Depth Conversion of 3D Seismic Data Through Visualization

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Time-domain on top with a velocity cube, seismic cube, and interpreted horizons. Depth domain below with the depth-converted seismic cube, wells, well tops, and reservoir simulation grid derived from the depth-converted horizons. Data used by permission of the owner.
Seismic depth conversion is a significant technological risk factor  for geologists and geophysicists. Uncertainty can be reduced with the ability to co-visualize and cross correlate seismic and well data during the development and revision of velocity models  on a single software platform. Data visualization and integration software such as DGI’s CoViz 4D can facilitate the accurate development of velocity models, allowing asset teams to reduce risk associated with seismic depth conversion.

Depth Conversion of 3D Seismic Data

Accurate depth conversion is a complex process that is crucial to ensure there is no miscalculation when estimating the drilling depth to targets. Even a subtle variation in subsurface rock properties can cause miss-ties between depth converted seismic data and well logs. Inaccuracy due to miss-ties can be economically burdensome for the project causing unreliable reserve estimates, unexpected depth to targets and drilling downtime . To eliminate such errors and variation in seismic depth data, a correlation between 3D visualization of depth conversion and well data can prove to be advantageous.

Time and depth data visualization and integration software platforms, such as DGI’s CoViz 4D, allow geologists, geophysicists, and reservoir engineers to perform time-to-depth conversion by creating an effective velocity model incorporating the various geological and petrophysical data and interpretations. The most effective software has layer-by-layer, as well as fault block-by-fault block, modeling capabilities which allow efficient calculation of the residual difference between seismic depth conversion and well tops.

Time-to-Depth Conversion and Velocity Modeling

Coviz4D’s time-to-depth capabilities assist asset teams by providing fast and efficient time-to-depth conversion using an existing average or instantaneous velocity model. Additional velocity calibration can be done as new well tops are brought in so your average velocity model always stays up-to-date. The velocity calibration workflow allows the asset team to:

  • Analyze the 3D depth uncertainty model to cross-correlate data and analyze different depth conversion error scenarios.
  • At each well location, calculate the residual difference between existing depth conversion and well tops to estimate discrepancies.
  • Apply the changes in the velocity model with any adjustment or addition in data from the drilling of new wells.
  • Recalculate the depth conversion to keep the data updated and accurate for future well planning.

CoViz 4D: Enhancing the Depth Conversion of 3D Seismic Data

CoViz 4D provides the interpreter with various time-to-depth calculation options along with the robust visualization capability required to quickly cross-correlate differing depth converted seismic data with well data to reach the best final depth conversion. The software provides geoscientists with options to:

  • Define horizons, import well tops/ picks data.
  • Back-interpolate well tops onto a seismic interpreted horizon to calculate the velocity estimate.
  • Integrate 2D, 3D grids, seismic interpretations of faults and horizons, or cellular grids with an average velocity grid for depth conversion.
  • Color code the well tops to efficiently visualize the residual.
  • Use symbol size to scale the residual.

These features allow asset teams to get a comprehensive view of the subsurface and enable them to spot the variations and inaccuracies in the depth conversion of 3D seismic data—which is crucial in minimizing the development and production uncertainties.

CoViz 4D, a data visualization analytics software from Dynamic Graphics Inc., gives geologists, geophysicists, and reservoir engineers the ability to easily access and combine all relevant data associated with subsurface environments. Powerful analytic capabilities enable users to explore data relationships, analyze the accuracy of depth conversion of 3D seismic, and visualize seismic well ties and velocity models to facilitate decisions that positively impact profit and reduce operational risk. To learn more about CoViz 4D contact our team.

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