Patent Application
20160319603
The present invention relates in subject matter to: Criteria for Jet Cavitation and Cavitation Jet Drilling, Zifeng Li, International Journal of Rock Mechanics & Mining Sciences 71 (2014) 204-207; and U.S. Pat. No. 7,517,430, to LeClair, issued Apr. 14, 2009 the disclosures of which are incorporated herein by reference and appended hereto.
The present invention pertains to drill bits for mining natural resources, and particularly to drill bits and methods of using the same that include a cavitation jet mask enabled with reentrant cavitation jet capability.
Cavitation Jet Drilling has been known about for some time, but it has not yet had widespread commercial acceptance or use. Essentially a stream of cavitation bubbles are directed towards earth to erode the rocks away. This has used simply spraying a fluid at high pressure through a nozzle at the substrate surface to erode. The bubbles formed in the fluid are cavitation bubbles. They are sprayed via a nozzle directly at rock. The inner burst impact pressure of the bubbles on the rock cause erosion of the rock.
However to effectuate formation of these bubbles, it is understood that the pressures in the nozzle need to be reduced from the static pressure to the vapor pressure. There are also problems using a nozzle because the ambient pressures in a bottom hole are typically high and not uniform. In the case of high environmental pressures found in bottom holes, cavitation may not occur unless special pressure-reducing technology is used. Thus formation of utilizable cavitation bubbles for mining applications is difficult and not yet commercially viable.
Further there is a large scatter in cavitation number, which can be used to predict cavitation. The cavitation number often cannot be used to accurately determine if cavitation will occur.
It is known that the impulse pressure due to the cavitation bubbles varies, because the bubbles form cavitation jets that are unpredictable and undirected. Although this variation of impulse pressure helps erode rock, there is still a need for improvement.
U.S. Pat. No. 7,517,430 to LeClair describes a recently discovered mechanism for using a directed energy source to create cavitation bubbles. This is a boiling phenomenon. What is interesting is that when the bubbles collapse, they generate a jet of fluid having high energy characteristics. LeClair discovered how to direct these reentrant cavitation jets by forming them at a precise distance from a mask plate, which causes the collapse to be directed through an aperture in the mask plate. These directed reentrant cavitation jets can produce surprisingly high velocities, i.e. greater than the speed of sound in water. The challenge is to utilize these reentrant jets in a drill bit for the mining industry.
The present invention includes a method of adapting drilling equipment to enable a new class of drill bits for mining applications, and any other application that involves drilling into the ground.
The present invention applies the cavitation phenomenon described by LeClair in U.S. Pat. No. 7,517,430 by controlling the reentrant cavitation jet formation reaction in a reaction chamber and directing the formed reentrant cavitation jet out from the reaction chamber toward a substrate. In this case, the substrate is rock or earth. The cavitation reactor is housed in a drill bit. The drill bit is a hammer bit in one embodiment of the invention, and the drill bit is a tricone bit in another embodiment of the invention.
LeClair specifically identifies the position within the cavitation reactor where the cavitation bubbles are to be formed. This also regulates the direction of the cavitation jets produced. Controlling the location of the cavitation bubbles and direction substantially improves energy efficiency and function of the present invention.
The drill bit has a face that contacts the rock, and the face includes an opening to enable cavitation jets to be directed through the face of the drill bit.
The cavitation reactor is enclosed in the drill bit. The cavitation reactor includes a cavitation mask including an array of openings that direct cavitation jets at high speed from the cavitation reactor through the opening in the drill bit. The cavitation mask directs cavitation jets through the face of the drill bit, and mitigates shock waves created by the cavitation jets.
This enables a relatively low energy laser, for example, to produce cavitation jets having precise direction and energy to assist the drill bit in excavating rock and earth. This yields a longer drill bit life, faster drilling speeds, lower heat production, and lower cost of ownership of the drill bit and a lower cost per foot of drilling.
The cavitation mask is particularly designed having apertures that are sized smaller than the cavitation bubble diameter to inhibit cavitation bubbles from passing through the cavitation mask and impinging upon the rock or earth substrate material. Instead the cavitation bubbles expand to 10-50 times of the focus volume of the laser of liquid in the cavitation reactor. The diameter of each aperture of the mask is at least a third of the size of the mean cavitation bubble size. Preferably, the aperture is approximately 1%-30% of the cavitation bubble diameter. Ideally the apertures are less than 1 millimeter, and preferably less than 100 microns in size. When the cavitation jets produced are 5-25 microns in width they fit nicely through the apertures of 100 microns, and smaller.
In an alternate embodiment, a laser producing infrared wavelength of approximately 10 microns in the cavitation reactor fluid. The laser has, for example, a 10 mm diameter beam of colliminated energy, for example. The beam is focused on liquid in the cavitation reactor to generate cavitation bubbles of 500microns in diameter, or less. Reentrant cavitation jets are produced having a mean diameter of approximately 0.1-10 microns. These reentrant cavitation jets pass easily through the apertures of the mask.
The cavitation mask is positioned between 1-6 cavitation bubble diameters away from the focal point of the laser. This distance is automatically, or manually adjustable from a remote control location.
In an alternate embodiment, the laser is replaced by an x-ray energy source producing a 0.1 micron wavelength beam to generate 0.5 micron cavitation bubbles or smaller. In a variant of this embodiment, reentrant cavitation jets having a mean diameter on the order of 1.1 nanometers are produced. In this example the apertures of the mask are between 2 nanometers to 0.5 microns.
Although various examples are provided many variations are enabled by the present invention, all with a drill bit including a cavitation reactor having a mask with sub-millimeter apertures.
The present invention includes the method 10. The method 10 includes providing a tricone drill bit, or hammer bit, that houses a cavitation reactor. The method includes the step 14 of directing the drill bit at a rock or earth substrate., the step 16 of providing a laser beam directed to the cavitation reactor, the step 18 of forming a cavitation bubble, or bubbles, with the cavitation reactor in response to the laser beam, the step 20 of controlling a cavitation bubble collapse sequence within the cavitation reactor to create reentrant cavitation jets, and the step 22 of directing the reentrant cavitation jets from the reactor, through a face of the drill bit, and to the rock or earth substrate. This erodes the rock or earth substrate.
The drill bit operates while the reentrant cavitation jets erode the rock or earth substrate. In one embodiment, the tricone bit spins to drill the rock or earth, and in another embodiment the hammer bit hammers the rock or earth. The cooperation of the mechanical force of the bit, combined with the cavitation forces yields a more efficient drilling methodology.
The present invention includes the method 24, which includes the step 26 of rotating a tricone drill bit having a face in a rock or earth substrate. The tricone drill bit houses a cavitation reactor that is liquid-filled with a substance capable of forming cavitation bubbles. Preferably the liquid is water.
The method 24 also includes the step 28 of directing an array of reentrant cavitation jets in concentric annular patterns from the cavitation reactor through the face of the tricone drill bit as it rotates. The step 30 etches generally annular patterns in the rock substrate with the reentrant cavitation jets to improve performance of the drill bit. The step 32 maintains an adequate volume of liquid in the cavitation reactor to enable continuous operation of the drill bit. The step 34 uses the reentrant cavitation jets to decrease drill bit wear over a given period of time, and improves the rate of drilling.
In another embodiment, where a non-rotating bit is used, the cavitation reactor includes an array of cavitation ports to direct cavitation jets into a pattern on the rock or earth substrate. This weakens the substrate. Natural vibration of the non-rotating bit further weakens the substrate.
The tri-cone drill bit 36 further includes a face 40 that enables the delivery of fluid such as air or water through the tri-cone drill bit 36. The fluid cools the drill bit 36 and operation and also excavates mud, earth and stones during the drilling process.
The face 40 is mounted at one end of a fluid conduit 38. The fluid conduit 38 defines a hollow portion of the drill bit 36. The hollow portion of the drill bit encloses a cavitation reactor 42. The cavitation reactor 42 further includes laser source 44 integral with the cavitation reactor 42. The cavitation reactor 42 is further housed inside a cylindrical case to protect the cavitation reactor from damage due to vibration, shock and the movement of fluid. The laser source 44 in one embodiment the laser source 44 includes a laser mounted above ground and connected to the cavitation reactor 42 by a fiber-optic cable. In another embodiment the laser source 44 is enclosed within the cavitation reactor 42.
The cavitation reactor 42 is positioned within the fluid conduit 38 and oriented to deliver cavitation jets through the face 40 towards rock or earth substrate to enable the cavitation reactor 42 to cooperate with the cones 48 in operation.
The cavitation reactor 42 is particularly positioned at an angle with respect to the face 42 enable cavitation jets produced by the cavitation reactor to etch annular patterns on rock or earth substrate.
The mask 49 is formed as part of the cavitation reactor 42 to direct reentrant jets, and not cavitation bubbles, from the cavitation reactor 42 through the face of the drill bit 46.
The cavitation reactor 42 can be similarly attached to a hammer bit that does not rotate. The advantage is that the cavitation reactor and reentrant jets can be more closely positioned to the substrate material.
Rotation of the drill bit 50 along the axis 58 enables the cones 52 to drill earth and rock. This rotation also enables the reentrant cavitation jets from the cavitation reactor 56 two etch an annular pattern on the earth and rock. Preferably numerous annular patterns are etched on the earth and rock and these patterns are concentric.
Although the cavitation reactor 56 is mounted on the body 54, dismounting can be flexible and selectively movable to create annular patterns that include a wave form representation having an amplitude and frequency to further improve performance of the drill bit 50. Further the natural vibrations of the drill bit 50 in will cause variations in the annular pattern.
In a preferred embodiment the mounting between the cavitation reactor 56 and the body 54 dampens vibrations and shock. This can be accomplished by utilizing a flexible mount between the cavitation reactor 56 in the body 54.
In each embodiment of the invention fluid flow through the drill bit is maintained while cavitation jets are produced and directed.
