A spallation drilling apparatus is also disclosed that uses jets of hot fluid for drilling. This is compatible with drilling wells in high temperature zones, such as a lava dome. A simplified pyrolysis reactor for use in a lava dome is also disclosed, in which the dome functions to contain the reaction, and the apparatus to facilitate pyrolysis is far more compact.

An example laser tool is configured to operate within a wellbore of a hydrocarbon-bearing rock formation. The laser tool includes one or more optical transmission media as part of an optical path originating at a laser generator configured to generate a laser beam having an axis. The laser tool includes an optical element for receiving the laser beam from the one or more optical transmission media and for output to the hydrocarbon-bearing rock formation. The laser tool includes a purging head for removing dust or vapor from a path of the laser beam. The purging head is for discharging two or more purging gas streams. The purging head may include a coaxial flow assembly and a helical flow assembly. A coaxial purging gas stream may flow in a direction parallel to the axis. A helical purging gas stream may flow in a helical pattern around and substantially along the axis.

A tunnel boring machine including a propulsion system, an enclosure carried by the propulsion system, and a torch support structure carried by the enclosure. The torch support structure can include a primary disc mounted on a rotatable shaft carried by the enclosure, a first plurality of plasma torches mounted to the primary disc, and a power supply cable coupled to the enclosure and adapted to supply power to the boring machine from one or more power sources.

A tunnel boring machine including a propulsion system, an enclosure carried by the propulsion system, and a torch support structure carried by the enclosure. The torch support structure can include a primary disc mounted on a rotatable shaft carried by the enclosure, a first plurality of plasma torches mounted to the primary disc, and a power supply cable coupled to the enclosure and adapted to supply power to the boring machine from one or more power sources.

An example laser tool is configured to operate within a casing or liner in wellbore of a hydrocarbon-bearing rock formation. The tool is configured to cut sections into the casing or liner material. The cut sections may break off or may be broken off using a breaking tool. The sections may be cut in a region of the casing or liner that includes a kick-off point for sidetracking operations.

A method of communication along a shared voltage line is disclosed. In pulse power drilling, a generator charges applies voltage to a shared voltage line, which capacitively charges electrodes for formation drilling. While the generator controls the charging rate, charge voltage, and post-delay time between the charging cycles, a pulse power controller determines the pre-delay time by firing electrodes to discharge the stored voltage. Communication from the pulse power controller to the generator is encoded in the pre-delay time, where pre-delay times longer than a minimum pre-delay time correspond to time bins with pre-determined communications between the pulse power controller and the generator. The generator can also communicate to the pulse power controller via manipulation of the post-delay time.

A downhole tool includes a housing configured to couple to a downhole conveyance; a laser tool positioned in the housing and configured to transmit a laser beam sufficient to form a tunnel in a subterranean formation; a chamber positioned in the housing and configured to enclose a shaped members that include at least two laser reflective surfaces; and a perforating head coupled to the housing. The perforating head includes an optical pathway formed to receive the laser beam from the laser tool and output the laser beam toward the subterranean formation through an outlet of the perforating head; and at least one conduit separate from the optical pathway and configured to receive the shaped members from the chamber and output the shaped members through the outlet of the perforating head.

A downhole tool includes a housing configured to couple to a downhole conveyance; a laser tool positioned in the housing and configured to transmit a laser beam sufficient to form a tunnel in a subterranean formation; a chamber positioned in the housing and configured to enclose a shaped members that include at least two laser reflective surfaces; and a perforating head coupled to the housing. The perforating head includes an optical pathway formed to receive the laser beam from the laser tool and output the laser beam toward the subterranean formation through an outlet of the perforating head; and at least one conduit separate from the optical pathway and configured to receive the shaped members from the chamber and output the shaped members through the outlet of the perforating head.

A system for monitoring and controlling downhole pressure of a well borehole relative to a lithostatic pressure of rock surrounding the borehole is provided. The system can include a millimeter wave drilling apparatus including a gyrotron configured to inject millimeter wave radiation energy into a borehole of a well via a waveguide configured for insertion into the borehole. The borehole can be formed via the millimeter wave drilling apparatus and having a downhole pressure monitored at a bottom of the well. The system can also include a compressor fluidically coupled to the borehole and configured to control the downhole pressure via a gas supplied into and/or received from the borehole. The compressor can be configured to control the downhole pressure relative to a lithostatic pressure determined for rock surrounding the well at the bottom of the well.

A method for monitoring and controlling a downhole pressure of a well during formation of a borehole of a well is provided. The method can include monitoring a downhole pressure of a well during formation of a borehole of the well using a millimeter wave drilling apparatus including a waveguide configured for insertion into the borehole. The monitoring can include determining the downhole pressure. The downhole pressure can include an amount of pressure present at a bottom of the well. The method can also include determining a lithostatic pressure of rock surrounding the well at the bottom of the well. The method can further include controlling the downhole pressure relative to the lithostatic pressure of the rock surrounding the well at the bottom of the well. Related systems performing the methods are also provided.