Dr Jungho Park of the CSIRO’s Urban and Industrial Water program is investigating the mechanisms and processes of microbially-enhanced oil recovery (MEOR) using multi-phase reactive transport modelling.
MEOR is the use of microbes in petroleum reservoirs to enhance the amount of oil that can be produced. These are typically hydrocarbon-utilising, non-pathogenic microorganisms either found naturally in, or introduced to, petroleum reservoirs. For MEOR, substances are injected into an oil reservoir in order to stimulate the metabolism of microorganisms to produce various chemical agents to modify oil mobility, potentially enhancing it and helping to recover additional oil.
MEOR is a complex process, and how each MEOR mechanism is quantitatively related to enhanced oil recovery is not clear. Experiments are notoriously difficult to undertake, due to the difficulty of culturing the required microorganisms and the slowness of the microbial processes taking place within oil reservoirs.
Replicating the conditions of these reservoirs requires elevated temperature and pressure conditions, further increasing the difficulty of such experiments. For these reasons, utilising computational modelling methods is preferable.
Traditionally this kind of multiphase modelling requires a lot of computing power, and in the past was not commonly done. Running these simulations required around 30,000 hours in situ time, a task that would take several years on a high-end desktop computer.
MEOR also presents a challenge in incorporating and coupling different geochemical, physical and biochemical processes. Describing the microbial metabolism, growth and decay processes is necessary as the microbial metabolism produces gas and chemicals that lead to changes in water chemistry and pressure, and the metabolites and biomass modify the properties of not only the reservoir rock, but of the oil, gas and water phases, changing the fluid flow behaviour.
Dr Park approached the task by combining all the microbial, chemical and multiphase behaviours in one model, linking microbial processes to residual oil recovery.
20 different scenarios were created, with 456 models running for each, using multiphase simulation software on up to 100 of the Pawsey Supercomputing Centre’s compute processors at a time. Simulations were run on microbial batch experiments using PhreeqC, core flooding experiments using TOUGH2 and an idealised field trial using Eclipse.
The MEOR experiments carried out by Dr Park and his team bridge the gap between laboratory oil recovery experiments and actual oil recovery in the field, demonstrating that the pattern of oil recovery obtainable in lab experiments may not necessarily reflect the pattern of oil recovery in the field.
Recovering even 1% more oil in the field has a great commercial value, and depending on a number of variables, different concentration strategies may be required for MEOR. In order to optimise an enhanced oil recovery method, multiphase modelling can help predict the outcome of the oil recovery procedure.
- January 28, 2015
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