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Go back to Data Model Work GroupsSeismic Velocities Work Group
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Project Description
The PPDM Seismic module was revised by the PPDM Association Seismic Workgroup for PPDM version 3.6. At this time, seismic velocities were included in the model. However, subsequent implementers have found that the tables are somewhat difficult to use, and cumbersome to query. This work group proposes to revise the velocities related tables in order to better meet member needs.
A velocity is defined in the Schlumberger Oilfield Glossary as “The rate at which a wave travels through a medium (a scalar) or the rate at which a body is displaced in a given direction (a vector), commonly symbolized by v. Unlike the physicist's definition of velocity as a vector, its usage in geophysics is as a property of a medium-distance divided by traveltime. Velocity can be determined from laboratory measurements, acoustic logs, vertical seismic profiles or from velocity analysis of seismic data. Velocity can vary vertically, laterally and azimuthally in anisotropic media such as rocks, and tends to increase with depth in the Earth because compaction reduces porosity. Velocity also varies as a function of how it is derived from the data. For example, the stacking velocity derived from normal moveout measurements of common depth point gathers differs from the average velocity measured vertically from a check-shot or vertical seismic profile (VSP). Velocity would be the same only in a constant velocity (homogeneous) medium”.
As of this writing, the work group hopes to complete this work in time to be included in PPDM 3.8 (late 2006). If the membership is in agreement, delivery of PPDM 3.8 may be deferred to ensure that this subject area can be accommodated.
Objectives and Vision
The seismic work group intends to ensure that the velocities module in PPDM fully supports the management and storage of velocity data, and that it makes the tables understandable and practical to implement. Ultimately, the work group would like to see velocity information made widely available in PPDM format, or in formats that are easily stored in PPDM.
Benefits
Velocities are an important component of geophysical interpretation. Velocity information can be captured and stored so that it is accessible across platforms, amongst projects and partners. This will improve the quality of interpretation and reduce the amount of time spent locating, transforming and migrating existing velocity data.