Microbial Community Structure And Metabolic Characteristics Of Typical Reservoir

Microbial enhanced oil recovery (MEOR) research was boosted by the petroleum crisis (1970s) and later became a scientific substantiated EOR method, supported by research projects carried out all over the world in countries such as the US, Canada, Australia, China and Russia. MEOR is an environmentally benign, low-cost means of oil recovery that uses oil-field equipment typically found on-site. It has great potential on the reservoir which is developed by other tertiary oil recovery or depleted, so it has gained increased attention from the world.The reservoir which has many endogenous microorganisms with the function of oil recovery is a anoxic, poor nutrient water cycle system. How to activate these microorganisms to clarify its metabolic features and oil displacement function, is the key to improve oil recovery. In this study, the distribution and metabolic characteristics of microbial community in the typical reservoir of Xinjiang oilfield are studied systematically. This paper mainly introduces three aspects, and expounds the process of the changes endogenous microbial community structure and metabolism in the reservoir of Xinjiang..(1) The optimization culture of functional bacteria and the change of the structure of the microflora.The effective of microbial recovery technology is influenced by many factors. As the core of this technology, many factors influenced the survival, growth and metabolism of the microbial in the reservoir, For example, the reservoir geological characteristics (temperature, pressure, porosity, permeability and rock type and group), the formation water physicochemical properties (pH, salinity and organic acids) and crude oil properties (density, viscosity and crude oil family group).Based on the above factors, the endogenous microbial of the reservoir in the Xinjiang oilfield was optimized by using the activated culture of Xinjiang oilfield field test, monitor the change of bacteria concentration, pH, emulsion stability, surface tension, other physicochemical properties, hydrocarbon oxidizing bacteria (HOB), saprophytic bacteria (TGB), anaerobic fermentative bacteria (FMB) nitrate reducing bacteria (NRB), sulfate reducing bacteria (SRB) and methane producing bacteria (MPB) and so on. A functional bacteria group which could utilize inorganic salt to grow and emulsified crude oil was obtained.(2) Study on the structural evolution and metabolic characteristics of microbial community in the reservoir.Using the device of microbial activation mechanism to simulate the reservoir environment (pressure, temperature and porous medium), meanwhile the air was injected into the device to simulate the environment change during stimulation. Thus the process was divided into aerobic, oxygen-limited and anaerobic stages. The bacterial community structure in aerobic stage changed obviously, the analysis of bacterial 16S rRNA clone library showed that Pseudomonas, Achromobacter and Bacillus became the dominant genera; the archaeal community structure in oxygen-limited and anaerobic stages changed sharply, the analysis of archaeal 16S rRNA clone library indicated that Methanosaeta, Methanosarcina became the dominant genera. Analysis of the microbial metabolism, the metabolic characteristics of the microbial community was different during the process, from aerobic to anaerobic stage, producing biosurfactant, oil degradation and biogas production became microbial prominent metabolic characteristics.At present, the emulsified crude oil, crude oil degradation and synthesis of biogenic gas is considered to be the main mechanism of indigenous microbial flooding to enhance oil recovery. The above results show that the mechanism sequentially worked to improving the flowability of crude oil in the reservoir during microbial flooding. The emulsification of crude oil is a major mechanism near inject well area; crude oil degradation has become a major mechanism near the transition area, microbial gas production become the prominent mechanism near the oil well area.(3) the evaluation of dominant species in functional floraIsolation and screening the bacteria from the cultured reservoir produced water, and then to evaluate the Performance of uncommon functional single bacteria (except Pseudomonas and Bacillus). Corynebacterium Q23, Exiguobacterium Q35 were selected to deeply research, the capacity of crude oil emulsion, biodegradation and metabolites were analyzed. Although the three strains were able to emulsify crude oil (5%) in inorganic salt culture, and the crude oil emulsion could remain stable for a long time.