Design and Field Application of a Composite Microbial Flooding Process for a High-Water-Content Oilfield

This study focuses on the problems encountered during the development of the ZB oilfield in the Ordos Basin, including high-water-cut oil wells, low production rate and low waterflooding oil recovery efficiency. First, based on an analysis of the development and the geological features of the study area, the feasibility of the injection of microbes into the well groups in the test area was demonstrated using the theories of microbial enhanced oil recovery (MEOR) in conjunction with a laboratory physical simulation experiment. In addition, an optimum combination of microbial strains was selected. A numerical model of composite microbial flooding in the oil reservoir in the study area was then constructed using a numerical simulation method, and the process parameters for microbial flooding (i.e. injected concentration, volume and mode) were optimized. Finally, the accuracy of the theoretical study was validated through a field experiment and effectiveness analysis. The results showed that a small-slug, high-frequency composite microbe–water alternating injection scheme (i.e. a combination of 3% (0.0003 pore volume (PV)) pre-slug +2% (0.005 PV) main slug and alternating injections of microbes and water) was favourable and increased the oil production, controlled the water cut and improved the oil recovery efficiency in the high-water-content oilfield. The results can be used as a reference for the use of microbial flooding technology to develop high-water-content oilfields of the same type as the ZB oilfield.