Optimization of Bacillus licheniformis’ nutrient system and oilfield trial for MEOR

Abstract

Abstract The efficacy of microbial-enhanced oil recovery (MEOR) is contingent upon the performance of oil recovery functional bacteria. The optimization of the nutrient system for oil recovery functional bacteria can enhance their performance. In this study, the nutrient systems of the strains underwent screening and optimization procedures, utilizing single-factor combined with response surface methodology. Subsequently, field trials were conducted to assess the efficacy of MEOR. The results indicated that the carbon source in the nutrient system was sucrose, the nitrogen source was NaNO3, and the phosphorus source was a combination of KH2PO4 and Na2HPO4 (in a 1:1 ratio). The combination of the results from the single-factor experiments and the response surface experiment led to the following formulation for the strain F-T nutrient system (g/L): sucrose 10.0, NaNO3 2.0, KH2PO4 1.5, Na2HPO4 1.5, CaCl2 0.12, FeSO4 0.12, MgSO4·7H2O 0.2, Na2MoO4 0.08, yeast powder 1.0, and pH 7.2-7.5. The optimized F-T bacterium has the potential to spread oil up to a diameter of 40.50 mm. The results of the MEOR field trial indicated a 2.95 × 10 t increase in oil production, with a success rate of 83.87%. Following the implementation of MEOR, production levels were observed to decline to levels comparable to those observed prior to the intervention. This indicates that continued MEOR field applications may be necessary to further enhance crude oil recovery.