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 sources of information about the suburface velocity to derive a three dimensional velocity model:
- "Well tops", i.e., depth of geological layers encountered in oil and gas wells
- Velocity measurements made in oil and gas wells
- Empirical knowledge about the velocities of the rocks in the area investigated
- Root Mean Square (RMS) stacking velocities which are derived from the processing of the seismic reflection data
This conversion permits to produce depth and thickness maps of subsurface layers interpreted on seismic reflection data. These maps are crucial in hydrocarbon exploration because they permit the volumetric evaluation of gas or oil in place. In the example subsurface map presented below, depth increases from red to blue. The highest zone in red is an oilfield at approximately 3000 m below sea level.
Software for depth conversion
- Seismic Unix - open source seismic software
- VelocityManager - Commercial software minimising uncertainty.
- DUG Insight - Commercial software by DownUnder GeoSolutions
- Promax - Commercial software by Halliburton
- TDQ - Commercial software by Halliburton
- VelPAK - Commercial software from Seismic Micro-Technologies
- Petrel - Commercial software from Schlumberger
External links
- Depth conversion definition in the Oilfield Glossary
- True depth conversion: more than a pretty picture - presentation of different methods for depth conversion
- A pdf document presenting different variations of the V0-K depth conversion method
See also
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