AVO

Question 1

AVA (AVO) characteristics

Answer 1

• Near offset amplitude anomalies => mostly fluid effects
• Far offset amplitude anomalies => mostly lithology effects
• Forward modelling essential
• Beware of “simple” rock physics
relations/approximations
• Typical technique for clastic provinces
• Potentially a good res-char technique

Question 2

Time-lapse (“4D”) seismic

Answer 2

• Reservoir properties that change during hydrocarbon extraction:
• Pore pressure
• Pore fluids (saturation, viscosity, compressibility, fluid type)
• Temperature
• Secondary effects include:
• Compaction
• Porosity
• Bulk density
• Fracturing
• Chemical changes

Question 3

Shear wave Characteristics

Answer 3

• Low velocities compared to P-velocities
• Shear wave splitting
• Difficult and slow acquisition
• Complex processing
• TIS’es not quite geared on S-wave interpretation
• Inversion to Elastic Impedance upcoming

Question 4

Exploration aspects shear waves

Answer 4

• Fracture identification and quantification
• S-waves propagate only in solids -> identification of fluid effects & imaging below gas-chimneys
• SS reflection coefficients different from PP -> may help in acoustically transparent sequences
• S velocities different from P velocities -> may help in multiple discrimination