Blueback ODiSI

A One Dimensional Stochastic Inversion method that produces high quality reservoir property estimates with associated uncertainties, developed jointly by BP and Cegal.

Blueback ODiSI, a unique one dimensional stochastic inversion method


Blueback ODiSI is a unique seismic inversion method that specifically includes only the most robust prior information in order to apply additional constraints to the solution.

Blueback ODiSI does not require any prior lateral constraints: the algorithm converges so that each trace can be inverted independently of its neighbors yet laterally continuity is still achieved.

The technology was originally developed by BP (Connolly & Hughes, 2013, 2014, 2016) while a Petrel version has been developed jointly by Cegal and BP. 

The solution is robust yet logical and comes fully integrated into Petrel, complementing Cegal’s Quantitative Interpretation solution Blueback Rocks QI.


  • Produces high-quality images of reservoir properties and uncertanties
  • Process is strictly based on geological concepts
  • Modeling is done using Markov Chains for vertical statistic lithofacies followed by an RPM to assign petrophysical and elastic parameters
  • Pseudo-wells are tied locally to geological interpretation
  • The computing intensive algorithm is simple, robust and multi-threaded


  • No low frequency model required
  • No lateral/spatial constraints applied
  • Jointly inverts to both facies and rock properties at the same time
  • Simultaneously inverts up to 5 color inverted angle stacks
  • Provides probable values and uncertainty
  • Works by generating 1000s of statistically correct pseudo-wells, generates a synthetic for each and matches to the seismic data. The best matching pseudo-wells are then selected to provide mean lithofacies and rock property values and their uncertainties
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"Cegal have done a tremendous job re-engineering BP`s internal code into an accessible, transparent and fully integrated product for the Petrel environment".
Patrick Connolly
PCA Ltd, Former BP Senior Advisor, Geophysical Analysis
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Dive in deeper

Cegal is delighted to showcase the result of an ODiSI study conducted on a central North Sea field. The reservoir is an Upper Jurassic Fulmar interpod (depocentre) and is flanked by Triassic Smith Bank shale pods. Underlain by Triassic shales and Zechstein evaporites and overlain by Cretaceous lithologies, the field provides a challenge for seismic analysis, particularly inversion and quantitative interpretation.

Cegal would like to thank Repsol Sinopec Resources UK Limited for their support and engagement to undertake the ODiSI Inversion and their partners for their agreement and support to publish the case study.

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