Exploration de-risking

Problem
Seismic amplitude anomalies near a recent discovery are observed on seismic AVO data. The interpretation of the seismic amplitude anomalies are non-conclusive.

Solution
A QI study was performed to quantify the lithology and fluid content associated with the observed amplitude anomalies.

Outcomes

  1. One potential prospect was discarded.
  2. Another potential prospect was identified which was not apparent from seismic AVO data alone.

Workflow

  1. A rock physics model was derived from the well log data and used for shear log prediction. The rock physics model provides valuable input for the interpretation of the results and makes it possible to identify different lithology and fluid scenarios (Figure 1).
  2. A simultaneous AVO inversion was performed to estimate the acoustic impedance, Vp/Vs and density (Figure 2). These elastic properties in conjunction with the dervied rock physics model were used to determine the lithology and fluid properties.
  3. Two approaches were used to determine the lithology and fluid content. The first approach is a Bayesian lithology classification scheme which provides the probabilities of selected lithologies (Figure 3). The second approach uses the derived rock physics model in an inversion to obtain estimates of porosity, volume of clay and water saturation (Figure 4).
Figure 1: Rock physics modeling to determine the relationship between elastic and petrophysical parameters.
Figure 2: Inverted elastic properties.
Figure 3: Bayesian lithology classification of selected lithologies.
Figure 4: Rock physics inversion using the derived rock physics model and AVO inversion results.