cryogenic-nitrogen injection
Post on 19-Jun-2015
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(NITROGEN INJECTION FOR RESERVOIR ENHANCED OIL RECOVERY.)
Emerging Applications in Cryogenics
The life of an oil well goes through three distinct phases
Primary recovery Secondary recovery Tertiary recovery
Primary recovery
Secondary recovery
Tertiary recovery
Enhanced Oil Recovery (EOR) they can substantially improve
extraction efficiency Much of these oils would be
recovered by various EOR methods which involve the injection of a fluid, or series of fluids
Three major EOR methods
Thermal injection Chemical injection Gas injection
Thermal injection
Chemical injection
Gas injection
Natural gas -limited availability -increasing value of natural gas Inert nitrogen-less expensive substitutes-provides a higher reservoir displacement
volume per standard volume of nitrogen-provides the lowest volume requirement for
pressure maintenance. -non corrosive.
Cryogenic processes
can produce 99.999% pure nitrogen Cryogenic processes can produce
very pure end products the most cost-effective choice Are more energy efficient
Non-cryogenic processes
employ membranes or adsorbents (PSA/VPSA) to remove the unwanted components of air
They produce nitrogen which is typically 95 to 99.5% oxygen-free
Non-cryogenic plants are less energy efficient than cryogenic plants
Non-cryogenic plants are relatively quick and easy to start up
The cost of nitrogen is depending upon the pressures, quantities and location
Because of increasing cost of natural gas, nitrogen injection is becoming more popular and attractive
In 1983-over 500 million cubic feet per day was being injected into thirty oil or gas reservoir
In 1985-becomes 600 million cubic feet per dayIn 1990-this number grew to 800 million cubic
feet per day in forty oil gas reservoir
EOR METHODS
With varying degrees of success, for the recovery of light and heavy oils.
Two major types of EOR methodThermal methods -supply heat to the reservoir, and vaporize
some of the oil. -the major mechanisms involve a large
reduction in viscosity, and hence mobility ratio.
-best suited for heavy oils and tar sands.
Non-thermal methods -are best suited for light oils.-applicable to moderately viscous oils,
which are not suitable for thermal methods
Objective:Lowering the interfacial tension and
improving the mobility ratio
There are two types of non-thermal EOR gas injection
miscible gas injection -the gas is injected at or above
minimum miscibility pressure immiscible gas injection-flooding by the gas is injected below
MMP
Comparison of nitrogen with other gas injectant
Hydrocarbon gas-require less treatment than other
gases-a corrosion problem-increasing natural gas priceMajor factor limiting CO2 injection-availability-the cost to build pipelines to carry
Advantage of carbon dioxide flooding
-miscibility can be attained at low pressures
-useful over a wider range of crude oils than hydrocarbon
Disadvantage of using CO2-availability of carbon dioxide resources-transportation cost-poor sweep and gravity segregation
and corrosion
Nitrogen-most available and cheapest universal
gas-no pipeline are required-no incremental cost and required for
corrosion control
Nitrogen application for EOR In 1970- it was first introduced In 1970 to 1977-almot all of the
nitrogen for the EOR projects was taken from onsite inert gas plants
In 1980-most of the EOR projects was supplied by onsite air separation plants
Offshore Cantarell oilfield in the gulf of Mexico
The largest oilfield in Mexico and one of the largest in the world
PEMEX heavy oilfield Have high productivity due to
presence of a gigantic natural gas cap
Rank second fastest producing oil field in the world behind Ghawar field in Saudi Arabia
Cantarell oilfield
Factor affecting the cost of nitrogen
The cost of energy necessary to produce and compress nitrogen
The air compressors for generating nitrogen can be operated with motors, gas turbines or gas diesel engines
Membrane produced nitrogen can be used in plants where natural gas is unavailable
Advantage of a membrane plant-compactness-simplicity-reliabilityResulting is low capital cost at smaller
capacitiesAnd moderate purities
CONCLUDING REMARKS: Recent advances in technology and the current
economic climate have resulted an increased interest in EOR, especially [N.sub.2] gas injection in the petroleum reservoirs for improved recovery. While the use of Thermal and Chemical EOR methods are decreasing, Gas injection method in EOR is increasing. Because cryogenic air separation plants can be constructed at or
near the field and no pipelines are required, nitrogen gas injection is rapidly increasing both in onshore and offshore application for reservoir enhanced oil recovery. The inert and non-corrosive nature makes it a preferred choice over other gases (i.e. [CO2.sub.2], Natural gas etc.). The long term supply security of nitrogen also makes preferable and reliable than other unsecured gases.
Nitrogen injection is believed to yield high recovery of the lightest hydrocarbon components. Nitrogen use in the oil field continues to grow as new opportunities are recognized, the demand being mainly satisfied with large scale cryogenic nitrogen plants. Perhaps the greatest task of the cryogenic industry is to develop more cost effective nitrogen producing plants and means for its effective injection to the reservoirs. In the mean time the Petroleum Industry needs to study the long term effect of Nitrogen on the reservoirs, including determining any side effects the nitrogen injection may have on the sustainability of the enhanced recovery. One important factor may be the study of the effect of nitrogen purity, as well as consideration for injection of a mixture of gases vs. pure nitrogen.
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