What We Do
After landowners and government agencies have granted the appropriate permission, the following operations usually occur:
Utilities will be located
It is normally the responsibility of the utility owner to mark out the location of its pipeline or cable; however, sometimes a locating company will conduct this work. Survey stakes, lath or pin flags typically marked with yellow flagging or the utility company’s logo will be placed along the route of the buried utility.
The points will be surveyed
The seismic line will be surveyed to enable an accurate coordinate and elevation to be calculated for each point along the line. Conventional surveys are performed by a surveyor traversing between survey control points using a Survey Instrument, which measures angles and distances to high standards of precision. On 3D programs several survey crews may be working in the area at the same time.
GPS layouts, surveying, and mapping may be done
The layout and surveying operation can also be accomplished by GPS (Global Positioning System) pack operators, who position and record points by receiving signals from a network of satellites that enable them to resolve an accurate position and height. Some of these crews may also collect cultural information for mapping (e.g. fences, water bodies, power lines, etc.).
Brush cutting and/or snowplowing will be done
If there is thick brush on the proposed seismic line, the surveyor or advance person will supervise the cutting, where allowed, using Cats or chainsaws. Receiver lines usually require a continuous straight-line path for cable and geophone layout. Source points can be “offset” to avoid cutting brush and soft or wet areas. When snowplowing is required, Cats or 4 wheel drive tractors are utilized.
The shot holes will be drilled
When dynamite is the energy source, each source point will be drilled, and then an explosive charge, detonator/blasting cap will be loaded to the required depth and the hole will be plugged according to federal and state regulations. Capwire will connect the charge to the surface for later detonation. In areas of difficult drilling, patterns with 2 to 5 shallower holes containing smaller charges, may replace the normal single hole. All shot holes will be plugged according to federal and state regulations. The seismic drilling rig can be on a wheeled or tracked vehicle. There are many types and sizes of drills that are designed to work in the different areas where subsurface conditions can vary considerably (e.g. sand, shale, gravel, and rock). Terrain, brush, and permit constraints will also affect the type of drill selected for each job. It is usual for more than one drill to be used. A drilling supervisor will coordinate seismic drilling operations. Some drills require water, so the drill buggy may have to travel the line more than once. In some cases, a water truck will ferry water to the drills as required.
The recording equipment will be laid out
Recording boxes (Sercel RAU or Inova Hawk), geophones (jugs) and batteries are normally carried aboard line trucks or RTVs. The recording boxes will be placed along the seismic line. In narrow brush cuts, over fences, across creeks and through wet or soft areas, the equipment will be hand carried by the line crew. The geophones and recording boxes will be connected at the prescribed locations. When all recording boxes and geophones are in position and have been QC’d, the line is ready to be recorded. Note: On some jobs, helicopters are used to transport geophones and recording boxes in heli-bags to planned locations, from the locations the line crew will manually position them.
The seismic line is recorded
When dynamite is the energy source, a shooter will sequentially visit each shot hole and detonate the charge. When the seismic line is to be vibrated, typically one to four vibrators mounted on trucks or buggies, will lower their pads and simultaneously vibrate the ground for a few seconds at each source point location. Vibrators will vibrate over several locations on either side of each source point.
Cleanup of the seismic program
Upon completion of recording, the seismic lines will be completely cleared of all recording equipment, survey material and debris. In the case of frozen ground conditions, a cleanup crew will return to the seismic program when ground conditions are suitable (non-frozen). They will ensure that all debris has been removed. All shot holes will be abandoned in accordance with the exploration regulation.
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Paragon Geophysical Services, Inc. commitment to excellence, in tangent with our extensive experience will keep us at the forefront of seismic acquisition. We look forward to working with you on your future projects.