PROJECT
BY
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EE/2017/167
SUBMITTED TO
DEPARTMENT OF ELECTRICAL ELECTRONIC ENGINEERING FACULTY OF ENGINEERING CARITAS UNIVERSITY, AMORJI-NIKE, ENUGU.
IN PARTIAL FULFILLMENT OF THE REQUIREMENT FOR THE AWARD OF BACHELOR OF ENGINEERING (B.ENG)
APPROVAL PAGE
This project has been read and approved by the undersigned as with the requirement at the department of Electrical Electronic Engineering of Caritas University Amorji Nike Enugu for the award of Bachelor of Engineering (B.Eng.) in Electrical Electronic Engineering.
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Engr. Ejimorfor Date
(Project supervisor)
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Engr. Ejimofor Date
(Head of Department)
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External Supervisor Date
DECLARATION
I declare that this project material is an original work done by me under the supervision of Engr. Ejimorfor, department of electrical electronic engineering faculty of engineering caritas university, amorji-nike, enugu
DEDICATION
This project is dedicated to Almighty God and to my parents Engr. & Mrs. Chukwu A. Orioha and to my beloved brothers and sisters whose ever loving kindness and support has seen me through my years of studies.
ACKNOWLEDGEMENT
I wish to express my immense gratitude to God Almighty for his mercy, guidance and protection towards me for seeing me through the rigors of this work. I am greatly indebted to my supervisor Engr. Ejimofor for his kind gesture and whose critics lead to the achievement of this work. I also will remain grateful to the tremendous contribution of my lecturers Engr. Ojobor (the Dean of Engineering Faculty), Engr. Ejimofor (Head of Electrical Electronic Engineering Department), Engr. Mbah, Engr. Ochi, and all the staff of Electrical Electronic Engineering both academic and non academic staff for their intellectual upbringing. My special appreciation goes to my loving parents Engr. & Mrs. Chukwu A. Orioha, my grandparent, my uncles and aunties, my brothers and sisters whose moral and financial support cannot be over emphasized. Also my sincere gratitude and special regards to my friends too many to mention whose encouragement also lead to the success of this work.
It is anticipated that over 2 trillion barrels of conventional oil will remain in reservoirs worldwide after conventional recovery methods have been exhausted. Other oil recovery methods depend on many economic and technological limitations. Microbial Enhanced Oil Recovery (MEOR), on the other hand, has been proposed for many years as a cheap and effective alternative to enhance oil recovery as its different processes generally do not depend on oil prices. Microbes offer useful metabolic products such as biosurfactants, biopolymers, biogas, biomass, in addition to bio-acids and bio-solvents for enhancing oil recovery. These bioproducts contribute to different microbial systems which tackle specific problems of oil recovery from a chosen target reservoir. The present review provides an overview of MEOR developments from its early stages until today. Basic aspects of petroleum engineering oil recovery stages and microbial characteristics suitable for MEOR are introduced to better link the two bioengineering technologies. The uses and types of different microbial bioproducts available in literature are reviewed and various recovery mechanisms are discussed. Successful MEOR field trials around the world are summarized which shows the potential of this technology as alternative oil recovery method. However, these processes have not been fully proven and did not receive large attention in the petroleum industry due to several reasons that are also discussed. One major reason is the absence of standardized field results and post trial analysis and the lack of structured research methodology. Also, the inconsistent technical performance and lack of understanding of the mechanism of oil recovery contributed to the fact that MEOR received little interest in the petroleum industry.
CHAPTER ONE
1.0 INTRODUCTIONMicrobial enhanced oil recovery (MEOR) is an enhanced oil recovery technique that uses bacteria in oil reservoirs through production of specific metabolic processes that can lead to enhance oil recovery. The concept of using microorganisms to enhance oil recovery was first proposed by Beckman [4]. However, it was not until the after the work of Zobell [30] that the research on MEOR gained wider attention. Since that time multiples of microbiological enhanced oil recovery projects have been carried out in different parts of the world. MEOR is a tertiary oil recovery process, where bacteria are supported via injection of nutrients. Some processes involved injecting fermentable carbohydrates into the reservoir. Other reservoirs require inorganic nutrients and oxygen to be introduced into the oil bearing strata in quantities that allow the microbes to release the residual oil into the water phase and substrates for cellular activities.
The mechanisms by which MEOR processes work can be highly complex. In general, the mechanisms of MEOR’s action are most probably due to multiple effects of the microorganisms on the environment and oil. These mechanisms include gas formation, and pressure increases, acid production and degradation of carbonate matrices, reduction in oil viscosity and interfacial tension by biosurfactant, solvent production, plugging by biomass accumulation and degradation of large molecules in oil resulting in enhanced oil recovery [9, 14, 19].
The actual mode of MEOR in a particular reservoir will be very dependent on the characteristics of the reservoir and the types of indigenous microbes present in a particular reservoir. MEOR differs from chemical enhanced oil recovery through the method by which enhancing products are introduced into the reservoirs. In MEOR, microbes produce all the necessary chemicals in- situ but generally, the application, conditions and cultures can be targeted to meet a particular oil recovery situation [12].
Although MEOR has many advantages compared to other enhanced oil recovery technologies its successful application requires the selection of microorganisms producing effective quantities of desired metabolites, processes which permits injection and dispersion of these microorganisms, and their supporting nutrients, predictable proliferation, and metabolic activity and an ability for the new ecosystem to persist for periods consistent with economic profitability [26]. The most active applications of the MEOR process are single well simulation treatments for removal of near wellbore formation damage or oil mobilization in the region around wellbore [5], use of microbial of microbial systems for permeability modifications to improve water flooding sweep efficiency [15], use of microorganisms to produce gas, surfactants, acids and alcohols useful for enhanced oil recovery [6]. Although the use of microorganisms has been studied and tested for many years, the success of its application can be limited by the extreme reservoir conditions.
Thus, finding the right bacteria candidate for MEOR to fulfill the environmental conditions normally encountered in the petroleum reservoirs can be very challenging. This has made the search for the bacteria that will perform the work of releasing residual oil in the reservoir environments a continuous process. One of such group of bacteria targeted for application in microbial enhanced oil recovery are members of the order Thermoanerobacteriales within the Firmicutes which are commonly encountered in oilfields and include isolates belonging to the genera Thermoanarobacter [7, 11]. This is because they are conducive for growth in deep seated environment such as oil bearing reservoirs [7]. Thermoanaerobacter br ockii is one of the thermophilic bacteria under current investigation for evaluation of the potential of these organisms for production of metabolites that can enhance oil recovery. Such metabolites include gas and acid production, surfactants, biomass etc. Their high growth temperature offers process advantage in high temperature oil reservoirs and their broad substrate spectrum may allow utilization of inexpensive carbon sources available such as molasses.
1.1 BACKGROUND OF THE PROJECT
There are three stages of oil recovery process employing mechanical, physical and chemical methods [1]. The first stage is the primary recovery stage where the natural energy of the reservoir, mainly reservoir pressure, is utilized. These natural driving forces include: water drive from the aquifer, solution gas drive that results from gas evolving from oil as reservoir pressure decreases, gas cap drive, rock and fluid expansion and others [2,3]. The next oil recovery stage is the secondary stage which takes place when the reservoir pressure tends to fall and becomes insufficient to force the oil to the surface. In this stage, external fluids are injected into the reservoir either to maintain the reservoir pressure or to displace the oil in the reservoir [4]. The usual fluid injected is water; however, immiscible gases could also be injected in this stage. While primary recovery stage produces generally between 5-10% of the total oil reserves, recovery efficiencies in the secondary phase varies from 30-40% [1,5]. Based on recent world reserves statistics, nearly 2 trillion barrels of conventional oil and 5 trillion barrels of heavy oil will remain in reservoirs worldwide after conventional recovery methods have been exhausted [6]. Hence, attention has been focused on the Enhanced Oil Recovery (EOR) techniques for recovering more oil from the existing and abandoned oil fields. The EOR methods may be divided to thermal, chemical and gas injection methods. The thermal methods are primarily intended for heavy oils and tar sands mainly to supply heat to the reservoir. These methods include steam or hot water injection and in situ combustion technique. Chemical flooding involves injection of certain chemicals that might change either the characteristics of the reservoir fluids or improve the recovery mechanisms. These include polymer, surfactants and alkaline flooding. Miscible flooding (either first- or multi- contact miscible) includes CO2 miscible gas injection, N2 miscible injection and others. Now, more advanced technologies are being implemented in the oil industry to recover the trapped oil. These include seismic/sonic stimulations and electromagnetic methods [1]. However, economics are the major deterrent in the commercialization of the above mentioned EOR methods [6].
Microbial Enhanced Oil Recovery (MEOR) is one of the technologies that can be potentially implemented with an exceptionally low operating cost. It has several advantages compared to conventional EOR processes where it does not consume large amounts of energy as do thermal processes, nor does it depend on the oil price as do many chemical processes [7]. MEOR is simply the process of utilizing microorganisms and their bio-products to enhance the oil recovery. Bacteria are the only microorganisms used for MEOR by researchers due to their small size, their production of useful metabolic compounds such as gases, acids, solvents, biosurfactants, biopolymers as well as their biomass [8]. Also, their ability to tolerate harsh environments similar to those in the subsurface reservoirs in terms of pressure, temperature, pH and salinity increased their attraction to be used for EOR purposes. Bacteria’s average cell size ranges between 0.5-5.0 µm which makes it easier for them to penetrate through the reservoir’s porous media [9]. For MEOR processes which involve the injection of bacteria into the reservoir, it was calculated that the microbes have to be small, spherical and less than 20% of the size of the pore throat in the formation [10,11]. Most of the oil reservoirs are sedimentary basins, reservoir lithology is usually sandstone or carbonates, mostly fractured limestone for the carbonates reservoirs, with pore size being greater than 30 µm for productive reservoirs and pore throat size not less than 10 µm [12]. It was reported that for reservoirs having permeability higher than 0.6 Darcy (D), an area of 60,000m2 was affected by microbial treatment [13]. It is also believed that sandstone reservoirs need to have permeability greater than 0.1 D for the microbes to be able to pass through them [9]. However, for reservoirs with tight formations having permeability around 0.1 D, the effect was limited to the wellbore region. Jang et al. [13] conducted a bench scale study on the transport of three bacterial species (Bacillus subtilis, Pseudomonas putida and Clostridium acetobutylicum) in highly permeable and porous rock. They have also provided a quantitative screening criterion for selecting proper potential bacterial strains for in situ MEOR applications. Jansheka [14] compiled a partial list of some bacteria that have been used in the MEOR experiments and field studies. It was found that Bacillus and Clostridium species are the most common species used for MEOR purposes since they can form dormant, resistant endospores that can survive under stressful environmental conditions and they can produce the useful bioproducts for MEOR [14-16].
The idea of using bacteria for the production of oil was first suggested by Beckman back in 1926 [17]. However in 1946, Zobell and his co-workers were the first to perform actual experimental work to confirm Beckman’s theory. Their work continued till 1955 and they patented a process for secondary recovery of petroleum using anaerobic bacteria, hydrocarbon utilizing, and sulfate reducing bacteria [18]. Later, extensive experimental work on the potential of microbes for MEOR purposes was conducted [19-22]. Although the results were promising, the research in this area lost its interest in the 1970s due to economic reasons [23]. However, in the 1980s and 1990s, the global decline in oil prices raised the need for a cost effective process that is both technically and economically feasible. Thus, considerable research in the area of MEOR was performed during that period [3,9,14,24-36].
MEOR is also considered as an inexpensive process since it can be implemented with minor modifications to existing field facilities [9]. However, despite the positive and promising experimental and field tests results, it did not receive wide spread attention in the oil industry due to several factors suggested by many researchers. Some of these reasons were the negative perception on the use of bacteria and handling them in the field for MEOR processes although it was verified by tests conducted by public health laboratories which reported that the mixed cultures of bacteria are safe to handle and pose no threat to the environment, plants, animals or human beings [15,39]. Besides, the reservoir’s environment is not favorable for the pathogenic organisms to grow. That’s why, it is recommended to perform a toxicity test for any organism to be used in the field for MEOR to assure the safety of involved parties. Another factor was the inconsistent technical performance and lack of understanding of the mechanism of oil recovery [38]. It is difficult to extrapolate the results from one microbial field trial to other reservoirs as each reservoir has its unique properties and microbial population for indigenous MEOR cases [39]. One of the major reasons for MEOR not receiving wide popularity was the absence of standardized field results and post trial analysis [16]. Most field trials were not followed for enough amount of time to determine the long term effect [2]. In addition, another reason might be that extensive laboratory tests are needed to determine the microbe to be used, its survival and competitiveness in the reservoir, feeding regime strategy and to evaluate the effectiveness of the process.
1.2 OBJECTIVE OF THE STUDY
The objective of this work is to highlight and study how microbes can be used to enhance oil recovery.
1.3 SIGNIFICANCE OF THE STUDY
Microbial Enhanced Oil Recovery (MEOR) is one of the technologies that can be potentially implemented with an exceptionally low operating cost. It has several advantages compared to conventional EOR processes where it does not consume large amounts of energy as do thermal processes, nor does it depend on the oil price as do many chemical processes [7]. MEOR is simply the process of utilizing microorganisms and their bio-products to enhance the oil recovery. Bacteria are the only microorganisms used for MEOR by researchers due to their small size, their production of useful metabolic compounds such as gases, acids, solvents, biosurfactants, biopolymers as well as their biomass [8]. Also, their ability to tolerate harsh environments similar to those in the subsurface reservoirs in terms of pressure, temperature, pH and salinity increased their attraction to be used for EOR purposes. Bacteria’s average cell size ranges between 0.5-5.0 m which makes it easier for them to penetrate through the reservoir’s porous media [9].
1.4 SCOPE OF THE STUDY
In this study we made use of thermophilic anaerobic bacteria, Thermoanaerobacter brockii subsp. lactiethylicus strain 9801 T for laboratory investigation of its potential for production of metabolites needed in microbial enhanced oil recovery processes. This strain of bacteria have been studied previously in terms of its characterization and genetic properties [7, 11] but little is known about its potential for enhance oil recovery purposes.
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