Possibilities of Microbial method of enhanced oil recovery Implementation in Danish chalk rocks
Multi-scale and/or multi-disciplinary approach to process-product innovation
Analysis of Energy Issues (T3-3a)
Keywords: microbiology, oil, recovery, increase, salinity
Conventional waterflooding techniques used in secondary oil recovery leave a large percentage of the oil still in place. Enhanced Oil Recovery methods were developed for use in the final after the water injection depletes its possibilities. Some of these processes employ gas (CO2), polymers or surfactants to help recover residual oil. Microbial Enhanced Oil Recovery (MEOR) uses bacteria, producing above mentioned substances as their metabolic products, to achieve this goal.
In the frame of research program of AAUE, two strains of Clostridia tyrobutiricum were investigated as possible candidates for MEOR implementation in Danish chalk reservoir rocks.
Parameters such as high salinity, low permeability, high temperature and toxic elements, being typical characteristics of Danish fields can cause limiting effects on MEOR applications. In a nutshell, the main tasks of the research program in the current period can simply be outlined as follows:
- To check the adaptation abilities of Clostridium tyrobutrycum (Strains I and II) to salinity up to 70g/l.
- To estimate the volume of gas (CO2) and acids produced by Strain II.
- To check the effect of microbial solution on rock (chalk) permeability and
- To establish a research procedure at the university by using its available equipment for this work and future research in this area.
From ancient civilizations period, it is known that 5% (50g/l) of NaCl is used as a preservation media for food storage. The work fulfilled showed that microbes can be adapted to higher salinities through a serial adaptation processes and our experimental microbes are able to survive, regenerate and produce gas and by-products in salinities of up to targeted 70 g/l, 20 g/l higher than salinities in which pure cultures can survive.
A chemical analytical method applied on the produced gas shows that it is predominantly CO2, with no traces of H2S present which can cause corrosion problems. Titrimetric method was proposed to determine the percentage of CO2 in the total gas produced. Firstly, it is flawed as pure artificial CO2 used in the same experimental setup and showed just a 30.3% CO2 presence instead of an expected 100%. After calibration the method showed that 67 % of the gas produced in the process of microbial fermentation with molasses is CO2. Application of titrimetric methods correctly showed that 0.42mmol of acids are produced during 14days of fermentation per 1 litre of substrate and all acids produced are organic acids. The microbial solution (fermenting medium) improved the permeability of three chalk samples by 8.12%, 16.36% and 2657.9% respectively during 14days of exposure having formed a big hole in the core sample in the latter case.
Charts predicting the change of pH, gas volume dependently on salinity and other interesting results obtained and conclusions made are described in the report.
Presented Monday 17, 15:00 to 15:20, in session Analysis of Energy Issues (T3-3a).
