Plugged and Abandoned Well Locating
Using the latest in geophysical and magnetic instruments we are able to precisely map and locate all your abandoned well structures quickly and cost-effectively.
Gravity Surveys and Tools
Gravity surveying is a valuable geophysical technique, used to measure lateral changes in density of the subsurface. Microgravity surveys search for targets with anomalies less than 0.1 mGal. We all experience the ‘pull’ of gravity on Earth’s surface, and this pull varies over distance. Thus, by precisely measuring how that pull varies over distance we can deduce heterogeneities in mass and volume within the subsurface. Firstly, this requires sensitive instrumentation to measure miniscule differences in the local gravitational field, as small as 1 part in 1,000,000,000 (one-billion). Secondly, expertise in geology and geophysics is essential in relating those lateral density changes to the underlying structure and composition of subsurface rocks and sediments. There are other factors governing the precision and accuracy of gravitational measurements such as instrumental drift, tidal forces, and topographic corrections, which reinforce the need for geotechnical expertise.
F = m * g
The force acting upon an object (of some mass), is equal to that object’s mass multiplied by its acceleration due to gravity.
Gravimeters are deployed in a geophysical survey, to measure differences less than a millionth of the surface gravity, g. Before a microgravity survey can be carried out, gravity stations are selected, spaced (orthogonally), and defined based upon local topography. Each station has a specific coordinate (x, y) and elevation (z), described as a single point on Earth’s surface. These coordinates and elevations are critical in ensuring accuracy of the gravity measurement and are instrumental in corrections applied to the data. All gravimeters rely on mass, supported by a spring, which then responds to the pull of Earth’s gravity. The greater the gravitational field, the greater the pull on that mass within the gravimeter. Likewise, the lesser the gravitational field, the lesser the pull. These relative changes of ‘pull’ on the mass within the gravimeter are reflected by an excess, or absence, of mass within the Earth and recorded by the instrument. However, before a measurement can be recorded the instrument must be levelled with precision, so as to be exactly orthogonal to Earth’s surface. Once data collection is completed in the field, all measurements are corrected for instrument drift, tides, latitude, elevation, terrain, etc., and a Bouguer anomaly map is calculated.
Depending on the regional geology, it is therefore useful to deploy gravity survey methods to find buried bodies, and structures, such as faults, caves and other karstic terrains, dissolution features, salt domes, hydrocarbon reservoirs, aquifers and other hydrologic features, metalliferous ore bodies, igneous intrusions, etc.
EMC’s Applications Include:
- Voids
- Dissolution Features
- Caves and Karst Topography
- Faults, and
- Salt Domes.
