oa Spectral Induced Polarization Monitoring during Microbial Enhanced Oil Recovery

Microbial Enhanced Oil Recovery (MEOR) has been established as a cost effective method for enhancing tertiary oil recovery. Although not commonly used for shallow heavy oils, it could be a viable alternative since it can offer sustainable economic recovery and minimal environmental impact. Successful MEOR treatments require accurate, real time monitoring of the biodegradation processes resulting from the Injection of microbial communities into the formation. Results of recent biogeophysical research suggest that minimally-invasive geophysical methods could significantly contribute to such monitoring efforts. <br>Here we present results of laboratory experiments to assess the sensitivity of the spectral Induced polarization method (SIP) to MEOR treatments. We used heavy oil from a shallow oilfield in SW Missouri to saturate three sand columns. We then followed common industry procedures and used a commercially available microbial consortia (Para-Bac/STM) to treat the oil columns. the active MEOR experiment was performed in duplicate while a control column maintained similar conditions, without promoting microbial activity. We monitored the SIP signatures, between 0.001 Hz and 1000 Hz, for a period of six months. to support the geophysical measurements we also monitored geochemical parameters, including pH, Eh and fluid conductivity, and collected weekly fluid samples from the outflow and inflow which were analyzed to confirm that microbes actively degraded the heavy oils in the column. Destructive analysis of the solid materials was performed upon completion of the experiment, <br>Preliminary analysis of the results suggests that SIP is sensitive to MEOR processes. in both inoculated columns, we recorded an increase in the low frequency polarization with time, where there were measurable changes up to 3.5 mrads in the phase shift recorded for both active columns, while no change was observed in the control column for the duration of the experiment. these results may indicate that remote geophysical methods could successfully complement current MEOR monitoring schemes for promoting sustainable oil recovery.