Research and application of indigenous and exogenous microbial compound huff & puff technique in conventional heavy oil low-effciency wells

Microbiological single-well huff and puff may effectively improve the productivity of heavy oil low-efficiency wells. In order to strengthen the microbial action effect, comprehensive study on the indigenous and exogenous microbes were carried out. Indigenous microbes were activated for formation water by using activating agent system (molasses 3 g/L, corn steep liquor 2 g/L, sodium nitrate 1.5 g/L, dipotassium hydrogen phosphate 1.2 g/L, potassium dihydrogen phosphate 1 g/L). Research on bacterial concentration and emulsifying capacity were carried out by adding geobacillus stearothermophilus SL-1. Microbial compound huff and puff technique was used for the single-well treatment of heavy oil low-efficiency wells. The results show that indigenous microbes are activated effectively with the bacterial concentration peak of 5×10⁸ cfu/mL and maximum emulsion index of 95% and the gas production is up to 260 mL. Compared with pure activation of indigenous microbes, the bacterial concentration is increased from 2×10⁸ cfu/mL to 9×10⁸ cfu/mL and emulsion index peak time is shortened from 20 d to 15 d after adding exogenous microbes. Both well GO7-53X145 and SJSH14-8 have achieved remarkable effects of increasing oil and decreasing water and provided a new idea for the application of microbial huff and puff technique.