Biosurfactant Production In MEOR For Improvement Of Iran's Oil Reservoirs' Production Experimental Approach
Authors: Abtahi Nima , Roostaazad Reza , Ghadiri Faramarz 
Published: December 2007

Abstract
Microbial Enhanced Oil Recovery (MEOR) as a tertiary oil recovery technique by using microorganism's activities for improvement of oil recovery from one of the Iran's oil reservoir with special attention to the role of biosurfactant production on MEOR performance was evaluated experimentally. Some experiments by using orthogonal arrays of Taguchi method as an efficient technique for experiment design were planed and conducted to probe and evaluate the effects of microbial formulation on oil recovery efficiency and also the importance of biosurfactant production in oil recovery. All experiments performed in two main scale, flask size and simple core flooding system.
There were five parameters, which their effects and also their importance were studied: source of carbon, nitrogen and phosphorus quantity, type of microorganism, temprature and salt concentration each one in three levels. Final results showed that using microbial treatment in oil recovery causes increase of oil recovery efficiency in comparison with water flooding oil recovery with no microbial treatment and also final results proved that among different mechanisms of microbial oil recovery biosurfactant production has had a major role in this specific study.
The highest oil recovery efficiency among different experiments was about 14.3% when indigenous microorganism of Paydar oil field, which has been isolated from oil samples, was used with 2% sucrose as the main carbon source and 0.2% (NH4)2HPO4 at temprature of 45°C. The best result for biosurfactant production was observed when B. Subtilis was used with 2% sucrose as the main carbon source and 0.4% (NH 4)2HPO4 in 1% salt concentration. Finally this study showed the relative possibility of MEOR application for Iran's Paydar oil field.

Introduction
Microbial Enhanced Oil Recovery (MEOR) as a tertiary oil recovery technique is the applications of biotechnology or biological activities of microorganisms for improvement of oil recovery from oil reservoirs which are in decline of production by using and stimulation of indigenous microorganisms of target reservoir or by injection of some isolated and appropriate microorganisms into the reservoir for biological production of some biological agents such as Biosurfactants, Biopolymers, Biogases, Acids, Biomass and etc. which are effective in an oil recovery by different mechanisms.1,2,3,4
The use of microorganisms to enhance oil recovery has been considered by many investigators for many years. Zobell performed the first detailed work of MEOR in the 1940's5 and after that many successful experimental investigation and field trails have been reported from the US, Eastern Europe, China, Malaysia, Argentina, Australia and Arabic countries etc.3,6
Despite the importance of Microbial Enhanced Oil Recovery as an efficient and economical method for oil recovery but unfortunatly no serious work in this field has been reported in Iran as a country with more than 8% of proved reserves of oil up to now.
One of the most important difficulties about application of microbial techniques for Iran's reservoirs is their complexity of structure, as there are a lots of natural fractured reservoir (NFR) which are more complex than the other kinds of reservoirs like conventional sandstone reservoir not only from production point of view but also from other views like oil recovery and tertiary methods of oil recovery enhancement.
The main problem about natural fractured reservoir from "Microbial Enhanced Oil Recovery" point of view is microbes' transport in double porosity system of matrix and fractures and also the effect of capillary pressure and wettability of rocks that can lead a huge part of oil to be trapped in pores of matrix.
Among different mechanisms of MEOR, Biosurfactant production seems to be the most effective mechanism for such a situation that has been mentioned above.
For this reason some experiments was designed by using Taguchi method, as an efficient technique for experiment design, and conducted for evaluation of the effects of microbial formulation on oil recovery efficiency and the importance of biosurfactant production in MEOR process.
Two main scales were selected for evaluation of different parameters and their part in this research. Flask size and a simple core flooding system.