Method for enhanced oil recovery
AssigneeThe United States of America as represented by the United States Department of Energy
InventorsJoseph R. Comberiati, Charles D. Locke, Krishna I. Kamath
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Abstract
The present invention is directed to an improved method for enhanced recovery of oil from relatively "cold" reservoirs by carbon dioxide flooding. In oil reservoirs at a temperature less than the critical temperature of 87.7.degree. F. and at a pore pressure greater than the saturation pressure of carbon dioxide at the temperature of the reservoir, the carbon dioxide remains in the liquid state which does not satisfactorily mix with the oil. However, applicants have found that carbon dioxide can be vaporized in situ in the reservoir by selectively reducing the pore pressure in the reservoir to a value less than the particular saturated vapor pressure so as to greatly enhance the mixing of the carbon dioxide with the oil.
Claims7
An improvement in the method of recovering oil from subterranean oil-bearing strata by carbon dioxide flooding where the oil-bearing strata is at a temperature less than the critical temperature of carbon dioxide and at an injection pressure greater than the saturated vapor pressure of carbon dioxide at said temperature, comprising the steps of injecting liquid carbon dioxide into a first well penetrating the oil-bearing strata for displacing the oil from the oil-bearing strata to a second well penetrating the oil-bearing strata at a location in the oil-bearing strata separated from the first well, and thereafter and prior to the displacement of the oil from the oil-bearing strata by the carbon dioxide reducing the pore pressure in substantially all of the oil-bearing strata intermediate the first and second wells to a value less than the saturated vapor pressure of carbon dioxide at said temperature to vaporize carbon dioxide in said strata at locations spaced from the first well for facilitating the mixing of the carbon dioxide with the oil in the oil-bearing strata at said locations.
Dependencies are inferred from the claim text.