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how do you know about subsurface
these technology of seismic survey simplify this proplems , incredible increase in the success rate of locating natural gas reservoirs and knowledge of the properties of underground natural gas deposits, to gather data that can later be interpreted and used to make educated guesses as to where natural gas deposits exist
It was discovered in the mid 1800's that anticlinal slopes had a particularly increased chance of containing petroleum or gas deposits
dome shape indicate great number of reservoir
the study of this begin with study of surface geology
search for places that petroloum and gas might be exist
like
outcroppings of rocks on the surface or in valleys and gorges
rock cutting and samples from oil and water digs
fluid content, porosity, permeability, age, and formation sequence of the rocks
when they know the possiplility of area to have oil and gas , tests can be performed to gain more detailed data about the potential reservoir area to give more accurate map of underground formations that done by geophysicisits
seismic
the basic seismology is to study where is the oil and gas
study of how energy, in the form of seismic waves, moves through the Earth's crust and interacts differently with various types of underground formations
this seismogram study (earthquakes )the vibration of seismic waves through earth
in 1921 this technology was applied to petrolum industry
as the earth crust composed of layers , seismic energy that emit from source and travel through crust interact with layers differently , reflect from some layers , this reflection data give more info about the subsurface geology
geophysicsits are to create vibration on the earth surface to penetrate the earth and how this reflect to the surface again
example
you have abouncing rubber ball
rubber ball that is dropped on concrete will bounce in a much different way than a rubber ball dropped on sand
like this seismic waves donot reflect at the same way from different layers
seismic waves sent underground will reflect off of dense layers of rock much differently than extremely porous layers of rock
that give info about what is in the earth subsuface at which depth
onshore seismc
involves seismic artificial source and sensetive detectors
geophones
data detected by geophones are transmitted through recording trunk
to be processed and interpreted by geophysicsit , geologists and engineers
while seismograms was designed to detect earthquakes , there is also more sources of vibration like dynamite that used in early survey
seismic waves were created using dynamite. These carefully planned, small explosions created the requisite seismic waves
now they almost donot use explosive sources , use non explosives
like that use large impacts series of vibrations These impacts or vibrations create seismic waves similar to those created by dynamite
large biston
like that shown
offshore seismic
When exploring for natural gas that may exist thousands of feet below the seabed floor
small different type of survey was done
use ship instead of trunk
hydrophones instead of geophones
use air gun instead of dynamites or impacts biston
hydrophones designed to detect vibration in water , towed behind the ship in various configurations depending on the needs of the geophysicist
air gun release bursts of compressed air under the water and then cause seismic vibration
be continued
عدل سابقا من قبل في 2007-11-17, 11:50 pm عدل 1 مرات