Publications

much as possible of the residual oil after primary and secondary recovery. Microbial Enhanced Oil Recovery (MEOR) as a tertiary oil recovery technique is the application of biotechnology or biological activities of microorganism for improvement of oil recovery from reservoirs by using and stimulating of indigenous microorganism or injecting of appropriate microorganism into the well. MEOR is an efficient alternative to improve oil recovery, especially in marginal and brown fields. A total of 5 bacterial strains, selectively isolated from brine water and crude oil of Handil oil wells at Kalimantan were studied to determine their potential to be used in MEOR. A laboratory bacterial screening based on the alteration of crude oil properties and growth rates under conditions representative for oil field revealed that 5 bacterial strains identified as Flavimonas oryzihabitans, Amphibacillus xylanus, Bacillus polymyxa, Bacillus macerans and Clostridium sp. demonstrated potential to be used in oil recovery. Growth factor optimization of the isolates was done in mixed cultured at the various inoculum concentrations, urea concentration and initial pH medium by using recovery liquid medium containing of brine water supplemented with 2% (v/v) molasse, 2% (v/v) crude oil and urea. The optimum inoculum concentration, urea concentration and initial pH medium were observed with the following sequence as 10% (v/v), 0.5% (b/v) and 7.5% which caused the decrease of viscosity and interfacial tension until 74.04% and 33.33% compared with control, respectively. Oil mobilization in a laboratory experiment using modified Lazar collector was 11.5% (v/v) of the total oil under statistic conditions. The recovery of oil in this simulation is caused by the changes of oil characteristics and the production of gas by bacteria resulting on oil swelling. Bacterial strains selected in this work could be valuable for further application in oil recovery at marginal and brown oil well sites.