Source: http://www.google.com/patents/US8235140?dq=6519629
Timestamp: 2015-06-03 05:09:36
Document Index: 171862802

Matched Legal Cases: ['Application No. 07759460', 'Application No. 09736532', 'Application No. 09736533', 'Application No. 09737302', 'Application No. 09793358', 'Application No. 2007230605']

Patent US8235140 - Methods and apparatus for thermal drilling - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsMethods and apparatus for spalling a material, for example to thermally drill a wellhole, are provided. Such methods may include directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile...http://www.google.com/patents/US8235140?utm_source=gb-gplus-sharePatent US8235140 - Methods and apparatus for thermal drillingAdvanced Patent SearchPublication numberUS8235140 B2Publication typeGrantApplication numberUS 12/575,852Publication dateAug 7, 2012Filing dateOct 8, 2009Priority dateOct 8, 2008Also published asCA2740052A1, CA2740055A1, CA2740059A1, EP2347082A2, EP2347084A2, EP2347085A2, US20100089574, US20100089576, US20100089577, US20100218993, US20130264118, WO2010042719A2, WO2010042719A3, WO2010042723A2, WO2010042723A3, WO2010042725A2, WO2010042725A3Publication number12575852, 575852, US 8235140 B2, US 8235140B2, US-B2-8235140, US8235140 B2, US8235140B2InventorsThomas W. Wideman, Jared M. Potter, Donald Dreesen, Robert M. PotterOriginal AssigneePotter Drilling, Inc.Export CitationBiBTeX, EndNote, RefManPatent Citations (80), Non-Patent Citations (27), Referenced by (2), Classifications (13), Legal Events (1) External Links: USPTO, USPTO Assignment, EspacenetMethods and apparatus for thermal drilling
US 8235140 B2Abstract
Methods and apparatus for spalling a material, for example to thermally drill a wellhole, are provided. Such methods may include directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile transition temperature of the material to a target location on the surface of the material, wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material.
1. A method of spalling a material, comprising:
directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile transition temperature of the material to a target location on the surface of the material; wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material.
2. The method of claim 1, wherein the fluid has a temperature greater than about 600� C.
3. The method of claim 1, wherein the fluid has a temperature less than about 900� C.
4. The method of claim 1, wherein the method further includes providing a spallation system comprising at least one nozzle.
5. The method of claim 4, wherein the fluid is directed through the at least one nozzle to the target location.
6. The method of claim 1, wherein the fluid produces a heat flux of about 1 to about 20 MW/m2 at an interface between the fluid and the target location.
7. The method of claim 1, wherein the fluid is directed through one nozzle.
8. The method of claim 7, wherein the nozzle is adapted to direct the heated fluid from the drilling system substantially along an elongate central axis of the drilling system.
9. The method of claim 7, comprising directing the fluid from the at least one nozzle in a cyclically pulsing flow.
10. The method of claim 7, comprising directing the fluid from the at least one nozzle in a substantially continuous flow.
11. The method of claim 1, further comprising selecting the fluid to have a specified value of a parameter selected from the group consisting of a temperature, a heat flux, an exciting jet velocity, a heat capacity, a heat transfer coefficient, a Reynolds number, a Nusselt number, a density, a viscosity, and a mass flow rate.
12. The method of claim 11, wherein the fluid has an exiting jet velocity of about 400 to about 700 m/s.
13. The method of claim 11, wherein the fluid has a heat capacity of about 2.26 to about 3 kJ/kg�K.
14. The method of claim 11, wherein the fluid has a heat transfer coefficient of about 38 to about 56 kW/m2�K.
15. The method of claim 11, wherein the directed fluid has a Reynolds number of about 0.5�106 to about 60�106.
16. The method of claim 11, wherein the directed fluid has Nusselt number of about 30 to about 45 or about 740 to about 1040.
17. The method of claim 11, wherein the fluid has a density of about 0.01 to about 0.1 g/cm3.
18. The method of claim 11, wherein the fluid has a viscosity of about 0.025 to about 0.045 cP.
19. The method of claim 1, further comprising monitoring at least one property of the spalls.
20. The method of claim 19, wherein the spall size and/or shape is monitored.
21. The method of claim 19, further comprising adjusting the fluid temperature and/or heat flux to maintain a pre-determined spall size.
22. The method of claim 19, further comprising adjusting at least one parameter of the method in response to a change in the at least one of a property of the spalls, a hole diameter, a rate of penetration, and a standoff distance.
23. The method of claim 1, further comprising monitoring the fluid after the fluid is in contact with the material and/or after spalls have formed.
24. The method of claim 1, wherein the fluid comprises water.
25. The method of claim 1, wherein the material is rock.
26. A method for excavation of a borehole in a geological formation, comprising:
using a thermal drilling system to create a pilot borehole in a geological formation;
measuring at least one property of the geology of the pilot borehole;
evaluating the at least one measured property to determine whether to enlarge the pilot borehole, wherein the evaluating step comprises evaluating whether the geological formation is suitable for use as an injection or production borehole for at least one of a geothermal system, resource mining, excavation, or CO2 or nuclear sequestration or storage; and
enlarging the pilot borehole if the at least one measured property meets a set requirement.
27. The method of claim 26, wherein the pilot borehole is enlarged by inserting at least one drilling system into the pilot borehole.
28. The method of claim 27, wherein the thermal drilling system is a spallation drilling system.
29. A method for excavation of a borehole in a geological formation, comprising:
measuring at least one property of the geology of the pilot borehole, wherein the property of the geology of the pilot borehole is evaluated by evaluating at least one property of a fluid exiting the borehole; evaluating the at least one measured property to determine whether to enlarge the pilot borehole; and
30. The method of claim 29, wherein the fluid is at least one of a spallation fluid, a cooling fluid, and a drilling mud.
31. A method for excavation of a borehole in a geological formation, comprising:
using a thermal drilling system to create a pilot borehole in a geological formation, wherein using a thermal spallation system comprises directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the rock and less than about the temperature of the brittle-ductile transition temperature of the rock to a target location on the surface of the rock; wherein the fluid produces a heat flux of about 0.1 to about 20 MW/m2 at an interface between the fluid and the target location;
evaluating the at least one measured property to determine whether to enlarge the pilot borehole; and
enlarging the pilot borehole if the at least one measured property meets a set requirement. Description
This application claims priority to U.S. Ser. No. 61/103,859, filed Oct. 8, 2008; U.S. Ser. No. 61/140,477 filed Dec. 23, 2008; U.S. Ser. No. 61/140,489, filed Dec. 23, 2008; U.S. Ser. No. 61/140,512, filed Dec. 23, 2008; and U.S. Ser. No. 61/236,958, filed Aug. 26, 2009, each of which is hereby incorporated by reference in its entirety.
In various embodiments, this disclosure relates to methods and apparatus for conducting processes capable of spalling or penetrating a material such as rock. For example, the disclosed methods may be used for preparing boreholes for geothermal energy systems.
Drilling very deep boreholes or enhancing existing wells in hard rock far below the earth's surface, e.g. 10,000 feet deep or more, is inherently incompatible with traditional mechanical or contact drilling or rock removal technologies. Low rates of penetration, extreme bit and drill string wear, and excessive time spent “tripping” to replace damaged or worn bits and drill string make conventional rotary and coiled tubing drilling economically non-viable for many deep, hard rock applications.
Several non-contact techniques have been developed for hard rock drilling but may be effective only in shallow and/or air filled boreholes. Most notably, air or flame jet spallation drilling uses a hot gas or flame directed against a rock surface to cause spalling and removal of the rock. This technique, however, is only feasible in shallow, air-filled boreholes. To drill deeper, a borehole must be filled with water or “mud” to provide mechanical stability. In this environment, flames are not viable in part because of the difficulty in generating or maintaining the required flame under the high pressure water column. For example, the high pressures at the bottom of deep, fluid-filled boreholes make behavior of the flames extremely unstable and difficult to maintain. Further, initiating combustion under these conditions is extremely challenging and typically requires an energy source to be provided at the bottom of the borehole. However, using an energy source such as a spark or glow plug would require, e.g., a power cable to be run from the surface, which is not feasible in deep applications. Other energy sources such as flame holders are inherently unstable, especially at such depths.
There is a need for a method that fulfills the promise of thermal spallation drilling in high pressure, water filled boreholes. If the challenge of drilling deep boreholes in hard rock is not solved, EGS may not become the much needed clean alternative to meeting our current and future global energy needs.
The present disclosure relates, at least in part, to a method of reducing near wellbore impedance, or reducing the restriction to fluid flow in the immediate vicinity (e.g. 1 inch to about 3 feet) of an existing borehole wall) by providing a spallation system to e.g. increase the diameter of a section of an existing borehole or well, for example a geothermal well.
For example, a method of spalling a material, in accordance with one aspect of the invention, includes directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile transition temperature of the material to a target location on the surface of the material; wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material. The fluid may have a temperature greater than about 600� C. and/or a temperature less than about 900� C.
In some embodiments, the method may further include providing a spallation system comprising one or more nozzles. The fluid may be directed through the at least one nozzle to the target location. The fluid may produce a heat flux of about 1 to about 20 MW/m2 at an interface between the fluid and the target location. The nozzle may be adapted to direct the heated fluid from the drilling system substantially along an elongate central axis of the drilling system.
Some embodiments of the invention may include directing the fluid from the at least one nozzle in a cyclically pulsing flow or in a substantially continuous flow.
In some embodiments, the method may further include selecting the fluid to have a specified value of a parameter selected from the group consisting of a temperature, a heat flux, an exciting jet velocity, a heat capacity, a heat transfer coefficient, a Reynolds number, a Nusselt number, a density, a viscosity, and a mass flow rate.
The fluid may have an exiting jet velocity of about 400 to about 700 m/s, and/or have a heat capacity of about 2.26 to about 3 kJ/kg�K. The heat transfer coefficient of the fluid may be about 38 to about 56 kW/m2�K. The directed fluid may have a Reynolds number of about 0.5�106 to about 60�106, and/or have a Nusselt number of about 30 to about 45 or about 740 to about 1040. The fluid may have a density of about 0.01 to about 0.1 g/cm3, and/or a viscosity of about 0.025 to about 0.045 cP.
Some embodiments further include monitoring at least one property of the spalls, such as, but not limited to, the spall size and/or shape. The method may, in some embodiments, include adjusting the fluid temperature and/or heat flux to maintain a pre-determined spall size. For example, at least one parameter of the method may be adjusted in response to a change in the at least one of a property of the spalls, a hole diameter, a rate of penetration, and a standoff distance.
The fluid may be monitored after the fluid is in contact with the material and/or after spalls have formed. Contemplated fluids include water or mud. The material may be rock.
Also contemplated herein is a method for penetrating or reacting rock including the steps of contacting a fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile transition temperature of the material to a target location on the surface of the material, wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and directing said fluid to said rock, thereby effecting penetration of the rock and/or forming a reacted rock region.
Contemplated methods may also include a method for excavation of a borehole in a geological formation, including using a thermal drilling system to create a pilot borehole in a geological formation, measuring at least one property of the geology of the pilot borehole, evaluating the at least one measured property to determine whether to enlarge the pilot borehole, and enlarging the pilot borehole if the at least one measured property meets a set requirement. The thermal drilling system may be a spallation drilling system.
In some embodiments, the pilot borehole is enlarged by inserting at least one drilling system into the pilot borehole.
The evaluating step may include evaluating whether the geological formation is suitable for use as an injection or production borehole for at least one of a geothermal system, resource mining, excavation, or CO2 or nuclear sequestration or storage. The property of the geology of the pilot borehole may be evaluated by evaluating at least one property of a fluid exiting the borehole. The fluid may be at least one of a spallation fluid, a cooling fluid, and a drilling mud.
In some embodiments, using a thermal spallation system includes directing a fluid having a temperature greater than about 500� C. above the ambient temperature of the rock and less than about the temperature of the brittle-ductile transition temperature of the rock to a target location on the surface of the rock; wherein the fluid produces a heat flux of about 0.1 to about 20 MW/m2 at an interface between the fluid and the target location.
Also contemplated herein is a method of monitoring an excavation of a borehole in a geological formation, including the steps of providing a thermal spallation system comprising at least one jet nozzle, directing a heated fluid, having a temperature from about 500� C. to about 900� C., from the jet nozzle against a target location at a distal portion of a borehole in the geological formation, wherein said heated fluid has a heat flux of about 0.1 to about 20 MW/m2, to create spalls in the target location, carrying the spalls and heated fluid from the target location to a surface location through the borehole, and measuring a property of at least one of the spalls and the heated fluid, wherein the at least one property of the spalls is related to a parameter of the excavation. The thermal spallation system may include a catalyst element.
Both a property of at least one of the spalls and a property of the heated fluid may be measured. The spalls may, for example, be measured at the surface location. Contemplated properties of at least one of the spalls include at least one of a size, a shape, a temperature, and/or a chemical composition. The heated fluid may, for example, be measured at a downhole location, or at a location removed from the downhole location. The property of the heated fluid may include at least one of a temperature and a chemical composition. In some embodiments, the measuring step includes at least one of a thermal measurement, an optical measurement, an acoustic measurement, a chemical measurement, and a mechanical measurement.
Some embodiments of the invention further include introducing a flow of water or mud into the borehole. The flow of water or mud may be carried down the borehole in at least one conduit. The flow of water or mud may at least partially form an ascending fluid stream capable of carrying spalls to a surface location.
Contemplated methods may further include adjusting a parameter of the thermal spallation system in response to a change in at least one of a property of at least one of the spalls, a property of the heated fluid, a hole diameter, a rate of penetration, and a standoff distance.
Also contemplated herein is an apparatus for spalling rock including a fluid heating means adapted to heat a fluid to a temperature greater than about 500� C. above the ambient temperature of a surrounding material and less than about the temperature of the brittle-ductile transition temperature of the material, and at least one nozzle adapted to direct the heated fluid onto a target location on the surface of the material, wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material.
The fluid heating means may be adapted to heat a fluid to a temperature greater than about 600� C., and/or a temperature less than about 900� C.
The apparatus may further include a spallation system comprising at least one nozzle. The at least one nozzle may be adapted to direct a fluid to the target location. The fluid may produce a heat flux of about 1 to about 20 MW/m2 at an interface between the fluid and the target location. The fluid may be directed through one nozzle.
In some embodiments, the apparatus may include a means of monitoring at least one of a property of the spalls, a hole diameter, a rate of penetration, and a standoff distance. For example, the spall size and/or shape may be monitored. The apparatus may further include a means of adjusting the fluid temperature and/or heat flux to maintain a pre-determined spall size.
In some embodiments, the apparatus may include a means of monitoring the fluid after the fluid is in contact with the material. The fluid may include water, mud, and/or an additive.
Also contemplated herein is a system for excavation of a borehole in a geological formation, including a thermal system to create a pilot borehole in a geological formation, a means of measuring at least one property of the geology of the pilot borehole, and a drilling system adapted to enlarge the pilot borehole. The thermal system may include a fluid heating means adapted to heat a fluid to a temperature greater than about 500� C. above the ambient temperature of a surrounding material and less than about the temperature of the brittle-ductile transition temperature of the material, and at least one nozzle adapted to direct the heated fluid onto a target location on the surface of the material, wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material. The fluid heating means may be self-energized.
The drilling system may include at least one of a spallation drilling system and a mechanical drilling system. The measuring means may be located substantially at the proximal end of the borehole and/or substantially at the distal end of the borehole. The thermal system may include a single nozzle, or a plurality of nozzles.
Also contemplated herein is method of spalling a material, including providing a thermal system capable of providing a heated fluid having a temperature greater than about 500� C. above the ambient temperature of the material and less than about the temperature of the brittle-ductile transition temperature of the material, and directing the heated fluid to a target location on the surface of the material, wherein the fluid produces a heat flux of about 0.1 to about 50 MW/m2 at an interface between the fluid and the target location, and thereby creating spalls of the material.
In some embodiments, the thermal system includes a catalyst. The method may further include contacting one or more unreacted fluids with the catalyst to generate the heated fluid. The unreacted fluid may include an oxidant and/or a fuel.
FIGS. 14A, 14B, and 14C show views of a rock core confinement system for laboratory drilling demonstrations;
The present disclosure relates, at least in part, to methods and systems for use in spallation, fracturing, loosening, or excavation of material such as rock, for example, methods of making or excavating boreholes, and/or enlarging existing boreholes. Such methods include using a disclosed working fluid or reacted fluid, e.g. a working fluid capable of producing a heat flux of about 0.1 to about 50 MW/m2 when in contact with rock.
For example, provided herein are systems and methods that may be capable of creating 20 feet of an e.g., 8 inch borehole in about hour, or 20 feet of a 4 inch borehole in about an hour or less, or about a 0.2 inches of ˜1 inch borehole in about 4 minutes. Also provided herein are systems or methods for opening a length of existing borehole, e.g. with an original diameter of that may be as small as 4 inches, to a final diameter of about 36 inches or more, which in some embodiments may be accomplished in 12-24 hours, or days. Contemplated systems and methods may be used to create boreholes, shafts, caverns or tunnels in a target material such as crystalline rock material, silicate rock, basalt, granite, sandstone, limestone, peridotite, or any other rocky material. Disclosed systems and methods may also be used for producing multilaterals from an existing borehole, which in turn may be opened. In certain embodiments, disclosed systems and methods may be used, for example, to create vertical boreholes, horizontal boreholes, deviated boreholes, angled boreholes, larger diameter boreholes, curved boreholes, or any combination thereof. Also provided herein are systems and methods that may spall rock at a rate of about 100 ft3/hour or more, which may be useful for example for the creation of tunnels, caverns, mineshafts, and the like.
For example, also provided herein are methods to reduce existing wellbore impedance and/or improve production of existing wells (e.g. EGS wells). Such methods may include, for example, increasing the diameter of at least portions (e.g. a working, producing, or production zone or portion—one or more sections that are typically significantly downhole, may be uncased, or cased with slotted or perforated casing, and where substantially most of the energy output or fluid production occurs, for example, in an EGS well) of an existing wellbore.
Methods contemplated herein also include hydrothermal reactions, explosions or detonations, which take place in the wellbore or fractures for only a finite period. For example, an unreacted fluid may be pumped into the wellbore and/or allowed to penetrate the fractures. A reaction may then be initiated by e.g. a catalyst “pill” sent down the drill string or by exposing a sample of catalyst in a downhole tool, initiating a hydrothermal reaction and causing spallation in fractures and macrofracturing in wellbore.
Alternatively, the wellbore may be cooled by traditional means of circulating fluids. An unreacted fluid which has a Self Accelerating Decomposition Temperature (SADT)—a temperature at which reaction runs away and propagates—that is below the formation temperature may then be injected into the wellbore and fractures. As the formation is allowed to recover from the cooling treatment, the reaction may initiate, with or without the use of a catalyst.
In some embodiments, two or more components of the unreacted fluid, e.g. fuel and oxidant may be delivered through the conduit in “slugs” so that there is no chance of a premature reaction in the conduit. Once the desired mixture of e.g. fuel and oxidant have been created in the wellbore, the reaction can be initiated by e.g. a catalyst pill, exposing a catalyst in the tool, auto-initiated, or by allowing the wellbore to warm. Since high concentrations of e.g. fuel and oxidant can be delivered by this “slug” flow, it may be possible to produce an unreacted fluid mixture e.g. above the detonation limits which allows for propagation of the reaction and shockwave throughout the producing zone and/or fractures, creating spallation and fracturing.
In general, as discussed herein, “spallation” refers to the breaking away of surface fragments of a material, e.g. rock “spall” refers to the fragments of material formed by a process of spallation. A thermal spallation process can refer to a spallation process that uses a working fluid other than air, such as working fluid that includes water (e.g., hydrothermal spallation resulting from the creation of high temperature water from hydrothermal oxidation reaction as disclosed herein), water or oil based drilling muds, supercritical fluids, and the like.
In some embodiments, such as hole opening using lower heat fluxes, created spalls may be on the order of inches to several feet; these spalls may be left in place, allowed to fall into an existing cavern or “rat hole” (existing below the production zone), or may be reduced and/or removed by a secondary process such as mechanical drilling. Non-removal of such formed spalls may be advantageous, e.g. smaller conduits may be needed to transport fluids to and from the bottom of the hole. Substantial non-removal of spalls may be particularly advantageous if larger spalls are generated by lower heat fluxes. In other embodiments, any rock that is removed may intentionally makes the hole less stable, resulting in break-out or cave-ins, further expanding the diameter without requiring the complete spallation of all of the loosened material.
Near wellbore impedance may occur where fractures intersect a wellbore, as shown, e.g., in FIG. 20A. In one embodiment, a method of fracture enlargement is provided, e.g. to reduce wellbore impedance, by using a provided working fluid in a wellbore. Pressure in an existing well may be controlled, in some embodiments, by e.g., “shutting in the well”, “zonal isolation” or by “packing off” the length of the borehole being treated such that the working fluid is forced into or near fractures (e.g. identified fractures or fractures along an isolated zone), inducing spallation or geomechanical changes at the surface of the fracture, enlarging the fracture, and thereby resulting in an improvement in the flow of fluids through the fracture, as shown, e.g., in FIG. 20D. In other embodiments, the pressure in an existing well may be controlled to prevent flow of the fluid into the fractures, by either maintaining neutrally or “underbalanced” conditions. In other embodiments, the pressure may be varied or cycled; this may assist in blowing produced spalls or fractured rock out of the fractures or away from the borehole wall. Pressure or flow may also be cycled to allow for the measurement of flow and temperature from the borehole to determine how effective the treatment has been, or if additional treatment is necessary. In other embodiments, the wellbore may be expanded more globally, by removing the rock in and around the fracture, also leading to a reduction in wellbore impedance, as shown, e.g., in FIGS. 20B and 20C. In other embodiments, the walls of the borehole can be spalled to create features such as slots or perforations that may be designed to better intersect the existing fractures or to weaken the walls of the wellbore in that location so as to induce further collapse and expansion of the wellbore, leading to a further reduction in impedance. In some embodiments, the reacted fluid may comprise other chemicals which may assist in the process of reducing wellbore impedance, e.g. chemicals which increase or decrease the solubility of certain minerals. Incorporation of these chemicals either from the unreacted fluid or from a separate stream, may be used to prevent minerals from being dissolved by the high temperature fluid jet and/or or being redeposited in the cooler fractures, or may be used to facilitate dissolution of the minerals in either the spalls or along the fracture walls. These chemicals may include alcohols e.g. methanol, or bases e.g. hydroxides, or combinations of the two, such as alcoxides. Alternatively, these chemicals may include acids, such as HCl, HF or the like.
In some embodiments, the working fluid includes a substantially aqueous fluid, e.g. water. Other exemplary fluids include oil or water based drilling mud. The fluids may be selected for optimum heat capacity and/or heat transfer properties. In alternate embodiments, a working fluid may include a gas such as neon or nitrogen. Contemplated working fluids may include by appropriate additives, e.g. viscosifiers, thermal stabilizers, density modifying additives such as barite, and those common in oil, gas and/or geothermal drilling.
For example, such as in hole opening applications provided herein, the shape of the openings may be controlled to make features in the walls of existing boreholes such as channels, perforations, slots, or multilaterals (multiple branches drilled out from the existing wellbore). For example, the shape of the openings may be controlled by controlling spall size, or may be controlled by the orientation of the nozzles. For example, an apparatus with at least one substantially perpendicular nozzle may be slowly run along the length of a production zone of an existing borehole, creating a slot. Alternatively, a single substantially perpendicular jet may sit on one position in the existing borehole creating a perforation. An apparatus with multiple perpendicular jets (within the same or different apparatus) or if the tool or apparatus is rotated, a series of holes or parallel slots can be created. The pressure from the surface pumps and/or reaction may be used to move the nozzle e.g., towards the rock face to maintain a small stand-off. A ring or peripheral gap nozzle can create disc-like openings if stationary (as shown, e.g., in FIG. 20B), or open the diameter along the length of the wellbore if translated. A less directed or more even heat flux may be applied to open the hole more evenly in all areas, or in the areas of greatest existing stress. In an embodiment, methods of reducing wellbore impedance are provided that include the use of less focused or directed jets, jets substantially axial with the wellbore or with greater stand-off distances or lower heat fluxes, to produce more global spalling of the area of a production zone. In some embodiments, “packers” or plugs (e.g., cement or ceramic plugs) may be used to isolate the areas of a production zone to be treated.
For example, a disclosed spallation system or apparatus that is capable of producing a fluid for use in the disclosed methods and apparatuses may include at least one jet nozzle, and a housing including a reaction chamber and, optionally, a catalyst element held within the reaction chamber. In operation, unreacted fluids or solids can be contacted with the catalyst element within the housing, resulting in the unreacted fluid or solid reacting, with the catalyst element and generating a reacted fluid. This reacted fluid may then be emitted through the at least one jet nozzle and directed to an excavation site within the geological rock formation, thereby creating spalls and/or a reacted rock region. In some embodiments, contemplated unreacted fluid or solids react in the presence of a catalyst substantially self-energized, e.g., does not require an additional energy or heat source such as e.g., a spark, flame holder, flame, or glow plug to initiate or maintain the reaction and produce the reacted fluid.
Contemplated catalysts include catalysts comprising transition metals and/or noble metals, e.g. lead, iron, silver, platinum, palladium, nickel, cobalt, copper, iridium, gold, samarium, cerium, vanadium, manganese, chromium, ruthenium, zinc, and/or rhodium, and or mixtures and/or alloys or salts thereof, and/or complexes, e.g. carbonyl complexes thereof. Contemplated catalysts include oxides and/or nitrides of e.g. metals. The catalyst may, in one embodiment, include lanthanum, zirconium, aluminum or cerium (e.g. lanthanum cerium manganese hexaaluminate, Zr—Al-oxides and Ce-oxides) or other mixed metal oxide catalysts. The catalyst may include promoters (e.g. cerium and/or palladium).
In an alternative embodiment, a catalyst bed can be used in conjunction with a heat exchanger to initiate the reaction and raise the temperature of a down flowing unreacted fluid, wherein once the system has an appropriate temperature and/or the reaction is self-sustaining, the catalyst bed may be by-passed and/or isolated by e.g. a thermally-actuated mechanical valve, which may improve catalytic longevity. A higher activity catalyst bed may also be used to “light off” the reaction, after which lower activity beds may be used to maintain its high activity. The use of higher pressures in the catalyst bed through e.g. choked flow across the nozzle, mud weight in the borehole, or back pressure at the wellhead, may increase the reaction rates per unit catalyst and decrease the pressure drops across the catalyst bed which may allow for smaller catalyst bed volumes and e.g. axial reactor beds.
For example, the unreacted fluid may include water and/or an oxidant and/or a fuel. In operation, the unreacted fluid may be, e.g., pumped to a drill head assembly of a disclosed spallation system. In the drill head, the unreacted fluid can be, for example, passed over a catalyst configured (or otherwise put in contact with the catalyst) to e.g., cause the flameless reaction with an oxidant and/or a fuel that may be present in e.g. the unreacted fluid. Such a reaction may produce a reacted fluid, e.g. a fluid at an elevated temperature, that may then be directed out of an e.g., distal jet nozzle of the spallation drill head assembly and impinge upon a target rock surface, creating thermally damaged rock and/or spalled rock. The reacted fluid, in some embodiments, may include water in gaseous (steam) or supercritical form, for example, may be a gas when in first contact with rock. After contacting the rock, the expelled water, gas or supercritical fluid can then, in some embodiments, flow up the borehole, carrying the spalled rock with it. In some embodiments, the reacted (hot) fluid is allowed to travel up the borehole to further spall the borehole walls and expand the diameter of the borehole. In other embodiments, the reacted fluid is cooled e.g. just above the drilling assembly by a heat exchanger and/or cooling-lift fluid, thereby substantially stopping the spallation reaction. In other embodiments, the reacted fluid is directed through a “shroud” which may reduce its interaction with the sides of the rock wall, and also substantially stopping the spallation reaction. In an alternative embodiment, some of the reacted fluid does not travel up the wellbore but rather enters the rock or formation through e.g. fractures. In some embodiments, the spalls or rock fragments are not carried up the wellbore but are allowed to fall further into the hole or remain on the borehole wall.
In one embodiment, the fuel and oxidant may be combined in a number of different ways to allow for transportation of the fuel and oxidant down the same conduit. For example, fuel and oxidant may be transported down a single conduit through use of a single molecule (“single-source”) or network/complex. The chemical heat source can be a monopropellant, such as hydrogen peroxide, nitrous oxide, or hydrazine. Alternatively, fuel and oxidant may be transported down a single conduit through use of methods including, but not limited to, slug flow (i.e. gases and/or liquids sent one after another), dissolved gases, or bubble flow (i.e. small bubbles suspended in a fluid and transported along with the fluid). In an alternative embodiment, the fuel and oxidant may be transported down the same conduit as two solid materials in one or more “pills”. In a further alternative embodiment, one or more of the fuel and/or oxidant may be transported in an encapsulated form such as, but not limited to, a material, such as a peroxide, encapsulated by e.g., wax.
Contemplated fuels include carbonaceous fuel, such as a fossil fuel (e.g. coal, biomass), gasoline, natural gas (e.g. liquefied natural gas) diesel, biodiesel or kerosene. For example, fuels contemplated for use in the disclosed methods include alcohols, alkyls, cycloalkyls, alkenes, alkynyls, ethers, alkoxyalkyls, (e.g. CH3CH2OCH2CH3), dioxanes, glycols, diols, ketones, acetone, aldehydes and/or aromatic organic compounds such as benzene or naphthalene, or combinations thereof. Hydrocarbons may be used as fuel, and include alkanes (e.g. C1-C20 alkanes) such as methane, ethane, propane, butane, pentane, hexane, heptane, octane, and higher alkyl fuels such as naphtha, kerosene, paraffin, hydrocarbon oligomers, and/or other waxes. Other contemplated fuels include ethylene vinyl acetate (EVA), polyvinyl chloride (PVC), boranes (such as B2H6 or B5H9), carboranes, ammonia, kerosene, diesel, fuel oil, bio-based oils, such as biodiesel, starch, sugars, carbohydrates, or other oxyhydrocarbons. A fuel may be, or include, hydrogen, hydrogen generating compounds, or hydrogen containing polymers such as polyethylene, polypropylene, or paraffin polymers. A fuel may also be, or include, reactive metals such as aluminum, beryllium, and coated or encapsulated sodium.
Contemplated oxidants include air, oxygen, peroxides, (e.g., hydrogen peroxide or methyl ethyl ketone peroxide) percarbonates, permanganates, permanganate salts, as well as combinations thereof. For example, contemplated oxidants include inorganic and/or organic peroxides such as peroxides of alkali metal peroxides, e.g. lithium, sodium, and/or potassium peroxides, e.g. sodium peroxide and/or barium peroxide. Alkyl peroxides such as t-butyl peroxide and benzoyl are contemplated. Oxidants contemplated herein may include hypochlorite and/or hypohalite compounds, halogens such as iodine, chlorite, chlorate or perchlorate compounds, hexavalent chromium compounds, sulfoxides, ozone, nitric acid, N2O, and/or persulfuric acid. Other possible oxidants include F2, OF2, O2/F2 mixtures, N2F4, CIF5, CIF3, NxOy, IRFNA IIIa: 83.4% HNO3, 14% NO2, 2% H2O, 0.6% HF: IRFNA IV HAD: 54.3% HNO3, 44% NO2, 1% H2O, 0.7% HF, RP-1, C10H18, and CH3NHNH9.
In an exemplary embodiment, the unreacted fluid is slightly oxidant rich to assure complete combustion of the hydrocarbons to reduce the amount of by-products caused by incomplete combustion, such as carbon monoxide, formaldehyde, and/or formic acid. In other embodiments, the unreacted fluid may be T-Stoff (80% hydrogen peroxide, H2O2 as the oxidizer) and C-Stoff (methanol, CH3OH, and hydrazine hydrate, N2H4.nH2O) as the fuel); nitric acid (HNO3) and kerosene; inhibited red fuming nitric acid (IRFNA, HNO3+N2O4) and unsymmetric dimethyl hydrazine (UDMH, (CH3)2N2H2), nitric acid 73% with dinitrogen tetroxide 27% (AK27), and kerosene/gasoline mixture, hydrogen peroxide and kerosene; hydrazine (N2H4) and red fuming nitric acid; Aerozine 50 and dinitrogen tetroxide, unsymmetric dimethylhydrazine (UDMH) and dinitrogen tetroxide; or monomethylhydrazine (MMH, (CH3)HN2H2) and dinitrogen tetroxide. In another embodiment, the unreacted fluid may include 50-98% hydrogen peroxide. The products from decomposing the 50-98% peroxide (e.g. H2O and/or O2) over a catalyst (e.g. platinum, silver, or palladium), may then be allowed to react with a fuel (e.g. methanol). The heat from the decomposition of the hydrogen peroxide, combined with downhole temperatures and pressures and/or the use of a heat exchanger, may auto-initiate or sustain the reaction of fuel and oxidant, such as peroxide and/or oxygen with methanol and/or ethanol.
A drill assembly may include a drill head with a nozzle. An exemplary drill head may have a diameter of approximately � inches with a 0.1 inch center nozzle through which the reacted fluid is expelled. In alternative embodiments, nozzles with different configurations and/or geometries may be utilized, such as a larger or smaller nozzle diameter. For example, the drill head may be about 5 to about 15, or 4 to about 29 times the diameter of the nozzle. In one embodiment, the drill head assembly may include a plurality of jet nozzles directed in either the same or different directions from a distal portion of the drill head assembly. In another embodiment, the drill head assembly includes one center jet nozzle. Rock “spalls” (e.g. grains or platelets of less than about 0.025 inch to about 0.1 inch) can be ejected and may be swept up the borehole by the reacted fluid (after the reacted fluid contacts the rock). In one embodiment, a larger flow of cooling-lift water (e.g., traveling in the annulus between the nested tube and coiled tubing), can be introduced after the heat exchanger (if used), to cool the fluid and help transport the spalls to the surface.
Gas Spallation
In one embodiment, a heating means may include a gas based spallation system, with the heated working fluid including a heated jet of a gas such as, but not limited to, air, combustion products, or any other appropriate gas or mixture thereof. An exemplary spallation method includes the use of air spallation drilling. This technique (also known as Flame Jet Drilling or Jet Piercing), uses a supersonic flame jet in an air-filled hole to apply heat to the rock surface. An example air spallation drilling process is shown in FIG. 2. Subsonic jets may also be used.
A working fluid may be provided using a heat generation chamber. The heat generation chamber may, for example, include a combustion chamber, which may be energized by a spark, flameholder, or glow plug. Alternatively, the combustion reaction may be initiated by a catalyst which may be later bypassed or isolated once the reaction is self-sustaining. In a combustion chamber, a focused or diffuse flame may exit into a working fluid to raise the temperature of the fluid prior to contacting a rock surface. In such an embodiment, the high temperature combustion reaction may not come into contact with rock, and therefore may avoid fusing or melting the rock surface. In hydrothermal flame drilling, the combustion flame is directly impinged on the rock surface.
A heat generation chamber may alternatively be an electric heating chamber, heated by an electric heating element or induction heater that is energized by a turbogenerator, driven by a flow of water delivered to the turbogenerator from the surface in a conduit. The electric heating element may be additional or optionally energized by an electrical power cable run from a surface generator or by transmission of electrical power along the drill string The heat generation chamber may also be heated by induction heating using permanent magnets which are rotated by a hydraulically driven turbine. Alternatively, a receiving material, such as steel, may be rotated in the field of permanent magnets. Permanent magnets may be cooled by a stream other than the working fluid. The induction heater or an induction generator may use a small permanent magnet generator cooled by the fluid exiting the turbine to flash the field of a much bigger induction generator that can operate at much higher temperatures. In some embodiments, fluid flowing through or past the inductive receiving material may increase in temperature. Coolant flow through channels in the permanent magnets may prevent overheating and loss of magnetization.
In an alternative embodiment, a working fluid including an aqueous fluid comprising water and hydroxides of Group I elements of The Periodic Table of Elements, and mixtures thereof, may be used. For example, an aqueous fluid may include a hydroxyl ion concentration of the hydroxides of Group I elements of The Periodic Table of Elements and mixtures thereof at ambient conditions is in the range of about 0.025 to 30 moles of hydroxyl ion per kilogram of water. In some embodiments, an upper limit of the range can be determined by the solubility of the Group I hydroxide. For example, a fluid may include about 0.1 to about 52 grams sodium hydroxide per 100 grams of solution at room temperature (but may include more at higher temperatures). In some embodiments, the fluid may comprise alcohols such as methanol or ethanol with hydroxides, which produce alkoxides. Such alkoxides may help solubilize minerals in rock.
One aspect of the present invention relates, at least in part, to drilling systems, and associated methods of use, that includes a heat source to thermally affect a target material and a mechanical drilling system. The drilling systems may be used to create boreholes or increase the diameter of existing boreholes in any of the target materials described herein including, but not limited to, crystalline rock material, silicate rock, basalt, granite, sandstone, limestone, or any other rocky material. The drilling systems may be used to create vertical boreholes, horizontal boreholes, angled boreholes, curved boreholes, as well as slots, perforations, fracture enlargement, or other forms of hole opening, or any combination thereof. In one embodiment, the methods and systems described herein provide for improved deep borehole drilling, for example from approximately 10,000 feet to approximately 50,000 feet below the surface, or more.
In one embodiment, the bulk of the fluid flow through the drilling assembly—e.g. the portion used for cooling and cuttings lift—may be relatively cool, while only a small portion—e.g. that used for thermal degradation—is hot. As a result, some, or all, of the cold fluid can be used to provide cooling to at least a portion of the drilling device. For example, cold fluid may be sent through or around the mechanical drilling structure to reduce its temperature and improve survivability. In one embodiment, cold water may be sent through flow channels in a traditional PDC or tricone bit, while the hot portion of the fluid is insulated directed substantially down against the rock. The channels transporting the hot water may be isolated from the bit by a layer of insulation, such as, but not limited to, a substantially solid, liquid, gas, or vacuum insulation layer, or a combination of the different insulation layers. In one embodiment, the relative ratio of hot/cold can be adjusted to balance the performance of the two drilling mechanisms.
One embodiment of the invention includes a spallation system including control systems, and associated methods, adapted, for example, to control the diameter of the wellbore produced by a e.g., hydrothermal jet, maintain the desired well hole trajectory, control the distance between the nozzle and the bottom of the hole (i.e. the “stand-off”), and/or ensure a sufficient temperature differential so as to induce spallation. These control systems may include software and/or hardware based control elements designed to ensure optimum performance of the thermal drilling system.
The total heat output—the thermal power of the drill divided by the cross sectional area of the borehole to be drilled—may be kept, for example, between 0.1 and 100 MW/m2. The heat flux—a product of the heat transfer coefficient and the temperature difference between the wall jet and the rock surface—may be kept, for example, between 0.1 and 100 MW/m2. In certain embodiments, if too low a value of heat flux is used, a thermal gradient may propagate and build in the rock, reducing the relative strain of the surface rock to the underlying layer, thereby reducing or preventing spallation. In one embodiment, it is possible to increase the heat flux by increasing the Reynolds number—a dimensionless number that gives a measure of the ratio of inertial forces to viscous forces—in the nozzle exit. In certain embodiments, the heat flux of a thermal jet for spallation drilling may be increased without having the jet exceed the temperature e.g. brittle-ductile transition of the rock, by increasing the mass flow, and/or reducing the nozzle diameter (to increase the exiting jet velocity). Increasing the velocity or mass flow of the jet may also provide a mechanical or erosive means of removing material or spalls from the rock surface, clearing and providing a freshly exposed surface for further spallation, and/or help with spall and cuttings lift.
The Nusselt number—a dimensionless ratio of convective to conductive heat transfer across (normal to) the rock-fluid boundary may, in a non-limiting example, for a working fluid in one or more of the disclosed systems, be between about 30 and 1040, depending on hole size. In one embodiment, working fluid properties can be optimized so as to produce an induced strain within the grains of the rock of between about 0-30%, thereby generating enough stress to cause structural failure, which may make use of existing flaws, discontinuities, or grain boundaries in the rock and/or in-situ stresses
The fluids used in the systems described herein, and/or the loose materials created by the process described herein, can, in one embodiment, strengthen and seal the walls against structural collapse and wellbore fluid loss, thereby greatly extending time interval between casing of the borehole. This may happen through processes such as, but not limited to, precipitation of materials on the surface walls of the borehole and/or depositing of loose materials within cracks and other cavities on the walls of the borehole.
An example method of testing the efficiency of a thermal spallation system is described below. This method may be used to test any appropriate spallation system on a material.
Repeatability and Other Rock Types
An experiment as in Example 1 was been repeated on Sierra White Granite, as shown in Table 2:
Borehole Drilling—4″ Diameter in Hard Rock
A 4″ diameter hole is pre-drilled to a depth of 5″ in Sierra White granite rock block measuring 24�24″ square and 36″ tall. A drill head interface is placed in the pre-drilled hole and sealed in place with high temperature cement. The block is centered in cylindrical steel mold 38″ diameter, 44″ in length, with a 0.375″ wall. This mold had been split down the side and support railings were welded onto the outside edge. Bolts are used to clamp the two halves of the mold together. Concrete is poured to fill the empty volume between the rock block and mold. The concrete is allowed to cure for 10 days, after which time the bolts are tightened to provide 150 psi clamping pressure on the sample. A diagram of the apparatus is shown in FIGS. 14A-C.
Approximately 450 g of Instant Steam catalyst obtained from Oxford Catalyst PLC is loaded into a converging radial flow reactor and placed inside a 2⅞″ OD drill head, as shown in FIG. 12. The drill head is slid into the drill head interface. Before the start of a test, the drill head is driven to the bottom of the predrilled hole and a depth is read off of the computer controls. The drill head is then retracted approximately 10″ from the bottom of the hole to allow cooling water from the drill head interface to enter the bottom of the hole. A mixture of 38% hydrogen peroxide and 12% methanol by weight is pumped into the catalyst bed at 3200 mL/min. Neither the catalyst nor the fuel/oxidant fluid is preheated, and no additional heat source such as a glow plug, spark, or flame for the reaction is used. The mixture “lights off” over the catalyst bed producing a 800� C. jet of steam which exits a single, 0.189″ diameter non rotating nozzle located along the central axis.
A thermal spallation system can be deployed on a customized AmKin 800 V track mounted coiled tubing unit. A 20′ long 2⅞-3�″ OD bottom hole assembly is prepared from instrumentation and controls subassembly (or “sub”), a release sub, a dynamic barrier sub, stabilizers and centralizers, and an iteration of the steam generation sub described in Example 4. The steam generation sub houses an axial catalyst bed 2�″ in diameter and 12″ long filled with Oxford Catalysts Instant Steam catalyst. The bottom hole assembly is attached to a Tenaris HS-90 2.00″ steel coiled tubing with a 0.134″ wall through a connector sub. Inside of the coiled tubing, a ⅜″ OD nitric-acid passivated stainless steel capillary is housed to transport the unreacted fluid to the steam generation sub, and a 5/16″ 7-conductor wireline cable is used for communication in the instrumentation controls sub.
The unreacted fluid is prepared at the surface by continuously metering 52% high test peroxide, reagent grade methanol, and deionized water into a mix tank to produce 38% peroxide and 12% methanol. The mixture is pumped through the capillary at 1 gallon per minute to the catalyst bed where it self-energizes and reacts with the catalyst element without the need for an external energy source (such as a spark, glow plug or flame holder) thus generating a 800 C reacted fluid, without an inherently unstable flame or the need for cooling water to protect the materials of construction or overheating of the rock. This reacted fluid is then emitting through a 0.189″ nozzle and directed at the bottom of the hole, causing rapid spallation of the rock. The coiled tubing is fed into the hole at a rate of 20′/h by means of the coiled tubing injector on the AmKin 800 V continuously drilling a 4″ borehole in the solid granite. Spalls are swept through the dynamic seal assembly where they meet a 50 gallon per minute flow of water flow, which has traveled down inside the 2″ coiled tubing and exited a series of upward pointing jets, to cool the reacted fluid and carry the spalls to the surface. At the surface, the spalls are removed by a series of “shakers”, cyclones, and filters, the water is cooled by a 200 kW mud cooler, and continuously recirculated.
Multilaterals with Hole Opening
A system as described in Example 4 can be used to create multilaterals. At the desired depth, the bottom hole assembly is deviated, the spallation jet is directed at the wall of the borehole causing the drill to create a hole off-axis from the existing borehole. The bottom hole assembly is advanced using the coiled tubing injector and intersects additional fracture networks which can provide flow to the main wellbore. When the final target depth (“TD”) is reached, the unreacted fluid is directed through a second catalyst bed that is in fluid communication with 6 jets oriented normal to the axis of the bottom hole assembly and spaced 60 degrees apart around the circumference of the tool. The unreacted fluid is pumped again and reacted fluid exits the circumferential jets, expanding the diameter of the wellbore as the bottom of the hole assembly is withdrawn on the coiled tubing. Periodically, this hole opening process is paused and the well is allowed to produce fluid, blowing produced spalls and loose rock from the fractures. Flow sensors including “spinners”, and thermocouples are used to infer the flow rate from a given fracture. If additional hole opening is required, the hole opening is restarted. In certain sections of the well where larger/global hole opening is desired, the bottom hole assembly can be held in place, causing extensive spallation, macrofracturing, breakout and collapse of sections in the producing zone.
Hole Opening of a 0.75″ Borehole
Using the procedure of Example 1, a Sierra White granite rock core measuring 4″ in diameter and 6″ long was prepared by pre-drilling a 0.75″ diameter hole 4″ deep on the top surface. The core was then loaded into a stainless steel pressure vessel described in Example 1.
Thermal and Mechanical Drilling
Spalls and/or a reacted rock region can be formed as described above. A reamer element, including one or more reamer elements mounted to the housing and located back from the distal portion of the thermal spallation system, can then be used to ream the thermally effected rock at the outer sides of the borehole created by the thermal spallation system to enlarge and/or shape the borehole, as required.
Thermal Heating and TSP Drag Bit
Spalls and/or a reacted rock region can be formed as described above. A drag bit with TSP cutters is then used to remove the thermally effected rock from the borehole more easily than if the rock was not heated.
Rock Sample Tests
Thin sections: samples extracted from rocks in Examples 1-4 were cut into small sections using diamond blades and sent to a thin section preparation laboratory. The samples were evacuated and saturated with a blue epoxy to identify pores and fractures. The samples were polished and then mounted to a glass slide and the section ground down to a thickness required using a transmission microscope with polarizing lens to determine mineral structure alteration and other microscopic features.
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