1. DHIs: Amplitude Anomalies
Anomalous amplitudes
Change in amplitude
along the reflector
Low
High Amplitude
Slide 19
These images are from some modeled seismic data with noise included
The left image shows two regions with anomalous amplitudes – dark blacks and big excursions in the troughs (whites)
In the upper region, the basal strong reflection also appears rather flat – another clue
In the right image, the modeled reservoir is thicker
There are several clues to note:
the reflection at the top (yellow line) changes from low to high amplitude as it goes from a water sand to a HC sand
the strong basal reflection on the right indicates the bottom of the HC-filled sand
towards the center, the strong black becomes nearly flat
this flat to dipping geometry at the base of the HC-bearing zone is called a “hockey stick”
the central (flat) portion is a reflection off the fluid contact – HC-filled sand above with water-filled sand below
although the sand properties are the same, having different fluids results in different velocities and densities
for the formation
So on the right we have two lines of evidence
an amplitude anomaly at the top and base of the HC-bearing rock, and
a fluid contact reflection
Courtesy of ExxonMobil
L12 – Data Analysis