Experimental Study on Microbial Induced Calcium Carbonate Precipitation to Enhance Reservoir Recovery

BACKGROUND: Bacillus subtilis can produce urease in the presence of urea as the main carbon source and induce mineralization in the presence of precipitable cations. OBJECTIVES: The objective of our study was to demonstrate that Bacillus subtilis catabolizes glucose first in the presence of both glucose and urea carbon sources. Using its feature of catabolizing glucose first to delay the mineralization time, it proved its potential application in enhancing the recovery of heterogeneous reservoirs. MATERIAL AND METHODS: The metabolic process of Bacillus subtilis was monitored by changing the glucose content in the bacterial medium by UV spectrophotometer and pH meter. Using a non-homogeneous physical model, experiments were conducted to improve reservoir recovery by microbial mineralization after polymer oil drive. RESULTS: The higher the glucose content in the medium, the longer the time for the pH of the bacterial solution to reach 7 and the longer the end of the logarithmic phase of growth. the glucose content of the 48 h medium was significantly correlated with the consumption of the bacteria and the quality of the precipitation. In the oil drive experiment the permeability of the high permeability model was reduced from 1200 md to 136 md with a reduction rate of 88.6 %, and the permeability of the low permeability model was reduced by 22 md, and the crude oil recovery was increased by 7.9 %. CONCLUSIONS: It was demonstrated that the addition of glucose to the culture medium retarded the mineralization of bacteria. Only 0.2 times the pore volume of the bacterial solution and the cementing solution is required to form an effective seal, thus improving the recovery of crude oil.