Mechanisms Of Enhanced Oil Recovery By Microbe Using Crude Oil As Carbon Source

In this paper, the methods of micro visualized observation, micro numerical simulation and mathematical physics were used, with three kinds of bacteria using crude oil as carbon source separated from the production water in an oilfield, to study the local enrichment laws of microbe and the metabolisms, the migration principles of microbial chemotaxis, the micro mechanisms of enhanced oil recovery, the estimating methods of microbial chemotaxis coefficients and the micro numerical simulation of bacterial flow through porous media. Furthermore, several methods were introduced and some systematic conclusions were also acquired.1. The chemotaxis motion of the microorganisms using crude oil as carbon source wasfound. When they were in the zone of the nutrient brine (the effective zone ofcarbon source dispersion)-water zone, and not far away from the oil-waterinterface, they made the irregular rolling motion, and a time later, they migrated to the interface directively.2. The visualized experiments indicated that, the microorganisms were able to migrateto the carbon source (oil-water interface) when they were in the water zone, and not far away from the oil-water interface. Not long time later, due to the continuous migration and not-stop reproduction, the microbial thalli were distributed widely in the confine between the initial places and the oil-water interface. And the distribution had evident laws:(1) There existed the grads of microbial concentration. After some time, from the initial thalli places to the oil-water interface, the distribution law of microbial concentration was that the concentration increased monotonicly from the minimum to the maximum, that was to say, the nearer to the oil-water interface, the bigger the microbial concentration, and the concentration was the biggest at the interface. Some time later, the concentration at any place increased to the highest, then it did not upgrade basically any more.(2) Bacteria tended to migrate into the three-phase boundary with oil-water-pore wall and get enriched, which was beneficial to the enhanced oil recovery of microbe and the metabolisms.(3) Within the scope of the effective nutriment concentration grads, the microbial motion velocity was not related with the distance from the oil-water interface at all and it was much influenced by the temperature, and there existed an optimum growing temperature. Under the optimum temperature, the motion velocity was the highest.(4) Between the initial bacterial places and the oil-water interface, there were the concentration grads of the microbial metabolisms, and the metabolic concentration was the highest at the oil-water interface.3. A system of methods to estimate the chemotaxis coefficients of microbe usingcrude oil as carbon source were constructed. The calculating examples demonstrated that, the smaller the capillary radius or the permeability of the porous media, the minor the motion velocity of microbial chemotaxis, and the chemotaxis coefficients would increased as the capillary radius or the permeability of the porous media became smaller.4. The physical simulation experiments of micro percolation were conducted toobserve the micro mechanisms of enhanced oil recovery by three microorganisms using crude oil as carbon source and the metabolisms, including peeling off the oil droplet by bacteria and the metabolisms, altering the wetability of pore surfaces, sealing the big orifices, emulsifying and starting the residual oil.5. The percolation theory and method to deal with the fluid motion in the stochasticstructure were taken use of to study the microbial chemotaxis motion in the porous media. Then a kind of simulation method of micro percolation to describe the microbial flow through porous media was proposed and the calculating software was also programmed, which could help to compute and predict the distribution probability of microbial concentration in the porous media.