographic feature in Italy, extending about 400 miles from the western Alps to the Adriatic Sea.
The area is a combo of flat to hilly, sometimes mountainous, terrain. Besides the abundance of features that appeal to nature lovers, it’s home to major cities, including Turin and Milan.
During the Po Valley seismic program, both wireless and cable acquisition systems were deployed concurrently to simultaneously record two independent data sets covering an area of 22.5 square kilometers. This resulted in a total 4,707 cableless receiver points and 2,770 shots.
The seismic source used was dynamite.
The survey was carried out in an area of plain ground but densely inhabited. It is characterized by the presence of little towns, several small rivers and watercourses.
A large gas storage plant sits in the middle of the area, along with farms, warehouses and cattle sheds.
Toss in differing networks of underground pipelines over the entire field of operations, and the need to be creative with such a seismic survey becomes obvious.
There were no significant differences in the quality of both raw and processed data acquired with the two different technologies.
Yet such a combination would be pointless in many locales.
It’s widely known in the industry that wireless would not add value if you’re shooting out in an open desert. To the contrary, if your program is in the deep jungle then you consider a total wireless spread.
“In every place where an area is spread with obstacles because of nature or human activity, we would consider wireless to be useful for sure,” said Michele Pellegrino, geophysicist at Eni.
With regard to survey areas where obstacles occur only randomly, the option to use a hybrid spread can be highly advantageous for a number of reasons. For example, hybrids can mitigate the myriad kinds of external noise sources that occur frequently in certain locales.
“The standard acquisition mode may be more valid from an economic point of view,” Pellegrino said. “But it’s good to have the possibility to integrate wireless where you need to work softer and in a more efficient way.”
The results of the seismic test in the Po Valley highlight the opportunity to exploit a hybrid spread incorporating both wireline and wireless systems to optimize recording operations with regard to field efficiency and data quality.