US 5,771,984 A · Continuous drilling of vertical boreholes by thermal processes: including rock spallation and fusion

Abstract

Various rock spallation devices and methods reduce the cost of deep hole excavation. A spallation head has rotating, circumferentially spaced jets. The jets may be combustion flame jets or very hot water. In a combustion embodiment, air and water are delivered to the spallation apparatus downhole in a mixture, and are separated. In a low density embodiment, the borehole is essentially empty. In a high density embodiment, more water is included in the mixture of air and water, and the borehole is filled with fluid. Instead of combustion, the kinetic energy of flowing water at the spallation device can be used to power a turbogenerator that generates electric energy to heat the water and spall the rock. The jets may also be aimed and configured to fuse the excavation material, if spallation is not feasible. New lengths of feed and return pipe can be added while spallation continues uninterrupted, either due to well head alternating equipment, or a downhole relative motion device.

Claims35

Dependent claims

An apparatus for excavation of a borehole in a geological formation by spallation, said apparatus comprising:

a. a rotationally stationary support;
and
b. connected to said support and rotatable with respect thereto, a jet housing having a central axis, said housing comprising:
i. a plurality of jet nozzles, spaced circumferentially around said central axis, each arranged to emit a jet of hot fluid having a directional component that is radial with respect to said central axis and a directional component that is parallel to said central axis;
ii. at least one return passage therethrough for the passage of excavated material;
and
iii. a plurality of cooling fluid conduits distributed throughout said jet housing.

4 more elements

A method for excavating a borehole in a geological formation, comprising the steps of:

a. excavating a pilot hole;
b. introducing a spallation apparatus into said pilot hole, said spallation apparatus comprising:
i. a rotationally stationary support;
and
ii. connected to said support, and rotatable with respect thereto, a jet housing having a central axis, said housing comprising:
(A). a plurality of jet nozzles, spaced circumferentially around said central axis, each arranged to emit a jet of hot fluid having a directional component that is radial with respect to said central axis and a directional component that is parallel to said central axis;
and
(B). at least one return passage therethrough for the passage of excavated material;
c. providing a working fluid to said jet housing through a conduit from the surface of said geological formation;
d. heating said working fluid to a temperature that will spall said rock formation;
e. emitting said hot fluid from said plurality of jet nozzles at an excavation site while rotating said jet housing relative to said rotationally stationary support and said pilot hole, thereby causing said geological formation to spall into chips;
f. removing said spalled chips from said excavation site through said return passage and a conduit to the surface of said geological formation;
and
g. advancing said jet housing deeper into said borehole being excavated.

11 more elements

Dependencies are inferred from the claim text.

Continuous drilling of vertical boreholes by thermal processes: including rock spallation and fusion

Life of this patent

Continuous drilling of vertical boreholes by thermal processes: including rock spallation and fusion

Life of this patent

Abstract

Claims35