GRAVITY SURVEYS
The heterogeneous density distribution of the Earth produces spatial changes in the observed gravity field, however most of the field variations are produced by density heterogeneities occurring in the crust.
The objective of any gravity surveys is to reconstruct the Earth’s gravity field over a given area of interest, and to identify its anomalies. These anomalies can be a few millionths of the average Earth’s gravity field, and high-resolution instruments and accurate procedures are necessary. Gravity measurements must also be associated with high-precision differential GPS measurements.
After the raw gravity data are corrected for instrumental drift, tide, elevation, density, topography and barometry, they are analyzed through the use of specific mathematical tools, derived from field’s gradient, and modelled by 2D/3D forward and inversions.
The data analysis and modelling may reveal important geological and structural features from local to regional scales, according to the surveyed area extension.
Applications:
OIL & GAS EXPLORATION
Gravity can be used to determine the location of a salt dome in which oil or gas could be present. Measuring the density change in an oil reservoir can assist in the oil and gas recovery process.
MINERAL EXPLORATION
Gravity can detect volcanic massive sulphides deposits associated with nickel deposits, diamond bearing kimberlites, banded iron formations, and impact basins. Gravity can also be used to determine the size of the deposit.
GEOLOGICAL MAPPING
Gravity can be used to complement the results of geological mapping.
CIVIL ENGINEERING
Gravity can be used to study the integrity of roads, dams, and dykes, looking for areas of weakness in the sub-surface.
GEOTECHNICAL
Gravity can detect voids or cavities whether they are tunnels, washouts or sink holes.
REGIONAL GRAVITY STUDIES
Gravity can determine the rock type, soil compaction and presence of water.
GEOID MAPPING
By measuring gravity changes on the Earth’s surface, a more accurate correction can be applied to GPS data to obtain a more precise surface elevation.
ARCHAEOLOGY
Gravity can be used to locate buried walls, buildings, and tombs.