ODiSI is now available in Cegal Blueback Avary

Blueback ODiSI, a one-dimensional stochastic inversion method, is now part of our new software Cegal Blueback Avary and gives the possibility to chain all processes end-to-end in a dynamic and interactive way.

ODiSi stands for 'One Dimensional Stochastic Inversion' and is a stochastic inversion scheme in a Bayesian framework. Prior data is all the information available about the reservoir, such as depositional environment and its corresponding lithofacies, well data to be used to calibrate rock physics models for each of the lithofacies, and the vertical statistics of the bed-thicknesses. Seismic on the other side is a ´low-resolution noisy data´.

Out of building possible random lithofacies columns, properties can be assigned to each of the lithofacies to build a set of petrophysical curves. These so-called 'pseudo-wells' are used to compute synthetic seismograms and matched against seismic traces. If the match is good, the trace is kept, otherwise, it is rejected. This process is repeated thousands of times. Later on, reservoir properties are averaged from a group of selected traces from the accepted pseudo-wells.

Fig. 1: ODiSI results example. Top: Mean VSand. Bottom: Joint lithofacies probability.

Obviously, this whole process, although simple enough in principle, requires a lot of computing power to execute. A crucial aspect of running an ODiSI inversion is the quality of the seismic data. Input partial angle stacks must be properly conditioned and a color inversion must be obtained beforehand for intercept and gradient and then the correct projections must be estimated to obtain the best possible Chi angle for the EEI cubes.

The advantage of being able to run the entire ODISI process within Blueback Avary (Avary) lies in the possibility to chain all processes end-to-end in a dynamic and interactive way. This allows for example to rapidly evaluate also the impact of the seismic pre-conditioning parameters on the results of the color inversion and finally on ODiSI.

Fig. 2 Avary example of a workflow from data pre-conditioning to ODiSI.