A downhole gas generator can be ignited downhole by an ignitor mixture combining with an oxidant. The ignitor mixture is provided by an ignitor subsystem. In one embodiment, the ignitor subsystem bubbles gaseous fuel through a chamber of liquid pyrophoric. The chamber is heated, wherein the fuel obtains a vapor content of the pyrophoric, forming a gaseous ignitor mixture. In another embodiment, gaseous fuel is turbulently injected into a chamber. Liquid pyrophoric enters the chamber through an orifice. The fuel passes through a nozzle wherein its pressure is reduced. This pressure drop is imposed on the pyrophoric, wherein the pyrophoric is drawn into the chamber. The fuel mixes with and atomizes the pyrophoric to form an ignitor mixture.

Means are provided for increasing the productivity of a hydrocarbon formation by modifying the formation in the vicinity of the borehole by a succession of treatments utilizing a first fluid which releases energy within the borehole and a second fluid modifying the fluid within the borehole. The means provides successive treatment of steam, carbon dioxide, oxygen, and inert gases in any order desired.

Disclosed is a catalytic combustor and systems for the boilerless stoichiometric production of a working fluid such as steam from a burn-mixture comprised of a carbonaceous fuel and a diluent. In a preferred burn-mixture, the diluent includes a first portion taken from an emulsion of the fuel and water mixed in a thermally self-extinguishing mass ratio, and a second portion taken in an amount from combustion products of a mixture previously combusted to heat the resulting burn-mixture so it combusts in the presence of a catalyst at an adiabatic flame temperature between upper and lower stability limits of the catalyst. Production of the steam is by a controlled substantially stoichiometric process utilizing a combustor to provide steam over a wide range of heat release rates, temperatures and pressures for steam flooding an oil bearing formation. Even though formation characteristics change during a steam flooding operation, output steam of the combustor may be kept at a constant heat release rate by dividing the total amount of water passing through combustor between a first portion which is included in the fuel-mixture and a second portion which is injected into the heated products of combustion. In this way, the linear velocity of the fluid stream passing through the combustor catalyst may be kept within operational limits of the catalyst while maintaining stoichiometric combustion. When necessary, preheating of at least one of the components of the mixture burned in the catalyst is provided by a portion of the heat of combustion.

Disclosed is a catalytic combustor and systems for the boilerless stoichiometric production of a working fluid such as steam from a fuel-mixture comprised of a carbonaceous fuel and a diluent such as water mixed in a thermally self-extinguishing mass ratio. Production of the steam is by a controlled substantially stoichiometric process utilizing a combustor to provide steam over a wide range of heat release rates, temperatures and pressures for steam flooding an oil bearing formation. Even though formation characteristics change during a steam flooding operation, output steam of the combustor may be kept at a constant heat release rate by dividing the total amount of water passing through combustor between a first portion which is included in the fuel-mixture and a second portion which is injected into the heated products of combustion. In this way, the space velocity of the fluid stream passing through the combustor catalyst may be kept within operational limits of the catalyst while maintaining stoichiometric combustion. When necessary, preheating of at least one of the components of the mixture burned in the catalyst is provided by a portion of the heat of combustion.

A process is disclosed for the in situ conversion and recovery of heavy crude oils and natural bitumens from subsurface formations using either a continuous operation with one or more vertical injection boreholes and one or more vertical production boreholes in which multiple, uncased, horizontal boreholes may extend from the vertical boreholes, or a cyclic operation whereby both injection and production occur in the same vertical boreholes in which multiple, uncased, horizontal boreholes may extend from the vertical boreholes. A mixture of reducing gases, oxidizing gases, and steam are fed to downhole combustion devices located in the injection boreholes. Combustion of the reducing gas-oxidizing gas mixture is carried out to produce superheated steam and hot reducing gases for injection into the formation to convert and upgrade the heavy crude or bitumen into lighter hydrocarbons. Communication between the injection and production boreholes in the continuous operation and fluid mobility within the formation in the cyclic operation is induced by fracturing, multiple horizontal boreholes extending from vertical boreholes, or other related methods. In the continuous mode, the injected steam and reducing gases drive upgraded hydrocarbons and virgin hydrocarbons to the production boreholes for recovery. In the cyclic operation, wellhead pressure is reduced after a period of injection causing injected fluids, upgraded hydrocarbons, and virgin hydrocarbons in the vicinity of the boreholes to be produced. Injection and production are then repeated for additional cycles. In both operations, the hydrocarbons produced are collected at the surface for further processing.