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The Case for Reprocessing Seismic vs 3D Acquisition: a success story from the North Sea.

Writer's picture: Alastair MacLeodAlastair MacLeod

Should O&G exploration companies invest millions in acquiring new seismic data using large 3D-capable vessels? Or can they achieve similar results by leveraging legacy datasets, cutting-edge processing technology, and the expertise of skilled geophysicists (or in RockWave’s case… geo-craftsmen)?


The IJssel discovery by ONE-Dyas in the Dutch North Sea presents a compelling argument for the latter.


 

F06-IJssel


ONE-Dyas B.V. has operated block F06b in the Dutch sector of the North Sea since 2019. In December of the following year, ONE-Dyas, together with partners EBN (40.0%) and Dana Petroleum (13.3%), discovered the F06-IJssel field with exploration well F06-07. The F06-IJssel gas & oil field is located approximately 200 km north of Den Helder in the geological basin of the Dutch Central Graben.


The F06-IJssel structure is a broad four-way-dip closure of the Tertiary Lower North Sea group. Subcropping within the closure are the Upper Cretaceous Chalk and Upper Jurassic Scruff groups. The subcropping units get progressively older towards the south. Hydrocarbons have accumulated in the sandstones of the Upper Jurassic Scruff group. Top seal of the trap is provided by the shales of the Lower North Sea group.


ONE-Dyas and partners made the discovery using interpretations from 3D seismic data originally gathered and processed in the late 1980s and early 1990s. These older datasets contained strong acoustic interference from the overlying Cretaceous chalk layer (see image below), which limited their effectiveness for detailed reservoir analysis.

F06-IJssel Dutch north sea development
(a) Location of the NL F06 IJssel discovery. (b) An example arbitrary line through the originally processed vintage 3D seismic (in TWT), indicating the Cretaceous chalk pinch-out (green shade) and the strong overprint of residual multiple at target level, highlighted by the red dashed lines.

The fluid contact was hard to establish in the IJssel discovery well (F06-07). The well also had significant data gaps in both compressional and shear sonic log coverage due to the unconsolidated nature of the reservoir, which was not expected pre-drill. Post-discovery, the greatest volumetric uncertainty was the depth of the oil-water contact. Rather than commissioning new seismic acquisition, it was hoped the data could sufficiently reduce the remaining uncertainty by reprocessing the existing datasets.


 

Why Choose Reprocessing Over New Acquisition?


Reprocessing legacy seismic data offers several advantages:

  1. 1Cost Efficiency – Acquiring new seismic data is a major financial commitment, requiring extensive planning and logistics. Processing existing data, in contrast, comes at a fraction of the cost, especially when there are publicly accessible datasets (multi-client field data can be much more expensive).

  2. Technological Progress – State-of-the-art processing techniques and their improved application/parametrisation, combined with greater and more efficient compute power, allow for better imaging of the subsurface than was previously possible.

  3. Environmental Considerations – Reducing the need for new seismic surveys minimises environmental impact, aligning with sustainability goals.

  4. Time Savings – Reprocessing takes significantly less time than planning and executing a new survey, providing faster access to high-quality seismic data.

  5. RockWave geophysicists bring the energy, enthusiasm, fascination and talent required to address and solve the key challenges that are impacting an accurate interpretation.


 

Revitalizing Vintage Seismic Data


RockWave were engaged by ONE-Dyas to provide seismic reprocessing services to upgrade the existing legacy 3D volumes, through key stages that included the following processing techniques:

  • Multiple Attenuation – Techniques like curvelet-domain adaptive subtraction and shallow-water multiple elimination removed interference that previously masked key Upper Jurassic reservoir features.

  • Broadband Imaging – Advanced deghosting and pre-stack amplitude inverse-Q filtering improved vertical resolution without amplifying noise.

  • Enhanced Velocity Models – Ray-based tomography and pre-stack depth migration allowed for a more accurate velocity model, leading to better subsurface interpretations.


You can read more about the details of the reprocessing sequence in this RockWave article.


By applying these techniques, outdated seismic images were refined into high-resolution data suitable for reservoir modeling, well planning, and risk mitigation.


 

Qualitative Bridging of Data Gaps Using Reprocessed Seismic


The upgraded seismic dataset not only provided clarity on the oil-water contact but also enabled highly accurate depth predictions for the subsequent appraisal wells F06-08 and F06-09. Scenario-based synthetic models were built to test different stratigraphic architectures and different oil-water contact depths. The synthetic models were then validated against the 3D seismic (see image below).

synthetic model used to model oil-water contact depths
Comparing (a) the reprocessed PSDM seismic, with (b) an example synthetic model used to evaluate the predicted oil-water contact.

Both appraisal wells confirmed the presence of gas and oil, and both encountered their targets within five meters of expectations, vindicating the decision to reprocess rather than undertaking new acquisition.


According to the ONE-Dyas website, a production licence has been granted in December 2023 for development of field F06-IJssel. This outcome highlights the significant value that can be obtained from legacy data when processed using modern workflows.


Access the technical paper by Nick Woodburn using the link below:


 

Final Thoughts


Processing vintage seismic data is not just a way to save money—it’s a strategy for achieving smarter, more sustainable exploration. For companies operating under budget constraints or in areas with environmental and regulatory challenges, this approach offers a practical way forward.


The Ijssel project demonstrated that by refining existing datasets, operators can achieve the necessary level of precision, often at a fraction of the cost compared to acquiring new seismic data.


As the industry evolves, tapping into the potential of older seismic surveys can open doors to new opportunities. Before investing in a new acquisition campaign, it's worth considering whether the insights needed are already available, waiting to be revealed.


Maximise the potential of your existing seismic data. Get in touch with RockWave today to discuss how reprocessing can enhance your project’s success.

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