Yuandong Ma

In the development of high-temperature and high-salinity oil fields, biopolymer scleroglucan flooding technology faces significant challenges. Traditional scleroglucan products exhibit poor injectability and high extraction costs. This study investigated the application potential of the original fermentation broth of exopolysaccharides (EPS) produced by microorganisms in a simulated high-temperature and high-salinity oil reservoir environment. The polysaccharide was identified as scleroglucan through IR and NMR analysis. Its stability and rheological properties were comprehensively evaluated under extreme conditions, including temperatures up to 150 °C, pH levels ranging from 1 to 13, and salinities up to 22 × 10⁴ mg/L. The results demonstrated that EPS maintained excellent viscosity and stability, particularly at 76.6 °C and 22 × 10⁴ mg/L salinity, where its viscosity remained above 80% for 35 days. This highlights its significant viscoelasticity and stability in high-temperature and high-salinity oil reservoirs. Additionally, this study, for the first time, examined the rheological properties of the original fermentation broth of scleroglucan, specifically assessing its injectability and enhanced oil recovery (EOR) performance in a simulated Middle Eastern high-temperature, high-salinity, medium-low permeability reservoir environment. The findings revealed an effective EOR exceeding 15%, confirming the feasibility of using the original fermentation broth as a biopolymer for enhancing oil recovery in extreme reservoir conditions. Based on these experimental results, it is concluded that the original fermentation broth of Athelia rolfsii exhibits superior performance under high-temperature and high-salinity conditions in medium–low permeability reservoirs, offering a promising strategy for future biopolymer flooding in oil field development.

The study of seepage laws during microbial enhanced oil recovery helps to elucidate the mechanisms behind microbial flooding, and the use of large-scale physical simulation experimental devices can more objectively and accurately investigate the seepage laws of microbes in porous media, and evaluate the oil displacement efficiency of microbial systems. In this study, physical simulation experiments of microbial flooding were conducted via a slab outcrop core, and the biochemical parameters such as the concentration of Bacillus subtilis, nutrient concentration, surface tension, and displacement pressure data were tracked and evaluated. The analysis revealed that the characteristics of the pressure field change during microbial flooding and elucidates the migration rules of microbes and nutrients, as well as the change rule of surface tension. The results show that after the microbial system is injected, cells and nutrients are preferentially distributed near the injection well and along the main flow paths, with the bacterial adsorption and retention capacity being greater than those of the nutrient agents. Owing to the action of microorganisms and their metabolites, the overall pressure within the model increased, From the injection well to the production well, the pressure in the model decreases stepwise, and the high-pressure gradient zone is mainly concentrated near the injection well. The fermentation mixture of Bacillus subtilis increased the injection pressure by 0.73 MPa, reduced the surface tension by up to 49.8%, and increased the oil recovery rate by 6.5%.

Biosurfactants have significant applications in various industries, including microbial-enhanced oil recovery (MEOR). While the state-of-the-art genetic approaches can generate high-yield strains for biosurfactant production in fermenters, there remains a critical challenge in enhancing biosurfactant-producing strains for use in natural environments with minimal ecological risks. The objectives of this work are enhancing the strain’s capacity for rhamnolipids production and exploring the genetic mechanisms for its improvement. In this study, we employed atmospheric and room-temperature plasma (ARTP) mutagenesis to enhance the biosynthesis of rhamnolipids in Pseudomonas sp. L01, a biosurfactant-producing strain isolated from petroleum-contaminated soil. Following ARTP treatment, we identified 13 high-yield mutants, with the highest yield of 3.45 ± 0.09 g/L, representing a 2.7-fold increase compared to the parent strain. To determine the genetic mechanisms behind the enhanced rhamnolipids biosynthesis, we sequenced the genomes of the strain L01 and five high-yield mutants. A comparative genomic analysis suggested that mutations in genes related to the synthesis of lipopolysaccharides (LPS) and the transport of rhamnolipids may contribute to the improved biosynthesis. To the best of our knowledge, this is the first instance of utilizing the ARTP approach to improve rhamnolipid production in Pseudomonas strains. Our study provides valuable insights into the enhancement of biosurfactant-producing strains and the regulatory mechanisms of rhamnolipids biosynthesis.