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Biostratigraphy at a distance

Biostratigraphy at a distance

It is 2020 and drilling is reaching a critical point on the latest deepwater well in the Gulf of Mexico. Despite millions of dollars spent on acquiring new seismic data, the old problems of sub-salt imaging and drilling remain: we can’t see what we think we are drilling. The solution is to call up a last millennium solution — biostratigraphy. Except on this well, despite the operations geologist asking, ‘What does the biostratigraphy say?’, there is no biostratigrapher on the rig, only a technician. That’s because Shell is using its imaging microscope on this rig.

It was in 2011 when looking at the microscope in my office while waiting for a remote support person to fix my computer, that the idea hit me. Why couldn’t we send a more modern microscope, with all its functionality controlled by a computer, to the wellsite and control the microscope remotely from onshore? The sedimentary petrologists in Shell have microscopes with image capture technology; by merging the two, we could build a potentially powerful new system.

The initial test of the concept was carried out in 2011, using a computer-aided petrology system located in Bernard Instruments office outside Houston, while I remained in Shell’s office across town. Despite some latency issues, it was possible to connect and control the microscope remotely.

To overcome the lag time, it was decided that initially a low-resolution scan of the whole slide would be made. For palynology, this could be at ×400 which is sufficient to identify most larger dinoflagellates. For nannofossils, it would be at ×630 or ×1000. This image would be displayed to the remote user, who could then click on a fossil and have the microscope automatically move the stage back to view it live.

Imaging software was evolving fast through 2012 making it possible to scan complete slides quickly at multiple focus levels. This of course generates a huge number of big files, but compression techniques are also improving significantly, such that this is not the problem it once was. The image capture software scans the microscope field of view at multiple focus levels (typically seven), compresses these files, and sends them onshore where they are stitched back together. If important fossils cannot be identified because the image stack resolution is too poor, it is possible to either use the remote connection to get a live view of the fossil, or to get the microscope to re-scan the fossil at an increased resolution.

Subsequently, Gunilla Gard and Jason Crux at BHP Billiton successfully tested the system operationally twice at a wellsite. While the existing microscope works, from a size and durability point of view it is not satisfactory. It is a Zeiss AxioMager 2ZM which requires three large sturdy plastic cases to transport offshore. It also requires careful handling and setup. Bernard Instruments are building a much smaller specialized scope which includes all the required features but will fit into one sturdy plastic case. This will be finished by mid 2015.

Theoretical example of fossils cut out from a scan and then streamed back in the form of a virtual database.

Theoretical example of fossils cut out from a scan and then streamed back in the form of a virtual database.

The next step is a nannofossil image recognition system, and this is also currently under development. Nannofossils are eminently suitable for this as, unlike dinoflagellates, they usually sit on the slide in a consistent orientation.

Image recognition for fossils has been tried numerous times over the last 25 years, usually with limited success. In some cases the shortfall has been attributable to a lack of computer processing power, or just that it has been applied to fossil groups that are inherently difficult to identify. But a number of technologies have improved to the point where a robust and fully operational system may be just around the corner.

Heterogeneity + sparse sampling = uncertainty

Heterogeneity + sparse sampling = uncertainty

My geophysical toolbox, circa 1973

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