title: Modification of rock/fluid and fluid/fluid interfaces during MEOR processes, using two biosurfactant producing strains of Bacillus stearothermophilus SUCPM#14 and Enterobacter cloacae: a mechanistic study.
abstract: During any microbial enhanced oil recovery process, both cells and the metabolic products of bacteria govern the tertiary oil recovery efficiency. However, very accurate examination is needed to find the functionality of these tiny creatures at different reservoir conditions. In this regard, the effect of cell structure on ultimate microbial recovery efficiency which is the most dominant mechanism based on the microorganism types (gram-negative or gram-positive) was systematically investigated. At the first stage, possible different active mechanisms using Bacillus stearothermophilus SUCPM#14 strain were tested using specially designed injection protocol, in situ and ex situ core flooding experiments, interfacial tension, viscosity, pH and Amott wettability index measurements. At the second stage, comparing functionality of B. stearothermophilus SUCPM#14 (a gram-positive type) with the previously examined strain namely Enterobacter cloacae as a gram-negative type, proposed this hypothesis that the cell structure significantly affects the interfacial behaviors. New designed protocols were utilized to check the individual effects of cells, bioproducts and interaction of these together on the oil/water and also fluids/rock interfaces. The final results showed that the cells of B. stearothermophilus SUCPM#14 adhere more into the oil/water interface compared to E. cloacae and change its rheological properties; e.g. its elastic properties which affect the ultimate microbial oil recovery efficiency. Eventually, contradicting results revealed that biosurfactant produced by E. cloacae was able to considerably reduce the interfacial tension and alter the wettability of the rock (to neutral conditions) while biosurfactant produced by B. stearothermophilus SUCPM#14 was not very effective.
authors.affiliation: School of Petroleum and Chemical Engineering, Shiraz University, Shiraz, Iran.
authors.forename: Pegah
authors.initials: P
authors.lastname: Sarafzadeh
authors.affiliation: Islamic Azad University, Dashtestan Branch, Borazjan, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Zeinolabedini Hezave
authors.affiliation: School of Petroleum and Chemical Engineering, Shiraz University, Shiraz, Iran.
authors.forename: Sahar
authors.initials: S
authors.lastname: Mohammadi
authors.affiliation: Institute of Biotechnology, Shiraz University, Shiraz, Iran.
authors.forename: Ali
authors.initials: A
authors.lastname: Niazi
authors.affiliation: School of Petroleum and Chemical Engineering, Sharif University of Technology, Tehran, Iran. Electronic address: dr.ayatollahi@gmail.com.
authors.forename: Shahab
authors.initials: S
authors.lastname: Ayatollahi
mesh_terms: D001422:Bacterial Adhesion; D016972:Enterobacter cloacae / Q000378:metabolism*; D001411:Geobacillus stearothermophilus / Q000378:metabolism*; D019015:Geologic Sediments / Q000382:microbiology*; D061329:Oil and Gas Fields / Q000382:microbiology*; D009821:Oils / Q000302:isolation & purification*; D013500:Surface Tension; D013501:Surface-Active Agents / Q000378:metabolism*; D017155:Wettability
chemical_list: D009821:Oils; D013501:Surface-Active Agents
keywords: Bacillus stearothermophilus SUCPM#14; Enterobacter cloacae; Hydrophilicity; Hydrophobicity; Titan process; Wettability alteration