The document discusses different geophysical methods used for subsurface exploration, including gravity, magnetic, electrical resistivity, and seismic methods. It focuses on explaining the gravity and magnetic methods. Gravity surveys measure differences in the gravitational field to detect variations in subsurface density distributions. Magnetic surveys map variations in the magnetic field caused by changes in magnetic susceptibility or structure of near-surface rocks. Both methods are used to locate features like hydrocarbon deposits, ore bodies, cavities, and buried structures or utilities.
4. The Gravity method, is a non
destructive geophysical
technique that measure
differences in the earth’s
gravitational field at specific
locations.
5. Gravity survey is used to measurements of the
gravitational field at a series of different
location over an area of interest. The object in
exploration work is to associate variations with
differences in the distribution of densities and
and hence rock types.
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7. Gravitymeter:
A gravity meter or gravimeter is an instrument used in gravimetery for
measuring the local gravitational field of the earth.
10. Hydrocarbon exploration
Regional geological studies
Isostatic compensation determination
Exploration for mass estimation of mineral deposits
Detection of subsurface cavities
Location of buried rock valley
Determination of glacier thickness
Shape of earth(geodesy)
Monitoring volcanoes
11. This is also called oil and gas exploration is
the search
by geophysicist for hydrocarbon deposits
beneath the Earth's surface such as oil
and natural gas . Oil and gas exploration are
grouped under the science of petroleum
geology.
12. Gravity surveys can be carried out
to locate iron rich accumulations
within furnace, cinder piles .
13. Gravity Surveys are used either alone or in
conjunction with magnetic surveys, to
determine the location and size of the
major source structures which contain
accumulations of hydrocarbons.
14. Gravity data in engineering and environmental
applications should be collected in a grid or
along a profile with stations spacing 5 meters
or less. In addition, gravity station elevations
must be determined to within 0.2m
Using the highly precise locations and
elevations plus all other quantifiable disturbing
effects, the data are processed to remove all
these predictable effects
15. A geophysical prospecting method that maps
variations in the magnetic field of the Earth that are
attributable to changes of structure or magnetic
susceptibility in certain near-surface rocks.
Sedimentary rocks generally have a very small
susceptibility compared with igneous or metamorphic
rocks, and most magnetic surveys are designed to
map structure on or within the basement, or to detect
magnetic minerals directly. Most magnetic
prospecting is now carried on with airborne
instruments
16. Magnetic survey is one of a number of
methods used in archaeological geophysics
Magnetic surveys record variation in the
Earth's magnetic field. In archaeology ,
magnetic surveys are used to detect and map
archaeological artifacts and features. Magnetic
surveys are used in both terrestrial and marine
archaeology
17. Magnetometer:
Magnetometers are measurement instruments used for two general purpose: to
measure the magnetization of a magnetic material like a ferromagnet, or to
measure the strenght, and in some cases, the direction of magnetic field at a
point in space.
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22. Locating buried Pipes, cables, tank and drums
Fault studies
Ore exploration identification of metalliferous deposits, for
example massive sulphides
Geothermal exploration
Mapping buried utilities
Exploration of fossil fuels (oil and gas)
Exploration of ore deposit
Regional and global tectonics
Large scale of geological structures ,volcanology
Engineering construction site investigation
Burried foundation ,fine pits for archeology
Mineral exploration
23. Magnetic geophysical surveys measure
small, localized variations in the Earth's
magnetic field. The magnetic properties of
naturally occurring materials such as
magnetic ore bodies and basic igneous
rocks.
Magnetometer surveys find underground
storage tanks, drums, piles and reinforced
concrete foundations by detecting the
magnetic anomalies they produce.
24. Magnetic survey, one of the tools
used by exploration mineral-bearing
ore bodies or even oil-bearing
sedimentary structures and locate on
map the remains of buried structures.
25. Magnetic methods, as employed in
marine applications, differ little in theory
from surface magnetic surveys. The
instrument measures the earth’s total
magnetic field at each measurement
location. However, practical
applications of field techniques, field
equipment, and geographic control can
vary greatly between surface and marine
surveys.
