Abstract A secondary recovery process for oil wet sands using underground combustion to produce a makeup effluent gas containing carbon dioxide. The effluent gas is mixed with a wet casing head gas enriched by ethane plus hydrocarbons and the mixture is injected into the reservoir at relatively low pressures to promote oil flow toward a production well. The enriched injected gas mixture reduces the oil''s adhesion to the sand and promotes oil flow. The production well is maintained under a vacuum pressure so as to pull the injected mixture through the formation. The mixture is recovered and reinjected. The production well vacuum pulls ethane plus hydrocarbons from the oil at the formation face to enrich the casinghead gas.
The method of claim 1 wherein the combustion is controlled and the mixture of casing head gas with the products of combustion is controlled so that the injected gas mixture has on the order of approximately two parts ethane plus to approximately one part of carbon dioxide.
Claim 2
Dependent Claim
26 words
The method of claim 2 wherein the gas mixture injected in the second injection well is on the order of 50,000 to 150,000 MCF per day.
Claim 3
Dependent Claim
19 words
The method of claim 1 characterized by and including the step of additionally withdrawing oil from the second well.
Claim 4
Independent Claim
127 words
The method of secondary recovery of oil from a reservoir having oil wet sands including the steps of mixing an exhaust gas, containing carbon dioxide and other gases resulting from combustion of a hydrocarbon oil, with a wet casing head gas having an ethane plus gas component, controlling the relative volumes of carbon dioxide and ethane plus in the mixture so that approximately two parts ethane plus to one part carbon dioxide are present in the mixture, injecting the controlled mixture in a reservoir well at pressures and tempeRatures such as to maintain the mixture during injection as a gaseous phase for driving oil in the reservoir toward a production well, maintaining the production well under vacuum, and separately withdrawing oil and gas from said production well.
Claim 5
Dependent Claim
20 words
The method of claim 5 wherein the withdrawn gas is recycled through the injection well at said pressures and temperatures.