Our journey for the South Asian leg has started in Singapore with our hosts being Arthur and Elita at National University of Singapore (NUS). Interestingly, the SEG DISC course has never previously been held here so this was new territory for the SEG as well as for us. We were very curious about what kinds of geoscience problems Singaporeans were concerned with and how they might be related electromagnetic (EM) geophysics.
Singapore is an island country approximately 20x40km in size. It is densely populated and mostly covered by infrastructure. Engineering is crucial but geophysics is not very visible; electromagnetics and its applications are even less visible. None of the universities has a majors program in geophysics and NUS has only two geophysicists. This was definitely going to be a challenge.
Day 1: DISC course
We started the day by querying attendees about the problems they were working on. Participants were primarily interested in hydrocarbon, hydrogeology, and geotechnical challenges and we quickly recognized that there had been minor use of geophysical techniques even though there were many areas where EM could make an impact. On the hydrocarbon side “Team Halliburton” was primarily interested in advanced EM tools and interpretation for logging while drilling; the hydro group was focussed on delineating boundaries between fresh and salt water; the geotechnical participants wanted to know how to characterize the distribution and quality of cement/clay mixtures that form the foundation for building Singapore up from reclaimed sea. The various EM techniques that are potentially useful in helping solve these problems were unfamiliar to many participants. This is reflected in a couple of comments provided on the feedback forms:
It was a long but extremely valuable experience. The lecture has broadened my knowledge and understanding of different types of EM surveys.
Good cover of the materials, techniques and applications. Very valuable to me and for my future geophysical surveys
DISC day at National University of Singapore
Again, the apps were a hit. This time Seogi introduced the apps before we broke for lunch. As a result we were able to use the lunch hour to have participants communicate with each other, play with the apps, and eat the delicious sandwiches that were generously provided by NUS. (thanks Arthur!).
I like very much about the visual and interactive of each EM problem with the apps
The day closed with the vision for the future and the anticipation of a more in-depth discussion about problems for the DISC Lab.
Day 2: DISC lab
DISC lab started at 9:00 am, which is a bit more relaxed schedule. We missed “Team Halliburton” but participants from the hydro and geotechnical groups presented their challenges.
To put the problems into perspective, Singapore is an island made up with a high component of soft clay. The large buildings require a solid foundation. Moreover, they are shortage of space to build their skyscrapers so usable land is being reclaimed from the sea. In fact about 24% of the current land area of Singapore has been reclaimed from the sea. Much more is currently under progress as barges continually haul sand from the South China Sea. Currently Singapore does not extract ground water; it uses surface run-off as well as water piped in from Malaysia. It would like to become self-sufficient and this means using its aquifer system for storage and retrieval. Unfortunately some of the subsurface water, especially on reclaimed lands, is brackish or saline. The goal is to push back the saline water interface by pumping fresh water in.
Participants gave talks about their research but, to prevent any potentially sensitive information from being put on the web, it was decided not to record lightning talks. We did however, capture the essence of their research projects on the 7-step forms. The title of the projects and links to the the 7-step forms are provided below.
- Faiben (7-steps)
Numerical modelling and geophysical techniques to monitor the fresh/salt water interface (Field experiments involve DC resistivity and maybe GPR).
- Aurelie and Martin (7-steps).
Building a scale model in the lab that can be used to monitor and visualize the fresh/salt water interface. Of special importance is monitoring the diffuse zone in the transition layer. As a result of the discussions the experimental setup was re-designed so that DC resistivity data could be, obtained by using permanent electrodes embedded in the experimental setup.
- Yannick (7-steps)
Soft clay generates a geotechnical challenge for construction. By law, any construction will be stopped if it causes ground deformation of 25 mm or more. To prevent this the clay is infused with cement. The injected cement may not be uniformly distributed and hence remote sensing techniques are required.
- Jun: (7 steps)
What changes in electrical resistivity occur when gas hydrate is dissolving. For instance, injecting CO2 is considered to produce methane gas. Can this chemical process can make any conductivity contrast? How do we setup a lab measurement to conceptualize this experiment?
- Du: (7 steps)
Using nano particles (possibly coated with conductive material) to monitor where fluid is moving while hydraulic fracking. Multiple physical property contrasts are considered, depending upon which materials are used as a tracer: magnetic permeability, conductivity, and chargeability.
We wrapped up the DISC Lab with a brief introduction of an open source geophysical simulation and inversion package, SimPEG. Participants were looking forward to having capability to simulate their problems related to EM geophysics.
Considering the logistical challenges that we had with respect to advertisements, and also the minor use of applied geophysics in Singapore, we believe DISC 2017 at Singapore was a success. The necessity of using various EM geophysical techniques to solve a number of geoscience problems closely related to Singaporeans daily life is beginning to be recognized. This is especially true for issues connected with ground water storage and monitoring the sea/fresh water interface. There is also a large need to characterize the subsurface for large scale engineering problems.
DISC2017 in Singapore would not have been successful without the support from local participants to help organize logistics and encourage people to attend. In particular, we thank: Arthur Chen, Li Yunye (Elita), and Glenn Wilson.