Patent ID: 8631871

Claim:
A method of extracting crude oil from oil-bearing ground comprising the steps of: (a) providing a once-through steam generator comprising: at least one steam-generating circuit extending between inlet and outlet ends thereof and comprising at least one pipe, said at least one steam-generating circuit comprising a heating segment at least partially defining a heating portion of said at least one once-through steam generator; at least one heat source for generating heat to which the heating segment is subjected; said at least one pipe comprising a bore therein at least partially defined by an inner surface, at least a portion of the inner surface comprising ribs at least partially defining a helical flow passage along the inner surface; (b) supplying feedwater comprising substantial initial concentrations of impurities to the steam-generating circuit at the inlet end, the feedwater being moved toward the outlet end and being subjected to heat from said at least one heat source as the feedwater passes through said at least one pipe to convert the feedwater into steam and water, the water comprising the impurities at concentrations thereof that increase as the water approaches the outlet end, wherein steam quality in the steam-generating circuit proximal to the outlet end is at least approximately 90%; (c) providing a water treatment means for producing the feedwater; (d) directing the water along the helical flow passage to impart a swirling motion thereto, to provide substantially consistent concentrations of the impurities in the water; (e) providing a first ground pipe subassembly in fluid communication with the steam-generating circuit via the outlet end thereof, the first ground pipe subassembly comprising: a distribution portion for distributing the steam in the oil-bearing ground; a first connection portion, for connecting the distribution portion and the steam-generating circuit; (f) providing a second ground pipe subassembly comprising: a collection portion for collection of an oil-water mixture comprising the crude oil from the oil-bearing ground and condensed water resulting from condensation of the steam in the ground; the collection portion being in fluid communication with the water treatment means; (g) supplying the steam to the first ground pipe assembly, through which the steam is distributed in the oil-bearing ground; (h) collecting the oil-water mixture in the collection portion; (i) supplying the oil-water mixture to the water treatment means; (j) using the water treatment means, separating the crude oil and the condensed water from each other; and (k) adding make-up water to the condensed water to provide the feedwater having the substantial initial concentrations of the impurities.