Gas Injection

In the production of petroleum from submersed authors, 65% of the embrocate initially in place (OIIP), on honest, is left-hand(a) in the reservoir after more rock oil as feasible has been recovered by natural depletion and with the aid of irrigate flooding. Residual oil and tout are enhanced oil recovery (EOR) methods.EOR techniques are class into thermal (such as steam or hot water jibe) techniques and non-thermal techniques (including antecedent water flooding, gaseous state crack and chemical flooding). The former is primarily mean for heavy oils, while the latter are normally applied in light oil reservoirs.There are some of the non-thermal enhanced oil recovery methods, such as polymer flooding, alkaline-surfactant-polymer (ASP) and alkaline flooding are a lot expensive and are also subjected to some operational restrictions, such as temperature (reservoir) and formation permeability. gasolene shooting techniques in various forms consisting of hydro snow gas inj ection (including natural gas, en prosperoused natural gas and a liquefied petroleum poking driven by natural gas) and non-hydrocarbon gas injection (such as carbon dioxide, northward and good fortune gas) are widely used to reduces the residual oil saturation.In gas injection, a compressed gas such as carbon dioxide (CO2), natural gas (consisting primarily of methane, CH4), nitrogen (N2), or flue gases are injected into the reservoir to displace oil toward the production wells. The injected gas every partially dissolves in the oil ( immiscible gas flooding) or mixes completely with it (miscible flooding), lede chief(prenominal)ly to swelling of the oil, viscosity reduction in the oil configuration and also for miscible flooding, lowering of the interfacial emphasis (IFT) between the displacing configuration and oil .CO2 injection is preferred because it applies for two different purposes ameliorate oil recovery and CO2 sequestration for diminish the greenhouse gases emissio ns. several(prenominal) problems such as corrosion in the production wells or injection and surface facilities as well , CO2 separation from the marketable hydrocarbons, colossal requirement of CO2 per increase in barrel and asphaltene downfall which causes formation damage and wettability alteration have been inform for CO2 injection process.Injection of N2 or nitrogen-contaminated tumble hydrocarbon gases are appropriate EOR processes for deep reservoirs, game pressure reservoirs, with light or volatile oil that are rich in light and also intermediate hydrocarbon components (C2C5) callable to their miscible shift key potential. Low cost, abundance and availability of nitrogen are the most reported advantages for nitrogen injection.Nitrogen is produced by cryogenic processes from air for a considerable period of time.CO2 (carbon dioxide) flooding enhances oil recovery by the following main mechanisms (1) oil swelling, (2) reduction of in the buff oil viscosity, and (3) r eduction of interfacial tension (IFT), the latter pertains to miscible flooding .The mechanism of swelling of oil by carbon dioxide injection which makes the majority of oil increase would help noncontinuous oil droplets trapped in a porous medium to mix with the flowing oil phase. Reduction in the viscosity is another major(ip) mechanism which is significant at even moderate pressures. The amount of theme gas or oil ratio in case of nitrogen injection is lower than that of CO2.The swelling factors of N2 were also lower than those of CO2 due to nitrogen lower solubility in the oil. If the pressure is low (lower than 3 MPa), solubility of nitrogen and flue gas is negligible. The viscosity reduction due to N2 injection is much lower than that of carbon dioxide injection. Addition of N2 to the injection gas implies that some mechanisms other than swelling and viscosity reduction are important. wizard possibility is the buildup of free gas saturation with the N2 containing injectants that may decreases the relative permeability to water, thereby improving the mobility ratio. Moreover, nitrogen has a eminenter(prenominal) molar glitz than CO2 which tells that one mole of nitrogen displaces a higher volume of gas than that of CO2. Therefore, N2 is more favorable in terms of displacement volume. So that our focus in this study is on N2.Literature review on N2 miscibilitynon-miscible gas injection can potentially recover a mountainous amount fraction of the remaining oil after primary depletion or water flooding (WF). However, such potential has hardly ever been recognize because of the low vertical efficiency and areal mop efficiency. Nitrogen injection process is also performed either by miscible or immiscible, depending on the injection pressure of N2, reservoir temperature and reservoir oil composition. Miscibility is theoretically defined as the conditions at which there is no interface between the reservoir oil and displacing phase .In other words, it c an be suppose that two phases are miscible when a single phase mentally ill is produced after intermingling of two gass with each other at any ratio. The utmost operating pressure, at reservoir temperature, at which miscibility is achieved between reservoir fluid and injection gas is termed as the minimum miscibility pressure (MMP) . There has been a few correlations in the literature for N2 MMP estimation producing different average coercive error values.A study done by Fathinasab, Ayatollahi and Hemmati-Sarapardeh had resulted in a correlation for MMP which will be used for pure N2, nitrogen mixtures and lean gases. The developed correlation yields the least error and is a function of average critical temperature of the injection gas, reservoir temperature, C7 + fraction molecular weight of crude oil, volatile components (mole fraction) and intermediate components (mole fraction) of crude oil.Since N2 is not as good a solvent for oils as carbon dioxide (CO2), or even methane ( CH4), the pressure indispensable for nitrogen to become miscible with any oil should be greater than that for methane which, in turn, is higher than CO2 . This especially makes nitrogen attractive for highly undersaturated reservoirs at immiscible conditions.Literature review on challenges in gas flooding and a solutionThe major technical challenge of immiscible gas injection is to maintain proper sweep efficiency of the injected gas, alter gas utilization and delay its breakthrough. These result from a combination of gravity override and gas channeling through high permeability streaks in the formation. Gas segregation, channeling and fingering through high permeability streaks are inherent in any gas injection they are due to the excessively higher mobility and far lower density of gas (displacing phase) compared to oil or water (displaced phase).Unfavorable mobility ratios lead to even more severe channeling in tangled reservoirs and heavier oil reservoirs. Consequently, the d rive fluid does not contact a large part of the reservoir and the volumetric sweep efficiency of the reservoir clay poor .Furthermore, a displacement is adversely affected by capillary vessel end effects, arising from the discontinuity of capillarity in the wetting phase at the proceeds end of the core, that, for the gas/oil system, cannot be overcome by high gas throughput rates. WAG injection is implemented to improve mobility ratio and sweep efficiency.