A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...
A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...
A Deterministic Evaluation of eismic Fidelity using Velocity Modeling ...
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1.2.3 <strong>Velocity</strong> <strong>Modeling</strong> and PreStack Depth Migration (PSDM) <strong>of</strong> 3-D Surface<br />
S<strong>eismic</strong> Land Data<br />
Since the early 1990's prestack depth migrations (PSDM) have been routinely applied to<br />
3-D s<strong>eismic</strong> data but almost exclusively to marine data. There are several reasons for<br />
this, uniform acquisition, long <strong>of</strong>fsets, and generally higher data quality. Essential to<br />
achieving the robust character <strong>of</strong> PSDM applied to 3-D surface s<strong>eismic</strong> land data is the<br />
ability to derive an initial sediment velocity model that minimizes the adverse effects <strong>of</strong><br />
degraded data quality. An accurate initial sediment velocity model is necessary for<br />
several reasons but primarily because it is the most critical step in PSDM. I used a novel,<br />
non-s<strong>eismic</strong> approach to generate an initial sediment velocity model. I assessed this<br />
method by a comparison <strong>of</strong> the fidelity <strong>of</strong> the PSDM volume generated in both a PSTM<br />
volume and a PSDM volume migrated <strong>using</strong> a traditional s<strong>eismic</strong>ally derived initial<br />
sediment model.<br />
Differences between 3-D marine data and 3-D surface s<strong>eismic</strong> land data result in marine<br />
data that are generally higher quality. Acquisition issues range from the uniform grid<br />
used to acquire marine data that allows for more accurate processing to the variety <strong>of</strong><br />
cultural influences that adversely impact land data. Geology can be an issue as<br />
demonstrated in the complexity <strong>of</strong> deriving the refraction static for land data. Differences<br />
in deriving a refraction static are apparent when considering the impact <strong>of</strong> the weathering<br />
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