Seismic Sources

Choice of the correct seismic source for a particular application requires consideration of a range of factors including the required target resolution, economics, environmental impacts, health and safety issues and access constraints.

Dynamite

In purely geophysical terms, dynamite is generally considered to be the ultimate land seismic source, since it provides a very broad bandwidth, particularly when relatively small charges are used. This broad frequency bandwidth corresponds to a sharp pulse shape, providing finer resolution in the seismic image. For optimum coupling the charge is placed in a drilled hole beneath the base of weathering. This approach has the added advantage of providing near-surface statics information, via an uphole geophone recording. Dynamite is the preferred source for high-resolution 2D and 3D imagery, such as is required for mine-planning purposes.

Mini-SOSIE

Where logistical, environmental or economic factors preclude the use of dynamite, Mini-SOSIE often provides a viable alternative.

Mini-SOSIE uses a conventional road impactor as the energy source, and employs a real-time stacking algorithm to generate the seismic record. The system provides cost-effective exploration of shallow (<1km) targets including oil and gas, coal-bed methane, coal seams, mineral deposits and groundwater. The source is effective on most ground surfaces and produces minimal surface disturbance. It can be used in environmentally sensitive situations (urban, agricultural, military) where other sources may be unsuitable.

Velseis pioneered the use of Mini-SOSIE in the Asia Pacific region, and has significantly expanded on the original Mini-SOSIE concept by integrating modern computer-control techniques. Velseis can now provide an efficient 3D configuration of the system.

Envirovibe

Velseis has recently acquired two IVI Envirovibe units, primarily for use in the shallow petroleum and Coal Bed Methane Areas. Initial trials indicate that for these targets the Envirovibe is competitive with heavier vibroseis units.

The Envirovibe is mounted on an articulated buggy, providing excellent maneuverability. The units can be configured to operate with a width of 2m, useful in narrow forrest situations.

Airguns

In shallow marine and transition zone situations, Velseis uses airguns ranging in capacity from 3 cubic inches (for very shallow work requiring very broad bandwidth) up to tuned arrays of 600 cubic inches.