1. Field of the Disclosure
The disclosure herein relates to in situ mining of ores from subsurface formations.
2. Background of the Art
Many high quality ore bodies are located at depths at which traditional mining methods, such as removal of overburden to extract the ore or creating mine stopes and shafts and using mining equipment or deploying humans are not feasible due to harsh environment or not economical to build open pits or underground mines. Also, a vast majority of the ore extracted, crushed and processed does not contain adequate amounts of the desired minerals. Also, current in situ leaching methods are limited to recover copper and uranium from ores. Also, very little sampling is currently performed in real-time. Such lack of information often results in ore rock being treated as waste. Many of the current mining methods also are not environmentally friendly.
This disclosure provides in situ methods of extracting ores from subsurface formations by drilling a large number of articulated boreholes through ore volumes and recovering additional ore from around the drilled boreholes utilizing fracturing and leaching of ores from around such boreholes.
In one aspect, the disclosure provides a method of extracting ores from a subsurface location or an ore deposit without removing the overburden. In one embodiment the method includes: defining an ore volume; drilling a large number of mother-bores and forming lateral boreholes from the mother-bores; transporting the ore cut during drilling to the surface; separating the ore received at the surface; and extracting minerals from the separated ore at the surface. In another embodiment, the method further includes fracturing the drilled boreholes to recover additional ore. In another embodiment, the method further includes supplying a leaching fluid into drilled borehole to leach the ore surrounding the already drilled borehole and transporting the leached ore to the surface for recovery of the minerals contained therein.
Examples of the more important features of in situ mining have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features that will be described hereinafter and which will form the subject of the claims.
For a detailed understanding of the apparatus and methods disclosed herein, reference should be made to the accompanying drawings and the detailed description thereof, wherein like elements are generally given same numerals and wherein:
In general, the disclosure herein provides methods of defining or identifying an ore field located below the earth surface that includes an element of interest, extracting the ore by drilling a large number of boreholes through the ore field and processing of the extracted ore at the drill site to recover the element of interest from the extracted ore.
In some ore fields, the ore desired to be extracted 106 may be present in the form of distributed deposits. In other ore fields, the ore desired to be extracted may be deposited in veins. The methods described herein may be used to extract ore from all such deposits. In the exemplary ore field 106, some boreholes 102a are shown to further include a number of lateral boreholes 108a branched off from boreholes 102a. Certain lateral boreholes 108a further include one or more sub-lateral boreholes 110a. Boreholes 102a, lateral boreholes 108a and sub-lateral boreholes 110a may include boreholes of any suitable orientation, including vertical boreholes, deviated boreholes and horizontal boreholes formed in any direction. In aspects, the use of a large number of boreholes 102a in conjunction with directional drilling, multiple kickoffs, trenchless drilling, and controlled drilling allow pin pointing deposits and veins containing desired elements and mining from such areas that were previously inaccessible for mining by conventional methods. Information from seismic surveys and pilot boreholes drilled through the ore field may be utilized to define an ore field, such as ore field 106. Defining an ore field may include developing the boundaries of the ore field 106 to develop a plan for the boreholes 102a, 108a and 110a to maximize recovery of the ore from the ore field 106. Any borehole pattern may be utilized for in situ extraction of the ore from the ore field 106.
In a non-limiting exemplary embodiment, drill bit 220 is steered by a steering device 222. The steering device 222 may include any available steering device, including, but not limited to, a device that includes a number of force application members that apply force on the inside of the borehole 202 to steer the drill bit 220 in the desired direction. In aspects, the sensors 224 provide information about the location of the drill bit 220 in the ore field 206 relative to a known location, such as true north. An operator and/or a control circuit or controller 260 in the drilling assembly 210 and/or a control circuit or controller 290 at the surface 201 may direct the steering device 222 to steer or maintain the drill bit 220 along the desired path. The controllers 260 and 290 may include processors, such as microprocessors, memory devices and programmed instructions for geosteering and to perform other downhole functions in real time. The controllers also may include circuits for processing measurements from the various sensors 224 to determine in real time the various properties of the constituents of the materials in the ore field 206. The sensors 224 also may provide information that enables the operator and/or the controllers 260 and/or 290 to maintain the drill bit 220 in the ore field 206. Thus, the sensors 224 provide information about elements in the ore and distances from the boundaries from subsurface faults and previously drilled boreholes. Such information may be utilized to maintain the drill bit in the desired ore zone and a desired distance from the previously drilled boreholes.
Sensors 224 may include a variety of sensors, including, but not limited to, accelerometers and magnetometers for providing the location and orientation of the drilling assembly 210 for geosteering. Sensors 224 may further include logging-while drilling sensors, including, but not limited to electrical sensors (such as resistivity sensors), electromagnetic sensors, acoustic sensors, nuclear logging sensors, elemental spectroscopy sensors, and pulsed neutron sensors. The sensors 224 may be characterized for a particular mineral or element of interest. For example, for a pulsed neutron sensor, peaks may be calibrated based on the mineral or element of interest in a particular ore field 206, such as copper, uranium, gold, manganese, nickel, and rare earths to provide optimal detection of such minerals. Downhole logging tools exist that perform pulsed neutron elemental analysis wherein the formation is temporarily irradiated with neutrons, which strike the nuclei of elements, which subsequently emit radiation including gamma rays of various energies whose unique spectral fingerprints then allow identification and quantification of those elements. Even when there is spectral overlap, it is possible to distinguish one spectrum from another because different radioisotopes have different half-lives so one can wait to collect spectral data until after radiation from an interfering species has decayed away. The sensitivity of this technique depends upon the element. Tables of sensitivities for various elements are well known. Therefore, operators can geosteer along a vein of a precious metal or some other element by performing real time elemental analysis. Downhole elemental analysis might also be performed by focusing a laser or a spark on cuttings lying just outside of an optical window analogous to the elemental analysis of a fluid by laser induced breakdown spectroscopy (LIBS) and spark-induced breakdown spectroscopy (SIBS) described in U.S. Pat. No. 7,530,265, which is incorporated herein by reference in its entirety. In another method of drilling a borehole through an identified vein containing a metal, such as gold, platinum, etc., a resistivity sensor in the BHA may be used to determine in real time the resistivity of the formation surrounding the borehole and in front of the drill bit. Such sensors can provide relatively accurate information relating to the presence of metals and concentrations levels in the ore. This information may be utilized to maintain the drill bit 220 in the vein containing the selected ore. In other embodiments, alternative sensors may be used to find other materials, such as platinum and diamonds. Information from sensors 224 may also provide rock type identification and correlation, rock mass characterization, litho-stratigraphic interpretation, ore body delineation, grade estimation, etc. The measurements from the sensors 224 may be processed by the downhole controller 260 to determine the various properties of the ore and the rock and to take actions, such as geosteering. Alternatively, or in addition thereto, information from the sensors 224 may be telemetered to the surface controller 290, which may process such information and take actions. Any suitable telemetry system may be used, including, but not limited to mud pulse telemetry, electromagnetic telemetry, or electrical conductors or optical fibers in the drill string 228. A telemetry device 292 in the drilling assembly 210 may provide two-way communication between the controllers 260 and 290. For ore processing at well site, small conventional smelting or leaching units may or more environmentally friendly bioleaching units may be set up at the rig site.
As the return fluid 238 is received at surface 201, the ore 240 (cuttings) may be separated from the fluid 232 and processed or partially processed near the rig site 201. In an exemplary embodiment, a separator 234 separates the ore 240 from fluid 232. An ore processor 236 may further refine the separated ore 240 into a material or form suitable for transportation away from in situ mining system 200. The ore processor may include a smelter, for example, for extracting a metal from the ore, a chemical processing unit for leaching the desired element from the ore or any other facility suitable for extracting the desired elements from the ore 240. In general, the amount of the desired element in the ore is often less than one percent by weight or volume. The ore or material remaining after processing (the “discarded material” or “residue ore”) may be disposed in any suitable manner. In certain embodiments, a disposal unit 238 receives and stores residue ore. In certain other embodiments, a disposal unit 238 recycles or reintroduces the residue ore into one or more boreholes already drilled or into an underground facility formed to store such undesired material. The ore residue may be mixed with a suitable fluid, such as water and pumped into the boreholes or storage facilities or contained by other known disposal methods including pumping cement and residual cuttings back into the boreholes. The ore recovery methods described in reference to system 100 of
In one embodiment, the isolated volume may be subjected to additional operations. The isolated volume may be subjected to in situ mining methods, fracturing methods, and leaching methods as described above. In certain other embodiments, traditional mining methods are used. In an exemplary embodiment, mine shaft 574 is formed and utilized to allow the ore inside to be retrieved. In alternative embodiments, in situ mining methods are utilized.
Thus in some aspects, the disclosure provides various methods of extracting ores from a subsurface location or the ore field without removing the overburden, i.e., without removing the earth material from above the ore field. In one method the ore volume or field may be defined or mapped from seismic surveys and/or from pilot or test wells drilled into the subsurface. The ore field may be several hundreds of feet (such as over 500 feet) or several thousand feet (such as over ten thousand feet) below the surface. The ore field may be relatively large, such more than ten miles wide, more than 20 miles long and more than 1,000 feet deep. In one non-limiting embodiment the method may further include developing a well plan that may include a very large number of vertical wells, such as a few hundred to a few thousand wells, some or all of the wells further including one or several lateral wells. The wells (vertical wells and lateral wells) are formed using drilling assemblies that include a drill bit, a steering device, sensors for providing the location of the drill bit, sensors for providing information about the ore desired to be recovered while drilling and a telemetry device that allows real time communication between the drilling assembly and a surface location. The wells are drilled by circulating a drilling fluid that discharges at the drill bit bottom and returns to the surface via an annulus between the drill string and the well. The ore drilled or disintegrated by the drill bit travels to the surface with the drilling fluid. The ore in the returning fluid is separated from the drilling at the surface. If a very large number of wells (such as several thousand) are drilled into the ore field, a substantial volume of the ore from the ore field may be recovered from the ore field without reducing or eliminating the overburden. Such a method is safe relative to conventional mining methods as it does not involve forming large shafts and transporting mining equipment or persons into the mines. Measurements from the sensors are used to geosteer, i.e., drill the wellbores along desired paths. In other method, some or all drilled wellbores may be treated, such as fractured and/or leached to recover additional ore from the ore field. In another aspect, a subsurface zone containing a desired ore may be isolated. Such zone may then be fractured and used for in situ mining according to the methods described herein and/or traditional mining methods, such as using mine shafts.
The foregoing disclosure is directed to the certain exemplary non-limiting embodiments of in situ mining methods and systems. Various modifications will be apparent to those skilled in the art. It is intended that all such modifications within the scope of the appended claims be embraced by the foregoing disclosure. The words “comprising” and “comprises” as used in the claims are to be interpreted to mean “including but not limited to”. Also, the abstract is not to be used to limit the scope of the claims.
This application takes priority from U.S. Provisional application Ser. No. 62/074,493, filed on Nov. 3, 2014, which is incorporated herein in its entirety by reference.
Number | Date | Country | |
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62074493 | Nov 2014 | US |