Hydrocarbon products from viscous tar sands are recovered by continuously injecting a hot solvent containing relatively large amounts of aromatics into the formation. Alternatively, steam and solvent are cyclically and continuously injected into the formation to recover the values. The last stimulation is by steam so that solvent is recovered. A third alternative is to continuously inject a mixture of steam and solvent vapors and liquid into the formation. In all cases, the solvent, except perhaps for startup, is produced at the site, as in a conventional topping unit, which alternatively is combined with a conventional visbreaking or reforming unit to increase the volume and/or aromaticity of the solvent produced.
Bitumen is recovered from a subterranean formation of heavy oil sands traversed by at least one injection well and at least one associated production well in fluid communication with each injection well. Air in admixture with a heating fluid selected from the group consisting of low quality steam, hot water, or mixtures thereof, and an alkalinity agent are injected into the formation by way of each injection well. The subterranean heavy oil sands are thereby raised to a temperature in the range of about 200.degree. to 350.degree. F. A portion of the bitumen at reduced viscosity is oxidized without burning to produce additional petroleum acids which are neutralized to form emulsifying agents. The condensed steam and/or hot water contacting the bitumen form with it a bitumen-water emulsion. By pressure from the injected mixture of air and heating fluid, the resulting bitumen-water emulsion is then recovered from each production well. Demulsification takes place at the surface and bitumen, hot water, and sand are separated. Increased oil recovery efficiency may be obtained by pressure controlled cycles.
In a cyclic method of solvent stimulation of a single oil well penetrating a viscous crude oil-containing formation, the well is first produced and a portion of the produced crude oil is subjected to a visbreaking operation to produce a hot visbroken crude oil having reduced viscosity. Production is terminated and a predetermined amount of the hot visbroken produced crude oil is injected into the formation via the well as a solvent, the formation is allowed to undergo a soak period, and the well is returned to production. Thereafter, production may be continued until the percentage of visbroken crude oil in the produced fluids is less than 12 percent and the above cycle may be repeated.
A process for the in situ recovery of viscous oil from a subterranean formation is disclosed. Steam is injected into the formation via a well, permitted to soak, and heated fluids including heated viscous oil are produced sufficient to create a substantial fluid mobility in the formation. Then a hydrocarbon solvent having a low concentration of low molecular weight paraffinic hydrocarbons is injected into the formation, and another steam injection, soak and oil production cycle is performed to recover significant additional quantities of oil.
The invention is a method of recovering hydrocarbons from underground hydrocarbon formations penetrated by at least one injection well and at least one production well, which comprises injecting into the formation a mixture of hot water and about 0.1% to about 5% by weight of a hydrocarbon liquid having an aromatic content greater than about 30%. The hot water and hydrocarbon mixtures should be injected at a temperature of at least about 80.degree.C. Hydrocarbons and other fluids are recovered from a production well after a suitable period of time.
Steam is produced from low quality feedwater. A feedwater stream and a superheated steam stream are introduced into a contactor vessel where the superheated steam is contacted with the feedwater thereby producing saturated steam in the contactor vessel and precipitating minerals from the feedwater in the contactor vessel. The produced steam is withdrawn from the contactor vessel and divided into a primary stream and a secondary stream. The primary stream of produced steam is flowed to a use terminal such as a well for injecting the same into a subsurface formation as part of a steam flood system or such as a steam turbine. The secondary stream of steam is superheated and recycled to the contactor vessel. Waste water containing the solid minerals precipitated from the feedwater within the contactor vessel is withdrawn from the contactor vessel through a waste water discharge conduit.
