Seismic survey is a method used during the exploration phase of oil and gas development. The method gives a first idea of what is present underneath the earth’s surface.
Seismic survey is a method used during the exploration phase of oil and gas development.
The method gives a first idea of what is present underneath the earth’s surface.
Of all the geophysical exploration methods, seismic surveying is unequivocally the most important, primarily because it is capable of detecting large-scale to small-scale subsurface features.
Simply stated, seismic methods involve estimation of the shapes and physical properties of Earth’s subsurface layers from the returns of sound waves that are propagated through the Earth.
- In a 2D survey, one source of energy and one set of receivers provide a two dimensional image of the rock layers below the surface. 2D survey shows one single cross section (slice) through the earth.
A 3D survey is used when a 2D survey reveal a geological structure or element that are suspected to contain oil or gas. It yields a more detailed picture by providing information about a smaller area in 3 dimensions.
A 4D survey is a 3D survey repeated multiple times in order to observe changes in the amount and the location of oil and gas in a particular field over a period of time.It helps companies predict the next steps in development for that field.
Energy produced by instruments such as a seismic vibrator (on land) or an airgun (in water) releases seismic waves that go through the earth’s layers and «bounce-back» from different rock layers.
The reflected and refracted seismic waves are recorded by a receiver (geophone or hydrophones in water) and give the first image of the subsurface.
This technique allows for interpretation of what is underneath the ground or seabed (oil, gas, water, faults, folds etc) without having to actually drill.
This technique helps companies to make decisions about where to drill a well.
Artificial seismic energy is generated on land by vibratory mechanisms mounted on specialized trucks.
Seismic waves reflect and refract off subsurface rock formations and travel back to acoustic receivers called geophones.
The travel times (measured in milliseconds) of the returned seismic energy, integrated with existing borehole well information, aid geoscientists in estimating the structure (folding and faulting) and stratigraphy (rock type, depositional environment, and fluid content) of subsurface formations, and determine the location of prospective drilling targets.