초록 ▼

A downhole delay assembly is provided which can be placed into a blasthole for initiation of explosive in the blasthole. The downhole delay assembly includes at least two detonating time delay devices in series in order to effect a time delay of longer than about 200 milliseconds in a round of explo

A downhole delay assembly is provided which can be placed into a blasthole for initiation of explosive in the blasthole. The downhole delay assembly includes at least two detonating time delay devices in series in order to effect a time delay of longer than about 200 milliseconds in a round of explosions. The downhole delay assembly provides a protective housing to prevent detonation of explosive in the blasthole in response to the detonation of the first detonating time delay device. There is further provided a connection between the first and second time delay devices. The connection is responsive to the detonation of the first detonating time delay device and initiates the second detonating time delay device. A plurality of such downhole delay assemblies are placed downhole in unfragmented formation and are initiated simultaneously for providing a round of explosive expansions. The explosive expansions can be used to form an in situ oil shale retort containing a fragmented permeable mass of formation particles.

대표청구항 ▼

A downhole delay assembly for detonating explosive placed in a blasthole, the assembly comprising: a first detonating time delay device for introducing a first time delay in a detonation sequence; means for preventing detonation of explosive in a blasthole in response to detonation of the first deto

A downhole delay assembly for detonating explosive placed in a blasthole, the assembly comprising: a first detonating time delay device for introducing a first time delay in a detonation sequence; means for preventing detonation of explosive in a blasthole in response to detonation of the first detonating time delay device; a second detonating time delay device for introducing a second time delay in the detonation sequence and for initiating explosive in the blasthole; means for connecting the first time delay device to the second time delay device for initiating the second time delay device in response to the detonation of the first time delay device; and support means for supporting the first and second time delay devices for placement in a blasthole.