12-11-2012, 05:55 PM
ROCK PHYSICS: SEISMIC INTERPRETATION
ROCK PHYSICS.ppt (Size: 4.33 MB / Downloads: 172)
AMPLITUDE TERMS
Bright spot: local increase in amplitude on a seismic section (presumably caused by a hydrocarbon accumulation).
Direct hydrocarbon indicator (DHI); Hydrocarbon indicator (HCI): measurement which indicates the presence or absence of a hydrocarbon accumulation (bright spot, dim spot, flat spot, shadow zone, etc.).
Amplitude variation with offset (AVO): the variation in amplitude of a seismic reflection within a trace source-receiver gather.
“Positive AVO”
A prospect with “Positive AVO” means the interpretation of the AVO is favorable for the presence of HC at the anomaly level and not just an increase in negative amplitude with offset.
A prospect with “Negative AVO” means the interpretation is unfavorable for the presence of HC.
Definition of AVO Class 3 Gas Sand (Bright Spots)
Unconsolidated reservoir – usually Tertiary age
Gross interval velocity usually < 8500 feet/sec (2650 meters/sec)
Typically a low impedance sand encased in a high impedance shale
HC zones are Bright Spots on the stack section and on all offset (angle) stacks
Can “separate” wet vs. HC sands using stack data –
works best with rock physics calibration
AVO: The HC reflection amplitude, with respect to background reflection amplitude, increases (at times slightly) with increasing offset (angle)