A 3D seismic land‐streamer system

Abstract

The 3D seismic reflection method has not been extensively utilized for shallow subsurface investigations because of the relatively high cost of performing 3D surveys. We have designed and constructed a system that could make 3D seismic reflection an affordable option for shallow subsurface exploration by significantly reducing time and labour. In a fashion similar to marine work, a vehicle tows an array of four parallel seismic cables, or land streamers. Each streamer consists of 24 gimballed geophones. The vehicle drags the array from station to station and shots are taken while the array is stationary. We tested our system near Belt, Montana, in an attempt to image an abandoned subsurface coal seam and associated mine workings at a depth of approximately 88 m. For this survey, receiver, receiver line, source and source line spacings were all 1 m. In total, we surveyed a surface area of 100 m x 34 m, achieving a nominal fold of 24. Typical combined advance and occupation times for each station were less than 30 s, using a crew of three people. We were able to image the layered geology in the area and the coal seam; although we were not able to view the individual mine workings because of limited resolution. This testing shows that our system has the potential to expand the application of 3D seismic reflection to shallow subsurface exploration by greatly increasing efficiency.