DESIGNED FOR

Geoscientists and engineers, especially seismic interpreters. Anyone involved in using seismic data who needs to understand the theory and procedures for creating velocity models and converting seismic data from time to depth.

This is a foundation level course. It is not designed or paced for the experienced velocity modeler.

YOU WILL LEARN HOW TO

• Understand the various types of velocities, their calculation, and the validity of their interpolation and extrapolation

• Compare, quality control, smooth, and combine the various velocity types into an integrated velocity model

• Validate model quality by examining the changes in velocity needed to tie the seismic data to depth

• Use the model to convert horizons, faults, and seismic data from time to depth

• Learn how velocity models are used for other studies such as forward modeling and pore-pressure prediction.

ABOUT THE COURSE

Seismic data is acquired in time – the time taken for the sound to travel from the source to reflectors and to return to receivers. However, wells are drilled in depth, not time. Variations in velocity can distort the depth, size, and shape of possible reservoirs. Therefore conversion from time to depth is needed for a clear picture of the prospect and the risks involved. This course will teach you how to use velocity information and structural inputs to build a consistent velocity model. First all input velocity data must be quality controlled and a calibrated velocity model created. Then the model is used to convert time horizons and seismic time data to depth. Both pre-stack and post-stack migrated data are considered. The class also covers some of the velocity problems encountered in depth-migrated data, now that is more widely available.

Each section of the course is supported with in-class exercises, included on a USB flash drive that contains the exercises and all needed data and software.

As a Foundation course, participants should have a basic understanding of geophysics such as offered in PetroSkills’ Basic Geophysics course. Little advanced math (calculus) is used, but algebra and diagrams are used to explain the needed concepts.

One personal computer is provided, at additional cost, for each two participants.

COURSE CONTENT

• Velocity: definition and comparison of the many types of velocity including average, interval, RMS, stacking, migration, pressure-wave, and shear-wave.

• Velocity Inputs: accuracy and regional extent of each, including check shots, VSPs, sonic logs, time/depth functions, well picks and pseudo velocities, seismic velocities, and horizons for structural control

• Synthetic Seismograms: creation, upscaling, and tie to seismic

• Advanced synthetics including synthetic gather creation, Zoeppritz equations, AVA, and AVO

• Matching Synthetics to VSPs and to seismic data

• Seismic Velocities: semblance, picking, multiples

• Migration and Migration Velocities: theory and applications, pre- and post-stack algorithms, tomography, and iterative velocity analysis

• Velocity Model Building: workflows to integrate stacking velocities, time/depth curves, well picks associated with seismic horizons (pseudo-velocities), and structure from horizons

• Time to Depth Conversions: vertical stretch, inverse raytracing, migration, and other methodology

• Advanced Topics: forward modeling, pore pressure prediction, anisotropy, and geostatistics