Remote sensing techniques record variations in subsurface petrophysical parameters, such as seismic, electromagnetic, and potential-field properties. Seismic is by far the most common technique, using acoustic and elastic waves to map boundaries between buried strata with contrasting pressure (P) and shear (S) wave velocities. High-resolution data provide information about geologic structures and potential hydrocarbon traps and can allow inferences to be made about the composition of reservoir pore fluids (oil, gas, brine, or combinations) and their relative saturations. Nevertheless, hydrocarbon-filled sandstone reservoirs are often better detected by electrical resistivity rather than seismic parameters (e.g., P-wave velocities are less affected by variations in brine saturation than electrical resistivity).

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