Recovering petroleum from subterranean formations

Claim 2

In a process for recovery of petroleum from a subterranean formation wherein steam is injected via an injection well into said subterranean formation, wherein petroleum is produced via a production well from said formation, wherein injection of steam into said formation is continued until a steam front reaches said production well such that steam condensate in admixture with petroleum enters the bore of said production well, the improvement which comprises: a. flashing within said production well bore, said mixture of petroleum and steam condensate produced from said formation at a pressure less than the pressures of said formation for production of a vapor phase comprising steam and light hydrocarbons and a liquid phase comprising petroleum; b. separating said vapor phase from said liquid phase; and c. injecting at least a portion of said separated vapor phase with additional steam, into said formation, via said injection well, for enhancing production of petroleum from said formation via said production well.

Claim 3

The process of claim 1 wherein the amount of light hydrocarbon contained in the portion of said vapor phase injected into said formation is equivalent toabout 1-100 percent of the total pore volume of that portion of the formation through which the steam and light hydrocarbon flow to said production well.

Claim 4

The process of claim 2 wherein the light hydrocarbon and additional steam injected into said formation are at an injection pressure sufficient to force a flow of steam, light hydrocarbon and petroleum toward said production well, and are at a temperature sufficient to maintain the additional steam completely in the vapor phase at said injection pressure.

Claim 5

A process for recovering petroleum from a subterranean formation, which process comprises: a. injecting steam into said formation via an injection well; b. producing petroleum from said formation via a production well; c. continuing injection of said steam and production of said petroleum until communication between said injection well and said production well is established through said formation such that a mixture of petroleum and steam condensate enters the bore of said production well; d. flashing, in a flash zone, said mixture of petroleum and steam condenstate for production of a vapor phase comprising steam and light hydrocarbon, and production of a liquid phase comprising petroleum; e. condensing, in a condensing zone, said vapor hase for production of a condensate comprising water and condensed hydrocarbon; f. separating, in a gravity separation zone, said condensate into a water phase and a hydrocarbon phase; g. injecting said condensed hydrocarbon with additional steam into said formation, via said injection well, for enhancing recovery of additional petroleum from said formation.

Claim 6

A process for recovering petroleum from a subterranean formation, which process comprises: a. injecting steam into said formation via an injection well; b. producing petroleum from said formation via a production well; c. continuing injection of said steam and production of said petroleum until communication between said injection well and said production well is established through said formation such that a mixture of petroleum and steam condensate enters the bore of said production well; d. flashing, in a flash zone, said mixture of petroleum and steam condenstate for production of a vapor phase comprising steam and light hydrocarbon, and production of a liquid phase comprising petroleum; e. condensing, in a condensing zone, said vapor hase for production of a condensate comprising water and condensed hydrocarbon; f. separating, in a gravity separation zone, said condensate into a water phase and a hydrocarbon phase; g. injecting said condensed hydrocarbon with additional steam into said formation, via said injection well, for enhancing recovery of additional petroleum from said formation.

Claim 7

The process of claim 4 wherein the liquid volume ratio of injected condensed hydrocarbon to additional steam is in the range of about 1:1 to about 1:100, and wherein the volume of injected condensed hydrocarbon is equivalent to about 1-100 percent of the pore volume of that portion of the formation swept by the injected hydrocarbon and additional steam.

Claim 8

The process of claim 5 wherein liquid volume ratio of injected hydrocarbon to additional steam is about 1:20, and wherein the volume of injected condensed hydrocarbon is equivalent to about 5-20 percent of the pore volume of that portion of the formation swept by the injected hydrocarbon and additional steam.

Claim 9

The process of claim 5 wherein, upon completion of injection of condensed hydrocarbon, the flow of additional steam is maintained for production of additional petroleum from said formation.