Enhanced oil recovery
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29-12-2010, 10:41 AM
EOR report.docx (Size: 601.4 KB / Downloads: 134)
Enhanced Oil Recovery is a generic term for techniques for increasing the amount of crude oil that can be extracted from an oil field. Using EOR, 30-60 %, or more, of the reservoir's original oil can be extracted compared with 20-40% using primary and secondary recovery. Its purpose is not only to restore formation pressure, but also to improve oil displacement or fluid flow in the reservoir.
Enhanced oil recovery is achieved by gas injection, chemical injection, microbial injection, or thermal recovery (which includes cyclic steam and fire flooding).Enhanced oil recovery is also called improved oil recovery or tertiary recovery and it is abbreviated EOR. During the life of a well, the cost of producing an additional barrel of oil is higher than the price the market will pay for the barrel; early stages EOR was not used but now due to low probability of locating significant new oil fields EOR techniques are used.
Enhanced oil recovery refers to a variety of industry methods and oil production systems implemented to increase production at oilfields with declining rates of produced oil (in barrels) or oilfields where operations had ceased due to unprofitable production rates.
Although EOR technologies frequently utilize some existing oilfield infrastructure, specialized products and equipment are frequently introduced in order to accomplish increased oil production through an EOR method. EOR follows primary and secondary oil recovery methods.
A defining feature of EOR technologies is their energy-intensive operation, or the additional energy required to recovery of remaining oil. The input of additional energy for continued recovery inevitably results in higher costs for EOR than primary or secondary oil recovery methods.
Enhanced oil recovery (EOR) technologies are becoming increasingly significant to global oil supply by increasing or reviving oil production at reserves or oilfields depleted of more easily recoverable oil through primary or secondary oil-recovery methods and technologies.
Enhanced Oil Recovery (EOR) has been getting a lot of attention lately in the media. There have been some who claim EOR will save the world from the pending Peak Oil anarchy and others who claim EOR, through carbon sequestration, will save the planet from the devastating effects of Global Warming. The purpose of this report is to give some basic insights into EOR, its benefits and limitations, and not to enter into the geopolitical debates.
Enhanced oil recovery is achieved by gas injection, chemical injection, microbial injection, or thermal recovery which includes cyclic steam, steam flooding, and fire flooding.
CONVENTIONAL OIL RECOVERY
EOR is an imprecise term that historically has been used to describe the third step (tertiary recovery) in oil and gas production The term “improved oil recovery” (IOR) has come into use to describe all recovery methods other than natural (primary) production, reserving the designation EOR for those processes beyond simple water flood and gas flood—basically, recovery by injection of anything not originally in the reservoir.
Traditional primary and secondary production methods typically recover one third of oil in place, leaving two thirds behind. The reasons for this are not difficult to understand. During the life of a well, there is always a point at which the cost of producing an additional barrel of oil is higher than the price the market will pay for that barrel. Production then halts. Under normal circumstances, the well is abandoned, with 70% of the oil left in the ground.
The first of hydrocarbon production in which natural reservoir energy such as gas drive, water drive or gravity drainage displaces hydrocarbon from the reservoir into the well bore and up to the surface.
Primary recovery is also called primary production. The reservoir pressure is higher than bottom hole pressure, by this hydrocarbon is recovered. It is called natural flow recovery. During course of production, reservoir pressure decreases. An external rod pump is used increase the differential pressure thereby increases in hydrocarbon production. It is called artificial lift recovery.
Primary recovery, in long accepted practice, is defined as production by natural reservoir pressure, or pumping, until depletion. Until the early 1940s, economics dictated when a well was to be plugged and abandoned, usually after recovery of 10 to 25% of original oil in place (OOIP).
While the underground pressure in the oil reservoir is sufficient to force the oil to the surface all that is necessary is to place a complex arrangement of valves on the wall head to connect the well to a pipeline network for storage and processing.
Secondary recovery methods are generally used to re-pressure the reservoir and drive out some of the remaining oil. Because water is usually readily available and inexpensive, the oldest secondary recovery method is water flooding, pumping water through injection wells into the reservoir. The water is forced from injection wells through the rock pores, sweeping the oil ahead of it toward production wells. This is practical for light to medium crudes. Over time, the percentage of water in produced fluids-the water cut-steadily increases. Some wells remain economical with water cut as high as 99%. But at some point, the cost of removing and disposing of water exceeds the income from oil production, and secondary recovery is then halted.
Extensive waterflooding, which began in the 1940s, within a few decades became the established method for secondary oil recovery, usually recovering about another 15% of OOIP. On average, about one-third of OOIP is recovered, leaving two-thirds, or twice as much oil as is produced, in the ground after secondary recovery.
Another recognized secondary recovery technique is injection of a hydrocarbon based gas into an existing gas cap or directly into the oil itself. Gas may be injected over a considerable period of time-up to a year-while producing wells are shut in, until reservoir pressure is restored and production resumed. Another method is injection of gas to sustain pressure during production. Gas injection requires a nearby source of inexpensive gas in sufficient volume.
While waterflooding is effective in nearly all reservoirs, no single EOR technique is a cure-all. Most reservoirs are complex, as are most EOR processes. Efficient reservoir management treats EOR as a high-cost, high-risk but critical component of a comprehensive plan that spans primary recovery through abandonment.
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29-12-2010, 10:48 AM
BINU B PILLAI
ENHANCED OIL.pptx (Size: 1.17 MB / Downloads: 91)
Enhanced oil recovery(E.O.R) is technique for increasing the amount of crude oil extracted from the oil field.
Efficiency of E.O.R is more than 30-60%
where other techniques have 20-40% efficiency.
E.O.R is achieved by gas injection, chemical injection, microbial injection and thermal recovery
Used for recovering heavy oils.
Principle: Increasing the oil temperature will reduce the viscosity.
Steam is injected into the well
Production of heat directly within the reservoir by burning some of the oil in place
Fastest growing E.O.R process.
A solvent is mixed with residual oil to overcome capillary force and increase mobility.
Solvents include L.P.G,N2,CO2,Alcohol.
Air cannot be used to re-pressurize the reservoir because oil will easily catch fire.
Factors affecting recovery rate are pressure, depth, temperature, oil gravity and viscosity of solvent should be less than oil.