# US 11,029,062 B2 · Geothermal heat mining system

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- Number: US 11,029,062 B2
- Document ID: US11029062B2
- Status: Granted
- Kind: B2
- Application number: 16/940,281
- Filed: 2020-07-27
- Published: 2021-01-28
- Granted: 2021-06-08
- Earliest claimed: 2019-07-25
- Assignees: Strabo Engineering, LLC
- Applicants: Strabo Engineering, LLC
- Inventors: Benjamin Holtzman
- Web page: https://patentgrep.com/patent/US11029062B2

## CPC

- F24T 10/20: using underground water as working fluid; using working fluid injected directly into the ground, e.g. using injection wells and recovery wells
- E21B 7/04: Directional drilling
- E21B 43/26: by forming crevices or fractures
- E21B 43/305: {comprising at least one inclined or horizontal well}
- F24T 10/00: Geothermal collectors
- F24T 10/15: using bent tubes; using tubes assembled with connectors or with return headers
- F24T 10/17: using tubes closed at one end, i.e. return-type tubes
- F24T 10/30: using underground reservoirs for accumulating working fluids or intermediate fluids
- F24T 2010/53: {Methods for installation}
- F24T 2010/56: {Control arrangements}
- Y02E 10/10: Geothermal energy
- F24T: GEOTHERMAL COLLECTORS; GEOTHERMAL SYSTEMS
- E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

A geothermal heat mining system can operate within a single primary borehole in a geothermal reservoir. A primary fluid loop can include a cold working fluid line leading into the primary borehole and a hot working fluid line coming out of the primary borehole. A secondary fluid loop can be located down the primary borehole, where the secondary fluid loop is in thermal contact with the geothermal reservoir. A downhole heat mining device can control a rate of heat transfer from the secondary fluid loop to the primary fluid loop by selectively controlling fluid flow through the primary fluid loop, the secondary fluid loop, or both.

## Claims

### Claim 1

A geothermal heat mining system, comprising:
a single primary borehole in a geothermal reservoir;
a primary fluid loop comprising a cold working fluid line leading into the primary borehole and a hot working fluid line coming out of the primary borehole;
a secondary fluid loop located down the primary borehole, wherein the secondary fluid loop is in thermal contact with the geothermal reservoir, wherein the secondary fluid loop is adapted to circulate a fluid isolated from the primary fluid loop, and wherein the secondary fluid loop flows within a lateral secondary borehole formed in the geothermal reservoir extending out from the primary borehole; and
a downhole heat mining device to control a rate of heat transfer from the secondary fluid loop to the primary fluid loop by selectively controlling fluid flow through the primary fluid loop, the secondary fluid loop, or both, wherein the downhole heat mining device comprises
a heat exchanger having the primary fluid loop connected to a cold side and the secondary fluid loop connected to a hot side and wherein the heat mining device further comprises a pump in the secondary fluid loop to control the fluid flow through the secondary fluid loop; and
a lateral drilling head oriented outward from the heat mining device to drill the secondary borehole transverse to the primary borehole.

### Claim 2 (depends on 1)

The system of claim 1, wherein the system comprises multiple secondary fluid loops flowing within multiple lateral secondary boreholes, and wherein the downhole heat mining device selectively controls fluid flow through the multiple secondary fluid loops.

### Claim 3 (depends on 1)

The system of claim 1, wherein the secondary fluid loop further comprises a microfracture network connecting at least a portion of the lateral secondary borehole, or a tertiary borehole extending out from the secondary borehole, or a combination thereof.

### Claim 4 (depends on 1)

The system of claim 1, wherein:
the heat mining device comprises a processor integrated in the heat mining device to generate control signals to selectively control the fluid flow; or
the heat mining device controls the fluid flow based on control signals received from a processor outside the primary borehole; or a combination thereof.

### Claim 5 (depends on 4)

The system of claim 4, wherein the processor communicates with a sensor.

### Claim 6 (depends on 5)

The system of claim 5, wherein the sensor is a pressure sensor, a temperature sensor, a position sensor, or a combination thereof.

### Claim 7 (depends on 1)

The system of claim 1, wherein the heat mining device comprises a drill head at a downhole end of the heat mining device, and wherein the heat mining device is adapted to extend a depth of the primary borehole using the drill head while heat is concurrently transferred from the secondary fluid loop to the primary fluid loop.

### Claim 8 (depends on 7)

The system of claim 7, wherein the drill head comprises a rotary drill head, a percussive drill head, a hot spallation drill, a cold spallation drill head, or a combination thereof.

### Claim 9 (depends on 1)

The system of claim 1, wherein the cold working fluid line and the hot working fluid line are not concentric, and wherein the cold working fluid line and the hot working fluid line are insulated.

### Claim 10

A downhole geothermal heat mining device, comprising:
a device body shaped to be lowered down a primary borehole;
a cold working fluid inlet connectable to a cold working fluid line that leads down the primary borehole;
a hot working fluid outlet connectable to a hot working fluid line that leads up the primary borehole, wherein the cold working fluid line and the hot working fluid line form a primary fluid loop;
a controller adapted to control a rate of heat transfer to the primary fluid loop from a secondary fluid loop, wherein the secondary fluid loop is located down the primary borehole, wherein the secondary fluid loop is in thermal contact with a geothermal reservoir, and wherein the controller controls the rate of heat transfer by selectively controlling fluid flow through the primary fluid loop, the secondary fluid loop, or both;
a heat exchanger adapted to connect to the primary fluid loop on a cold side and adapted to connect to the secondary fluid loop on a hot side;
a pump adapted to control the fluid flow through the secondary fluid loop; and
a lateral drilling head oriented outward from the device to drill a secondary borehole transverse to the primary borehole, wherein the secondary fluid loop includes the secondary borehole.

### Claim 11 (depends on 10)

The device of claim 10, wherein the device further comprises a micro-damage head adapted to form microfractures fluidly connected along the secondary borehole, wherein the secondary fluid loop includes the microfractures.

### Claim 12 (depends on 10)

The device of claim 10, wherein the device further comprises:
a valve installation unit adapted to install a valve connecting the secondary borehole to the cold working fluid line or the hot working fluid line, wherein the secondary fluid loop includes the secondary borehole.

### Claim 13 (depends on 12)

The device of claim 12, wherein the valve installation unit is adapted to receive a valve lowered down the primary borehole and connect the valve to the secondary fluid loop and to the cold working fluid line or the hot working fluid line.

### Claim 14 (depends on 12)

The device of claim 12, wherein the valve installation unit includes an additive manufacturing device to manufacture a valve downhole and connect the valve to the secondary fluid loop and to the cold working fluid line or the hot working fluid line.

### Claim 15 (depends on 10)

The device of claim 10, further comprising a drill head at a downhole end of the device, wherein the drill head comprises a rotary drill head, a percussive drill head, a hot spallation drill head, a cold spallation drill head, or a combination thereof.

### Claim 16 (depends on 15)

The device of claim 15, wherein the drill head comprises a cold spallation drill head that is connected to the cold working fluid inlet to eject cold working fluid from the cold spallation drill head.

### Claim 17

A geothermal heat mining method, comprising:
forming a single primary borehole;
placing a geothermal heat mining device downhole in the primary borehole, wherein the heat mining device comprises a lateral drilling head oriented outward from the heat mining device;
forming a primary fluid loop comprising a cold working fluid line leading into the primary borehole and a hot working fluid line coming out of the primary borehole;
forming a secondary fluid loop located down the primary borehole which includes drilling a lateral secondary borehole extending out from the primary borehole using the lateral drilling head, wherein the secondary fluid loop is in thermal contact with the geothermal reservoir;
transferring heat from the secondary fluid loop to an energy storage or production unit outside the primary borehole via the primary fluid loop; and
controlling a rate of heat transfer from the secondary fluid loop to the primary fluid loop by selectively controlling fluid flow through the primary fluid loop, the secondary fluid loop, or both.

### Claim 18 (depends on 17)

The method of claim 17, wherein the heat mining device further comprises a cold spallation drill head at a far end of the heat mining device, and wherein the method further comprises extending a depth of the primary bore using the cold spallation drill head or extending a length of the lateral secondary borehole while concurrently performing the transferring heat.

### Claim 19 (depends on 1)

The system of claim 1, wherein the lateral drill head comprises a rotary drill head, a percussive drill head, a hot spallation drill, a cold spallation drill head, or a combination thereof.

### Claim 20 (depends on 10)

The device of claim 10, wherein the lateral drill head comprises a rotary drill head, a percussive drill head, a hot spallation drill, a cold spallation drill head, or a combination thereof.

### Claim 21 (depends on 17)

The method of claim 17, wherein the lateral drill head comprises a rotary drill head, a percussive drill head, a hot spallation drill, a cold spallation drill head, or a combination thereof.

### Claim 22 (depends on 4)

The system of claim 4, wherein the heat mining device further includes a thermoelectric cooling device to maintain the processor at a safe operating temperature.