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What is Seismic?
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Seismic technology, when well designed and executed, is by far the most essential component of successful oil and gas exploration. Seismic surveys allow geoscientists to visualize the subsurface of the earth using waves of sound to "map" geologic structures and determine the location of oil and gas reservoirs. The seismic data acquired helps them decide where - or where not - to spend millions of dollars in drilling operations. More importantly, seismic data significantly decreases the risk of drilling a non-producing well.
Generating the Sound
Seismic crews use various methods for creating or "shooting" these waves of sound into the earth. Controlled charges of dynamite or vibrator trucks are normally used onshore, while airguns are used when shooting seismic offshore.
Capturing The Sound
 | Onshore: When the waves of sound vibrate through the subsurface of the earth, they also bounce back to the surface where they are received on recording devices called "geophones". These geophones are placed in a specific pattern across the terrain. Their number and placement pattern varies depending on the design, cost, and size of the survey.
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| Offshore: When a survey of the earth's substructure takes place over a body of water, a receiving device called a "hydrophone" is employed to capture the waves of sound. Ship crews lay out and pull long strings, or "streamers" of these hydrophones behind their vessel along with the airguns that generate the sound waves. |
Recording the Sounds
As the waves of sound vibrate into the geophone or hydrophone they are recorded on magnetic tape. When printed, the sound patterns appear as "traces" of the subsurface, each individual "wavelet's" path revealing a specific contour of the geologic structure.
The configuration of these wave generators and their recording devices can create various complexities of seismic data.
| 2D (Two Dimensional Seismic Data) represents the intersection of two axes, one horizontal and one vertical.
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| 3D Three Dimensional surveys involve shooting and recording an additional horizontal axis, creating the perception of depth and providing additional data points for a potentially more accurate geophysical survey. 3D, consequently, has made 2D somewhat obsolete. Nonetheless, oil and gas companies will often use the less expensive 2D survey to roughly identify a potential hydrocarbon reservoir, then focus the more expensive 3D seismic survey in a strategic grid of that area. Exploration companies can also reference existing archives of 2D seismic data before initiating 3D surveys in order to design a more effective and cost efficient shoot.
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| 4-D Seismic technology, composed of 3-D readings of the same location over time (the fourth dimension), displays the movement patterns of subsurface hydrocarbons and allows companies to plan their future drilling activity accordingly.
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| 4C ( Four Component) technology is our most sophisticated seismic technology. 4C surveys measure sound waves both horizontally and vertically and produces more detailed and precise readings. |
Knowledge Creating Opportunity and Profit
Seismic data translates to informed decision making. Before the use of modern seismic technology one out of ten drilling operations produced hydrocarbons. Today four out of ten are a success. Seismic generates discovery -from the wavelet to the well.
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