Browsing by Subject "Microbial enhanced oil recovery"
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Item Experimental study of microbial enhanced oil recovery and its impact on residual oil in sandstones(2016-12) Cui, Alexander; Balhoff, Matthew T.The objective of this research project was to determine experimentally, using core floods, whether providing additional nutrients to accelerate the growth of nitrate-reducing bacteria alongside aerobic bacteria would result in an improved oil recovery in sandstone rocks. The hypothesis was that indigenous reservoir microbes only need additional nutrients to be able to alter the forces enacting within an oil-water-rock system drastically. As a microbial population grows, individual bacteria strains may colonize to form biofilm and produce microbial byproducts. In general, enhanced oil production from microbes can be categorized into three mechanisms, fluid diversion, interfacial tension (IFT) reduction, and solvent production. Moreover, the distribution and connectivity of the remaining oil could influence the response time and quantity of additional oil production. From the Computed Tomography experiments conducted in this study, it was made apparent that oil distribution does not change considerably when changing brine injection rate after reaching residual oil saturation. However, future experiments are recommended to determine if the waterflood flow rate before reaching residual oil saturation will influence the distribution of capillary-bound oil. Conventional Microbial Enhanced Oil Recovery (MEOR) projects involving the injection of surface-produced byproducts to release oil has proven to be costly, inefficient, and unpredictable. Recent research suggests stimulating indigenous reservoir microbes with inorganic nutrients would increase oil production in a cost-effective manner. In this study, an optimal methodology of conducting microbial corefloods with live reservoir microbes and inorganic nutrients is devised. Corefloods performed in absence of sodium dithionite had overall better microbial growth. Experiments conducted with 1% salinity brine yielded little tertiary oil production (0.1% Sor reduction). MEOR experiments in both 2.5 and 5% salinity systems showed significantly more oil release (1 to 6.5% Sor reduction). Furthermore, secondary waterflood flow rate did have an impact on the tertiary oil recovery (more than 5% difference in Sor reduction). The work presented in this study can be used as a precursor to analyze MEOR performance on high viscosity oil or in heterogeneous rocks.Item Further model development and application of UTCHEM for microbial enhanced oil recovery and reservoir souring(2016-08) Hosseininoosheri, Pooneh; Liljestrand, Howard M. (Howard Michael); Sepehrnoori, Kamy, 1951-; Lashgari, HamidrezaThis research presents an improved simulator to predict the enhanced oil recovery after applying microbial enhanced oil recovery (MEOR) technique and the onset of reservoir souring in sea-water injected reservoirs. The model is developed to study the effect of temperature, salinity, and pH on the growth of bacteria which are responsible for producing in-situ bioproducts in MEOR and causing microbial reservoir souring. The effects of environmental factors (i.e., pH, salinity, and temperature) are implemented into a four-phase chemical flooding reservoir simulator (UTCHEM). In the MEOR process, nutrients and natural bacteria are injected into a reservoir and both indigenous and injected microorganisms are able to react and then generate bioproducts based on in-situ reactions. In this study, we considered three different mechanisms proposed for MEOR: biosurfactant-dominated MEOR, biopolymer-dominated MEOR, and biomass-dominated MEOR. Results show that in-situ bioproduct generation rates can be thoroughly modeled based on environmental factors. Simulation results show 10-15% incremental oil recovery using in-situ biosurfactant compared to waterflooding, biopolymer can increase the oil recovery by 3%, and biomass can contribute to oil production by increasing the recovery by 6%. The simulation results show that nutrient concentration, salinity, and temperature are the most significant parameters influencing oil recovery, whereas pH has an insignificant effect. Reservoir souring is a phenomenon that occurs because of in-situ biodegradation reactions and is modeled in the present study. Sulfate-reducing bacteria (SRB) can convert sulfate ions into hydrogen sulfide by oxidizing a carbon source. This phenomenon is called reservoir souring when it occurs in water-flooded reservoirs. The generated H2S content affects the properties of rocks, reduces the value of produced hydrocarbon, causes corrosion in production facilities, and has health and safety issues. Because of the severity of the problem, several attempts have been made to model and predict the onset of souring. However, there are high uncertainties because of many inestimable and uncertain parameters (e.g., biodegradation parameters, sulfate concentration, reservoir pH, salinity, and temperature). Therefore, the capability of UTCHEM for calculating the maximum growth rate in terms of temperature, salinity, and pH helped us to show the environmental effect on the process. We also investigated the effect of maximum growth rate and available sulfate on the biodegradation process that leads to reservoir souring. In summary, our results show that the microbial reservoir souring process can be modeled based on environmental factors. More importantly, the results show the high sensitivity of the process to different parameters.