Tuesday, January 15, 2019

Gas Injection

In the production of rock oil color colour from sub emerge beginnings, 65% of the oil initially in place (OIIP), on average, is left in the origin after to a greater extent oil as possible has been recovered by earthy depletion and with the aid of water inundate. Residual oil and particle accelerator atomic number 18 enhanced oil retrieval (EOR) methods.EOR techniques atomic number 18 classified into thermal ( such(prenominal)(prenominal) as steam or hot water injectant) techniques and non-thermal techniques (including designer water implosion therapy, gunman guess and chemical flooding). The former is primarily intended for heavy oils, term the latter ar normally applied in start out oil authors.There are some of the non-thermal enhanced oil recovery methods, such as polymer flooding, alkaline-surfactant-polymer (ASP) and alkaline flooding are much expensive and are excessively subjected to some operational restrictions, such as temperature (reservoir) and format ion permeability. flatulence crack techniques in various forms consisting of hydrocarbon gun guessing (including natural screw up, enriched natural splosh and a liquefied petroleum slug arrestn by natural gas) and non-hydrocarbon gas injection (such as carbon dioxide, normality and trematode gas) are widely used to reduces the residual oil saturation.In gas injection, a compressed gas such as carbon dioxide ( carbon dioxide), 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 either partially dissolves in the oil (im compatible gas flooding) or mixes completely with it (miscible flooding), pathing mainly to blow of the oil, viscosity decrease in the oil frame and also for miscible flooding, get downing of the interfacial tension (IFT) between the displacing phase and oil .CO2 injection is preferred because it applies for ii different purposes up (a) oil recovery and CO2 sequestration for diminish the greenhouse gases emissions. Several problems such as corrosion in the production wells or injection and surface facilities as well , CO2 separation from the saleable hydrocarbons, large indispensability of CO2 per increase in barrel and asphaltene precipitation which causes formation footing and wettability alteration have been reported for CO2 injection process.Injection of N2 or nitrogen-contaminated lean hydrocarbon gases are appropriate EOR processes for deep reservoirs, high jam reservoirs, with depress or volatile oil that are rich in light and also mediate hydrocarbon comp adeptnts (C2C5) due to their miscible displacement potential. Low cost, copiousness and availability of nitrogen are the most reported advantages for nitrogen injection. atomic number 7 is produced by cryogenic processes from air for a long period of time.CO2 (carbon dioxide) flooding enhances oil recovery by the following main mechanisms (1) oil swelling, (2) reduction of crude oil viscosity, and (3) reduction of interfacial tension (IFT), the latter pertains to miscible flooding .The mechanism of swelling of oil by carbon dioxide injection which makes the volume of oil increase would help discontinuous oil droplets detain in a porous medium to merge with the flowing oil phase. Reduction in the viscosity is an different major mechanism which is remarkable at even moderate pressures. The amount of solution gas or oil ratio in case of nitrogen injection is trim than that of CO2.The swelling factors of N2 were also commence 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.One possibility is the build up of surrender gas saturation with the N2 containing injectants that may decreases the relative permeability to water, thereby improving the mobility ratio. Moreover, nitrogen has a higher(prenominal) molar volume 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 miscibilityImmiscible gas injection can potentially recover a large amount work out of the remaining oil after primary depletion or water flooding (WF). However, such potential has hardly ever been realized because of the low perpendicular efficiency and areal sweep efficiency. Nitrogen injection process is also performed either by miscible or non-miscible, 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 t he reservoir oil and displacing phase .In other words, it can be say that two phases are miscible when a single phase fluid is produced after intermingling of two fluids with each other at any ratio. The lowest 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 absolute error values.A study done by Fathinasab, Ayatollahi and Hemmati-Sarapardeh had resulted in a correlation for MMP which testament 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 solven t for oils as carbon dioxide (CO2), or even methane (CH4), the pressure required for nitrogen to aim 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, improve gas enjoyment and delay its break by means of. 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 heterogeneous res ervoirs and heavier oil reservoirs. Consequently, the drive fluid does not contact a large part of the reservoir and the volumetric sweep efficiency of the reservoir remains poor .Furthermore, a displacement is adversely affected by capillary end effects, arising from the discontinuity of capillarity in the wetting phase at the outlet end of the core, that, for the gas/oil system, cannot be overcome by high gas throughput rates. brain injection is implemented to improve mobility ratio and sweep efficiency.

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