www.acsprf.org

The objective of this project is to investigate the sensitivity and applicability of geo-electrical methods for high resolution temporal and spatial monitoring of microbial enhanced oil recovery (MEOR) processes. It is important to note that although the use of such methods has been proposed in the past, there has never been a conclusive study on the applicability of the methods. The approach taken in our research is to perform laboratory experiments of MEOR processes while geophysically monitoring the progress. Our experiments up to know showed that geophysical methods can qualitatively monitor MEOR processes (at least under laboratory conditions) and experiments are under way for quantitative interpretation of MEOR processes using geophysical methods. For this experiment our method of choice is the spectral induced polarization (SIP).

A significant effort has been put into the experimental design. Laboratory measurements on heavy oils, for the purpose of oil recovery, have not been performed in the past, or at least are not documented in the current literature, so we had to optimize the existing experimental set up.
We successfully modified existing column design to meet our needs, and finalized a set up that provides us with reliable, and repeatable, high resolution data. Part of this effort involved the re-designing the current spectral induced polarization (SIP) laboratory set up that resulted in broader range of high resolution monitoring capabilities – this was critical for that experiment since the geophysical conditions during MEOR processes, can significantly vary – from very resistive to very conductive depending on the oil and amendment properties.
After obtaining heavy oil (shallow oilfields, SW Missouri), we proceeded with identifying the right microbes for enhanced oil recovery; for this experiment the proprietary consortia Para-Bac/S (Micro-bac, International Inc.) is the best candidate

Experimental Progress. We have already completed a full experimental cycle. After completing all preliminary tests, we moved ahead with the full scale experiment. This experiment involved 3 experimental columns containing 5% (BW) heavy oil. All columns were prepared under the same conditions, and treated under identical protocols. One column served as a control, and the other two as active, with the only difference being the saturating solution; sterile ionic solution for the control, proprietary consortia mix for both active columns.

Geophysical measurements. The geophysical monitoring of the three MEOR experimental columns resulted in very interesting, and promising, results. The control column showed no change in the geophysical response over the course of the experiment. On the contrast both active columns showed changes in certain geophysical parameters, over the course of the experiment. Specifically the recorded phase shift consistently increased for most of the experimental period, reaching to maximum values ~2 weeks before experimental termination; this time coincides with the proprietary microbial consortia expected life. The response of the active columns fully agreed with our hypothesis. We should note that both active columns behaved similarly, confirming that the response is real and not some experimental artifact.
Geochemical measurements. The standard recorded geochemical parameters did not show any significant change during the course of the experiment, at least not adequate to explain the observed geophysical changes.
Following the completion of the experiment we employed a more robust geochemical characterization approach for our columns. Microbial and geochemical analysis of samples, collected throughout the experimental cycle, confirmed that microbial driven degradation of oil occurred in the active columns.

The first full experimental cycle showed that geophysical measurements are indeed sensitive to MEOR processes – at least under laboratory conditions. After the injected microbial consortia colonized the column and presumably reached high growth rate we recorded a consistent and steady change of geophysical parameters while no change observed in the control column. This observation, backed by the microbiological and geochemical monitoring, suggests that geophysical methods, and especially the SIP method, are sensitive to MEOR processes.
Moving ahead with the geophysical data we performed further data processing, which involves the use of Debye Decomposion (DD) – a phenomenological model – as a modeling tool. This approach was successful in providing global measures of the geophysical parameters of interest, namely the chargeability magnitude (m) and time constant (t); the former (m) clearly showed that geophyical signal change as a response to MEOR processes in our system.

Current and future work. Due to the success of the initial experimental cycle we are moving ahead with a second experimental cycle in an effort to quantify the geophysical response associated with MEOR processes. The 2nd experiment will follow the same basic layout of the initial experiment with some important modifications:
use of a specific microbial species for enhanced oil degradation processes to better monitor the microbial and geochemical evolution of our system.
each column will be made in 5 replicates to allow for destructive analysis of the full column material during the experimental cycle and not only after the end of the experiment
with this approach we expect not only to qualitatively show the link between MEOR processes and SIP signals, but also quantify the response and provide additional insight on the signal source mechanisms.
Additionally, we are working on adapting existing mechanistic models that can describe the recorded geophysical response in an effort to shed more light on the contributing factors of the geophysical responses and better describe the physical meaning of these changes.

Impact. Jeffrey Heenan, supported under this grant, started as an Msc student on environmental geophysics and switched to the PhD program; part of the reasons for his decision was the impact of this project on his research interests. Additionally, as part of this project he had to enhance his microbiological and modeling skills.
This project also benefited my career. The novel results initiated new collaborations, and expanded previous ones, with other academic institutions and also the oil industry. There is interest for further laboratory testing of MEOR process and a possible field project. I also established working relationships with microbiological groups that is now being expanded into other research areas.