HEAVY CRUDE OIL

FIELD OF INVENTION

The present invention relates to a method of enhancing the fluidity of a viscous fluid, and more particularly to a method that is useful for conveying a viscous fluid within a vessel. BACKGROUND OF THE INVENTION

Heavy crude oil is a natural occurring hydrocarbon characterized by its high pour points, high viscosity and low American Petroleum Institute (API) gravity. These properties lead to low mobility in the oil, and are causing difficulties in transporting the oil. Particularly, heating and dilution using solvents are common methods for altering the composition, viscosity or flow properties of the oil prior to the transportation. Cold Heavy Oil Production with Sand (CHOPS), Steam Assisted Gravity Drainage (SAGD), steam or vapour injection, and Huff-and-Puff of heated oil or hot water, are examples of techniques used to alter flow properties of the oil for the production of heavy oil and assist in oil transportation. The techniques generally provide high production yield, but are associated with poor energy efficiencies, and low recovery rate.

Several prior art suggests to disperse heavy crude oil in water to form an oil-in-water emulsion to facilitate the oil transportation in a pipeline. A United States patent application no. 6279653 B1 discloses a process that applies an ultrasonic energy to the heavy crude oil, water or brine and an alkaline chemical to generate a stable low viscosity emulsion. Another method of enhancing heavy crude oil mobility as described in United States patent application no. 3490471 introduces an alkali metal hydroxide and a solubilizing agent comprising pyridine and quinolone to the oil to form an oil-in- water emulsion. Another United States patent application no. 4343323A provides a method of forming an oil-in-water emulsion by contacting the heavy crude oil with deaerated water containing a strong base, and then reacting the emulsion with slaked lime to form a water-in-oil emulsion prior to separating the oil and water. None of the prior art suggests to create a lubrication layer between the heavy crude oil and the pipeline to facilitate conveyance of the oil within a subterranean formation or a pipeline.

SUMMARY OF INVENTION The present invention aims to provide a method of enhancing the fluidity of a viscous fluid constrained to flow within a vessel having a surface which interfaces with the fluid to facilitate conveyance of the fluid within the vessel.

Another objective of the present invention is to provide a method of enhancing the fluidity of a viscous fluid constrained to flow within a vessel having a surface which interfaces with the fluid, by creating an intermediate layer between the fluid and the surface of the vessel, in which the nanoemulsion-induced intermediate layer provides a lubrication effect to enhance the fluidity of the fluid relative to the surface as compared to the fluidity of the fluid relative to the surface in the absence of the intermediate layer.

Further objective of the present invention is to provide a method of enhancing fluidity of a viscous fluid without altering the chemical composition of the viscous fluid. As used herein, the“chemical composition” refers to the chemical makeup of the viscous fluid that determines the properties of the fluid including but not limited to molecular weight, density, viscosity, vapour pressure, boiling point, pour point, specific volume, specific weight, and specific gravity.

At least one of the preceding objects is met, in whole or in part, in which the embodiment of the present invention describes a method of enhancing the fluidity of a viscous fluid constrained to flow within a vessel having a surface which interfaces with the fluid, the method comprising the introduction into the fluid of a substance which reacts with the surface of the vessel and/or the fluid so as to create an intermediate layer between the fluid and the surface of the vessel which causes the fluidity of the fluid relative to the surface to be enhanced as compared to the fluidity of the fluid relative to the surface in the absence of that substance.

In one preferred embodiment, the substance is adsorbed onto the surface of the vessel to induce formation of the intermediate layer.

Preferably, the substance is a nanoemulsion, a microemulsion or a combination thereof.

In a preferred embodiment, the substance comprises an aqueous phase, a non-aqueous phase, a surfactant and a compound having Chemical Structure I, in which R ₁ , R ₂ , R ₃ and R ₄ are linear, branched or aromatic carbon-containing substituents having 2 to 26 carbon atoms and n is integer ranges from 1 to 100, wherein each of the substituents comprises an alkyl group, carbonyl group, a carboxylic group, an amine group, or an amide group.

In another preferred embodiment, the substance comprises the aqueous phase in 0.5 to 40% by weight of total composition, the non-aqueous phase in 15 to 90% by weight of total composition, the surfactant in 2 to 60% by weight of total composition, and the compound having Chemical Structure I in 1 to 30% by weight of total composition.

Preferably, the substance further comprises a co-surfactant in 1 to 30% by weight of total composition. As used herein, a“co-surfactant” refers to a compound that participates in aggregation of molecules into a micelle but does not aggregate on its own. Suitable co-surfactant useful with the composition of the present invention is selected from the group consisting of C3 to C18 alcohols, C3 to C18 alkyl lactates, lecithin, C3 to C18 fatty acids, alkane diols, amino acids, and any mixtures derived thereof. In an embodiment, a co-surfactant may be included in the composition of the present invention in an amount ranging from about 1 to 30% by weight of total composition. More particularly, the surfactant and the co-surfactant can be used in a ratio of 20: 1 to 1 :20. In another preferred embodiment, the intermediate layer comprises a substantially immiscible top layer comprising the surfactant and the aqueous phase.

In another preferred embodiment, the viscous fluid comprises a viscosity ranging from 4cps to 400,000 cps

Preferably, the viscous fluid comprises an aqueous phase.

Preferably, the viscous fluid is a heavy crude oil. BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of facilitating an understanding of the invention, there is illustrated in the accompanying drawing the preferred embodiments from an inspection of which when considered in connection with the following description, the invention, its construction and operation and many of its advantages would be readily understood and appreciated.

Figure 1 illustrates an embodiment of the present invention in creating an intermediate layer between a viscous fluid constrained to flow within a vessel and a surface of the vessel which interfaces with the fluid.

DETAILED DESCRIPTION OF THE INVENTION

One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objects and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiment described herein is not intended as limitations on the scope of the invention.

The present invention discloses a method of enhancing the fluidity of a viscous fluid constrained to flow within a vessel having a surface which interfaces with the fluid, the method comprising the introduction into the fluid of a substance which reacts with the surface of the vessel and/or the fluid so as to create an intermediate layer between the fluid and the surface of the vessel which causes the fluidity of the fluid relative to the surface to be enhanced.

The“viscous fluid” refers to a hydrocarbon fluid extracted from a subterranean formation that cannot flow easily under a normal reservoir condition. The viscous fluid is preferably an oil, and more preferably a heavy crude oil. Particularly, the fluid contains high amount of asphaltenes, wax and resins, high ratio of aromatics and napthenes to linear alkanes, and a substantial amount of nitrogen, sulphur, oxygen and heavy metals. More particularly, the viscous fluid has an American Petroleum Institute (API) gravity lesser than 20°, a pour point of greater than 24°C, and a viscosity ranging from 4 cps to 400,000 cps. The viscous fluid can be an emulsion, possibly comprising an aqueous phase. Preferably, the viscous fluid comprises a predetermined amount of the aqueous phase. As described herein, the terms“aqueous phase” and“water” may be used interchangeably. The“vessel” refers to a means for holding the viscous fluid, and more particularly to a means for fluid communication of the fluid between a first location and a second location, in which the location can be a source of the fluid and/or a facility for processing the fluid. The material for use herein is preferably a material with high surface energy, and more preferably a metal. The vessel may optionally comprise a heating feature.

In a preferred embodiment, the substance comprises an aqueous phase in 0.5 to 40% by weight of total composition; a non-aqueous phase in 15 to 90% by weight of total composition; a surfactant in 2 to 60% by weight of total composition; and a compound having Chemical Structure I in 1 to 30% by weight of total composition, in which R ₁ , R ₂ , R ₃ and R ₄ are linear, branched or aromatic carbon-containing substituents having 2 to 26 carbon atoms and n is integer ranges from 1 to 100, wherein each of the substituents comprises an alkyl group, carbonyl group, a carboxylic group, an amine group, or an amide group. Particularly, the surfactant is selected from the group consisting of an anionic surfactant, a cationic surfactant, a zwitterionic surfactant, a polymer, a silicone, and a fluorosurfactant. Preferably, the substance is a nanoemulsion, a microemulsion or a combination thereof, and more preferably a water- in-oil emulsion, that is cost-effective and environmental friendly. Preferably, the substance further comprises a co-surfactant in 1 to 30% by weight of total composition. Fluidity of the viscous fluid is enhanced by the method, in which the fluidity is enhanced without altering the chemical composition of the fluid. Particularly, the method comprises the introduction of the substance to induce formation of the intermediate layer between the fluid and the surface of the vessel, such that the fluidity of the fluid relative to the surface is enhanced as compared to the fluidity of the fluid relative to the surface in the absence of that substance. The formation of the intermediate layer is induced via an adsorption process, in which the top layer of the intermediate layer is stabilized by the surfactant. Preferably, the fluidity is enhanced in a temperature ranging from 25 to 180°C.

In a preferred embodiment, the substance acts independently to induce formation of the intermediate layer. The substance is introduced into the fluid within the vessel and dispersed therein in a form of droplets as shown in Fig. 1 A. Preferably, the droplets are nanoscopic droplets having sizes lesser than 500 nm. Nanoemulsion droplets that has low interfacial tension tends to partitioning at an interface of the fluid and the surface of the vessel to form a preform layer as shown in Fig. IB. Subsequently, water droplets inside the nanoemulsion are dispersed and remain adsorbed to form the intermediate layer as shown in Fig. 1C. In another preferred embodiment, the substance reacts with the surface of the vessel and the fluid. Particularly, the substance reacts with the aqueous phase of the fluid, and causes the aqueous phase to coalesce to one another. Once the substance is dispersed inside the fluid, the surfactants partition at the oil-water interface and reduce the interfacial tension between emulsified water droplets within the fluids. The water molecules from the emulsified fluids will then aggregates together to further coalescence, in which the coalescence can be displaced out from the fluid and adsorbed onto the high surface energy surface upon reaching a certain size. The water is displaced out from the fluid and adsorbed onto the surface of the vessel to form the intermediate layer having an aqueous environment. As such, the intermediate layer creates a partial or complete non-wet barrier on the surface of the vessel, therefore allowing the fluid to be easily transported or mobilized by means of pressure differentiation.

The substance can be introduced directly into the fluid or to the vessel as a coating for use therein. The introduction can be conducted via various well control techniques, such that fluidity of the fluid relative to the surface of the vessel is enhanced. In an exemplary embodiment, the substance is introduced to a subterranean formation directly using a bull heading method by pumping the substance into a wellbore in addition to applying an appropriate amount of pressure that is sufficient to introduce the substance. In another exemplary embodiment, the substance is introduced to a wellbore via a coil tubing method, in which location of contact between the substance and the fluid is manageable.

In one mode of action, the method comprises subjecting a native form of the substance to the viscous fluid for enhancing fluidity of the fluid within the vessel. In another mode of action, the substance can be further diluted with water, seawater, or brine with sodium, potassium, calcium, magnesium, zinc or ammonium salt, where the amount of organic or inorganic salt for use therein can be adjusted to balance the hydrostatic pressure to suit an application.

The formation of the intermediate layer may occur spontaneously without assistance of a mechanical aid such as an ultrasonic means or an agitating means. The method preserves chemical composition of the viscous fluid within the vessel, in which the substance is chemically unreactive towards the fluid and reacts only with the aqueous phase therein. As such, a native high molecular weight fluid can be delivered to a facility, and broadened the process-ability of the fluid. In addition, the method may dewater the viscous fluid prior to a refining process. It is to be noted that the intermediate layer acts as a lubrication layer between the surface and the fluid, such that the fluid transportation within the vessel can be enhanced as compared to a similar setup in absence of the substance. Optionally, the method may further comprise the introduction of a secondary fluid to provide a driving force for conveying the viscous fluid within the vessel.

The present disclosure includes as contained in the appended claims, as well as that of the foregoing description. Although this invention has been described in its preferred form with a degree of particularly, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangements of parts may be resorted to without departing from the scope of the invention.