Fault imaging

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Fault imaging is the process in which faults are processed, identified, and visualized in various ways while conducting seismic exploration. There are multiple motivations for seismically imaging faults. Generally, the goal is to better understand the structural geology of an area, which can range in scale from basin to small-scale reservoir modeling of single formations.

Fault terminology

Source 1: Structural Geology textbook by Haakon Fossen

File:Fault types.png
Figure 1: Types of faults

A fault is "any surface or narrow zone with visible shear displacement along the zone" (Fossen). It is comprised of a hanging wall and a footwall in non-vertical faults like the normal and thrust faults as seen in the Figur The hanging wall is above the fault plane and "hangs" on the fault zone, while the footwall is below the fault zone.e 1.

A fault's displacement is described by its heave in the horizontal axis and throw in the vertical axis. Calculating this throw will be discussed in the following section.

Fault importance and interpretation in seismic exploration

Faults are very important in the petroleum exploration industry for many reasons. They can behave as a seal or a conduit for hydrocarbon transportation to a trap. If a fault trap has a large enough volume to store oil and gas, it can become economically viable to drill and produce. When geoscientists interpret seismic data, the most straightforward way to identify a fault is by seeing a significant displacement in a set of seismic reflectors. It does not take a highly trained eye to see the many faults in the New Zealand seismic line if Figure 2.

Great South Basin NZ Seismic Line.PNG

velocity modeling corrections

Processes of seismic imaging of faults

Ray-based Seismic Modeling

Post vs pre-migration

seismic attributes

Common issues

Fault Shadow

Fault Shadow Illustration

Fault shadow is an issue that occurs in seismic imaging that is caused by the formations in the hanging wall having a lower seismic velocity than the rocks in the footwall. This occurs from the faulting itself, and since the hanging wall layers have a slower velocity than the velocity model predicted, it lowers the layers in the footwall. This can be corrected mathematically by updating seismic velocity models and correctly identifying the slower rocks.

Sources

Correct citations to come

Fault Interpretation During SeismicInterpretation and Reservoir Evaluation: Fractured Reservoirs: Origin, Description, Evaluation by M. E. Badley, B. Freeman, A. M. Roberts, J. S. Thatcher, J. Walsh, J. Watterson, G. Yielding

Fault Shadow Correction Methodology P. Julien1, J. L. Broyer2, O. Bernet-Rollande3

Advances in Seismic Fault Interpretation Automation* By Randolph Pepper1 and Gaston Bejarano1

Structural Geology texbook by Haakon Fossen

Practical Seismic Data Analysis by Hua-Wei Zhou

Elements of Petroleum Geology by Richard Selley

References

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Important Papers

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