reflection seismology Reflection seismology (or seismic reflection) is a method of exploration geophysics that uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. The method requires a controlled seismi ...

, a flat spot is a seismic attribute anomaly that appears as a horizontal reflector cutting across the

stratigraphy Stratigraphy is a branch of geology concerned with the study of rock (geology), rock layers (Stratum, strata) and layering (stratification). It is primarily used in the study of sedimentary rock, sedimentary and layered volcanic rocks. Stratigrap ...

elsewhere present on the seismic image. Its appearance can indicate the presence of hydrocarbons. Therefore, it is known as a direct hydrocarbon indicator and is used by geophysicists in hydrocarbon exploration.

Theory

A flat spot can result from the increase in acoustic impedance when a gas-filled porous rock (with a lower acoustic impedance) overlies a liquid-filled porous rock (with a higher acoustic impedance). It may stand out on a seismic image because it is flat and will contrast with surrounding dipping reflections.

Caution

There are a number of other possible reasons for there being a flat spot on a seismic image. It could be representative of a mineralogical change in the subsurface or an unresolved shallower multiple. Additionally, the interpretation of a flat spot should be attempted after

depth conversion Depth conversion is an important step of the seismic reflection method, which converts the acoustic wave travel time to actual depth, based on the acoustic velocity of subsurface medium (sediments, rocks, water). Depth conversion integrates several ...

to confirm that the anomaly is actually flat.

References

{{Reflist Seismology measurement Petroleum geology

Theory

Caution

See also

References