CBE 555: Chemical EngineeringConnections: Impact of Chemical Engineering on the Outside World Tertiary Oil Recovery Steve Ng Kim Hoong 16 October 2007

Outline of This Presentation Reasons for supporting tertiary oil recovery Primary Oil Recovery Secondary Oil Recovery Tertiary Oil Recovery - Thermal Processes - Miscible Processes - Chemical Processes - Biological Processes

 $86 per barrel of crude oil  Primary oil recovery – can only recover 10 percent of a reservoir’s original oil in place  Secondary oil recovery – 20 to 40 percent  Tertiary oil recovery – 30 to 60 percent  Undeveloped domestic oil resources still in the ground total more than 430 billion barrels. Why are we doing this??

Primary Oil Recovery The initial stage of producing oil from a reservoir Use natural forces such as - expansion of oil, gas or both - displacement by naturally pressurized water - drainage from a reservoir in high elevation to a well in lower elevation - artificial techniques (pumps)

Secondary Oil Recovery Injection of fluids in a series of wells to force oil into another series of wells (essentially augmenting the natural forces used in primary methods) Waterflooding

Thermal Processes Viscosity is a measure of a liquid’s ability to flow High viscosity of oil makes it difficult to flow Reduce the viscosity with high temperature Steam Injection - Cyclic steam injection - Steam drive

Cyclic Steam Injection High pressure of steam (or steam and hot water) injected into well for days/weeks Injection is stopped and the reservoir is “soaked” Well is then allowed to backflow to surface Condensed steam/ hot water vaporizes to drive oil out When production is low, process is repeated “Huff and Puff” method

Steam Drive “Steam flooding” Same method as water flooding Continuous injection of steam (or steam and hot water) A reservoir is developed with interlocking patterns of injection and production wells Series of zones developed as the fluids move from injection wells to production wells

Miscible Processes Injected fluid dissolves the oil that it contacts Variety of fluid: - Alcohol - Carbon dioxide - Petroleum hydrocarbons (propane, propane-butane) - Petroleum gasses (ethane, propane, butane, pentane) Fluid selectivity depends on the type of reservoir and crude oil Expensive fluid (supplementary process to recover fluid or use it sparingly) “Slug” – 5% to 50% of reservoir volume pushed through by gas/water brine or chemically treated brine

CO 2 Enhanced Oil Recovery All the petroleum hydrocarbons are expensive (not viable in economic sense) CO 2 is cheap and widely available (mostly use natural CO 2 deposits) Complete mixing depends on reservoir temperature, pressure, chemical nature and density of oil Generally, it’s deeper than 1200m and oil lighter than 22 0 API CO 2 is stable in supercritical state (6.9 MPa and 31 0 C) Injected CO 2 will diminish the interfacial tension between itself and the crude oil

Chemical Processes Involved the usage of surfactant/polymer, polymer, alkaline flooding Surfactant/polymer flooding: - microemulsion/micellar flooding - detergent-like material injected to modify the oil interactions with its surroundings - emulsify/partly dissolve oil - high cost, small volume

Polymer flooding - a chemically augmented waterflood - polyacrylamides/polysaccharides - increase effectiveness of water in displacing oil Alkaline flooding - sodium hydroxide, sodium silicate, sodium carbonate - react with constituents in the crude oil or rock/crude oil interface - detergent-like material to reduce the ability of the formation to retain oil

Biological Processes Utilize microbes to enhance oil recovery Occupy pore spaces to release trapped oil and reduce water cut Microbial response: - larger - shrink - oleophilic - attach and surround oil droplets - deform droplets to form smaller droplets - smaller droplets able to escape pore spaces - byproduct of metabolism (CO 2 and biomass) - biosurfactants (slimy substances – exopolysaccharides) - Xanthomans campestris bacteria (Xantan) Reservoir response: - microbes attached to water and oil droplets move faster through high permeable sections of the field (thief zones). This combination and fast flow creates a natural emulsion only in the thief zones. - thief zones are temporarily blocked - water is diverted to unswept areas of the field, thus increasing sweeping efficiency

Case Study: Beatrice Field, North Sea, England The Beatrice Field is in a steep North Sea production decline Scheduled to be abandoned in Applied the microbial enhanced oil recovery (Titan Process) from Oil production scheduled to decline to 5000 bopd (now producing bopd) 5.5 million barrels of excess oil was produced

REFERENCES tml Enhanced Oil Recovery Potential in the United States, Congress of the United States, Office of Technology Assessment, January 1978, #PB Enhanced Oil Recovery Scoping Study, A. Amamath, 1999

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