Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1999-11-30
2001-06-26
Reifsnyder, David A. (Department: 1723)
Liquid purification or separation
Processes
Chemical treatment
C210S766000, C210S768000, C210S774000, C405S128350, C588S253000
Reexamination Certificate
active
06251290
ABSTRACT:
DESCRIPTION
The present invention relates to methods for recovering petroleum-like hydrocarbons from hydrocarbon-containing geological reservoirs, and more particularly to a method for processing hydrocarbon-containing geologic material, including tar sands, oil sands, oil sandstones, and oil shales, to recover petroleum-like hydrocarbons, and especially crude oil, therefrom and to render the rock substrate residues suitable for environmentally-acceptable disposal.
As used herein, hydrocarbonaceous deposit is to be taken to include tar sands, oil sands, oil sandstones, oil shales, and all other naturally-occurring geologic materials having hydrocarbons contained within a generally porous rock-like inorganic matrix.
Tar sands are naturally-occurring geological formations found in, for example, Canada (Alberta). Such sands have potential for yielding large amounts of petroleum. Tar sands are porous sands generally containing substantial amounts of clay and filled with heavy, relatively solid asphaltic hydrocarbons. Most of these tar-like bitumenous materials are residues remaining in reservoir rocks after lighter (lower molecular weight) crude oils have escaped. The largest of the world's tar sand deposits occur in northern Alberta along the Athabaska River. Tar sand layers in this area may be more than 60 meters thick and lie near the surface over a total area of about 50,000 km. They are estimated to contain a potential yield in excess of 1.6 trillion barrels of oil.
Oil shales are related to oil sands and tar sands; however, the substrate is a fine-grained laminated sedimentary rock containing an oil-yielding class of organic compounds known as kerogen. Oil shale occurs in many places around the world. Particularly kerogen-rich shales occur in the United States, in Wyoming, Colorado, and Utah, and are estimated to contain in excess of 540 billion potential barrels of oil.
In the known art of petroleum recovery from hydrocarbonaceous deposits, the high molecular weight asphaltic or kerogenic material may be driven out of the sands, sandstones, or shales with heat. For example, in a known process for recovering kerogen from oil shale, crushed shale is heated to about 480° C. to distill off the kerogen which is then hydrogenated to yield a substance closely resembling crude oil. Such a process is highly energy intensive, requiring a portion of the process output to be used for firing the retort, and thus is relatively inefficient. Also, a significant percentage of the kerogen may not be recovered, leaving the process tailings undesirable for landfill.
Other known processes, for recovering bitumen from tar sands for example, may require the use of caustic hot water or steam. For example, a process currently in use in Canada requires that a hot aqueous slurry of tar sand be mixed with high concentrations of aqueous caustic soda to fractionate the bitumen into lower molecular weight hydrocarbons which may then be separated from the inorganic rock residues and refined further like crude oil. This process has several serious shortcomings. First, it is relatively inefficient, recovering less than about 70% of the hydrocarbons contained in the sands. “Free” hydrocarbons, that is, compounds mechanically or physically contained interstitially in the rock, may be recovered by this process; but “bound” hydrocarbons, that is, compounds electrostatically bound by non-valence charges to the surface of clays or other fines having high electronegative surface energy, are not readily released by the prior art process. In fact, high levels of caustic may actually act to inhibit the desired release of organic compounds from such surfaces. Thus, the prior art process is wasteful in failing to recover a substantial portion of the hydrocarbon potential, and the substrate residue of the process may contain substantial residual hydrocarbon, making it environmentally unacceptable for landfill.
Second, both the aqueous residual and the sand/clay residue are highly caustic and may not be spread on the land or impounded in lagoons without extensive and expensive neutralization.
Third, the caustic aqueous residual may contain high levels of dissolved petroleum, which is non-recoverable and also toxic in landfill. Such residual also has a high Chemical Oxygen Demand (COD), making such residual substantially anoxic and incapable of supporting plant or animal life.
Fourth, oils recovered by the prior art process typically have high levels of entrained or suspended fine particulates which must be separated as by gravitational settling, filtration, or centrifugation before the oils may be presented for refining.
Fifth, because of relatively long settling times required for separation of solid particulates from the aqueous medium and the recoverable hydrocarbons, which typical are highly and stably emulsified as a colloidal suspension, the prior art process is not generally amendable to a continuous-feed operation.
Sixth, the present-day cost of oil recovered from Albertan tar sands by a prior art process requires a substantial Governmental subsidy to match the world spot price of crude oil.
It is a principal object of the invention to provide an improved process for recovering hydrocarbons from hydrocarbonaceous deposits in greater than 90% yield.
It is a further object of the invention to provide an improved process for recovering hydrocarbons from hydrocarbonaceous deposits in greater than 99% yield.
It is a still further object of the invention to provide an improved recovery process which provides a substrate residue which is acceptable under applicable guidelines for landfill disposal.
It is a still further object of the invention to provide an improved recovery process which can recover both free and bound hydrocarbon compounds from geologic substrates and thereby recover a high percentage of all of the hydrocarbons therein.
It is a still further object of the invention to provide an improved recovery process which is substantially less expensive to operate on a per-unit of ore basis than are known treatment processes.
It is a still further object of the invention to provide an improved recovery process which can yield oil at a unit cost competitive with that of well-produced crude oil.
Briefly described, hydrocarbonaceous ore containing bitumen and/or kerogen is crushed or otherwise comminuted to the consistency of sand. The comminuted ore is mixed with water to form a slurry, is heated to between about 60° C. and about 100° C., and is blended with an oxidant in aqueous solution, preferably hydrogen peroxide. Both free interstitial hydrocarbons and those hydrocarbons bound electrostatically to the surfaces of clay-like particles are released from the rock substrate, possibly by an electrophysical reaction in the presence of the oxidant. A portion of the released bitumenous and kerogenic compounds are then cleaved by the oxidant in a controlled Fenton's reaction to yield organic compounds having lower molecular weights which are suitable for refining as oil after separation from the process water phase and the residual rock substrate. The water and rock tailings from the process are substantially free of hydrocarbon contamination and are environmentally suitable for disposal.
REFERENCES:
patent: 4416786 (1983-11-01), Knorre et al.
patent: 5259962 (1993-11-01), Later
patent: 95/30627 (1995-11-01), None
Continuum Environmental, Inc.
Harris Beach LLP
Reifsnyder David A.
LandOfFree
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