|
-
“In the case of petroleum exploration, wells are seldom targeted using only one
exploration method. Seismic surveys are almost always included. As a
consequence, there is hardly ever a direct link between a single exploration
method and the discovery of hydrocarbons.”
- BHP Billiton in
www.sgl.com
Sander Geophysical.
-
Geological surveys, for which a UA is ideally suited to criss-cross a region
under computer control for up to 30 hours at a time, using GPS signals and
precision flight control, to follow an exact flight path. The value of a UA is
its ability to operate in a “low, slow, fly mode”, down to 20m above ground
level, to get better resolution.
-
The typical cost of a manned aircraft survey is in the range from $15 to $20 per
line mile, whereas it drops to $2 to $3 per line mile for a lower cost,
pilotless, UAV.
|
-
The
small physical size
of the UA and its low metal content relative to that of a manned aircraft,
enables the UA to make less of a perturbation to the magnetic and gravitational
fields being measured, enabling more accurate measurements of:
-
field strength and field gradient measurements:
-
of magnetic field strength (“aeromagnetic”)
-
of the vertical and horizontal magnetic field gradients
-
of the differential gravity field (gradiometry)
-
electromagnetic measurements:
-
of electromagnetic phase and magnitude reflection ratios over a wide frequency
-
time domain electromagnetic pulse reflection signal measurements
-
Ground Penetrating RADAR sensing of ground and rock dielectric constant
-
gamma ray spectrometer and neutron reflection level measurements
-
using a photo-ionization detector, to measure ethane levels in the air
-
high resolution multi-spectral imaging, including thermal imaging
return to top
|
Using satellite technology for geophysical survey work
|
- from Hart’s Exploration and Production, June 2005
return to top
|
Survey size and low level flying
|
'The big driver in exploration is to find a way to cover the largest area we
can, and obtain data of acceptable quality, all within the budget we have,'
explains Summers. 'In a development survey, we might be looking to cover an area
of 400 square kilometres. But exploration surveys, in contrast, might cover
10,000 square kilometres.'
from
http://www.bp.com/sectiongenericarticle.do?categoryId=9017637& contentId=7031832
BP Frontiers Magazine: Issue 18, April 2007: “Surveys in silicon”.
In a gravity field survey, performed for example using the BHP Billiton
gradiometer,the lower the flight altitude and the better the plane hugs the
ground (known as a “tight drape” in analogy to a curtain covering a non-flat
surface) the higher the resolution of the gravity field plot. Low altitude
flying is stressful to a pilot, particularly over long periods of time and is
dangerous, if done at night. This is an ideal application for UA.
The FALCON system is a differential gravity meter, or gradiometer.
From
www.bhpbilliton.com
Falcon gravity meter
return to top
|
Introduction to survey planning and prediction of line Km required
|
We have developed a simple airborne survey planner called GeoSurvey, using the
above nomenclature. Note that we have converted a Microsoft EXCEL spreadsheet to
an HTML script using the SpreadsheetConverter software, and have incorporated
the resultant HTML script in this web page. Consequently, depending on the
security setting on your computer, you might be asked whether you would like to
allow your computer to run the following HTML script.
|
Select
GeoSurvey
to call up our Airborne Survey planning Utility.
|
return to top
|