Coreflood Experiment of Heavy Oil by Thermus SP3
Authors: Hao R. , Wang G. 
Published: March 2010

Abstract
One low-cost improved oil recovery (IOR) technology making significant advances is reservoir flooding with thermophilic microbes. The gram-negative cells of the Thermus SP3 strain were grown at high temperatures up to 85 ° C in the neutral to alkaline pH range. Depending on the culture conditions, the organism occurred as single rods, or as filamentous aggregates. Thermus SP3 was grown chemoorganotrophically and produced volatile fatty acids, 4-hydroxy-4-methyl-2-pentanone, xylene, undecane, 1,2-benzenedicarboxylic acid, bis (2-methyprophl) ester, dibutyl phthalate, di-n-octyl phthalate and surfactants, which had various effects on crude oil. Thermus SP3 could decrease the viscosity and paraffin content of crude oil, degrade heavy fractions, increase the content of light compositions of crude oil, improving the physical and chemical properties, and improve oil recovery (12.59%). Thermophilic Thermus SP3 strain was screened to begin optimizing the process and coreflood was performed to quantify oil recovery. A laboratory coreflood experiment using microbial flooding methodology showed that oil recovery was better than with chemical flooding oil recovery.

Introduction
The diminished opportunity for the discovery of major high quality oil reserves and the oil production decline in mature fields have stimulated an increase in the application of improved oil recovery (IOR) technologies. The increased demand for IOR has initiated recent advances in the research of low cost microbial flooding(1).
Microorganisms have potential use in Microbial Improved Oil Recovery (MIOR) due to the metabolites produced during in situ fermentation. Laboratory studies have shown that these metabolites, which include biopolymers, biosurfactants, biogas, solvents, and organic acids, are useful in modifying the relative permeability of the reservoir as well as increasing the mobility of the oil trapped in the rock(2–7).
Heavy oil is of higher viscosity and density, and contains many resins and asphaltenes. At present, the conventional method to recover heavy oil is a physical method, but it is expensive and makes the ambient environment polluted. Microbial systems have been used in heavy oil reservoirs in order to overcome these problems and improve oil recovery. There are two main methods to improve heavy oil recovery by microbes. One method is to reduce the viscosity of heavy oil; the other method is to change the relative permeability by microbes clogging the high permeability zones.
Generally, temperatures in most reservoirs vary from 60 ° C to 110 ° C, which are higher than the ambient temperature. However, the growth temperature for most bacteria is 20 ° C to 50 ° C, and many bacteria are not suitable to high temperature environments. Thermophilic bacteria isolated from the oil field can grow in a high temperature environment, and be adapted to the reservoir conditions.
The simulation represents a laboratory attempt to replicate the field environment. This allows some of the nonessential complexity of field studies to be eliminated while it simultaneously facilitates experimental control. Ideally, there should be continuity from the simple laboratory system, through the experimentally manageable simulation, to the naturally complex field environment(8).
Coreflood simulations are an important part of MEOR research.