There isn't any way to be absolutely sure where new oil and natural gas reserves are located, so petroleum engineers need to collect clues as to what lies deep beneath the earth's surface. Advanced technology has revolutionized the exploration process for oil and natural gas, and helps them pinpoint potential reserves with greatly improved accuracy. This results in fewer wells, and lowered exploration costs.
Engineers can gather above-ground clues using airplanes and satellites to map the surface, to identify promising geological formations, and to look for oil and natural gas seeps. Ships can do the same for the ocean floor.
But engineers often get much more useful information by looking at geological structures and rock properties below the surface. They use a number of strategies including:
Seismic surveys are done by sending high-energy sound waves into the ground and measuring how long they take to reflect back to the surface. Since sound travels at different speeds as it passes through different materials, computers can use seismic data to create a 3-D map of what lies below the surface.
Geologists and geophysicists – known as "explorationists" – use these 3-D seismic images to look for accumulations of oil and natural gas. Engineers then use the data to plan the safest, most cost-effective well path to the reservoir.
Once a reservoir has been located and put into production, a series of 3-D seismic surveys can be taken over time to see if all of the oil and natural gas reserves are being efficiently drained. If not, additional wells can be drilled to produce these bypassed pockets of reserves.
While seismic data are extremely useful to geologists, these surveys are also very expensive.
When the data indicate a likely site for oil and natural gas reserves, an exploration well is often drilled. Rock samples from the well are brought to the surface and analyzed. Well logs measure the electrical, magnetic and radioactive properties of the rocks.
By examining this information, a geologist can learn a great deal about the sub-surface structures and whether or not the site is likely to produce oil and natural gas in economic or "paying" quantities.
Gravity and Geomagnetic Surveys
These relatively inexpensive techniques can identify potential oil and natural gas bearing sedimentary basins and structures. High-resolution aero-magnetic surveys done by special aircraft can also show fault traces and differentiate between different rock types near the surface.»next