Cooling for geothermal well drilling
A method for drilling a geothermal well in a subterranean zone includes drilling, with a drill string, a wellbore of the geothermal well in the subterranean zone. An inherent temperature of the rock adjacent a rock face at a downhole end of the wellbore is at least 250 degrees Celsius. While drilling, a drilling fluid is flowed at a temperature at the rock face such that a difference between the inherent temperature of the rock adjacent the rock face and the temperature of the drilling fluid at the rock face is at least 100 degrees Celsius.
1 . A method for forming a geothermal well system, the method comprising:
in a formation in a subterranean zone, forming a wellbore having an interface between the wellbore and the formation substantially impermeable to fluid, wherein the forming the wellbore comprises:
drilling, with a drill bit at a downhole end of a drill string, into the formation by breaking the rock at a rock face ahead of the drill bit, wherein an inherent temperature of the rock adjacent the rock face ahead of the drill bit is at least 250 degrees Celsius;
simultaneously with breaking the rock at the rock face with the drill bit flowing a water- or oil-based drilling fluid having a temperature at the rock face less than the inherent temperature of the rock adjacent the rock face ahead of the drill bit, a difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit being at least 100 degrees Celsius;
sealing the wellbore without the use of casing to form the interface; and
circulating a geothermal working fluid in a closed loop through the wellbore.
2 . The method of claim 1 , wherein the drill string comprises composite tubing.
3 . The method of claim 2 , wherein the composite tubing has a normalized thermal resistance of at least 0.002 meters kelvin per watt.
4 . The method of claim 2 , wherein the composite tubing has a normalized thermal resistance of at least 0.01 meters kelvin per watt.
5 . The method of claim 1 , wherein the drill bit is a contactless drill bit.
6 . The method of claim 1 , wherein a downhole end of the wellbore is at a measured depth of at least 4000 meters.
7 . The method of claim 1 , wherein the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 175 degrees Celsius.
8 . The method of claim 1 , wherein the inherent temperature of the rock adjacent the rock face ahead of the drill bit is at least 350 degrees Celsius and the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 200 degrees Celsius.
9 . The method of claim 1 , wherein the inherent temperature of the rock adjacent the rock face ahead of the drill bit is at least 500 degrees Celsius and the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 350 degrees Celsius.
10 . The method of claim 1 , wherein the drilling fluid has a temperature of greater than twenty-five degrees Celsius when flowing in the drill string at a surface location at an uphole end of the wellbore.
11 . A system for forming a geothermal system comprising a wellbore of a geothermal well in a subterranean zone, wherein an inherent temperature of the rock adjacent a rock face at a downhole end of the wellbore is at least 250 degrees Celsius, the system comprising:
a drill string comprising a drill bit to break the rock at the rock face;
a water- or oil-based drilling fluid, the system configured such that, simultaneously with the breaking the rock at the rock face with the drill bit, the drilling fluid flows at a temperature at the rock face less than the inherent temperature of the rock adjacent the rock face ahead of the drill bit and a difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 100 degrees Celsius; and
a sealing material configured to seal the wellbore after drilling without the use of casing such that an interface between the wellbore and the formation is substantially impermeable to fluid and a geothermal working fluid can flow in a closed loop through the wellbore.
12 . The system of claim 11 , wherein the drill string comprises composite tubing.
13 . The system of claim 12 , wherein the composite tubing has a normalized thermal resistance of at least 0.002 meters kelvin per watt.
14 . The system of claim 12 , wherein the composite tubing has a normalized thermal resistance of at least 0.01 meters kelvin per watt.
15 . The system of claim 11 , wherein the drill bit is a contactless drill bit.
16 . The system of claim 11 , wherein the downhole end of the wellbore is at a measured depth of at least 4000 meters.
17 . The system of claim 11 , wherein the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 175 degrees Celsius.
18 . The system of claim 11 , wherein the inherent temperature of the rock adjacent the rock face is at least 350 degrees Celsius and the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 200 degrees Celsius.
19 . The system of claim 11 , wherein the inherent temperature of the rock adjacent the rock face ahead of the drill bit is at least 500 degrees Celsius and the difference between the inherent temperature of the rock adjacent the rock face ahead of the drill bit and the temperature of the drilling fluid at the rock face ahead of the drill bit is at least 350 degrees Celsius.
20 . The system of claim 11 , wherein the drilling fluid has a temperature of greater than twenty-five degrees Celsius when flowing in the drill string at a surface location at an uphole end of the wellbore.
21 . A method for drilling a wellbore in a formation in a subterranean zone, the method comprising:
inducing, by a contactless drill bit at a downhole end of a drill string, tension to break rock in tension at a rock face ahead of the bit, wherein an inherent temperature of the rock adjacent the rock face ahead of the bit is at least 250 degrees Celsius;
simultaneously with inducing tension by the contactless drill bit, stressing the rock in tension at the rock face ahead of the bit by flowing a drilling fluid through an interior of the drill string, the drill string having a specified normalized thermal resistance to radial heat transfer across a wall of the drill string between the interior and exterior of the drill string to thereby flow, at the rock adjacent the rock face ahead of the drill bit, the drilling fluid at having a temperature at the rock face at least 100 degrees Celsius less than the inherent temperature of the rock adjacent the rock face ahead of the bit.
22 . The method of claim 21 , wherein the wall of the drill string comprises composite tubing.
23 . The method of claim 22 , wherein the specified normalized thermal resistance across the wall of the drill string is at least 0.002 meters kelvin per watt.
24 . The method of claim 22 , wherein the specified normalized thermal resistance across the wall of the drill string is at least 0.01 meters kelvin per watt.
25 . A system for forming a geothermal system comprising a wellbore in a geothermal well in a subterranean zone, wherein an inherent temperature of the rock adjacent a rock face at a downhole end of the wellbore is at least 250 degrees Celsius, the system comprising:
a drill string comprising a contactless drill bit configured to induce tension to break the rock in tension at the rock face;
a drilling fluid, the system configured such that the drilling fluid flows through an interior of the drill string having a specified normalized thermal resistance to radial heat transfer across a wall of the drill string between the interior and exterior of the drill string to thereby flow, at the rock adjacent the rock face ahead of the drill bit, at a temperature of at least 100 degrees Celsius less than the inherent temperature of the rock adjacent the rock face ahead of the bit, thereby stressing rock in tension simultaneously with the drill bit inducing tension to break the rock at the rock face ahead of the bit.
26 . The system of claim 25 , wherein the wall of the drill string comprises composite tubing.
27 . The system of claim 26 , wherein the specified normalized thermal resistance across the wall of the drill string is at least 0.002 meters kelvin per watt.
28 . The system of claim 26 , wherein the specified normalized thermal resistance across the wall of the drill string is at least 0.01 meters kelvin per watt.