Development index prediction of multi-slug microbial flooding in low permeability reservoir

Key words:  low permeability reservoir  multi-slug injection  microbial flooding  development index  field application  water cut variation rule  exponential decline

Abstract:

Different reservoir conditions cause the different effect of microbial enhanced recovery and its adaptability to the reservoir, the optimized injection parameters predicting the development index are needed. On the basis of frontal advance theory and experienced regression method using experiment data, plus considering some objective factors, such as the oil viscosity reduction by the microorganism and oil-water relative permeability influence, a prediction model was established. This model can predict the development index for microbial flooding through the combination of oil well productivity and variation of water cut. Microbial flooding experiments show that the multi-slug can improve the recovery by 9.24％ compared with single-slug. Also the water breakthrough time of multi-slug microbial flooding can be extended by 40.10％-40.14％, and the water-free oil recovery can be increased by 18.44％. This model can predict almost exactly the dynamic oil production, liquid production and water cut of the microbial stimulation well. The max relative forecasting error of single well is less than 10％, the total error of the block is less than 3％, and the forecasting error of water cut is only 0.25％. In the field experiment, five slugs are adopted to inject the profile control microorganism and oil displacement microorganism alternately. In the test block the increased rate of water cut decreases from 8.1％ to -4.3％, and the composite decline rate decreases from 13.3％ to 4.4％, indicating the effect of water control and oil production stabilization is significant.