Abstract Hydrocarbons are produced from hydrocarbon bearing formations, including oil shale, in situ through fractures communicating with production wells by injecting combustion supporting materials such as an oxygen-containing gas substantially completely throughout the fractures and then initiating in situ combustion (supported by the injected gas) at an extremity of the fractures prescribed by either injection or production wells or a subterranean detonation zone or cavity and directing the resultant in situ combustion front along the axis of the fractures and maintaining combustion at a level sufficient to fuse the formation adjacent the fractures whereby the resistance of the fractures to collapse under compressive stress is increased. Collapse of fractures treated in this manner under the influence of formation expansion promoted by subsequent temperature elevation accompanying retorting is substantially retarded. Therefore the strengthened fractures can be employed to facilitate heat transfer throughout the formation.
The method of claim 1 wherein said combustion-supporting material is an oxygen-containing gas.
Claim 2
Dependent Claim
105 words
The method of claim 2 wherein said formation further comprises a subterranean nuclear chimney and accompanying radially outwardly extending fractures in communication with at least one injection well bore, and said oxygen containing gas is injected into said fractures through said injection well and passed through said fraCtures at least to the periphery of said chimney, igniting said hydrocarbon in said sidewalls of said fractures adjacent said chimney and continuing the passage of said oxygen-containing gas into said fractures to direct said combustion radially outwardly from said chimney and axially along said fractures to said injection well and thereby fusing the walls of said fractures.
Claim 3
Dependent Claim
31 words
The method of claim 3 wherein the temperature of said chimney is at least about 600* F. and said hydrocarbons are autoignited by contact with said oxygen-containing gas at said temperature.
Claim 4
Dependent Claim
25 words
The method of claim 3 wherein the injection pressure of said gas is up to about 150 p.s.i. above the formation pressure adjacent said fractures.
Claim 5
Dependent Claim
35 words
The method of claim 3 wherein said chimney is retorted prior to the injection of said oxygen-containing gas via said injection wells and is at a temperature of from about 750* to about 1,000* F.
Claim 6
Dependent Claim
16 words
The method of claim 6 further comprising retorting said formation following said fusing of said fractures.
Claim 7
Dependent Claim
24 words
The method of claim 7 wherein said formation is retorted by injecting a heating medium into said formation via said chimney and said fractures.
Claim 8
Dependent Claim
46 words
The method of claim 8 wherein said heating medium is steam produced at a temperature of from about 750* to about 1,000* F. by injecting one of steam and water into said detonation zone to heat the same via an injection well communicating with said chimney.