Borehole geophysics are part of the multi-disciplinary approach adopted by Ardara International Limited. These methods are often
used in conjunction with surface geophysics and hydrogeological services. Our logging personnel are highly skilled geophysicists
with experience of logging both deep (1500m) and shallow (10m) boreholes in many different environments. Drilling a borehole is
an expensive investment, therefore, it is a good idea to acquire as much data as possible from the borehole. Geophysics is a
relatively cheap method of achieving this. The following types of downhole survey are available:
Fluid Properties
From the correct use of temperature / conductivity and flowmeter tools, water quality and zones of water inflow and / or outflow
can be determined. These data are important for the correct design of a water well. Fluid logging can also be used by the
environmental industry to monitor contaminant plumes.
Formation Properties Measurements of sonic transit time, clay content, formation density, resistivity and porosity are also important in the design of a
water well. These properties are also be used for lithological determination, petrophysical calculations, stratigraphical analyses and
correlation between boreholes. Formation properties are also of use in the civil engineering industry when evaluating rock
strength.
Downhole / Crosshole Seismic
Use of a tri-axial downhole geophone with a seismic source at surface or in a nearby hole yields primary and shear wave velocities
at regular intervals. The ratio of these velocities is used to calculate Poisson's Ratio and when combined with rock density (from lab
analyses or logging), shear modulus, Young's modulus and bulk modulus can also be calculated. Downhole seismic is also used to
correlate surface seismic data with borehole data.
Seismic Tomography
Similar to crosshole seismic, this technique uses a multi-geophone array in 1 hole with a source in a nearby hole. Large amounts of
travel time data are acquired and processed to produce an image or tomogram of the velocities between the holes. Poisson's Ratio
etc are also determined.
|
|
 |
| |
Preparing to
run flowmeter tool |
|
| |
 |
| |
A downward view of
stainless steel filter |
|
|