Mechanism of microorganisms to relieve reservoir water sensitivity damage

Reservoir water sensitivity damage means that the contact between the external fluid and reservoir rock lead to the hydration, expansion, dispersion, and migration of clay minerals, thereby reducing the formation permeability and causing damage to the reservoir. In this study, the transformation of smectite to illite (S-I) is promoted by endogenous microorganisms to achieve anti-swelling of the clay minerals and reduce the water sensitivity damage of the reservoir. The microbial community reducing Fe(III) was enriched from the samples of Karamay Oilfield, Xinjiang, and microbial community diversity was analyzed by the 16S rRNA gene sequencing. The Fe(II) ion concentration in the interaction medium was monitored, and the maximum iron reduction rates reached 60.2%. The structural changes of smectite before and after microbial treatment were observed by Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy. The result demonstrated that the reduction of Fe(III) was accompanied by the transformation of S-I. There may be some endogenous microorganisms that transform S-I in low permeability reservoirs. This study is of great significance for oilfields to realize clay mineral anti-swelling and eliminate reservoir water sensitivity damage by endogenous microorganisms.