Oranje-Nassau Energie

De-risk of Rotliegend prospect by a combination of conventional seismic interpretation methods, by seismic reservoir characterization and structural modeling techniques.

Oranje-Nassau Energie and Cegal case study

Oranje-Nassau Energie (ONE) is a private Dutch exploration and production company, with a long track record in running a diversified upstream portfolio. The company is well positioned in some of the world´s most exciting regions, with the ambition to expand its operated asset base to become the Southern and Central North Sea operator of choice.

In 2014 ONE approached Cegal to help assess the potential of a list of near-field prospects using new technologies and techniques that are currently underused in the Netherlands. Cegal received from ONE a very large volume of reprocessed and depth migrated seismic data, comprising time and depth volumes as well as multiple offset (AVO) stacks.  The challenge was to harvest this data and extract the maximum relevant information from these volumes, in combination with sparse information from the available well logs.

Cegal employed techniques in seismic reservoir characterization using their tool, Blueback Seismic Reservoir Characterization (SRC), to extract as much from the data as possible. An initial screening phase using AVO and Extended Elastic Impedance with Colored Inversion techniques was performed on the full list of prospects provided, and eventually narrowed down to one prospect which showed the most potential.

This prospect, named Gillian, was also the prospect being focused on by ONE. The observations made inside the prospect coupled with the findings by Cegal strengthened the reasoning behind deciding to drill it first in the upcoming drilling campaign in mid-2015. The findings of Cegal were primarily a bright and laterally consistent (with structure) Class II and III AVO anomaly that fitted very well with the overall understanding and previous development of the area.

“Cegal`s contribution has been of great help. Your work de-risked the prospect significantly and gave us confidence to proceed with the well”, says R. Gras, Principal Geoscientist in ONE.

ONE, operator of the Gillian Unit joint venture, drilled the L11-14 exploration well targeting the Gillian prospect in 2015. The well encountered gas-bearing reservoir sandstones, which was consistent with the AVO and amplitude work carried out by Cegal.

The experience was documented and presented at the 78th EAGE Conference & Exhibition in June 2016.

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