Seismic reflection surveys furnish explorers with detailed structural images of the sub-surface. The resulting product of a seismic reflection survey is a sub-surface profile image, where the vertical axis represents seismic wave travel time or, in advanced processing cases, depth. These profiles enable explorers to discern geological structures such as unit boundaries, faults, and folds, aiding in informed decision-making for further exploration activities.
Seismic reflection surveys generate 2D profiles or 3D imagery (cubes) illustrating the seismic reflection coefficient, which quantifies the energy reflected at sub-surface boundaries. This coefficient correlates with seismic impedance, which, in turn, relates to the velocity of seismic waves through the sub-surface and the density of sub-surface materials.
Onshore seismic reflection surveys often span vast geographical regions, encompassing diverse terrains such as desert lands, transition zones like swamps and mangroves, hills, farmlands, lakes, or tidal flats. EGSE boasts extensive experience in conducting surveys across these varied landscapes worldwide. In instances where objectives are shallower, such as in geotechnical sectors, high-resolution seismic reflection surveys are conducted in smaller areas.
The survey process commences with meticulous design, wherein EGSE’s geophysicists and geodetic experts collaborate with clients and local representatives to plan the placement and orientation of seismic lines. Geophone receivers are strategically positioned along seismic receiver lines, impacting the resolution of the final product. Meanwhile, seismic sources, whether seismic vibrator vehicles or specialized explosives, transmit seismic waves into the ground along seismic source lines.
Following design approval, geodetic surveying and permitting with local communities and landowners ensue. The surveying team utilizes advanced GPS technology to create precise geodetic grids and mark the location of every geophone. Simultaneously, the permitting team secures consent from every landowner whose property will be traversed during the survey.
Once surveying and permitting are completed, geophone layout commences, tailored to the chosen recording system—be it cabled or nodal geophones. In cases where explosives serve as the seismic source, seismic shot holes are drilled parallel to surveying and geophone planting.
Production kicks off as seismic sources transmit waves into the ground, with daily in-field quality control conducted by expert geophysicists to ensure the highest data quality. Subsequent steps involve advanced processing and interpretation of the seismic data.
Seismic Sources
- Seismic Vibrator Buggy: INOVA AHV-IV 364 PLS Commander
- Shallow Borehole Explosives
- Accelerated Weight Drop (AWD)
- Drop Hammer
- Sledge Hammer
Recording Systems
- INOVA ARIES-II 24-bit cabled system
- INOVA Quantum Nodal Systems
- Geode 24 cabled system
Ancillary Equipment
- Portable and 4×4 tractor-mounted shot-hole drilling rigs
- GPS Systems: Trimble R-10 and R-8 GNNS, Topcon GR-3
- Garmin handhelds