Google Earth of the subsurface By Rie Jerichow

Florian Smit has a half-time position at the University of Copenhagen. The remaining time he works with his company Green Growth Scientific that offers 3D subsurface models for the exploration and production of geothermal energy and natural resources.

Google Earth of the subsurface

By loading existing seismic datasets into state-of-the-art seismic interpretation software and adding geological knowledge and interpretation, PhD Florian Smit has succeeded in exposing the buried sea floor of the hydrocarbon-bearing Chalk Group in the North Sea, like ‘Google Earth of the subsurface’. The aim is to enhance the prediction of reservoir quality.

Google Earth is a fascinating program. You can zoom in and out and see details that you never noticed before - or you can get a much greater understanding of the structure of the landscape. Now industry and academia working with recovery of oil and gas from the North Sea have a similar tool, making it possible to peel apart the hydrocarbon-bearing layers of the Chalk Group as a stack of buried Late Cretaceous sea floors.

3-D seismic images of sub-seafloor strata below the North Sea are not new. In the last 30 years, the area has been thoroughly mapped seismically with the acquisition of individual 3-D seismic datasets which have recently been stitched together to allow a regional perspective.

The computational power to visualize these giant datasets has among other things led to an updated seismic chalk paradigm that provides new geological models for seismic features. These features were previously labelled ‘Funny Looking Things’, but now they have got a geological explanation.

”Within the last 20 years, the rapid development of processors and graphics cards have made desktop computers incredibly powerful, enabling them to perform comprehensive calculations of seismic attributes that we add as extra data to the buried sea floors. This allows us to extract more information from the seismic data and visualize it in a geologically intuitive manner,” Florian Smit says.

Geomorphological elements are revealed

In September 2018, Florian Smit defended his PhD thesis “Integrated seismic geomorphological analysis of syn- and post-deposition fluid migration features in the Chalk Group in the Danish North Sea” at Danish Hydrocarbon Research and Technology Centre.

In his study, he used algorithms from new software packages on these very big data sets in order to reveal geomorphological elements that made up the chalk sea floor, just as you would classify rivers and forests with satellite imagery of a landscape. By integrating well data into those elements, the added data provide clues to their geological origin.

Florian Smit explains: “Exposing these buried sea floors with advanced visualization techniques helps to generate initial ideas about what you are looking at. Adding petrophysical and geochemical data gives further information to what happened to the rock after it was buried, possibly affecting the reservoir quality.”

He stepped back a little and observed the different types of reflectors, asking himself what they could indicate in terms of geology; i.e. does a certain reflector indicate, that it once outlined a channel, a fluid expulsion event or an area of localized diagenesis – that is the chemical and physical change of sediments during burial.

“All of this might end up in seismic data as certain reflectors, depending on the velocity and density of the rock,” Florian Smit explains.

Florian Smit has a half-time position at the University of Copenhagen. The remaining time he works with his company Green Growth Scientific that offers 3D subsurface models for the exploration and production of geothermal energy and natural resources.

Florian Smith

Within the last 20 years, the rapid development of processors and graphics cards have made desktop computers incredibly powerful, enabling them to perform comprehensive calculations of seismic attributes that we add as extra data to the buried sea floors. This allows us to extract more information from the seismic data and visualize it in a geologically intuitive manner.

Useful findings

“When you understand what you see in the buried seafloors and understand their impact on reservoir quality, you can extrapolate the data from these findings to provide input for future well planning. Let me give a few examples. If we for instance see fluid expulsion features (e.g. craters) in a gas field, and we see the same fluid expulsion features in an area where we did not drill yet, it might indicate that it could be interesting to drill there as well. On the other hand, wells through these craters show highly variable reservoir quality, which lead to poor sweeping efficiencies as seen on time-lapse seismic data that can now be better understood. Being able to predict where the good reservoirs are in those craters will be crucial for field development plans and future well planning” he says.

Florian Smit is now working on a new project, including all partners in the DHRTC. Here the researchers look at the Lower Cretaceous chalks from the same perspective to enhance the prediction of reservoir quality. In short, the project sheds light on where to drill and what areas to avoid, and it seeks possible answers to why one area is producing well and another area only poorly.

“Everybody is doing a different part of the project – integrating geology, geophysics, and geochemistry from seismic to nanoscale. I enjoy this way of working because we can progress much further when we work together. We have the same goal, but we are attacking it from different angles and at different scales”, says Florian Smit.

PhDs expected to finalise in 2019

Maiya Medetbekova, Radial Jet Drilling, DHRTC

Søren Dollerup Nielsen, Self-healing Cement, Aarhus University

Michael Vigsø, InDirect Estimation of Loads from Abnormal Waves, Aarhus University

Arifian Agusta Irman, Risk-based inspection Planning and Value of Information, DTU Civil Engineering

Steen Hørsholt, Production Optimization, DTU Department of Applied Mathematics and Computer Science

Jesper Dramsch, Deep Learning, DHRTC

Leonardo Meireles, Rock mechanics and Fluid saturation study, DTU Civil Engineering

Mattia Tagliavento, Sedimentology and reservoir geology, University of Copenhagen

Janina Kammann, Onshore P- and S-wave seismic surveys on Chalk Group, University of Copenhagen

Iris Fernandes, Geostatistical models based on deviated wells, University of Copenhagen

Kasper Blinkenberg, The role of Silica, University of Copenhagen

First DHRTC PhD student to finish his studies

On Monday 25 June, researcher Frank Niessen defended his PhD project ‘Phase transformations in supermartensitic stainless steels’, making him the first DHRTC PhD student to finish his studies. The project examines the major phase transformations in supermartensitic stainless steels which have the prospect of partly replacing Duplex-steels in offshore pipeline applications. The project generates a deeper understanding of the phase transformations and their impact on the mechanical properties. Frank’s project was a part of the CTR 2 work programme at DHRTC.

Florian Smith

When you understand what you see in the buried seafloors and understand their impact on reservoir quality, you can extrapolate the data from these findings to provide input for future well planning.