Examining Enhanced Oil Recovery (EOR) Techniques

Examining Enhanced vegetable coarse anele convalescence (EOR) TechniquesEnhanced Oil Recovery (EOR) is a generic term for techniques utilize for increasing the marrow of crude anele that sight be extracted from an fossil embrocate hale up. Using EOR, 30-60 % of the root original crude ignore be extracted comp ard with 20-40% utilize primary and supplementary recuperation techniques.Enhanced fossil anele detecty is in addition called improved embrocate color convalescence or tertiary retrieval. This improved extraction is achieved by be adrift shooting, chemical substance crack and thermal date fromy (which includes cyclic stream, stream flooding, and come alive flooding). botch up scene is the most ordinaryly implementd EOR technique here(predicate) bumble such as century paper dioxide (CO2), inherent turgidity, or north is injected into the beginning whereupon it expands and thitherby zipes redundant cover color to a output wellbore , and except thaws in the petroleum to early baseer its viscidness and improve the pay heed lay of the fossil crude oil. Oil mislayment by carbon dioxide stab relies on the period behaviour of carbon dioxide and crude oil mixture that be powerfully dependent on rootage temperature, printing press and crude oil composition. These mechanisms orbital cavity from oil swelling and viscosity reduction for injection of immiscible stills (at low drive) to completely miscible displacement in game hale applications. In these applications, more than half and up to two-third of the injected carbon dioxide returns with the holdd oil and is familiarly re-injected into the reservoir to minimize operating(a) cost. The remainder is trapped in the oil reservoir by various bastardlys.Other techniques include thermal recuperation (which uses love to improve flow wander) and, more r arly, chemical injection, where polymers ar injected to increase the speciality of wet floo ds or the use of detersive-like surfactants such as to help swallow the capillary mash that ofttimes prevents oil droplets from moving through and through a reservoir. Surfactant raise piss floods atomic number 18 utilise for oil recuperation where surfactants argon injected with polymer. piddlingbic Enhanced oil Recovery (MEOR) is leave-takingicularly meet for application in carbonate reservoir, after secondary oil retrieval, there argon so far large descend of oil left in the reservoir. Some bacteria be able to increase the oil action when injected into the oil reservoir. To stimulate such an aerophilic microbial increased oil recovery, nutrients is injected together with the injection water.Oil recovery begs two to three periods which are briefly described belowStage 1 Primary Recovery 12 15 % of the oil in the well is find without the sine qua non to introduce other substances into the well.Stage 2 Secondary Recovery The oil well is flooded with water or ot her substances to obtain an additional 15-20% more oil from the well.Stage 3 3rd Recovery This stage may be accomplished through several methods which includes MEOR to additionally recover up to 11% more oil from the well.Layout for dissimilar recovery techniques are shown in figure 1. Primary and secondary recovery techniques are normally called conventional recovery. Primary recovery is through with(p) by innate flow which is usually intensify by reservoir natural pressure, and artificial overcharge such as pumps and particle accelerator short-change, etc. Secondary recovery is done by water folding and pressure maintenance by gas reinjection. Tertiary recovery techniques cover enormous area which includes thermal recovery such as in-situ combustion and travel flooding, solvent recovery is done by methods such as polymer flooding and surfactant enhanced water flood. Chemical enhanced recovery methods include gas injection or hydrocarbon miscible injection and nitrogen a nd flue gas flooding. littlebial enhanced oil recovery which is the main focus of this project go out be explained better in the next chapter, yet it is basically injection of microbes such as bacteria into oil reservoir to help recover oil. All these methods of oil recovery go forth be explained briefly.PRIMARY recoveryIf the underground pressure in the oil reservoir is sufficient, thus this pressure will force the oil out to the surface of the earth. Gaseous fuel, natural gas or water is usually empower, which to a fault supply subscribe toful underground pressure. In this situation, it is sufficient to place a complex administration of valves (Christmas tree) on the well head to connect the well to a product line network for storage and processing. Normally oil is recovered by natural means and artificial lift like pumps and gas lift.SECONDARY retrievalOver a lifetime of an oil well, the pressure will drib and at close to point there will be inadequate underground p ressure to force the oil to the surface of the earth. If economical, as often is, more oil in the well is extracted using secondary recovery methods. Secondary oil recovery uses various techniques to aid in convalescent oil from depleted or low pressure reservoir. Sometimes, pumps such as beam pumps and electric submersible pumps (ESPs) are used to pump the oil to the surface of the earth. Other secondary recovery techniques increases the reservoirs pressure by water injection, natural gas reinjection and gas lift, which inject air, carbon dioxide or some other gases into the reservoir. Together, primary and secondary recovery generally allows 25-35 % of the reservoir oil to be recovered.Water injectionThe productivity of existing oil rise bum be authoritatively increased by the use of water injection. Statistics has shown that a reservoir get under ones skins just 37% oil in the first-year recovery. By using water injection, a reservoir drop pay back more than 50% of its oi l. One of the most important issues during oil output signal is to keep the matrix/ mannikin angleation as clean as contingent to maintain maximum oil output. Water is injected for two reasons first is for pressure support of the reservoir. Second is to sweep or displace the oil from the reservoir, and push it outward.Gas liftGas lift is one of a add together of processes used to artificially lift oil from a well, where there is short reservoir pressure. The process involves injecting gas through the tube-casing annulus. Injected gases aerate the liquified and go down its density so the formation pressure is then able to lift the oil column and forces the fluid out of the wellbore. Gas may be injected continuously or intermittently, depending on the producing characteristics of the well and the ar sayment of the gas-lift equipment. Although the gas is recovered from the oil at a latter separation stage, the process requires vitality to drive a compressor in monastic order to raise the pressure of the gas to a level where it back end be reinjected.TERTIARY RECOVERYTertiary recovery reduces the oil viscosity to increase oil output. Thermally enhanced oil recovery methods (TEOR) are tertiary recovery techniques that heat the oil and make it easier to flow or extract. Steam injection is the most common form of TEOR, and is often done with a cogeneration plant. In this type of cogeneration plant, a gas turbine is used to generate electricity and the waste heat is used to produce steam, which is then injected into the reservoir. un give-up the ghostd(p) burning is another form of TEOR, save when instead of steam, some of the oil is burnt to heat the surrounding oil. Occasionally, detergents are also used to decrease oil viscosity as a tertiary oil recovery method, another method to reduce viscosity is carbon dioxide flooding. Tertiary recovery begins when secondary oil recovery isnt exuberant to continue adequate output signal, nevertheless only w hen the oil can still be extracted profitably. (Hitzman 1983)Gas injection or Hydrocarbon Miscible injectionGas injection is the most commonly used EOR technique, here, gas such as carbon dioxide is injected into the reservoir whereupon it expands and thereby pushes additional oil to a production wellbore, and moreover dissolves in the oil to get off its viscosity and improves the flow rate of the oil. Oil displacement by carbon dioxide injection relies on the micro telescope stage behaviour of carbon dioxide and crude oil mixture that are powerfully dependent on reservoir temperature, pressure and crude oil composition. These mechanisms celestial orbit from oil swelling and viscosity reduction for injection of immiscible fluid (at low pressure) to completely miscible displacement in racy pressure applications. In these applications, more than half and up to two-third of the injected carbon dioxide returns with the produced oil and is usually reinjected into the reservoir by var ious means. normality and gas floodingnorthward and flue gas rough 87 % nitrogen and 12 % carbon dioxide is used in place of hydrocarbon gases because of economical reasons. Nitrogen competes with carbon dioxide because it is economical and its compressibility is much let down. For a given quantity at well-worn condition nitrogen will occupy much more home at reservoir pressure than carbon dioxide and methane at the same condition. Nitrogen has a poor solubility and lower viscosity in oil and requires much gameyer pressure to create miscibility.THERMAL RECOVERYIn-situ combustionFire flooding is world cheapest means of thermal recovery, however, significant amount of amount of fuel must be burned, both prouder up the ground to compress the air, and below ground in the combustion process. truly the worst part of the crude oil is burnt, the lighter end are carried forward in advance of the burning zone to upgrade the crude oil.Stream floodingIn the steam drive, steam Is continu ally introduced in the injection well to reduce the viscosity of the oil and provide a capricious force to move oil towards the production well. Steam driving may work by driving water and oil to form an oil bank in front of steamed zone. Ideally this steam bank remains n front, increasing in size until it is produced by the well offsetting the injector. However, in many cases the steam flows over the oil and depute heat by conduction. Oil at the interface will then be less viscous and dragged along with the steam to the producing well. Recoverability is increased because the steam lowers the oil viscosity and improves the oil mobility. The more mobile oil displace the steam zone expands vertically, and the steam oil interface is maintained.Chemical injectionOther techniques which uses heat to improve flow rates (and more rarely) is chemical injection, where polymers are injected to increase the effectiveness of water floods, or the use of detergent like surfactants to help lower the capillary pressure that often prevents oil droplets from moving through a reservoir. Alkaline flooding is an effective chemical EOR method.SOLVENT RECOVERYPolymer floodingBoth synthetic polymer such as polyacrylamides and natural polymers are used for improvement of sweep efficiency. Additional polymer makes the water more viscous so that oil is produced faster. Obviously, this is not a nice idea n a low permeability reservoir or one with tall clay content that absorb the polymer. However, polymer-augmented water floods can be profitableSurfactant-Enhanced Water floodThree types of chemical floods exist. The first is an alkaline-augmented polymer flood. Another is an alkaline-surfactant polymer flood. The third is a mi cellular telephonear or low interface emphasis flood (Donaldson, 1989).AIM AND OBJECTIVESThe aim of this project is to study the adaptability of anaerobic bacteria (Clostridium Thyrobutyricum 633) to different salinities and check the effect of the microbial st rain on permeability of the Danish Nord ocean Chalk.To achieve this aim, the following(a) objectives have been set fall in adaptability of microbial strain to high salinitiesMicrobial gas production and kinetics of metabolismCarry out plate count prove notification of unrest process and microbial analysisTo determine and bill the mountain of carbon dioxide gas produced by these microbes when exposed to different salinitiesTo determine the amount of acid produced during zymolysis processStatistical analysis of results to derive nonplusImprovement of experimental bitThe project work is based on studying of the microbial enhanced oil recovery method and the possibilities of using this in the Danish sector of the Nord Sea. The project task applies experimental procedure and the specific to investigate if these microbes can survive under reservoir conditions and produce products important in oil recovery.CHAPTER TWOLITERATURE REVIEW microbial ENHANCED OIL RECOVERY (MEOR)MEOR is used in the third phase of oil recovery from a well, it is a tertiary oil recovery technique. MEOR is the use of micro-organisms to retrieve additional oil from an existing well, thereby enhancing the petroleum production of an oil reservoir. In this technique, selected natural micro-organisms are introduced into oil well to produce harmless spin-offs like carbon dioxide. These process help to taunt the oil and facilitate oil flow by reducing the viscosity of the oil and making the rock n roll leaky, thereby allowing more amount of oil to be recovered from a well. Amongst the available tertiary oil recovery techniques, MEOR is arguably the best for many reasons. One key factor in the selection of microbial enhanced oil recovery is the economical potential, by which desirable chemicals and gases are produced to enhance oil recovery. MEOR processes are also zipper efficient and environmental friendly as compared to other recovery techniques. record of microbes usedMEOR is a techn ology that has a history based on over 60 years of research and field studies. The earlier workings by ZoBell CE and Updegraff D (USA), Kuznetsov SI and Shturn DL (USSR), shows the international scope of the work. This work was expanded in the 1950s mainly by investigators Coty VF, Yarborough H and Hitzman DO in the major oil companies in the United States. In MEOR, the process that facilitates oil production is complex and may involve fivefold biochemical processes. Microbial biomass or biopolymers may plug high permeability zones and lead to a redirection of water flood, produce surfactants which lead to increased militarization of residual oil, increase gas pressure by the production of carbon dioxide or reduce the oil viscosity due to digestion of large molecules. action of MEOR technologiesMEOR technologies have the common basis of introducing or stimulating viable micro organisms in an oil well reservoir for the purpose of enhancing oil recovery. However, this broad generic definition of MEOR is not a single methodology but is a broader technology which can be designed for different and selective applications. It is convenient to divide the MEOR technology into the following application groupsSingle well stimulationMEOR water floodsParaffins removalViscosity modificationWater warpHeavy oil modificationThe classification of MEOR technology by the proposed oil releasing mechanism shows the range of microbial effects which can be identified or expected to occur to which the MEOR system can be directed.MEOR Oil Releasing MechanismGas generation The production of gases will aid the displacement of oil in the pore spaces.Acid production Organic and inorganic acid production by microbes will dissolve carbonate deposits, iron sulphide and dis stem and sulfate materials.Surfactant production Biosurfactants produced by the organisms result in the reduction of interfacial surface tension of the oil/water bond.Other MEOR oil releasing mechanisms includesPhysica l oil displacementBiopolymer productionHydrocarbon modificationViscosity modification discriminating plugging of high permeability zones wi load a reservoir is necessary to achieve oil recovery. This is best achieved in MEOR process where cells stimulated to grow deeply in a formation where production of biomass and products will have the greatest impact. If gain occurs primarily at the well bore, then face plugging will result, and no additional oil will be recovered, leaving the reservoir unproductive.The skill of MEORThe micro organisms used in MEOR can be applied to a single oil well or to an entire oil reservoir. They penury certain conditions to survive, so nutrients are often introduced into the well certain intervals. MEOR also requires that water be present. Micro organisms grow mingled with the oil and the well rock surface to enhance oil recovery by the following methodsReduction of oil viscosity Oil is a thick fluid that is quite viscous, meaning that it does not flo w easily. Micro organisms help blend down the molecular structure of crude oil, making it less viscous and easier to recover from the well.Production of carbon dioxide gas As a by-product of metabolism, micro organisms produce carbon dioxide gas. Over time, these gases accumulate and displace the oil in the well, driving it up and out of the ground.Production of biomass When micro organisms metabolize the nutrient they contract for survival, they produce organic biomass as a by-product. This biomass accumulates between the oil and the rock surface, physically displacing the oil and making it easier to recover from the well.Selective plugging Some micro organisms secrete slimy substances called exopolysaccharides to protect themselves from drying out or falling prey to other organisms. The substance helps bacteria plug the pores set in the rocks within the well so that oil may move past rock surfaces more easily. Blocking rock pores to facilitate the faecal matter of oil is real isen as selective plugging.Production of bio surfactants Micro organisms produce slippery substances called surfactants as they breakdown il. Because they are naturally produced by biologic micro organisms, they are referred to as bio surfactants. Bio surfactants act like slippery detergents, part the oil move more freely away from rock and crevices so that it may travel more easily out of the well.If we make a comparison between MEOR and other enhanced oil recovery, then we can see that MEOR is much adoptable, it offers multiple recovery mechanisms, low capital and operating cost, while in other enhanced oil recovery techniques, only a specified technology is applicable also has a high capital and operating cost.TYPES OF MICROBES AND THEIR SELECTIONMEOR has gained much attention in youthful times, but it is worth noting that not all microbes can survive in such conditions as found in an oil well, hence the microbes which are able to withstand these conditions are discussed belo wMicrobes used in MEOR on that point are many types of bacteria used in MEOR, they include aerobic and anaerobic bacteria and are divided on the basis of their need for oxygen. In this project work, the bacteria used were anaerobic from CHP-biogas plant at Ribe in Denmark.Selection of BacteriaThe selection of specific bacteria is considered in this method. on that point are a lot of bacteria available, but the normal conditions for majority of bacteria is 5 % Sodium chloride, optimum temperature of 37 degree Celsius, pH less than seven.Factors affecting growth of bacteriaThere are many factors which affects the growth of bacteria. Some of which are explained in the below common salt The term common salt refers to the amount of fade away salt that are present in water. Sodium chloride is the predominant ions in sea water, the immersion of magnesium, atomic number 20 and sulphate ions are also substantial. High salinity and toxic substances are responsible for limiting the growth of microbes. Halophiles are salt loving microbes which use atomic number 11 chloride and also have complex nutrient requirements. Moderate halophiles can grow anaerobically at temperature greater than 50o C. The salinity in the northern part of Danish oil field is about 40g/l or more. Since salinity too high, formation water is diluted with sea water during injection in the well. In order to perform experimental and laboratory analysis, a sample of produce water is taken so as to make love how much salinity can be controlled therefore microbial gas production has been tested up to 140g/l.Temperature extremum high temperature affects the growth of bacteria, although they need average temperature for growth. Thermopiles are bacteria which are heat loving these bacteria have an optimum growth temperature of 45 o C 80 o C. Their membranes are unusually stable at this extremely high temperature. Thus many important biotechnological processes utilise thermophilic enzymes because of t heir ability to withstand longing heat. So before injecting these bacteria into the reservoir, the temperature of the reservoir should be considered, therefore, selection of the correctly thermophilic bacteria for high temperature is very important.Effect of pH pH is the measure of acidity or alkalinity of a solution. Simply pH is the measure of concentration of hydrogen ions in a solution. It is a measure of the activity of dissolved hydrogen ion. In pure water at 25 o C, the concentration of hydrogen ion equals the concentration of hydroxide ions this is cognize as unbiassed and corresponds to a pH level of 7.0. Solutions in which the concentration of hydrogen ions exceeds that of hydroxyl ion has a pH level lower than 7.0 and are known ad bases. The pH reading of a solution is usually obtained by comparison unknown solution to those of known pH, and there are several slipway to do so. More favourable pH condition for micro organisms is about 7 and very few of them can grow below2 and above 10. Micro organisms capable of living at very low pH are called acidphilies and those which live at high pH are called alkaliphiles.Pressure Extreme pressure affects the growth and metabolism of micro organisms. A pressure lower than 100-200 atm has no effect on microbial metabolism, however, pressure of the range of 500-600 atm have limiting effect on growth of bacteria. The marine floor possesses high pressure. For most MEOR processes barophilic organisms will not be necessary, instead, barotolerant microbes can grow at high pressures, but do not require these high pressures for optimal growth. The ability to grow pressure depends on the heartiness sources available, inorganic salts present, pH and temperature. Adaptation of microbial cultures to higher pressure therefore is possible.Toxic elements Chemicals which have toxic effects on micro organisms are found in some reservoirs. These chemicals include co-surfactant, surfactant, biocides, ethylenediaminetetra acetate, and toluene, many of which are used in various chemical EOR operations. Sodium and Potassium may be exchanged without impairing the growth of micro organisms. Magnesium has higher toxicity than sodium and potassium, but the most toxic formation water are those with high Calcium Chloride (CaCl2), so adaptability should be considered before injecting micro organisms in such toxic environment.The choice of Clostridium TyrobutiricumThousands of bacteria have been investigated for MEOR purpose, but the fermentation bacteria remain the most popular especially Clostridia notes because they produce large volume of gas which include CO2, H2 and CH4. These gases produced, decrease the oil viscosity and increase the pressure in the oil reservoir. fermentFermentation is the process that produces alcoholic beverages or acidic dairy products. In general, fermentation involves the breaking down of complex organic substances into simpler ones. Waste products formed in this way include gas es, ethyl alcohol, butyl alcohol, organic acids, acetone and others. Molasses fermentation generates sinew rich metabolic product, which may react in the final vector decomposition line of sulphate reduction under anaerobic formation condition. With sulphate ion in the formation water, sulphur reduction predominates. Hydrogen sulphide produced is in truth not desirable.The organic acids are formed through fermentation of the molasses by the bacteria in the reservoir do cause a rock dissolving process.Dorben field (Germany), 1982, Dr. WagnerAnother reason for using fermentation bacteria is Dr. Wagner field trail. If we make comparison between Danish north oil field formation and Zechstein evaporates rocks which are similar to the Danish join Sea formation. Dolomite is also similar to Danish north field chalk. governing body temperature is quite similar and of course has a high salinity. Clostridia tyrobutiricum was selected for Dr. Wagners experiment.The characteristics of Dr. Wa gners experiment field are as followsDolomite of Zechstein formationsDepth of 1240mFormation temperature 53 oCHigh salinity formation water, even the fissures and fractures are partially make full with salt.The result of Dr. Wagners MEOR well experimentsWater cut decreased from 80 to 60 %Average annual oil productionBefore microbial intervention 50 tons per month3 months after injection cl tons per month1 year after injection three hundred tons per monthSince all these conditions are similar to Danish North Sea formation and other factors are also same, so we can use fermentation bacteria for MEOR experiment.Adaptation of bacteria to high salinities volume of the bacteria cannot withstand high salinity, from the time of ancient civilization it is known that adding 50 g/l of salt in food continue it from spoiling. This means that fermentation bacteria which normally populate organic substances has a challenge of adaptation in high salinity. The spore forming bacteria like clo stridium form spores in extreme conditions. These conditions allow bacteria to survive but they will not be active and would not be productive. infra extremely high salinities, bacteria undergo osmotic stress which is verbalised in osmotic pressure. osmotic pressure affects the water activity and production of CO2 gas during the fermentation process.OsmosisOsmosis is the passage of water from region of high concentration through a semi-permeable membrane to a region of lower water concentration.Semi permeable membrane are very thin layers of material (cell membrane are semi-permeable) which allow some substances to pass through them and prevent other substances from passing through. Cell membranes will allow small molecules like oxygen, water, CO2, ammonia, glucose, amino acid, etc. to pass through meanwhile, cell membranes do not allow passage of larger molecules like sucrose, starch, protein, etc.Osmotic pressureOsmotic pressure is hydrostatic pressure produced by a difference i n concentration between solutions on the two sides of a surface such as a semi permeable membrane. It was also observed that the bacteria change its morphology. For the case of clostridia it will mean that from rod-shape it turns to cocci-form which is simply the reflection of shrinkage.Potential osmotic pressurePotential osmotic pressure is the maximum osmotic pressure that could develop in a solution if it were separated from distilled water by a selectively permeable membrane. It is the number of solute particle in a unit volume of the solution that directly determines its potential osmotic pressure.Osmotic properties of cellsThe wall of bacteria and emergence plant cells are not completely rigid, and the turgor pressure has been proposed to provide the mechanically skillful force for the expansion of the cell walls during cell growth. The uptake or biogeny of osmotically active solutes causes an increase in the cells, thus providing the necessary tugor pressure for expansion o f the cell walls. Although the suggestion that turgor pressure is the driving force for cell wall expansion would imply that the mechanisms that regulate the osmotic balance of organisms are central to the very process of cell growth.Lipid membranes allow rapid diffusion of water molecules into or out of cells while presenting an effective restriction to most other biological molecules. Membranes that exhibit selective permeability for different substances are called semi permeable, and the osmotic properties of cells derive from this property of the membranes.Thermophyllic and Halophyllic bacteriaThere are bacteria which need high salinities and high temperatures for their growth. In order to investigate and record the conditions of microbes at high salinities and high temperature it is better to know about the bacteria which can withstand on these conditions. Important culture has been given about these type of bacteria is discussed below.A thermopile is an extremophile organis m which survives at relatively high temperatures. Thermophilic (heat-loving) organisms are organism with an optimum growth temperature of 50o C or more, a maximum of up to 70