Finding oil and gas

• Oil and gas are lighter than water, and move toward the surface.
• Impermeable barriers hold the hydrocarbons within the porous reservoir rocks below.
• Modern 3D seismic data provides an image of the strata below.
  • The stratal geometry reveals favorable structural locations, such as anticlines
  • In many cases, the hydrocarbons themselves can be recognized in these images
• 3D seismic imagery makes it possible to locate and develop oil and gas reservoirs more cost-effectively than ever before, even though the remaining reserves are more difficult to find.
  • We need fewer dry holes.
  • We find more of the productive reservoirs.

• An artificial seismic source generates elastic waves that propagate into the earth
• Subsurface stratal boundaries and pore fluid changes produce reflected waves that are observed in the surface ground motion or pressure fluctuations.
• Use of a multitude of sources and receivers permits the reconstruction of a 3D image of the stratal boundaries and fluid changes below the surface.

• 3D seismic data cube - 8x vertical exaggeration
• 15000 ft by 15000 ft by 600 ms or ~2400 ft
• Strata dip up to the left toward a salt dome
• Gas trapped in a porous sandstone layer shows up as a brightly colored layer of red over blue -- a low impedance layer

QuickTime Movie!
A presumed image of a gas reservoir in a 600 millisecond by 15000 ft by 15000 ft seismic data cube (2,435 kb in size).
The data used in this movie were provided by Amoco (New Orleans).