Methods for efficient mining and leaching of minerals utilizing advanced directional drilling technology and extraction via boreholes

Abstract

A method for underground mining in a rock body includes directionally drilling two or more service boreholes from surface to extend underneath a subsurface rock body. One of the service boreholes is disposed substantially in parallel above a second service borehole below the subsurface rock body. The two service boreholes are to each other at one or more points below the subsurface rock body by removing rock between the service boreholes. The subsurface rock body is above said service boreholes using explosives in blast holes drilled from surface into the subsurface rock body. A mechanism is extended in the first service borehole to control crushing of and to control flow of fragmented rock into the second service borehole.

Description

METHODS FOR EFFICIENT MINING AND LEACHING OF MINERALS UTILIZING ADVANCED DIRECTIONAL DRILLING TECHNOLOGY AND EXTRACTION VIA BOREHOLESBackground

[0001] This disclosure relates to the field of underground mining of minerals. Known underground mining methods include open pit excavation where overburden rock is removed prior to mining the target ore, and underground mining. Open pit excavation results in very large surface expression of the mine, which can disrupt and / or contaminate very large areas. Underground mining requires miners to work underground, necessitating expensive supporting structures, ventilation, cooling and de-watering, as well as risks to the life and health of the miners.

[0002] Known mining methods use explosives placed in blast holes drilled in the rock zone of interest to blast the rock into small fragments, which can then be extracted to surface and processed to remove the valuable ore minerals. It is widely accepted that blasting is the most energy efficient way of fragmenting rock.

[0003] Copper and other critical metals and minerals are required for energy transition and to reduce dependency concentrated resources. Open pit mining requires the stripping of overburden at great cost and environmental damage; the disadvantages of underground mining have been briefly stated above.

[0004] What is needed is a method for mining that eliminates the need to have personnel underground and eliminates the need for extensive surface expression of the mine.Summary

[0005] One aspect of the present disclosure is a method for underground mineral mining. A method according to this aspect includes directionally drilling two or more service boreholes from surface to extend underneath a subsurface rock body. One of the service boreholes is disposed substantially in parallel above a second service borehole below the subsurface rock body. The two service boreholes are to each other at one or more points below the subsurface rock body by removing rock between the service boreholes. The subsurface rock body is above said service boreholes using explosives in blast holes drilled from surface into the subsurface rock body. Amechanism is extended in the first service borehole to control crushing of and to control flow of fragmented rock into the second service borehole.

[0006] In some implementations, the removing rock to connect the first and second of the two or more boreholes comprises high pressure hydraulic jetting.

[0007] In some implementations, the first one of the two or more boreholes has a pipe inserted from surface used to crush blasted rock to pass into the second one of the two or more service boreholes.

[0008] In some implementations, the first one of the two or more service boreholes has a pipe inserted from surface used to control flow of rock fragments passing into a container in the second one of the two or more service boreholes.

[0009] In some implementations, the second one of the two or more service boreholes is directionally drilled at a first diameter and reamed to enlarge the first diameter to a diameter 2 or more times the first diameter.

[0010] In some implementations, one or more the two or more service boreholes is drilled from surface using a horizontal directional drilling unit.

[0011] Another aspect of this disclosure relates to a method for stabilizing an underground stope used for mining. A method according to this aspect includes inserting one or more explosive charges into each of one or more blast holes drilled from surface into a subsurface rock body. One or more rock bolt assemblies is inserted into each of one or more blast holes above the one or more explosive charges. The one or more rock bolt assemblies is affixed in place, tension is applied to the one or more rock bolt assemblies and the one or more tensioned rock bolt assemblies are locked in place.

[0012] In some implementations, the rock bolts assemblies are inserted via a drilling rig at surface, and placed in tension by pulling action of the drilling rig.

[0013] In some implementations, at least one of the rock bolt assemblies has a hollow section, and the at least one of the rock bolt assemblies is cemented in place by moving cement through hollow section into a space between the rock bolt assembly and the respective blast hole.

[0014] In some implementations, a rock bolt assembly is placed into each of a plurality of blast holes above at least one explosive charged disposed in each of the plurality of blast holes each drilled from surface into the subsurface rock body, the rock bolt assemblies placed at depths arranged to create an arch structure of supported rock located above a stope created by detonating the at least one explosive charge in each blast hole, thereby enabling a larger stope to be mined.

[0015] In some implementations, a shock absorbent material is placed between the one or more explosive charges and the one or more rock bolt assemblies to reduce blasting shock wave effects on the one or more rock bolt assemblies.

[0016] A method for underground mining in a rock body according to another aspect of this disclosure includes drilling a plurality of blast holes from a drilling rig on surface, each of the plurality of blast holes exceeding 100 meters in depth, wherein a trajectory of each of the plurality of blast holes is controlled by a closed loop drilling control system during drilling that steers trajectory during drilling based on measurements from a sensor in a bottom hole tool of one or more of acceleration, magnetic field or gyroscopic positional change; and wherein trajectories of said plurality blast holes are controlled to optimize rock fragmentation by explosive detonation.

[0017] In some implementations, each of the plurality blast holes is loaded with a plurality of explosive charges, spaced apart from each other by cement or stemming material, and at least one rock bolt assembly is secured in place above an uppermost one of said plurality of explosive charges in each of the plurality of blast holes.

[0018] Some implementations further comprise detonating the plurality of explosive charges in each of the plurality of blast holes, and extracting blasted rock and transporting the blasted rock to surface through at least one service borehole drilled from surface and extending below a bottom of the rock body.

[0019] A method for underground mining in a rock body according to another aspect of this disclosure includes drilling one or more service boreholes from at least one surface location into a subsurface rock body and then out to an exit point at surface. The one or more service boreholes is enlarged using a cutting system extending from the exit point into the one or more service boreholes to create one or more enlarged service boreholes having diameter larger than 0.5 meters. A plurality of multilateral blast holes branching from at least one of the one or more service boreholes is drilled into the subsurface rock body. Each of the plurality of multilateral blast holesis loaded with one or more explosive charges and one or more detonators. The one or more explosive charges and the one or more detonators are inserted from surface using a drilling assembly extending from the surface. The one or more explosive charges to fragment the subsurface rock body and fragmented rock is extracted using fluid flow through the one or more enlarged service boreholes to an exit point at surface.

[0020] A method for extracting a mineral from a volume of rock in Earth’s subsurface, wherein the rock volume has been previously fragmented by blasting into a void space created by a prior mining method. A resulting permeability of the volume of rock is then at least one order of magnitude more than existing in the volume of rock prior to blasting. The method includes drilling a first service borehole from surface, wherein the first service borehole is hydraulically connected to the volume of rock. A second service borehole is drilled from surface, wherein the second service borehole is hydraulically connected to the volume of rock. The mineral is leached from the volume of rock by pumping lixiviant into the first service borehole and extracting leached minerals in the lixiviant from the second service borehole. A hydrostatic pressure of the leaching is maintained below a hydrostatic pressure of rock volume.

[0021] In some implementations, the hydrostatic pressure is maintained by extracting a larger or equal volume of liquid through the second service borehole than a volume of the lixiviant pumped into the first service borehole, the volumes averaged over a time duration of the leaching.

[0022] In some implementations, the hydrostatic pressure is maintained by foaming the lixiviant prior to the pumping.

[0023] In some implementations, prior to the leaching, an oxidizing agent is injected into the first service borehole. The oxidizing agent comprises one or more of oxygen gas, compressed air, or peroxide solution.

[0024] In some implementations, resulting sulfur dioxide is reacted with water to create sulfuric acid, subsequently is used as the lixiviant.

[0025] In some implementations, a temperature of the rock body is elevated by injecting steam into one of the first and second service boreholes.

[0026] In some implementations, fragmented rock is filled with liquid lixiviant and then substantially drained of all the lixiviant.

[0027] In some implementations, carbon dioxide is injected into the volume of rock to react to form a carbonate precipitate thereby sequestering the injected carbon dioxide.

[0028] Other aspects and possible advantages will be apparent from the description and claims that follow.Brief Description of the Drawings

[0029] FIG. 1 shows a side view of a hypothetical mine operations under mountainous terrain prior to blasting and the ore body to be mined.

[0030] FIG. 2 shows the same after the first section has been blasted and partially extracted.

[0031] FIG. 3 shows the same after the second section has been blasted and partially extracted.

[0032] FIG. 4 shows a side view of the mechanics of primary crushing and extraction for this configuration.

[0033] FIG. 5 shows a cross section view of the mechanics of primary crushing and extraction for this configuration.

[0034] FIG. 6 shows a detailed cross section view of rock bolts that would be inserted via blast holes.

[0035] FIG. 7 shows a cross section of the mining operations

[0036] FIG. 8 shows a cross section view of the mining operations prior to blasting for leaching.

[0037] FIG. 9 shows a cross section view of the leaching operation after blasting.

[0038] FIG. 10 is a summary view of three possible additional implementations of the inventions that would be applicable to an existing open pit mine. Three scenarios are considered ore that is (A) adjacent horizontally to the mine accessed via service borehole (a), (B) ore that is both adjacent and below the lowest level in the mine accessed via service borehole (b), and (C) ore directly below the lowest level in the mine accessed via a vertical service borehole (c)

[0039] FIG. 11 shows various stages in one possible realization of the proposed mining process adjacent to an open pit mine and shows the view after the service boreholes and blast holes have been drilled.Detailed Description

[0040] In methods according to the present disclosure, all ore extraction (mining) operations are performed from the Earth’s surface using precision directional drilling. Such directional drilling may make use of either oil and gas well drilling rigs, or horizontal directional drilling (HDD) rigs that are commonly used to drill pipelines underneath rivers, canyons, and man-made infrastructure. The entire mining system is such that no persons ever work underground. One feature of such methods is that they can extract very large volumes of rock from the subsurface without creating an open pit or inducing block caving. Ore in a subsurface rock body can be extracted by leaching in place after being blasted.

[0041] The entire mining operation is performed using equipment operated from surface, or a prior mined location similar to operations performed using a drilling rig for oil and gas drilling via one or more boreholes. Blasting is known as the most cost and energy efficient method of fragmenting rocks in the mining industry today and is the primary method of creating fragmented rock that can be extracted in this method.

[0042] The disclosed method uses novel drill and blast geometry, and drilling technology not currently used in the mining industry that is primarily used in the oil and gas industry. The disclosed method uses longer blast holes than are ordinarily used in mining known in the art and these blast holes may be are drilled using precise directional control and survey accuracy to ensure the burden and spacing between explosive charges in adjacent blast holes is consistent so the most effective blasting fragmentation is obtained. Such directional control requires the use of advanced technologies not currently used in blast hole drilling in the industry such as measurement while drilling (MWD) bottom hole assemblies (BHAs) with real time telemetry to surface, containing accelerometers, magnetometers or gyroscopes. Techniques to drill precisely vertical holes such as rotary steerable BHAs may also be used. The method disclosed herein enables development of massive subsurface mining operations without the need to develop an open pit or for personnel to work underground. Preferable depth range operation for the disclosed methods would be greater than 100m and less than 1000m.

[0043] In general, “drilling” and “drill” refers to rotary-bit drilling as is commonly used in drilling oil, gas and water wells into subterranean formations. The disclosed method assumes the use of directional drilling equipment and methods used in such well drilling for its execution. Ingeneral, when using these methods in this application, several differences will allow for lower cost of execution.

[0044] For all of the example implementations of subsurface equipment shown herein, it is within the scope of this disclosure that a drilling rig system similar to those used for drilling oil, gas or water wells is disposed at the surface to provide: a means of running j ointed pipe in and out of the borehole(s), a means of providing mechanical forces on said pipe vertically and in torsion, means of high pressure pumping of water or drilling fluid, means of taking returns of drilling fluid, water and rock cuttings and removing them from the fluid.

[0045] In some situations, it may be advantageous to use air drilling where compressed air is used instead of drilling fluids. Due to depth, permeability and rock types air drilling may result in lower operating costs and lower demand for drill water. In air drilling applications communication with bottom hole tools is likely via electromagnetic signals.

[0046] In some situations, it may be advantageous to use a horizontal directional drilling (HDD) drilling rig or unit. An HDD drilling rig is a directional drilling machine that is ordinarily used to install underground utilities without trenching. HDD units are used to drill tunnels that follow an arcuate path, after which a pipeline or other utility structure (e.g., cable) is pulled through the tunnel. HDD units are used for a variety of underground infrastructure, including water pipelines, telecommunication cables, electrical cables, gas pipelines, and oil pipelines.

[0047] In general, “surface” refers to the Earth’s surface, however a method according to the present disclosure may be used to deepen a mine from an existing excavation, where people are engaged in the mining process from such existing excavation, and the foregoing should be considered throughout the present description as being within the scope of the present disclosure. In this case “surface” can be considered to be a position where there are manned operations in an existing mine.

[0048] The disclosed method creates a plurality of stopes and reduces the waste rock normally generated in known mining methods to create connecting tunnels and roadways. Also, separate stopes that are hydraulically isolated and dewatered can then be used to dispose of tailings eliminating the need for surface tailings dams.

[0049] In some cases where minerals are soluble after blasting, the muck pile may remain in situ and be extracted via leaching or solution mining processes.

[0050] The disclosed method may be used to exploit the remaining ore in areas that have been previously mined using conventional methods, but cannot be exploited further due to water ingress, instability of the rock or other hazards or economic impediments. In this case the multilateral drilling and blasting may be used to create rock muck piles that are then extracted via the methods described herein or using existing mine workings, using traditional methods, or via in-situ leaching.

[0051] The method disclosed herein may comprise initially using equipment from oil and gas drilling or horizontal directional drilling with some modifications and relatively simple mechanical devices. Once the disclosed method is established innovation in robotics may lead to further development of robotic devices to improve the performance of various key function of the disclosed method. These may include control of jetting process, breaking of oversize rock fragments, loading of multiple decks of explosives efficiently, insertion and fixing of rock bolts in place. The drilling and loading of blast holes will be highly repetitive and lend themselves to automation, and use of robotic devices on the drilling rig and in the mining process. As such, the use of robotic devices should be considered as a logical evolution of the disclosed methods and therefore within the scope of the present disclosure.

[0052] The disclosed method is described herein as a sequence of actions to obtain the result of extracting ore from an underground ore body in a safe, environmentally conscious and economically attractive way. The present descriptions refer to some, but not all, of the possible realizations described in the drawings; in some cases, a specific action may have different implementations than are described herein and shown in the drawings.

[0053] The overall mining method disclosed herein uses four main innovations that combine to enable an entirely new approach to mine development. These main innovations are:

[0054] First, one or more of service boreholes is drilled parallel to each other using a magnetic and / or electromagnetic ranging device to keep the service boreholes parallel over long distance. An example implementation of electromagnetic ranging and associated devices is set forth in, B.A. Tarr, A.F. Kuckes, and M.V. Ac, Use of New Ranging Tool To Position a Vertical Well Adjacent to a Horizontal Well, SPE Drilling Engineering, June 1992, SPE International, Richardson, Texas,USA. The two or more service boreholes are drilled so that they extend underneath the rock body to be mined. The two or more service boreholes may in some implementations penetrate the lower part of the rock body; other implementations may be entirely underneath the rock body. An upper one of the two or more service boreholes is then used to cut, e.g., by using a drilling or jetting tool, a plurality of draw points into the rock body above the upper service borehole, to collect the blasted rock and provide an initial void space for further blasting. The cutting mechanism to create the draw points may be, for example and without limitation, mechanical drilling, reaming and cutting tools, explosives, laser, or hydraulic jetting. Hydraulic cutting my include abrasive cutting material suspended in water or other fluid. The cutting mechanism is then also used to cut an “ore pass”, opening or passageway between the upper and the lower service borehole, which may extend generally in parallel to the upper service borehole below the rock body and be disposed substantially vertically below the upper service borehole. These two service boreholes then allow the control, primary crushing and extraction of fragmented rock through the lower borehole. The upper borehole may have a pipe (e.g., drill pipe or jointed tubing) and a drill bit or similar device to crush the blasted rock as it falls under gravity after blasting into the draw point. This same device by means of its positioning can control the flow of crushed rock from the draw point into the ore pass and thence into the lower borehole, where the crushed rock may be collected in a skip or rail cart that is hauled out of the lower service borehole, e.g., by means of a winch.

[0055] As used in the present disclosure, the term “service” as applied to a borehole or wellbore is intended to mean any activity that can be carried out or performed in a borehole, including, without limitation, movement of tools and equipment, movement of fluids and movement of solids, such as rock fragments. The term “service” is not intended to limit the scope of activities performed in any borehole but is used only to clearly identify the relevant borehole(s) when needed for purposes of clarity of the disclosure.

[0056] Second, “blast holes” according to the present disclosure are drilled with precise trajectories so that effective burden and spacing are maintained to enable effective blasting. The blast holes may be loaded with multiple decks of explosives and the explosives detonated electronically or more specifically with wireless detonators. To drill with precision trajectories, a closed loop directional drilling control system may be used; such control system may comprise using an accelerometer disposed near the drill bit for vertical drilling or a set of magnetometers, for directional blast holes, and in some cases a gyroscope may be used to obtain well trajectorydirectional information. The trajectory may be steered using a directional drilling tool bottom hole assembly (BHA) such as a bent sub and motor, or a rotary steerable directional drilling system.

[0057] Third, to keep open a large stope in shallow rock bodies and low rock quality mines, rock bolts may be used above the blasted interval, inserted into the blast holes and set in great tension to prevent the collapse of the rock above the blasted interval. These rock bolts are used in conjunction with a blast design to create a rock arch supporting a large open stope.

[0058] Fourth, after some volume of rock is extracted, a large blast may be conducted to create an in place fragmented leach heap that allows rapid and controlled leaching of the remaining material. The main environment concern with leaching is the loss of lixiviant into the groundwater. Low grade rock requires a design to optimize efficient leaching without contaminating groundwater. With this in mind the disclosed method uses precise measurement of material balance or low density leaching fluid such as foam to ensure the leaching process occurs in a negative hydrostatic pressure environment. By controlling the leaching pressure to be below or equal to the hydrostatic pressure, on balance ground water is extracted rather than lixiviant injected.Description of Example Implementations

[0059] FIG. 1 shows a side view of an example implementation of mine operations under mountainous terrain prior to blasting and the ore body to be mined. (1) shows the ore body to be mined as being shaded. A drilling rig (2) at the surface drills blast holes that may be multilateral as shown on the left, directionally drilled from a single surface site (9) disposed in the center of the multilateral boreholes, or individual boreholes drilled from surface in parallel, e.g., precisely vertically on the right-hand side (10).

[0060] To extract the rock, in the present example implementation, two service boreholes are drilled, in this example in parallel, one above (4) and one below (3). The service boreholes may be drilled use ranging technology to steer the second hole (4) in close proximity above and parallel to the first (3). Ranging technology may be used because conventional directional drilling survey technology has errors in positioning which accumulate with distance (i.e., the length of the drilled borehole), especially at high inclination from vertical. Electromagnetic ranging technologies are usedin oil well drilling to steer wells in parallel paths to avoid unintended intersection of boreholes or to allow the drilling of relief wells in the case of blowout or other loss of well control.

[0061] The service boreholes may be drilled using known oil and gas drilling equipment likely to have diameters between 150mm and 400mm. However, for efficient extraction of rock, a larger diameter of service borehole may be needed, and the service boreholes may be enlarged using reaming or reverse circulation drilling methods.

[0062] The lower service borehole (3) may be enlarged to enable a cylindrical skip to pass and carry material to surface as a drift or train would in conventional mine. This would be done using typical borehole diameters in a range of 1 5m to 2m, depending on rock quality. It is contemplated thar the drilling rig for drilling such diameter boreholes may be a horizontal direction drilling rig at a surface location shown at (5). In some cases, it will be advantageous for the service boreholes (3), (4) to be drilled back to surface at the far side of the ore deposit. This would enable push and pull of equipment in and out of the service boreholes (4), (3).

[0063] In some cases, a pipe (not shown) may be inserted into one or more of the service boreholes to prevent collapse of the service borehole. Such pipe may be inserted part or all of the relevant borehole. To enable future connecting, cutting and jetting to be done it is contemplated that composite pipe such as glass reinforced plastic (GRP) may be used for such pipe. The pipe (not shown) may or may not be cemented in place. In the case of service boreholes that are drilled back up to surface, the pipe (not shown) can be pulled into place in the same manner pipelines are pulled through boreholes under river crossings or other structures.

[0064] The service boreholes (3), (4) may be connected to each other either by drilling or hydraulic jetting. In this case to enable the connection of the service boreholes a jetting assembly is inserted into the upper service borehole (4), using a small diameter, high pressure nozzle and a directional tool that enables the orientation of a jet discharged from the nozzle to be measured. High pressure water is pumped, and forms an ultra-high velocity jet at the nozzle. In some cases, an abrasive material such as fine grained sand is added to increase cutting efficiency. The jet cuts through rock to create the desired shapes described in later Figure 4 and Figure 5.

[0065] In some cases, one or more of the blast holes may be drilled with precise surface or ranging technology to intersect with borehole (6) and (7) shown here. Blast holes (10) are loaded with explosives and detonators (8) either as a single charge or divided into multiple sections or decks (12). The detonators (not shown separately) may be wireless detonators to eliminate complex wiring. Such wireless detonators can be used in combination with conventional miningexplosives. The explosives may be inserted into respective blast holes as pre-packages charges or injected as a slurry via the drill rig.

[0066] To blast effectively, the blast holes (10) preferably have a relatively even spacing between adjacent blast holes; this is described in the mining industry as burden and spacing. Errors in the position of the blast holes (10) can lead to either blast holes (or service boreholes) colliding or being too closely spaced, or some volumes of rock may lack sufficiently proximal blast hole to effectively break the rock.

[0067] The positioning of the blast holes (10) relative to each other and the service boreholes is important. Hence at the depths contemplated for the present example method, 100 m to 1000 m deep, the blast hole drilling may comprise using directional drilling tools such as a bottom hole assembly (BHA) that contains directional sensors and a steering assembly. The directional sensors, such as a combination of magnetometers and accelerometers, or gyroscopes provide the direction the blast hole is being drilled and can be used to calculate its trajectory in space. The steering assembly, such as bent sub and hydraulic motor or a rotary steerable directional drilling assembly allows the borehole to be steered along the desired trajectory.

[0068] To provide the required precision to enable effective blasting, a closed loop directional drilling system may be used, wherein a computer system continuously calculates the spatial position of the blast hole during drilling, and controls the settings of the steering assembly to obtain steer the trajectory of the blast hole toward the desired trajectory.

[0069] For the innovations described above, the accuracy of drilling position is critical. Long blast holes are proposed. Blast hole spacings between 2-6 meters will be common. Errors in blast hole traj ectory of more than 25% of these spacings may result in height irregular blasting and large blast fractions of oversize rock fragments. Further, trajectory errors may increase risk of inadvertent intersection of blast holes. Relationships between accuracy of blast hole drilling and oversize material are explained in, e.g., A Fragmentation Modeling Framework for Underground Ring Blasting Applications, I. Onderra.

[0070] Directional drilling systems known in the art to be used in oil and gas drilling are more accurate than equipment used in mine drilling, and several such systems are applicable. However, mines may contain large amounts of magnetic rock, making methods using magnetic surveys that are commonly used in oilfield drilling inaccurate. In some implementations, precisely verticaldrilling may be used for the blast holes as this only requires the measurement of the Earth’s gravity vector; no measurement of the Earth’s magnetic vector is required. In some implementations, gyroscope measurements while drilling can be used. Using these methods, trajectory accuracy of 0.1 degrees is possible, so blast holes hundreds of meters in length can be drilled with adequate positional accuracy.

[0071] Another method of controlling blast hole spacing is electromagnetic ranging, where the position of one blast hole is referenced to a second blast hole using a magnetic or electric signal from the first blast hole detected in the second blast hole. Using ranging, blast holes can be drilled substantially parallel to each other for thousands of meters.

[0072] To keep the rock stable at depths above the blasting, innovative methods may be used that include plugs, cement, shock absorbing materials and prestressed rock bolts inserted above the explosives in one or more blast holes, as will be explained in more detail with reference to FIG. 6. Presently such bolts are shown in the context of some of the blast holes, they are applicable to all blast holes in any specific implementation.

[0073] Above the explosives, a cushioning or shock absorbing material (11) may be inserted into the blast hole(s); such material may be foamed materials, foamed cement, or other materials with shock absorbing properties. The shock absorbing materials may have lower acoustic velocity and Young’s modulus than surrounding rock, such that shock waves dissipate in the blast hole rather than traveling in the blast hole before they reach the rock bolt. A cement plug may serve the function of blocking gas pressure from the explosive detonation.

[0074] Where needed, a rock bolt (see FIG. 6) is inserted into the relevant blast hole(s), tensioned, locked in place and in some cases may be cemented in place. All the foregoing may be performed using the drilling rig (2) and through the respective blast hole. When all the drilling and loading of explosives and other materials is complete, the first explosives may be detonated in the respective blast holes in a predetermined sequence. After blasting, ore extraction begins.

[0075] FIG. 2 shows the same cross-sectional view as FIG. 1 after a first section of an underground rock body has been blasted and partially extracted. Gravity moves the blasted rock to an extraction point (16). In the event water enters the blasted rock volume, the water may be extracted through one of the service boreholes (15).

[0076] FIG. 3 shows the same cross-sectional view as FIG. 2 after a second section of the rock body has been blasted and partially extracted. A section of rock is left un-blasted as it would be able to fall to the extraction point (18) the next blast patten is loaded.

[0077] FIG. 4 shows a side view of mechanics of a possible implementation primary rock crushing and extraction for the configuration shown in FIGS. 2 and 3. The lower enlarged, service borehole (20) has an extraction skip (23) inside, running on rollers and pulled out with a wire cable. The upper service borehole (21) has drill pipe (22) or other pipe inside which may be used to break the blasted rock with a hardened bit or crusher (22A) at its longitudinal end. The drill pipe (22) can be rotated, pushed or have a pneumatic, hydraulic or electric powered hammer crusher at its end.

[0078] FIG. 5 shows a cross section view of mechanics of a possible implementation of primary crushing and extraction for the illustrated configuration. The section above (21) is cut with hydraulic jetting prior to blasting. It is cut to allow the blasted rock to fall to the point where it can be crushed. A second hydraulic jet cut may be made below (21) to connect to the lower service borehole (20).

[0079] FIG. 6 shows a detailed cross section view of rock bolts that would be inserted via blast holes. The explosive is loaded with a wireless detonator (30); likely explosives are pumped via pipe from surface. Stemming material or cement (31) covers the explosives and then a shock absorbing material (33) may be inserted into the blast hole (10). In this case, the shock absorbing material (33) may be foamed cement pumped from surface. Stemming material may be defined as an inert material, such as sand or rock, that is placed on top of or between explosive charges in a blast hole to contain the gas energy emitted by the explosive upon detonation.

[0080] Then a rock bolt (34) is inserted from surface. The rock bolt (34) serves to transfer part of the weight of overburden from the roof of the blast volume to shallower parts of the formations above the blast volume. A lower clamp (38) attached to or disposed on the rock bolt (34) is set in the blast hole (10), and then tension is applied to the rock bolt (34) using the hoist on the drilling rig, then an upper clamp (35) on the rock bolt (34) is set. In some cases the clamps (35, 38) may be set by rotating a screw section that extends the respective clamp. The result is that rock bolt (34) is set in the blast hole (10) under very high tension. In some implementations, the rock bolts may be in the form of cylindrical pipes similar to oil well tubulars that can support tensile loads ofhundreds of tons or more. In some cases, the rock bolts may be made from fiber composite material that can be later drilled or crushed. In some cases, the rock bolts may be made of metals or polymers that can subsequently be dissolved with acid or solvent. The high-tension on the rock bolt(s) may prevent the collapse of the stope when blasting is initiated. As a result large spans can be created, and large volumes of rock can be extracted prior to caving and collapse.

[0081] The present example method uses a new type of rock bolt. Historically a mining rock bolt is a long steel rod that is inserted into a drilled hole in rock to stabilize the roof or walls of a tunnel or underground excavation. Rock bolts are used to prevent movement in unstable rock masses and to hold fractured or jointed rock together. Rock bolts transfer load from a plate at the unstable exterior of mine excavation to the confined (and much stronger) interior of the rock mass.

[0082] The present example implementation of rock bolt (34) is different from known mining rock bolts in several ways. First, the rock bolts may be much longer than known rock bolts, rock bolts of 10 to 30 meters or more are possible in the present example implementation. The rock bolts in the present example implementation have both longitudinal ends disposed inside the blast hole. Rock bolts known in the art prior to the present disclosure have one end in a drilled hole and the other end attached to a plate supporting the face of a tunnel or other excavation. The present example implementation of the rock bolt (34) may be a in the form of a tube with an expanding clamp (35, 38) proximate each longitudinal end. Such clamps may be set, e.g., by rotating the top of the tube, with the bottom clamp (38) being spring loaded to resist rotating; rotation of the top of the tube will rotate a threaded section (36) that expands radially and locks the lower anchor. At this point the required tension is applied, and then torque shears pins (36) on the upper clamp (35), whereupon the upper clamp (35) is also expanded and locked in the blast hole (10) as a result of further rotation.

[0083] FIG. 7 shows a cross section of an example implementation of mining operations. The view in FIG. 7 is perpendicular to the views in FIGS. 1, 2, and 3. The rock bolts support a stable arch over the stope to enhance stope stability. In rock mechanics, a "stable arch" refers to a naturally formed or induced arch-shaped structure within a rock mass that effectively distributes compressive stresses, allowing the rock above it to remain stable and resist failure, typically used in situations like underground excavations where the rock naturally forms an arch to support the overlying load; In the present example implementation, with the aid of the rock bolts describedabove, a self-supporting, arched configuration within the rock mass maintains stability under overburden stress.

[0084] The ore mass to be blasted and extracted is shaded (42). The upper service borehole (40) is at the base of the blasted rock volume, directly below and linked by the ore pass that has been cut into the lower service borehole (41).

[0085] FIG. 8 shows a cross section view of the mining operations prior to blasting and subsequent leaching. Here after extracting a certain volume of rock, additional blast holes (10A) may be added to blast up to 5 times the extracted volume of rock, to create a highly permeable volume of broken rock that can be leached efficiently.

[0086] FIG. 9 shows a cross section view of the leaching operation after blasting. The rock in place has been blasted to give a fragmentation suitable for in place leaching (53). Fluids and gases can be injected in to blast holesand the lower service borehole (50). The level of free liquid in the blasted volume can be controlled by the volumes injected. Pressure can be measured at points in the system (50, 51) to ensure the system does not excessively leak liquids into the host rock. Fluids can be precisely metered in and out of the said boreholes to ensure leaching fluids are not leaking into the ground water. Fluids may also have relatively low density (e.g., foam) to reduce hydrostatic pressure to below the hydrostatic pressure of fluid in the blasted rock mass.

[0087] The service boreholes are hydraulically connected to the fragmented rock mass. Hydraulically connected in the present context means a condition where the highly permeable material is connected to the service boreholes and allows free movement of water or effluent under a hydraulic gradient.

[0088] Leaching is well known in the mining industry; Leaching is a chemical process in mining for extracting valuable minerals from ore. Leaching also takes place in nature, where rocks or constituents thereof are dissolved by water. Post leaching, the rocks are left with a smaller proportion of the leached out minerals than they originally contained.

[0089] In the present example implementation several possible advantages are obtained by having an enclosed, finely fragmented rock mass. This fragmented rock mass may have two or more boreholes to inject and extract fluids and gases, that connect with the top and bottom of the enclosed rock mass. The possible advantages may comprise the following:(i) In the case of copper bearing sulfide rocks, the process may begin with high pressure air injection to the lower service borehole to oxidize the sulfide, producing sulfur dioxide which then reacts with water to produce sulfuric acids. This process is exothermic resulting in higher temperatures and faster reaction rates;(ii) Heat is retained in the subsurface resulting in higher temperatures and faster reaction rates;(iii) The blasted volume acts like a vat, which can be filled and drained entirely ensuring all rock surfaces are wetted with the lixiviant;(iv) the pressure or free fluid level can be controlled via a material balance to keep the internal pressure below that of the host rock, preventing the lixiviant and other liquids escaping and causing contamination;(v) At the end of the process the volume can be pumped out;(vi) It is possible to inject neutralizing solutions to balance the pH of the solution or otherwise stop the reactions; and(vii) It is possible to inject carbon dioxide gas at the end of the process to form precipitates of carbonate minerals that will form a cementitious material and stabilize the volume and permanently sequester the carbon.Other Example Implementations

[0090] Two additional example implementations are described in detail with reference to FIGS. 10 and 11. Three scenarios are considered in FIG. 10, first, ore (104) that is adjacent horizontally to the mine accessed via service borehole (100) drilled from surface, second, ore (106) that is both adjacent and below the lowest level in the mine accessed via service borehole (102), and ore (108) directly below the lowest level in the mine accessed via a vertical service borehole (110).

[0091] When working in existing mines, the geotechnical effects of drilling, blasting and rock extraction need to be considered. As such the following features of the techniques are disclosed.

[0092] Firstly, stopes or void spaces are created that have stable three-dimensional shapes such as arched roof shapes. The size of the stopes and voids are limited to avoid caving, rock bursts andcollapse. The hydraulic radius (stope area divided by perimeter) of the workings would be designed to be within a stable range for the rock mass being mined, to avoid uncontrolled caving.

[0093] Secondly the precision mining removes ore in elongated shapes that would radiate out from the base of the mine parallel to the stresses in the mine walls, minimizing the risk of wall slides. Between each set mining operations an area of rock would be left untouched until the stopes had been fdled and cemented.

[0094] Thirdly, after extraction of ore or leaching operations a mixture of mine tailings and cement materials would be injected in a slurry form to fill the void space or cement the leached materials restoring the mechanical strength of the rock to some extent to allow additional mine workings.

[0095] FIG. 11 show a cross section of an open pit mine prior with the mine process underway. In this case mine cannot advance economically to the right as increasing volumes of overburden would need be extracted due to the mountain rising at the side of the open pit. There is a volume of ore (302) that can be mined or leached shown.

[0096] The trajectory of a service borehole (302) drilled from outside the pit from a conventional drilling rig (201) used in oil and gas drilling, is downward vertically (202) then directionally to exit from the pit wall at (301) at the base of the mine as is shown as the lowest line (303) in FIG. 11.

[0097] A section has been back reamed through the section in the ore (302) to create an enlarged service borehole. It is envisaged that this will be the order of 1 to 2 m in diameter. This is done using back reaming equipment commonly used in horizontal directional drilling to pull pipelines underground for sections such as river crossing. The back reaming assembly is pulled from the exit point of the hole (301).

[0098] One innovation is the use of a back reaming device where a large cutting devices is pulled and rotated back along a directionally drilled hole using a reaming tool. This type of method is used in horizontal directional drilling for burying pipelines or other utilities. In the present example implementation it is used to create a void space for blasting rather than installing pipelines or other utilities.

[0099] Limitations on the use of back reaming may comprise the maximum torque and power that can be applied via the drill pipe pulling the reaming tool into the preexisting hole. In this case two innovations are proposed to alleviate this limitation. Firstly, torque can be applied to both drill pipe pulling the assembly, and correspondingly pushing it through the hole. Secondly, a hydraulically operated motor may be inserted between two opposing rotary cutting systems such that fluid pumped down the drill pipe drive one set of cutting blades in an opposite direction of rotation to the rotation of the pipe, which may reduce torque on the pipe and increase the maximum power transmitted. In other implementations an electrical cable can be attached, and an electric motor driven to operate dual opposing cutting devices.

[0100] When blast holes are loaded with explosives, the service boreholes may in desired sections be loaded with explosives. The explosives may be directional or shaped explosives to fragment the rock close to the borehole as needed. In some example implementations, the explosives may be placed adjacent to the upper side of the enlarged service borehole. This may be performed with cement or adhesive. In some cases, an inflatable bag may be used to place the explosives against the borehole wall in the desired position.

[0101] In multilateral blast holes that are drilled from the original borehole via a multitude of branches (401), sections of such blast holes may be loaded with explosives and detonators (402) from surface; sections of the blast holes maybe blanked off with cement and other forms of fill. The first blast hole branch (401) closest to the service borehole (303) may be drilled close to and parallel with the service borehole using ranging technology as explained previously. In some implementations, some or all of the blast holes may be drilled from one or more different locations at surface. In some implementations, explosives may be placed in the enlarged borehole (service or blast?).

[0102] Blasted sections are fragmented and fill the void space created by backbreaking. In some cases, sections are left un blasted (502). The material is extracted from a draw point (503) at the lowest point of the section. Various mechanisms are used to remove the material from the lower service borehole (504). A system similar to a horizontal drilling rig or “HDD horizontal directional drilling rig” (505) may be used. The fragmented rock is collected in a tank or lagoon (506) and solids may be processed to recover ore. The system inserted as shown at (504) may be a pipe or plurality of pipes using water to flush rock out, a low friction slide, or a conveyer belt to extractrock fragments with maximum efficiency. In some cases, drill pipe may also be inserted with drill bits or jetting nozzles to break oversize rocks.

[0103] A low friction slide can be inserted into the lower service borehole (504) in sections. The sections may be attached in sections to pipe underlaying the slide. Inside pipe jointed or coiled pipe may be inserted to provide drilling, cutting, crushing, jetting action on oversized rocks using a drill bit or jetting assembly. A high-pressure water jet may be used to cut oversize rocks. The rock fragments then are carried by gravity, and water flow down the slide to exit at the surface of mine workings below at (504). In some cases, the slide may be vibrated using methods including rotation of the pipe with an eccentric mass or bearing to create vibration of a desired frequency and amplitude to aid the removal of fragmented rock on the slide

[0104] Subsequent to some volume of extraction a final blast to create a large volume of fragmented rock that can be leached in subsequent in place recovery mechanisms. Acid or other lixiviant can then be injected via to flood and drain the fragmented ore body. In some cases, specific chemicals, bacteria or other biologically active agents may be used to improve or enable effective leaching. The solution of minerals to be extracted (or pregnant solution as referred to in mining) is drained form the lower point into the base of the open pit mine.Industrial Applicability

[0105] The mining technologies and methods described herein are broadly applicable to all forms of mining. The application of such methods, e.g., to massive porphyry copper ore bodies where open pit mining is environmentally unacceptable is one example of its application. The leaching of a massive, fragmented rock enables rapid highly economic leaching in low grade ores. Elements of the method may be applicable in deeper and higher-grade ores with the use of multilateral blast holes. The innovation of inserting a rock bolt into the blast hole from a drilling rig at surface will enable this type of mining in geological settings where poor rock quality would otherwise prevent the application of these techniques.

[0106] In light of the principles and example implementations described and illustrated herein, it will be recognized that the example implementations can be modified in arrangement and detail without departing from such principles. The foregoing discussion has focused on specific implementations, but other configurations are also contemplated. In particular, even though expressions such as in “an implementation," or the like are used herein, these phrases are meant togenerally reference implementation possibilities, and are not intended to limit the disclosure to particular implementation configurations. As used herein, these terms may reference the same or different implementations that are combinable into other implementations. As a rule, any implementation referenced herein is freely combinable with any one or more of the other implementations referenced herein, and any number of features of different implementations are combinable with one another, unless indicated otherwise. Although only a few examples have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible within the scope of the described examples. Accordingly, all such modifications are intended to be included within the scope of this disclosure as defined in the following claims.

Claims

ClaimsWhat is claimed is:

1. A method for underground mining in a rock body, comprising: directionally drilling two or more service boreholes from at least one surface location to extend underneath a subsurface rock body, a first one of the two or more service boreholes disposed substantially in parallel above a second one of the two or more service boreholes in locations below the subsurface rock body; connecting the two or more service boreholes to each other at one or more points below the subsurface rock body by removing rock between the two or more service boreholes; blasting the subsurface rock body above said service boreholes using explosives in blast holes drilled from surface into the subsurface rock body; and extending a mechanism in the first one of the two or more service boreholes to control crushing of and to control flow of fragmented rock into the second one of the two or more service boreholes.

2. The method of claim 1 wherein the removing rock to connect the first and second of the two or more boreholes comprises high pressure hydraulic jetting.

3. The method of claim 1 wherein the first one of the two or more boreholes has a pipe inserted from surface used to crush blasted rock to pass into the second one of the two or more service boreholes.

4. The method of claim 1 wherein the first one of the two or more service boreholes has a pipe inserted from surface used to control flow of rock fragments passing into a container in the second one of the two or more service boreholes.

5. The method of claim 1 wherein the second one of the two or more service boreholes is directionally drilled at a first diameter and reamed to enlarge the first diameter to a diameter 2 or more times the first diameter.

6. The method of claim 1 wherein one or more the two or more service boreholes are drilled from surface using a horizontal directional drilling unit.

7. A method for stabilizing an underground stope used for mining, comprising: inserting one or more explosive charges into each of one or more blast holes drilled from surface into a subsurface rock body; inserting one or more rock bolt assemblies into each of one or more blast holes above the one or more explosive charges; and affixing the one or more rock bolt assemblies in place, applying tension to the one or more rock bolt assemblies and locking the one or more tensioned rock bolt assemblies in place.

8. The method of claim of 7 wherein the rock bolts assemblies are inserted via a drilling rig at surface, and placed in tension by pulling action of the drilling rig.

9. The method of claim 7 wherein at least one of the rock bolt assemblies has a hollow section, and the at least one of the rock bolt assemblies is cemented in place by moving cement through hollow section into a space between the rock bolt assembly and the respective blast hole.

10. The method of claim 7 wherein a rock bolt assembly is placed into each of a plurality of blast holes above at least one explosive charged disposed in each of the plurality of blast holes each drilled from surface into the subsurface rock body, the rock bolt assemblies placed at depths arranged to create an arch structure of supported rock located above a stope created by detonating the at least one explosive charge in each blast hole, thereby enabling a larger stope to be mined.

11. The method of claim 7 wherein a shock absorbent material is placed between the one or more explosive charges and the one or more rock bolt assemblies to reduce blasting shock wave effects on the one or more rock bolt assemblies.

12. A method for underground mining in a rock body, comprising:drilling a plurality of blast holes from a drilling rig on surface, each of the plurality of blast holes exceeding 100 meters in depth, wherein a trajectory of each of the plurality of blast holes is controlled by a closed loop drilling control system during drilling that steers trajectory during drilling based on measurements from a sensor in a bottom hole tool of one or more of acceleration, magnetic field or gyroscopic positional change; and wherein trajectories of said plurality blast holes are controlled to optimize rock fragmentation by explosive detonation.

13. The method of claim 12 wherein each of the plurality blast holes is loaded with a plurality of explosive charges, spaced apart from each other by cement or stemming material, and at least one rock bolt assembly is secured in place above an uppermost one of said plurality of explosive charges in each of the plurality of blast holes.

14. The method of claim 13 further comprising detonating the plurality of explosive charges in each of the plurality of blast holes, and extracting blasted rock and transporting the blasted rock to surface through at least one service borehole drilled from surface and extending below a bottom of the rock body.

15. A method for underground mining in a rock body, comprising: drilling one or more service boreholes from at least one surface location into a subsurface rock body and then out to an exit point at surface; enlarging the one or more service boreholes using a cutting system extending from the exit point into the one or more service boreholes to create one or more enlarged service boreholes having diameter larger than 0.5 meters; drilling a plurality of multilateral blast holes branching from at least one of the one or more service boreholes into the subsurface rock body; loading each of the plurality of multilateral blast holes with one or more explosive charges and one or more detonators, the one or more explosive charges and the one or more detonators inserted from surface using a drilling assembly extending from the surface; detonating the one or more explosive charges to fragment the subsurface rock body; andextracting fragmented rock using fluid flow through the one or more enlarged service boreholes to an exit point at surface.

16. A method for extracting a mineral from a volume of rock in Earth’s subsurface, the rock volume having been previously fragmented by blasting into a void space created by a prior mining method such that a permeability of the volume of rock is at least one order of magnitude more than existing in the volume of rock prior to blasting, the method comprising: drilling a first service borehole from surface, the first service borehole being hydraulically connected to the volume of rock; drilling a second service borehole from surface, the second service borehole hydraulically connected to the volume of rock; leaching the mineral from the volume of rock, by pumping lixiviant to the first service borehole and extracting leached minerals in the lixiviant from the second service borehole; and wherein a hydrostatic pressure of the leaching is maintained below a hydrostatic pressure of rock volume.

17. The method of claim 16 wherein the hydrostatic pressure is maintained by extracting a larger or equal volume of liquid through the second service borehole than a volume of the lixiviant pumped into the first service borehole, the volumes averaged over a time duration of the leaching.

18. The method of claim 16 wherein the hydrostatic pressure is maintained by foaming the lixiviant prior to the pumping.

19. The method of claim 16 wherein prior to the leaching, an oxidizing agent is injected into the first service borehole, the oxidizing agent comprising one or more of oxygen gas, compressed air, or peroxide solution.

20. The method of claim 19 wherein resulting sulfur dioxide is reacted with water to create sulfuric acid, subsequently is used as the lixiviant.

21. The method of claim 16 wherein a temperature of the rock body is elevated by injecting steam into one of the first and second service boreholes.

22. The method of claim 16 wherein fragmented rock is filled with liquid lixiviant and then substantially drained of all the lixiviant.

23. The method of claim 16 wherein carbon dioxide is injected into the volume of rock to react to form a carbonate precipitate thereby sequestering the injected carbon dioxide.

Images