Abstract
The high viscosity and low flow properties of some crude oil make them difficult to extract from oil reservoirs. This study investigated the mechanisms responsible for the enhancement of oil recovery using fractured dolomite core models. Bacterial strains, Nocardia cyriacigeorgica, Bacillus species, and Pseudomonasputida, isolated from Libyan oil fields, had the ability to biotransform heavy crude oil by reducing its viscosity and converting heavier components into lighter ones. The efficiencies of the three bacterial strains were assessed using sand-packed column experiments through the injection of bacteria to mimic in-situ oil recovery. The optimum biotransformation values of Libyan Bouri crude oil were determined as 77.1, 61.2, and 61.1% using the Bacillus sp., P. putida, and Nocardia cyriacigeorgica, respectively, at 55 °C. Viscosity analyses showed that these strains resulted in the reduction of the viscosity of the crude oil at two different temperatures of 37 and 55 °C. The highest recovery of residual oil was about 11.3% using Bacillus sp. The study confirmed that the selected bacterial species were capable of displacing additional oil under simulated oil field conditions.
Highlights
The high viscosity and low flow properties of some crude oil make them difficult to extract from oil reservoirs
Oil mobility can be improved by a reduction of oil viscosity; lowering the viscosity of crude oil is essential in the oil extraction industry
This study aimed to demonstrate the potential of using bacterial isolates Bacillus species, Pseudomonas putida, and Nocardia cyriacigeorgica in the biotransformation of heavy crude oil (26◦ American Petroleum Institute (API)) and to evaluate the viscosity reductions of the heavy crude oil to enhance its flow properties and increase its extraction efficiency from the reservoir
Summary
The high viscosity and low flow properties of some crude oil make them difficult to extract from oil reservoirs. Nocardia cyriacigeorgica, Bacillus species, and Pseudomonas putida, isolated from Libyan oil fields, had the ability to biotransform heavy crude oil by reducing its viscosity and converting heavier components into lighter ones. Many investigations of the MEOR technique have injected microorganisms or their products into oil reservoirs to improve the efficiency of oil recovery [4,5,6]. Bacteria can ferment readily available organic compounds to produce gases such as CH4 , CO2 , and H2 These gases, which are produced in situ, can increase the pressure of the reservoir and enhance oil recovery
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