Kuala Lumpur
Feb. 16–17
Although Kualar Lumar (known as KL) is very close to Singapore (~1h by plane) the atmosphere around the city seems different. Perhaps it is the construction and architecture. Buildings rocket skyward and one of the most significant, the Petronas twin tower, is an architectural anchor for the city. Just from looking at this huge twin tower, we could feel the impact that Petronas is making to Malaysian society. The DISC course was on the 42nd floor.
Day 1: DISC course
The DISC course in KL was largely a Petronas event and almost all of the 50+ attendees were from Petronas. The two exceptions were from an engineering company closely related to Petronas and interested in hydrocarbons. A room for the DISC day was cozy, and not quite large enough to handle everyone, so about 10 people had to watch the lecture in an adjacent room. We started the day by asking people about their backgrounds, interests, and connections with EM geophysics. The primary interests were: a) marine controlled-source EM (CSEM) acquisition and inversion, b) geohazard investigation with respect to gas hydrates, c) time-lapse reservoir monitoring, and d) multi-physics.
The backgrounds of attendees varied widely with respect to the use and understanding of EM techniques. Some were very knowledgeable while others were novices in EM but had extensive backgrounds in seismic processing and interpretation. The motivation for everyone however was to see how EM geophysics (particularly marine CSEM) could be used to help them find deep hydrocarbon reservoirs. We had lots to present and, overall, this was the most interactive audience we have had thus far.
Excellent. A lot of information was delivered, which is useful for oil & gas exploration.
The course provided a good review of EM methods for me, providing some valuable reminders on EM fundamentals not seriously studied since university.
Attendees were mostly practitioners, each having their own projects, and were curious about how they can use EM geophysics for their applications. The atmosphere in the room was energetic, and attendees asked number of questions. Many of these stemmed from trying to relate unfamiliar EM material to their seismic background. For instance, in the DC resistivity section:
Do you usually use any tie-lines for a DC survey?
But they quickly caught concepts and articulated important questions. For instance in the EM fundamentals section one of the first questions asked was:
How do you differentiate primary and secondary effects?
This was a critical question, and in fact it is an important aspect for frequency domain EM techniques. The secondary magnetic from the earth is small compared to the primary magnetic field hence effectively removing primary magnetic field in the observation is crucial. The answer was provided in the inductive source EM section, when a bucking coil is introduced.
After marine EM case history at Barent sea:
Can we distinguish gas and oil with EM geophysics?
From the Barent sea case history, it was shown that the marine EM technique can be used to differentiate a good hydrocarbon (HC) reservoir (>70% HC saturation) from a poor one. Importantly, EM was guiding other information from well-logging and seismic rather than being interpreted directly as a hydrocarbon indicator. Still, Petronas people wanted more information. They wanted to distinguish between oil and gas, and wanted to know whether EM geophysics could help solve this problem. That is a challenge since oil and gas have similar resistivities.
Day 2: DISC lab
DISC lab started at 9:00 am, and we only had three hours. So, this time we tried a different format. In the first two locations we: a) asked each participant to give a 5 minute lightning talk about their geoscience problem, b) introduced a 7-step approach for breaking down a geophysical problem, and c) had further discussion with attendees about their problems in the context of the 7-steps. This time we merged the three-steps. While a participant was speaking through their problem, we sketched their problem into the 7-steps. A main theme of discussion was a potential use of induced polarization for detecting and also monitoring hydrocarbon reservoirs.
Max opened up our conversation, and we started to put things together into a 7-step procedure. We suggested the following lab experiment as shown below. Make a lab setup having a thin sand layer (berea sand stone) embedded in shale background. Then measure potentials along a vertical profile with a broad transmission frequency band (may be 0.1 Hz -1 MHz). With the same measurement setup, we can try three different scenarios: a) unsaturated sand, b) brine water saturated sand, and c) hydrocarbon saturated sand.
When we saturate the sand layer with brinewater, its electrical conductivity will increase. After we substitute some portion of brinewater with hydrocarbon (oil or gas), the conductivity of the sand layer will decrease i.e. become more resistive. Hence, the electrical conductivity can be diagnostic. What about chargeability? Are hydrocarbons chargeable? If so, then what polarization characteristics are connected to hydrocarbons? What are the sources of chargeability? Those were main questions that posed in our discussion.
In addition, Max commented that a landfill site could be an analog experimental site where we test the IP method for hydrocarbons because methane gas generated from a landfill can be trapped in a clay layer above making pyrite, in a process similar to the migration of deep gas to a caprock above. Note that pyrite is chargeable.
For a current application, Roger introduced a monitoring problem connected with enhanced oil recovery (EOR).
Roger Miller: (7 steps)
A gas reservoir is buried a kilometer below from the seafloor; the sea is shallow, only ~70 m. A straightforward case for enhancing oil recovery is to carry out a water flooding, procedure where brine water is injected. The injected brine water has a significant conductivity contrast compared to the resistive hydrocarbon. Typically the fluid in the reservoir can move about four hundred meters per year.
Conversely, the injection fluid can be CO2 rather than water. In this case, both gas and CO2 are resistive. Hence, we need to consider a different physical property, which makes a contrast between gas and injected CO2. Again the potential of using chargeability was discussed.
Much of the subsequent discussion focussed on the identifying suitable geophysical surveys for monitoring enhanced oil recovery (EOR). Borehole to surface EM was first considered, and the challenge of dealing with casing (which is extremely conductive and susceptible) was discussed.
Our DISC events wrapped here. Again presenting EM fundamentals, and applications in a national oil company was such an adventure. Attendees from Petronas were engaged, and eager to find which EM application can help solve their own project. We hoped that the DISC helped their fundamental understanding of EM geophysics so that they could differentiate what could work and also what does not work for their problems.
Acknowledgement
DISC 2017 in Kuala Lumpur would not have happened without the support from local participants to help organize logistics and encourage people to attend. In particular, Sandeep Kumar, Ang Chin Tee, Max Meju, and Roger Miller.
Behind the scene …
Doug’s brand new macbook pro had a number issues, and we ended up reaching to a repair store called Machine which was in the Petronas Twin Towers. Unfortunately, the macbook has not fixed but it could still be used with an external keyboard and mouse!
