Mining or in situ disintegration of hard material – Processes – Breaking down by direct contact with fluid
Reexamination Certificate
1999-06-19
2002-10-08
Bagnell, David (Department: 3673)
Mining or in situ disintegration of hard material
Processes
Breaking down by direct contact with fluid
C299S005000, C299S001050, C175S067000, C175S040000
Reexamination Certificate
active
06460936
ABSTRACT:
BACKGROUND OF THE INVENTION
(a) Field of the Invention
This invention relates to a system for providing remote hydrojet borehole mining, and more specifically, but not by way of limitation, to a hydraulic borehole mining system with interchangeable components that allow the use of a single device for a plurality of tasks. Some of the tasks that the instant invention could be used for: extraction or the mining of a mineral resources; the creation of a subsurface cavity or void space; to stimulate liquid and/or gas production; clean lake bottoms; recover either liquid or solid environmental contaminates; or other related uses which require a remotely operated tool.
The Borehole Mining Tool (tool) is intended for mining of mineral resources, through boreholes. This tool may be applied from the Earth's surface, underground mines and ocean platforms. The tool also will find an application in geological exploration for bulk sampling, in building of subterranean storages, in-situ leaching, production stimulation for oil/gas and water, in custom foundations, underground collectors construction, environmental clean up of subterranean spills and more. The tool can be used to solve other environmental problems, such as cleaning of lake bottoms and removing ooze, cleaning of oil reservoirs, radioactive contamination (nuclear missile silos), and other applications requiring remote operating.
(b) Discussion of Known Art
Borehole mining (BHM) as a remote underground mining method is based on water jet cutting of rock material. This is accomplished by pumping high pressure water down to the working area from the Earth's surface (or underground mines, or floating platforms) to the borehole mining tools lowered into pre-drilled holes. The slurry created by the water jet is simultaneously pumped out by the same tool. By removing the broken materials, underground cavities (stopes) can be created.
The BHM approach has many recognized advantages, but the method has not gained acceptance commensurate with its potential due to several important issues that have yet to be finalized. One of the most significant problems has been the specialized tooling needed for mining of different type of material and specific geo-technical and environmental tasks to be performed, which requires that the user needs to carry and the use of different tools to the work site instead of a universal one. These tools are typically large and heavy units having a minimum number of joints, couplings, threads and other easy-and-quick connectors which complicates the tool's assembly, accessibility, serviceability and replacement. In case of a failure of some part of the tool, the replacement of this disabled unit(s) usually requires a replacement of most, if not all, of the tool.
Another problem is that borehole mining is a blind method; there is no data about the current cutting direction as well as the current configuration of the driving space (cavern/stopes). All geophysical measurements (logging) may be executed only after all operations are stopped and the BHM tool is removed from the hole. This typically equates to several hours of down time. Additionally, because borehole mining is carried out in friable, unconsolidated (unstable) material, the shape of the created stopes can be easily changed by collapsed rock masses. Thus, measurements, made after stopping of operation can not always be used for estimation of production. Best downhole measurements must be made while mining: or “logging-while-mining” (LWM). This instant tool will allow for the attachment of monitoring devices which will give “eyes” to borehole mining.
In certain circumstances it is necessary to build vertical slots using several boreholes and then connecting them to each other, for example to create an extended underground collecting ditch. In this task, information about orientation of the tool's nozzle down in a borehole becomes very critical. But, through assembling and lowering the tool in a hole, its bottom part (which contains the head and the hydromonitor's nozzle) is twisted relative to the upper portion of the tool. Thus, after the tool is assembled and lowered down in a hole, there is no further information about the current bottom head's nozzle orientation; as it is lost while assembling.
In borehole mining, a hole is first drilled from the surface to a depth where the mineral deposit or work area is located. A metal or plastic casing, which is nothing more than a heavy pipe, is then inserted into the hole to prevent sidewall caving or capsizing of the hole. The casing bottom end, called a casing shoe is placed immediately above the future working (production) interval. Then, the borehole mining tool is lowered into this casing until its bottom (working) end portion reaches the “open” hole, right bellow the casing shoe.
The BHM tool consists of three main parts: an upper head, an intermediate column and a bottom (working) head. The upper head includes stub-pipes for pumping in a working high-pressure fluid (usually water) and for discharge of production slurry; a swivel; a turn table; and a mechanism for raising/lowering the tool while mining. The intermediate column is comprised of two or more pipes assembled in “pipe-in-pipe” manner by numerous dual conduit sections. At the end of this column is the bottom head with its hydromonitor and eductor (also known as hydro-elevator, or jet-pump). In most cases, a drill bit can also be placed at the bottom end of the tool.
The inner and outer columns of the tool form an O-shape gap. Thus, the tool has at least two hydraulic channels: one is the inner pipe's channel (inner channel), and the other is the aforementioned ring gap, or outer channel. These channels are used for delivery of high pressure working fluid (water) to the bottom head and for elevating production slurry back to the surface. It is obvious that two channels are the minimum required in borehole mining. Therefore, in BHM two main schematics of water/slurry circulation are used: (1) the “direct”; water is pumped by inner pipe and slurry is received by the gap and (2) the “return”; opposite circulating. Because of its relative simplicity, over 90% of existing BHM tools are based on these two schematics. The schematic of fluids circulating is reflected on the configuration of the top head and other surface equipment.
The borehole mining tool functions as follows: The tool is lowered into a borehole until the hydromonitor (which is located in a bottom head) is placed below the casing shoe in an open hole to the depth that the actual mining is to take place. Next, the high pressure (working) water, approx 2000 psi at a flow rate of 1000 GPM, is pumped down to the tool through one of the two channels or annulus' contained in the intermediate pipe. In the bottom head one part of this water is split off to the hydromonitor which contains a nozzle directing the water to the area to be worked-out. As it passes through the nozzle, this flow accelerates to a water jet that is sufficiently powerful to break and scale away the material being mined. The loosened rock/ore material from the worked out area is fluidized through mixing with water to create a productive (pregnant) slurry.
The created slurry must be drawn to the surface to clean the working space (stope/cavern) and to recover the desired mineral(s) or create the desired cavity. For this purpose, the remaining portion of the working water continues flowing down until it reaches the eductor which forces it to turn which creates a vacuum in front of the Venturi pipe opening. This vacuum sucks the incoming slurry, drawing it into the slurry channel of the tool and then it is transported up the pipe until it reaches the surface.
On the surface, the water contained in the slurry is separated from heavy particles (rock/ore chunks and other solids)in a collecting pond or tank by gravity force (and/or other standard equipment, if needed). The clarified water is pumped down to the working interval again. This completes the BHM water re-circulating cycle. Wh
Abramov Grigori Y.
Babichev Nikolai I.
Novikov Mikhail M.
Polic Ratko
Tkach Sergey D.
Bagnell David
Kreck John
LandOfFree
Borehole mining tool does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Borehole mining tool, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Borehole mining tool will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2965083