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KR-102965251-B1 - Cooling for geothermal well drilling

KR102965251B1KR 102965251 B1KR102965251 B1KR 102965251B1KR-102965251-B1

Abstract

A method for drilling a geothermal well in an underground area includes the step of drilling a well bore of a geothermal well in an underground area using a drill string. The intrinsic temperature of the rock adjacent to the rock face at the downhole end of the well bore is at least 250°C. During drilling, a drilling fluid is flowed on the rock face at a temperature such that the difference between the intrinsic temperature of the rock adjacent to the rock face and the temperature of the drilling fluid on the rock face is at least 100°C.

Inventors

  • 토위스 매튜
  • 홀름스 마이클
  • 토레 아리엘
  • 베트사크 알레크산드르
  • 호더 마르크

Assignees

  • 이버 테크놀로지스 인크.

Dates

Publication Date
20260513
Application Date
20210827
Priority Date
20200828

Claims (20)

  1. A method for forming a geothermal well, wherein the method comprises: A step of forming a wellbore having a fluid-impermeable interface between the wellbore and the stratum in a stratum within an underground area, The above wellbore formation step is, A drilling step for drilling into a stratum by using a drill bit at the downhole end of a drill string to crush a rock face in front of the drill bit, wherein the intrinsic temperature of the rock adjacent to the rock face at the downhole end of the well bore is at least 250°C; A step of simultaneously crushing a rock face with a drill bit on the rock face and flowing a water-based or oil-based drilling fluid at a temperature lower than the intrinsic temperature of the rock adjacent to the rock face in front of the drill bit on the rock face, wherein the difference between the intrinsic temperature of the rock adjacent to the rock face in front of the drill bit and the temperature of the drilling fluid on the rock face is at least 100°C; and It includes a wellbore sealing step of forming an interface by sealing the wellbore without using a casing; and A geothermal well formation method characterized by including the step of circulating a geothermal working fluid through a well bore in a closed loop.
  2. A method for forming a geothermal well according to claim 1, characterized in that the difference between the intrinsic temperature of the rock adjacent to the rock face and the temperature of the drilling fluid on the rock face causes the thermally induced stress within the rock on the rock face to be greater than the tensile strength of the rock on the rock face.
  3. A geothermal well formation method according to claim 1, characterized in that the downhole end of the well bore is at a measured depth of at least 4,000 m.
  4. A geothermal well formation method according to claim 1, characterized in that the downhole end of the well bore is at a measured depth of at least 6,000 m.
  5. A method for forming a geothermal well according to claim 1, characterized in that the difference between the intrinsic temperature of the rock adjacent to the rock face and the temperature of the drilling fluid at the rock face is at least 175℃.
  6. A method for forming a geothermal well according to claim 1, characterized in that the intrinsic temperature of the rock adjacent to the rock wall is at least 350°C, and the difference between the intrinsic temperature of the rock adjacent to the rock wall and the temperature of the drilling fluid on the rock wall is at least 200°C.
  7. A method for forming a geothermal well according to claim 1, characterized in that the intrinsic temperature of the rock adjacent to the rock wall is at least 500°C, and the difference between the intrinsic temperature of the rock adjacent to the rock wall and the temperature of the drilling fluid on the rock wall is at least 350°C.
  8. A geothermal well formation method according to claim 1, characterized in that the well bore is a lateral well bore.
  9. A method for forming a geothermal well according to any one of claims 1 to 7, characterized in that the downhole end of the drill string includes a rotary drill bit.
  10. A method for forming a geothermal well according to any one of claims 1 to 7, characterized in that the downhole end of the drill string comprises a non-contact drill bit configured to crush geological material on a rock face without the bit and the rock face coming into contact.
  11. A method for forming a geothermal well according to any one of claims 1 to 7, further comprising the step of forming a closed-loop geothermal well system, wherein the closed-loop geothermal well system comprises a well bore.
  12. A method for forming a geothermal well according to claim 11, wherein the well bore is a lateral well bore and the step of forming a closed-loop geothermal well system comprises drilling a lateral well bore from a first surface well bore and connecting the first surface well bore to a second surface well bore by means of the lateral well bore.
  13. A geothermal well forming method according to any one of claims 1 to 7, wherein the intrinsic temperature of the rock adjacent to the rock wall is at least 500°C, and the difference between the intrinsic temperature of the rock adjacent to the rock wall and the temperature of the drilling fluid on the rock wall causes a radial tensile crack in at least a portion of the wall of the well bore, and further comprising the step of sealing the radial tensile crack with a sealing material.
  14. A method for forming a geothermal well according to any one of claims 1 to 7, wherein the drill string comprises a plurality of tubular segments, at least one of the tubular segments comprises a coating layer that at least partially covers the circumferential surface of the tubular segment, and the length normalized thermal resistance of the coated wall portion of the tubular segment is at least 0.002 meter Kelvin (mk) per watt.
  15. A geothermal well forming method according to claim 14, characterized in that the length-normalized thermal resistance of the coated wall portion is at least 0.01 mk per watt.
  16. A method for forming a geothermal well according to claim 14, wherein a plurality of tubular segments are connected to each other at a connecting joint, and the coating layer covers at least one or more circumferential surfaces of the connecting joint.
  17. In any one of paragraphs 1 through 7, the Welbore is the first Welbore, and A step of forming a second wellbore that intersects with a first wellbore, and A step of flowing a second stream of drilling fluid below a second well bore, wherein the second stream provides at least a portion of the drilling fluid flowing on the rock face, and a step of flowing a second stream. A geothermal well forming method characterized by additionally including at least one step of diverting a return stream of drilling fluid from the downhole end of a first well bore to a second well bore.
  18. In claim 1, the step of positioning an intermediate tubular string within the well, The step of positioning a drill string within the intermediate tubular string, thereby positioning an inner annular portion between the outside of the drill string and the intermediate tubular string, at least partially expanding a downhole along the entire length of the drill string, and A method for forming a geothermal well characterized by additionally including the step of filling the inner annular portion at least partially with an insulating material.
  19. A method for forming a geothermal well according to claim 18, wherein the insulating material comprises gas.
  20. A geothermal well forming method characterized by additionally including the step of adding a phase change material that undergoes a phase change near the downhole end of a drill string to the drilling fluid in any one of claims 1 to 7.

Description

Cooling for geothermal well drilling The present disclosure relates to geothermal well drilling. Wells drilled for geothermal systems may face high ground temperatures. These high temperatures can cause problems related to seepage rates, the function of downhole electronics, and other factors. FIG. 1a is a schematic diagram of a closed-loop geothermal system according to the concept of the present specification. FIG. 1b is a plan view of the closed-loop geothermal system exemplified in FIG. 1a. FIG. 2 is a schematic diagram of a drilling system according to the concept of the present specification. FIG. 3a is a schematic diagram of a drill bit according to the concept of the present specification. FIG. 3b is a schematic cross-sectional view of a drill bit cone according to the concept of the present specification. FIG. 4a is a graph showing the temperature-pressure relationship for the transition from brittle to semi-brittle in ductile or plastic rocks according to the concept of this specification. FIG. 4b is a graphic representation of a brittle-halfbrittle transition in brittle igneous rocks according to the concept of the present specification. Figure 5 is a graphic representation of the effects of deformation and stress on brittle and ductile rocks according to the concept of the present specification. Figure 6a is a graph showing the relationship between rock brittleness and seepage rate. Figure 6b shows the relationship between rock damage caused by drilling operations and the difference in cooling temperature. Figure 7 is a graphical representation of laboratory test results of the penetration rate as a function of the temperature difference between the drilling fluid and the rock being excavated. FIG. 8a is an example of a coated tubing segment of a tubing string for drilling according to the concept of the present specification. FIG. 8b is an example of a coated tubing segment of a tubing string for drilling according to the concept of the present specification. FIGS. 9a to 9d illustrate the relationship between the vertical depth and temperature of a drill pipe, an annular section, and a rock having tube segments with different coating configurations according to the concept of the present invention. FIG. 10 illustrates the relationship between the maximum excavatable rock temperature and the thermal gradient for different tubular segment coating configurations according to the concept of the present specification. FIG. 11 is a schematic diagram of the resistance to heat transfer through an annular portion of a tube and different configurations according to the concept of the present specification. FIG. 12 is a schematic diagram of a well system having a second insulating annular portion according to the concept of the present specification. FIGS. 13a and FIGS. 13b are drawings illustrating the thermal effect of the second insulating annular section of FIG. 12. FIG. 14 is a schematic diagram of a wellbore system for drilling into a second well that serves as an inlet and/or outlet for a drilling fluid according to the concept of the present specification. FIG. 1a illustrates a closed-loop geothermal system according to the concept of the present application. A closed-loop geothermal wellbore system may be a system such as that developed, for example, by Eavor Technologies Inc. of Calgary, Alberta. This system comprises a downhole layer and a sealed horizontal well network that serves as a radiator or heat exchanger. Descriptions of methods and apparatus used in some cases of such closed-loop geothermal systems are disclosed, for example, in U.S. Patent Application Publications 20190154010A1, 20190346181A1 and 20200011151A1, the contents of which are incorporated herein by reference. Referring to FIG. 1a, a closed-loop geothermal system (100) comprises an inlet surface wellbore (104) and an outlet surface wellbore (106) connected within an underground zone (108) by a network of lateral wellbores (110). The underground zone (108) is a geological formation, a part of a geological formation, or multiple geological formations. In the illustrated example, the surface wellbores (104, 106) are substantially vertical; in other examples of the present disclosure, one or both of the surface wellbores may not be substantially vertical. In the illustrated example, the lateral wellbore (110) connecting the surface wellbores (104, 106) is substantially horizontal. In some examples of the present invention, some or all of the lateral wellbores may not be substantially horizontal and may be substantially straight, curved, spiral, or have other shapes. The lateral wellbores (110) may be sealed, and an operating fluid may be added to the closed loop as a circulating fluid. The power plant (112) is positioned on the surface (114) between the inlet surface wellbore (104) and the outlet surface wellbore (106) to complete a closed-loop system. Heat from the underground area (108) is recovered from the working fluid cir