WO2014047597A1

WO2014047597A1 - System and method for wireless drilling and non-rotating mining extenders in a drilling operation

Info

Publication number: WO2014047597A1
Application number: PCT/US2013/061264
Authority: WO
Inventors: Daniel Codazzi; Raphael Gadot; Brian Oliver Clark
Original assignee: Schlumberger Canada Limited; Services Petroliers Schlumberger; Schlumberger Holdings Limited; Schlumberger Technology B.V.; Prad Research And Development Limited; Schlumberger Technology Corporation
Priority date: 2012-09-24
Filing date: 2013-09-24
Publication date: 2014-03-27
Also published as: US20140083770A1

Abstract

Various embodiments of methods and systems for wireless power and data communications transmissions to a sensor subassembly below a mud motor in a bottom hole assembly are disclosed. Power and/or communications are transmitted through stationary or fixed coils. By leveraging resonantly tuned circuits and impedance matching techniques for the stationary coils, power and/or communications can be transmitted efficiently from one stationary coil to the other stationary coil despite any vibration and/or misalignment of the two coils.

Description

SYSTEM AND METHOD FOR WIRELESS DRILLING AND NON- ROTATING MINING EXTENDERS IN A DRILLING OPERATION

DESCRIPTION OF THE RELATED ART

[0001] Bottom hole assemblies ("BHA") at the end of a typical drill string used in the drilling and mining industry today may be a complex assembly of technology that includes not only a drill bit, but also an array of serially connected drill string components or tools. The various drill string tools that make up a BHA commonly include electrically powered systems on a chip ("SoC") designed to leverage local sensors for the collection, processing and transmission of data that can be used to optimize a drilling strategy. In many cases, the various tools that make up a BHA are in bidirectional communication.

[0002] As one might expect, a BHA may be an equipment assembly with a hardened design that can withstand the demands of a drill string. Failure of a BHA, whether mechanically or electrically, inevitably brings about expensive and unwelcomed operating costs as the drilling process may be halted and the drill string retracted from the bore so that the failed BHA can be repaired. In many cases, retraction of a drill string to repair a failed BHA can range in cost from hundreds of thousands of dollars to millions of dollars.

[0003] A common failure point for BHAs is the point of connection from tool to tool, which is naturally prone to failure from adverse fluid ingress and/or misalignment between adjacent tools. While the individual tools may be robust in design, the mechanical and electrical connections between the tools may be a natural "weak point" that often determines the overall reliability of the BHA system.

SUMMARY OF THE DISCLOSURE

[0004] Various embodiments of methods and systems for wireless power and data communications transmissions in a BHA are disclosed. The efficient transfer of electrical power and/or communication signals between two otherwise weakly, stationary coupled coils in a BHA may be accomplished in various embodiments that may leverage resonantly tuned circuits and impedance matching techniques. In this way, a wireless coupling may be provided between two fixed or stationary tools so that a direct mechanical connection for power and/or communications is not required when assembling the tools together and while they are operated in a bore hole. A gap between the tuned coils may exist and does not degrade performance of power and communications transfer between the coil. To compensate for any potential flux leakage, embodiments resonate inductively coupled primary and secondary coils at the same frequency. Further, in some embodiments, the source resistance is matched to the transmitting coil impedance and the load resistance is matched to the receiving coil impedance.

[0005] Power and/or communications may be transmitted through a stationary annular coil to an inductively coupled stationary second, mandrel coil (it is envisioned that various embodiments may employ any combination of annular and mandrel coils). By using resonantly tuned circuits and impedance matching techniques for the stationary coils, power and/or communications may be transmitted efficiently from one stationary coil to the other despite relative movement/vibration and misalignment of the two stationary coils. For example, to compensate for flux leakage, embodiments resonate inductively coupled primary and secondary coils at the same frequency.

[0006] Additionally, in some embodiments, the source resistance is matched to the transmitting coil impedance and the load resistance is matched to the receiving coil impedance.

[0007] This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In the Figures, like reference numerals refer to like parts throughout the various views unless otherwise indicated. For reference numerals with letter character designations such as "102A" or "102B", the letter character designations may differentiate two like parts or elements present in the same figure. Letter character designations for reference numerals may be omitted when it is intended that a reference numeral to encompass parts having the same reference numeral in figures.

[0009] Figure 1A is a diagram of a system for wireless drilling and mining extenders in a drilling operation;

[0010] Figure IB is a diagram of a wellsite drilling system that forms part of the system illustrated in Figure 1A;

[0011] Figure 2 is a schematic drawing depicting a primary or transmitting circuit and a secondary or receiving circuit; [0012] Figure 3 is a schematic drawing depicting a primary or transmitting circuit and a secondary or receiving circuit with transformers having turn ratios Ng : 1 and N_L : 1 that may used to match impedances;

[0013] Figure 4 is a schematic drawing depicting an alternative circuit to that which is depicted in Figure 3 and having parallel capacitors that are used to resonate the coils' self- inductances;

[0014] Figures 5A-5B illustrate an embodiment of a receiving coil inside a transmitting coil;

[0015] Figures 6-7 are graphs illustrating the variation in k versus axial displacement of the receiving coil when x = 0 is small and the transverse displacement when z = 0 produces very small changes in k ₀f given embodiments, respectively;

[0016] Figures 8-9 are graphs illustrating that power efficiency may also be calculated for displacements from the center in the z direction and in the x direction, respectively, of given embodiments;

[0017] Figure 10 is a graph illustrating that the sensitivity of the power efficiency to frequency drifts may be relatively small in some embodiments;

[0018] Figure 11 is a graph illustrating that drifts in the components values of some embodiments do not have a large effect on the power efficiency of the embodiment;

[0019] Figure 12 depicts a particular embodiment configured to convert input DC power to a high frequency AC signal, f_Q , via a DC/AC converter;

[0020] Figure 13 depicts a particular embodiment configured to pass AC power through the coils;

[0021] Figure 14 depicts a particular embodiment that includes additional secondary coils configured to transmit and receive data;

[0022] Figures 15A1-15C2 are diagrams of tools in a bottom hole assembly of a drill string that are coupled via embodiments of a wireless drilling and mining extender;

[0023] Figure 16A illustrates a wireless power distribution scheme between stationary tools that leverages alternating current ("AC") to transmit power across various tools in a

BHA that includes wireless drilling and mining extenders; and

[0024] Figure 16B illustrates wireless power distribution scheme between stationary tools that leverages alternating current ("AC") and direct current ("DC") to transmit power across various tools in a BHA that includes wireless drilling and mining extenders. DETAILED DESCRIPTION

[0025] The system described below mentions how power and/or communications may flow from one drill collar to another. The inventive system may transmit power and/or communications in either direction and/or in both directions as understood by one of ordinary skill in the art.

[0026] Referring initially to Figure 1A, this figure is a diagram of a system 102 for controlling and monitoring a drilling operation. The system 102 includes a control module 101 that is part of a controller 106. The system 102 also includes a drilling system 104, which has a logging and control module 95, a bottom hole assembly ("BHA") 100, and wireless power and data connections 402. The wireless power and data connections 402 may exist between several elements of the BHA as will be explained below.

[0027] The controller 106 further includes a display 147 for conveying alerts 1 10A and status information 115A that are produced by an alerts module HOB and a status module 1 15B. The controller 106 in some instances may communicate directly with the drilling system 104 as indicated by dashed line 99 or the controller 106 may communicate indirectly with the drilling system 104 using the communications network 142

[0028] The controller 106 and the drilling system 104 may be coupled to the communications network 142 via communication links 103. Many of the system elements illustrated in Figure 1A are coupled via communications links 103 to the communications network 142.

[0029] Figure IB illustrates a wellsite drilling system 104 that forms part of the system 102 illustrated in Figure 1A. The wellsite can be onshore or offshore. In this system 104, a borehole 1 1 is formed in subsurface formations by rotary drilling in a manner that is known to one of ordinary skill in the art. Embodiments of the system 104 can also use directional drilling, as will be described hereinafter. The drilling system 104 includes the logging and control module 95 as discussed above in connection with Figure 1A.

[0030] A drill string 12 is suspended within the borehole 11 and has a bottom hole assembly ("BHA") 100 which includes a drill bit 105 at its lower end. The surface system includes platform and derrick assembly 10 positioned over the borehole 11, the assembly 10 including a rotary table 16, kelly 17, hook 18 and rotary swivel 19. The drill string 12 is rotated by the rotary table 16, energized by means not shown, which engages the kelly 17 at the upper end of the drill string. The drill string 12 is suspended from a hook 18, attached to a traveling block (also not shown), through the kelly 17 and a rotary swivel 19 which permits rotation of the drill string 12 relative to the hook 18. As is known to one of ordinary skill in the art, a top drive system could alternatively be used instead of the kelly 17 and rotary table 16 to rotate the drill string 12 from the surface. The drill string 12 may be assembled from a plurality of segments 125 of pipe and/or collars threadedly joined end to end.

[0031] In the embodiment of Figure IB, the surface system further includes drilling fluid or mud 26 stored in a pit 27 formed at the well site. A pump 29 delivers the drilling fluid 26 to the interior of the drill string 12 via a port in the swivel 19, causing the drilling fluid to flow downwardly through the drill string 12 as indicated by the directional arrow 8. The drilling fluid exits the drill string 12 via ports in the drill bit 105, and then circulates upwardly through the annulus region between the outside of the drill string 12 and the wall of the borehole 1 1, as indicated by the directional arrows 9. In this system as understood by one of ordinary skill in the art, the drilling fluid 26 lubricates the drill bit 105 and carries formation cuttings up to the surface as it is returned to the pit 27 for cleaning and recirculation.

[0032] The BHA 100 of the illustrated embodiment may include a logging-while-drilling ("LWD") module 120, a measuring-while-drilling ("MWD") module 130, a roto- steerable system ("RSS") and motor 150 (also illustrated as 280 in FIGURE 15 described below), and drill bit 105.

[0033] The LWD module 120 is housed in a special type of drill collar, as is known to one of ordinary skill in the art, and can contain one or a plurality of known types of logging tools. It will also be understood that more than one LWD 120 and/or MWD module 130 can be employed, e.g. as represented at 120A. (References, throughout, to a module at the position of 120A can alternatively mean a module at the position of 120B as well.) The LWD module 120 includes capabilities for measuring, processing, and storing information, as well as for communicating with the surface equipment. In the present embodiment, the LWD module 120 includes a directional resistivity measuring device.

[0034] The MWD module 130 is also housed in a special type of drill collar, as is known to one of ordinary skill in the art, and can contain one or more devices for measuring characteristics of the drill string 12 and drill bit 105. The MWD module 130 may further include an apparatus (not shown) for generating electrical power to the BHA 100.

[0035] This apparatus may include a mud turbine generator powered by the flow of the drilling fluid 26, it being understood by one of ordinary skill in the art that other power and/or battery systems may be employed. In the embodiment, the MWD module 130 includes one or more of the following types of measuring devices: a weight-on-bit measuring device, a torque measuring device, a vibration measuring device, a shock measuring device, a stick slip measuring device, a direction measuring device, and an inclination measuring device.

[0036] The foregoing examples of wireline and drill string conveyance of a well logging instrument are not to be construed as a limitation on the types of conveyance that may be used for the well logging instrument. Any other conveyance known to one of ordinary skill in the art may be used, including without limitation, slickline (solid wire cable), coiled tubing, well tractor and production tubing.

[0037] Figure 2 is a schematic drawing depicting a primary or transmitting circuit 210 and a secondary or receiving circuit 220. In this description, the time dependence is assumed to be exp(/&>i) where ω = 2πί and / is the frequency in Hertz. Returning to the

Figure 2 illustration, the transmitting coil is represented as an inductance and the receiving coil as L^ . In the primary circuit 210, a voltage generator with constant output voltage V_s and source resistance R_s drives a current through a tuning capacitor and primary coil having self-inductance and series resistance R₁ . The secondary circuit 220 has self-inductance and series resistance R₂ . The resistances, ^and ^, may be due to the coils' wires, to losses in the coils magnetic cores (if present), and to conductive materials or mediums surrounding the coils. The Emf (electromotive force) generated in the receiving coil is V₂, which drives current I₂ through the load resistance R_L and tuning capacitor C₂ . The mutual inductance between the two coils is M , and the coupling coefficient k is defined as:

[0038] While a conventional inductive coupler has ~ 1 , weakly coupled coils may have a value for k less than 1 such as, for example, less than or equal to about 0.9. To compensate for weak coupling, the primary and secondary coils in the various embodiments are resonated at the same frequency. The resonance frequency is calculated as:

[0039] At resonance, the reactance due to is cancelled by the reactance due to C_x . Similarly, the reactance due to is cancelled by the reactance due to C₂ . Efficient power transfer may occur at the resonance frequency, / = ΰ¾ / 2π . In addition, both coils may be associated with high quality factors, defined as:

_ coL _ coL.

Q_{1 =} -^ and Q₂ = -^ . (3)

[0040] The quality factors, Q, may be greater than or equal to about 10 and in some embodiments greater than or equal to about 100. As is understood by one of ordinary skill in the art, the quality factor of a coil is a dimensionless parameter that characterizes the coil's bandwidth relative to its center frequency and, as such, a higher Q value may thus indicate a lower rate of energy loss as compared to coils with lower Q values.

[0041] If the coils are loosely coupled such that k < \ , then efficient power transfer may be achieved provided the figure of merit, U, is larger than one such as, for example, greater than or equal to about 3 :

[0042] The primary and secondary circuits are coupled together via:

ν_λ = jcoL^I^ + JcoMI₂ and V₂ = )ωΙ^Ι₂ + jcoM Ι_λ , (5) where is the voltage across the transmitting coil. Note that the current is defined as clockwise in the primary circuit and counterclockwise in the secondary circuit. The power delivered to the load resistance is:

while the maximum theoretical power output from the fixed voltage source V_s into a load is:

|2

P^jliAX ⁼ o n ' ^

[0043] The power efficiency is defined as the power delivered to the load divided by the maximum possible ower output from the source,

[0044] In order to optimize the power efficiency, η , the source resistance may be matched to the impedance of the rest of the circuitry. Referring to Figure 2, is the impedance looking from the source toward the load and is given by:

ω²Μ²

- j I {eoC_x ) + jeoLy + (9)

R₂ + R_L + ;ω∑2 - j I (coC₂ )

[0045] When ω = ω₀ , Ζ_λ is purely resistive and may equal R for maximum efficiency.

[0046] Similarly, the impedance seen by the load looking back toward the source is

ω²Μ²

- j I (coC₂ ) + jcol^ + (1 1)

[0047] When ω = ω₀ , Z₂ is purely resistive and R_L should equal Z for maximum efficiency

[0048] The power delivered to the load is then:

and the power efficiency is the power delivered to the load divided by the maximum possible power output,

4 R_sR_L o M²

η

^■ MAX 2^■ (14)

(Z_S + ZI ){Z2 + ZL ) + ^M2

[0049] The optimum values for R_L and R_L may be obtained by simultaneously solving

ω²Μ² ω²Μ²

and R_T R₂ + (15)

R₂ + R_L R_{1 +} R_s

with the result that:

R_s = i?_{x >}/l + i:²<¾<¾ and R_L = R₂ ^]l + k²Q Q₂ . (16)

[0050] If the source and load resistances do not satisfy equations (16), then it is envisioned that standard methods may be used to transform the impedances. For example, as shown in the Figure 3 illustration, transformers with turn ratios Ng : 1 and N_L : 1 may be used to match impedances as per equations (16). Alternatively, the circuit illustrated in Figure 4 may be used. In such an embodiment in Figure 4, parallel capacitors are used to resonate the coils' self-inductances according to equation (2). As before, Ζ_λ is defined as the impedance seen by the source looking toward the load, while Z₂ is defined as the impedance seen by the load looking toward the source. In addition, there are two matching impedances, Z _s and Z_T which may be used to cancel any reactance that would otherwise be seen by the source or load. Hence Ζ_λ and Z₂ are purely resistive with the proper choices of Z_s and _r . Notably, the source resistance R_s may equal

Z- , and the load resistance R_L may equal Z^ . The procedures for optimizing efficiency with series capacitance or with parallel capacitance may be the same, and both approaches may provide high efficiencies.

[0051] Turning now to Figures 5A and 5B, a cross sectional view of two coils 232, 234 is illustrated in Figure 5A and a side view of the two coils 232, 234 is illustrated in Figure 5B. In these two figures, a receiving coil 232 inside a transmitting coil 234 of a particular embodiment 230 is depicted. The receiving coil 232 includes a ferrite rod core 235 that, in some embodiments, may be about 12.5mm (about 0.49 inch) in diameter and about 96mm (about 3.78 inches) long with about thirty-two turns of wire 237. Notably, although specific dimensions and/or quantities of various components may be offered in this description, it will be understood by one of ordinary skill in the art that the embodiments are not limited to the specific dimensions and/or quantities described herein.

[0052] Returning to Figure 5, the transmitting coil 234 may include an insulating housing 236, about twenty-five turns of wire 239, and an outer shell of ferrite 238. The wall thickness of the ferrite shell 238 in the Figure 5 embodiment may be about 1.3mm (about 0.05 inch). In certain embodiments, the overall size of the transmitting coil 234 may be about 90mm (about 3.54 inch) in diameter by about 150mm (about 5.90 inches) long. The receiving coil 232 may reside inside the transmitting coil 234, which is annular.

[0053] The receiving coil 232 may be free to move in the axial ( z ) direction or in the transverse direction ( x) with respect to the transmitting coil 234. In addition, the receiving coil 232 may be able to rotate on axis with respect to the transmitting coil 234. The region between the two coils 232, 234 may be filled with air, fresh water, salt water, oil, natural gas, drilling fluid (known as "mud"), or any other liquid or gas. The transmitting coil 234 may also be mounted inside a metal tube, with minimal affect on the power efficiency because the magnetic flux may be captured by, and returned through, the ferrite shell 238 of the transmitting coil 234.

[0054] The operating frequency for these coils 232, 234 may vary according to the particular embodiment, but, for the Figure 5 example 230, a resonant frequency f = about 100kHz may be assumed. At this frequency, the transmitting coil 234 properties are: Ly = 6.76 · 10^~5 Henries and R₁ = 0.053 ohms, and the receiving coil 232 properties are

L₂ = 7.55 · 10^~5 Henries and R₂ = 0.040 ohms. The tuning capacitors are

C = 3.75 · 10^"8 Farads and C₂ = 3.36 · 10^~8 Farads. Notably, the coupling coefficient k value depends on the position of the receiving coil 232 inside the transmitting coil 234. The receiving coil 232 is centered when x = 0 and z = 0 and there is k = 0.64 .

[0055] The variation in k versus axial displacement of the receiving coil 232 when x = 0 may be relatively small, as illustrated by the graph 250 in Figure 6. The transverse displacement when z = 0 may produce very small changes mk , as illustrated by the graph 252 in Figure 7. The receiving coil 232 may rotate about the -axis without affecting k because the coils are azimuthally symmetric. According to equations (16), an optimum value for the source resistance may be R_s = 32 ohms, and for the load resistance may be R_L = 24 ohms when the receiving coil 232 is centered at x = 0 and z = 0 . The power efficiency may thus be η = 99.5% .

[0056] The power efficiency may also be calculated for displacements from the center in the z direction in mm (as illustrated by the graph 254 in Figure 8) and in the x direction in mm (as illustrated by the graph 256 in Figure 9). It is envisioned that the efficiency may be greater than about 99% for axial displacements up to about 20.0 mm (about 0.79 inch) in certain embodiments, and greater than about 95% for axial displacements up to about 35.0 mm (about 1.38 inches). It is further envisioned that the efficiency may be greater than 98% for transverse displacements up to 20.0 mm (about 0.79 inch) in some embodiments. Hence, the position of the receiving coil 232 inside the transmitting coil 234 may vary in some embodiments without reducing the ability of the two coils 232, 234 to efficiently transfer power.

[0057] Referring now to Figure 10, it can be seen in the illustrative graph 258 where the Y-axis denotes efficiency in percentage and the X-axis denotes frequency in Hz that the sensitivity of the power efficiency to frequency drifts may be relatively small. A ±10% variation in frequency may produce minor effects, while the coil parameters may be held fixed. The power efficiency at 90,000 Hz is better than about 95%, and the power efficiency at 1 10,000 Hz is still greater than about 99%. Similarly, drifts in the component values may not have a large effect on the power efficiency. For example, both tuning capacitors and C_j are allowed to increase by about 10% and by about

20% as illustrated in the graph 260 of Figure 11. Notably, the other parameters are held fixed, except for the coupling coefficient k . The impact of the power efficiency is negligible. As such, the system described herein would be understood by one of ordinary skill in the art to be robust.

[0058] It is also envisioned that power may be transmitted from the inner coil to the outer coil of particular embodiments, interchanging the roles of transmitter and receiver. It is envisioned that the same power efficiency would be realized in both cases.

[0059] Referring to Figure 12, an electronic configuration 262 is illustrated for converting input DC power to a high frequency AC signal , , via a DC/AC converter. The transmitter circuit in the configuration 262 excites the transmitting coil at resonant frequency ^ .

The receiving circuit drives an AC/DC converter, which provides DC power output for subsequent electronics. This system 262 is appropriate for efficient passing DC power across the coils.

[0060] Turning to Figure 13, AC power can be passed through the coils. Input AC power at frequency Jj is converted to resonant frequency by a frequency converter. Normally this would be a step up converter with f₀ » f_x . The receiver circuit outputs power at frequency^ , which is converted back to AC power at frequency [. Alternatively, as one of ordinary skill in the art recognizes, the Figure 13 embodiment 264 could be modified to accept DC power in and produce AC power out, and vice versa.

[0061] In lieu of, or in addition to, passing power, data signals may be transferred from one coil to the other in certain embodiments by a variety of means. In the above example, power is transferred using an about 100.0 kHz oscillating magnetic field. It is envisioned that this oscillating signal may also be used as a carrier frequency with amplitude modulation, phase modulation, or frequency modulation used to transfer data from the transmitting coil to the receiving coil. Such would provide a one-way data transfer. [0062] An alternative embodiment includes additional secondary coils to transmit and receive data in parallel with any power transmissions occurring between the other coils described above, as illustrated in Figure 14. Such an arrangement may provide two-way data communication in some embodiments. The secondary data coils 266, 268 may be associated with relatively low power efficiencies of less than about 10%. It is envisioned that in some embodiments the data transfer may be accomplished with a good signal to noise ratio, for example, about 6.0 dB or better. The secondary data coils 266, 268 may have fewer turns than the power transmitting 234 and receiving coils 232.

[0063] The secondary data coils 266, 268 may be orthogonal to the power coils 232, 234, as illustrated in Figure 14. For example, the magnetic flux from the power transmitting coils 232, 234 may be orthogonal to a first data coil 266, so that it does not induce a signal in the first data coil 266. A second data coil 268 may be wrapped as shown in Figure 14 such that magnetic flux from the power transmitters does not pass through it, but magnetic flux from first data coil 266 does. Notably, the configuration depicted in Figure 14 is offered for illustrative purposes only and is not meant to suggest that it is the only configuration that may reduce or eliminate the possibility that a signal will be induced in one or more of the data coils by the magnetic flux of the power transmitting coils. Other data coil configurations that may minimize the magnetic flux from the power transmitter exciting the data coils will occur to those with ordinary skill in the art.

[0064] Moreover, it is envisioned that the data coils 266, 268 may be wound on a non-magnetic dielectric material in some embodiments. Using a magnetic core for the data coils 266, 268 might result in the data coils' cores being saturated by the strong magnetic fields used for power transmission. Also, the data coils 266, 268 may be configured to operate at a substantially different frequency than the power transmission frequency. For example, if the power is transmitted at about 100.0 kHz in a certain embodiment, then the data may be transmitted at a frequency of about 1.0 MHz or higher. In such an embodiment, high pass filters on the data coils 266, 268 may prevent the about 100.0 kHz signal from corrupting the data signal. In still other embodiments, the data coils 266, 268 may simply be located away from the power coils 232, 234 to minimize any interference from the power transmission. It is further envisioned that some embodiments may use any combination of these methods to mitigate or eliminate adverse effects on the data coils 266, 268 from the power transmission of the power coils 232, 234. [0065] Figures 15A1-16C2 are diagrams of tools 305, 310 in a bottom hole assembly 100 of a drill string 12 that are coupled via embodiments of a wireless drilling and mining ("D&M") extender 301. Advantageously, a wireless D&M extender 301 provides for replacement of a physical pin connection of the conventional art with a stationary tuned- inductive coupler mechanism configured to pass power and data communication transmissions from tool to tool. As is understood by one of ordinary skill in the art of inductive coupling or magnetic coupling, a change in current flow through one coil may induce a voltage across an adjacent coil through electromagnetic induction.

[0066] The amount of inductive coupling between two conductors is measured by their mutual inductance. Inductive coupling may be leveraged in this manner between two wires, however one of ordinary skill in the art will recognize that the coupling between two wires can be increased by winding them into coils and placing them close together on a common axis, so the magnetic field of one coil passes through an and in and me the other coil.

[0067] It is envisioned that embodiments of a wireless D&M extender may include separate stationary coils or wires for power and data communications transmission. Power exchanged between the stationary coils would have a frequency in hundreds of kiloHertz (kHz) while data transmissions between the stationary coils would likely occur in the megahertz (MHz) range as understood by one of ordinary skill in the art.

[0068] As described above, smaller stationary coils, such as coils 266, 268 of Figure 14 would be used in conjunction with larger coils 232, 234. The smaller stationary coils 266, 268 may transmit data communications while the stationary larger coils 232, 234 would transmit power signals. As understood by one of ordinary skill the art, the larger coils 232, 234 and the smaller coils 266, 268 may share a common ferrite core 235 such that one ferrite core 235 has two sets of coils: one coil having a higher number of windings for power transfer while a second coil has a lower number of windings for data transfer.

[0069] Returning to Figures 15A1-15C2, Figure 15A1 depicts a stationary/fixed "mandrel to mandrel" embodiment of a wireless D&M extender 301 A for stationary tools that do not move, translate, or rotate relative to each other. In the Figure 15A1 embodiment, tool 310A includes a mandrel type coil 311A that is communicatively coupled to a mandrel type coil 306A of tool 305A via a tuned-inductive coupler arrangement. As explained above, power and/or data communications may be transmitted between tools 305A, 310A via inductive coupling between coils 306A, 31 1A for tool 305, 310 that are generally fixed or do not move relative to each other. [0070] Advantageously, although stationary coils 306A, 31 1A may be juxtaposed such that a change in current flow in one coil induces a voltage in the other, the coils 306A, 31 1A are not required to be mechanically coupled or rigidly aligned when the tools 305, 31 1 are connected together. That is, it is envisioned that in a wireless D&M extender, a gap (not easily seen in Figure 15A1 but see Figure 15A2) may exist between coils 306A and 311A even though the tools 305, 310 may have a fixed coupling 323 (see Figure 15A2), such as screw threads, rivets, or welds for engaging each other. As such, mechanical wear, misalignment, and/or vibration in the physical connections between various tools 305 A, 310A of a given BHA may not adversely affect or otherwise cause the failure of the communications bus.

[0071] Figure 15A2 depicts an enlarged view of the stationary "mandrel to mandrel" embodiment of a wireless D&M extender 301 A. The fixed coupling 323 between the two tools 310A and 305A, in which the first tool 310A may include a drill collar pin connection while the second tool 305A may include a drill collar box connection, is illustrated in further detail. The coupling 323 between tools 305, 310 may include screw threads and/or other secure mechanical fasteners, like bolts, screws, rivets, welds, and other similar fasteners as understood by one of ordinary skill the art. The coupling 323 is designed to provide a rigid and non-moving connection between the tools 305, 310.

[0072] Meanwhile, the stationary coils 311 A, 306A may be coupled to respective and extenders 1605. The extenders 1605 may be coupled to respective pressure housings (not illustrated) which enclose or shield electronics that generate at least one of communication signals and power signals. The extender 1605 may be made from a metal that is non-magnetic, such as stainless steel. A gap distance g may exist between the two coils 31 1C, 306C. The gap distance g is usually not greater than twice the diameter T of a respective ferrite core 235.

[0073] In the Figure 15B embodiment, tool 310B includes an annular type coil 31 IB that is communicatively coupled to a mandrel type coil 306B of tool 305B via a tuned- inductive coupler arrangement. As explained above, power and/or data communications may be transmitted between tools 305B, 310B via inductive coupling between coils 306B, 31 IB. Advantageously, although coils 306B, 31 IB are positioned juxtaposed such that a change in current flow in one coil induces a voltage in the other, the coils 306B, 31 IB are not required to be mechanically coupled or rigidly aligned. [0074] That is, it is envisioned that in a wireless D&M extender, a gap 315 may exist between coils 306B and 31 IB. As such, mechanical wear, misalignment, and/or vibration in the physical connections between various tools 305B, 310B of a given BHA may not adversely affect or otherwise cause the failure of the communications bus. The stationary annular type coil 31 IB is described in more detail above in connection with Figures 5A-5B.

[0075] In the Figure 15C1 embodiment, tool 3 IOC includes a stationary annular type coil 31 1C that is communicatively coupled to a stationary annular type coil 306C of tool 305C via a tuned- inductive coupler arrangement. As explained above, power and/or data communications may be transmitted between tools 305C, 3 IOC via inductive coupling between coils 306C, 31 1C. Advantageously, although coils 306C, 311C are juxtaposed such that a change in current flow in one coil induces a voltage in the other, the coils 306C, 31 1C are not required to be mechanically coupled or rigidly aligned.

[0076] That is, it is envisioned that in a wireless D&M extender, a gap (not easily seen in Figure 15C1 but see Figure 15C2) may exist between coils 306C and 311C. As such, mechanical wear, misalignment, and/or vibration in the physical connections between various tools 305C, 3 IOC of a given BHA may not adversely affect or otherwise cause the failure of the communications bus.

[0077] Figure 15C2 provides an enlarged view of the stationary annular type coil 31 1C that is communicatively coupled to a stationary annular type coil 306C of tool 305C in Figure 15C1. The ferrite cores 235 of this arrangement may have a hollow cylindrical shape. As noted previously, a gap distance g may exist between the two coils 31 1C, 306C. The gap distance g is usually not greater than twice the thickness T of a respective ferrite core 235.

[0078] Figure 16A illustrates a wireless power distribution scheme 402 between two stationary tools such as a MWD 130 and a LWD 120 that leverages alternating current ("AC") to transmit power in a BHA 100. In the Figure 16A illustration, MWD tool 130 is the power source for LWD tool 120. The power is generated in MWD tool 130 via a turbine 425, although other power sources such as, but not limited to, batteries are envisioned. The power generated by turbine 425 is supplied through AC/DC module 420 and switching amp 415 to source resonators 410 and 430. The source resonators 410, 430 may be leveraged to wirelessly transmit power and/or data communications to a receiving device resonator in a juxtaposed tool, such as device resonator 440 in LWD tool 120. The transmissions are then used within LWD tool 120 and relayed to subsequent tools in the given BHA via source resonator 450.

[0079] Figure 16B illustrates a wireless power distribution scheme 402 between two stationary tools like a MWD 130 and LWD 120 that leverages alternating current ("AC") and direct current ("DC") to transmit power in a BHA 100. The wireless power distribution scheme 402 largely mirrors that of scheme 402 in Figure 16A with the exception that the AC transmission is converted within LWD tool 120 to DC and then back to AC for subsequent transmission to other tools via source resonator 450.

[0080] Although a few embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents, but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface, in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. It is the express intention of the applicant not to invoke 35 U.S.C. § 112, sixth paragraph for any limitations of any of the claims herein, except for those in which the claim expressly uses the words 'means for' together with an associated function.

Claims

CLAIMS What is claimed is:

1. A drilling and mining ("D&M") extender device for communicatively coupling two stationary tools in a bottom hole assembly of a drill string, the extender device comprising:

a first stationary coil associated with a first tool; and

a second stationary coil associated with a second tool;

wherein electrical transmissions between the first and second tools are transmitted wirelessly between the first and second stationary coils via inductive coupling between the coils; the first stationary coil positioned proximate to the second stationary coil; the coils are inductively coupled such that: k = M I -^L^ I^ < 0.9 , wherein k is the coupling coefficient of the coils, M is the mutual inductance between the coils, and Li and L₂ are the self-inductances of the respective coils; each coil is resonantly tuned with a capacitor such that: f_x∞f₂ , wherein Jj = } and f₂ = } and fi and f₂ are the frequencies in Hertz of the respective coils, Li and

L₂ are the self-inductances of the respective coils, and Ci and C₂ are capacitances of tuning capacitors associated with the respective coils; and the coils have an associated

, 2π ∑, figure of merit, U, such that: U = Ic Q₁Q₂≥ 3 , wherein Q₁ = and

2;z^"J2J2

Q₂ = and Ql and Q2 are the quality factors associated with the respective coils, i and f₂ are the frequencies in Hertz of the respective coils, Li and L₂ are the self- inductances of the respective coils, and Ri and R₂ are the resistances of the respective coils.

2. The drilling and mining extender device of claim 1, wherein the first tool has an impedance as a source, Rs wherein the impedance is governed by the equation:

wherein R j is the series resistance of the first coil, k is the coupling coefficient of the pair of coils, Qi is the quality factor associated with the first coil and (¾ is the quality factor associated with the second coil.

3. The drilling and mining extender device of claim 2, further comprising approximately matching an impedance of the second tool with an impedance of the source by setting:

wherein R₂ is the series resistance of the second coil, k is the coupling coefficient of the pair of coils, Qi is the quality factor associated with primary coil and Q2 is the quality factor associated with the second coil.

4. The drilling and mining extender device of claim 1, wherein one or more of the electrical transmissions are selected from the group of power transmissions and data communication transmissions.

5. The drilling and mining extender device of claim 1, wherein the first coil is of a mandrel type and the second coil is of a annular type.

6. The drilling and mining extender device of claim 1, wherein the first coil is of a mandrel type and the second coil is of a mandrel type.

7. The drilling and mining extender device of claim 1, wherein the first coil is of an annular type and the second coil is of an annular type.

8. The drilling and mining extender device of claim 1, wherein the first tool and second tool mate together using a fixed and non-movable coupling.

9. The drilling and mining extender device of claim 8, wherein the fixed and non- movable coupling comprises a mechanical fastener.

10. The drilling and mining extender device of claim 9, wherein the fixed and movable coupling comprises at least one of screw threads, rivets, and welds.

1 1. A drilling and mining ("D&M") extender device for communicatively coupling two stationary tools in a bottom hole assembly of a drill string, the extender device comprising:

a first stationary coil associated with a first tool; and

a second stationary coil associated with a second tool;

wherein electrical transmissions between the first and second tools are transmitted wirelessly between the first and second stationary coils via inductive coupling between the coils; the first stationary coil positioned proximate to the second stationary coil, the first tool and second tool mate together using a fixed and non- movable coupling.

12. The drilling and mining extender device of claim 11, wherein the fixed and movable coupling comprises at least one of screw threads, rivets, and welds.

13. The drilling and mining extender device of claim 1 1, wherein the coils are inductively coupled such that: k = M I ^L^ I^≤ 0.9 , wherein k is the coupling coefficient of the coils, M is the mutual inductance between the coils, and L j and L2 are the self-inductances of the respective coils; each coil is resonantly tuned with a capacitor such that: _x ~ ₂ , wherein f_x = and fi and /

are the frequencies in Hertz of the respective coils, Li and L2 are the self-inductances of the respective coils, and Ci and C2 are capacitances of tuning capacitors associated with the respective coils; and the coils have an associated figure of merit, U, such that:

U = k and Ql and Q2 are the

quality factors associated with the respective coils,/; and / are the frequencies in Hertz of the respective coils, Li and L₂ are the self- inductances of the respective coils, and Ri and R2 are the resistances of the respective coils.

14. The drilling and mining extender device of claim 1 1, wherein one or more of the electrical transmissions are selected from the group of power transmissions and data communication transmissions.

15. The drilling and mining extender device of claim 11 , wherein the first coil is of a mandrel type and the second coil is of a annular type.

16. The drilling and mining extender device of claim 11 , wherein the first coil is of a mandrel type and the second coil is of a mandrel type.

17. The drilling and mining extender device of claim 11, wherein the first coil is of an annular type and the second coil is of an annular type.

18. A wireless coupling for drilling comprising:

a first stationary coil attached to a first drilling structure; and

a second stationary coil attached to a second drilling structure;

wherein electrical transmissions between the first and second coils are transmitted wirelessly via inductive coupling between the coils; the first stationary coil positioned proximate to the second stationary coil, the first drilling structure and second drilling structure being held in position with a fixed and non-movable fastening mechanism.

19. The wireless coupling of claim 18, wherein the fixed and non-movable fastening mechanism comprises at least one of screw threads, rivets, and welds.

20. The wireless coupling of claim 19, wherein the coils are inductively coupled such that: k = M I -^ ^ I^ < 0.9 , wherein k is the coupling coefficient of the coils, M is the mutual inductance between the coils, and Lj and L₂ are the self- inductances of the respective coils; each coil is resonantly tuned with a capacitor such that: f_x∞ f₂ , wherein f_x = and fi and f₂ are the frequencies in Hertz of

the respective coils, Li and L₂ are the self- inductances of the respective coils, and Ci and C₂ are capacitances of tuning capacitors associated with the respective coils; and the coils have an associated figure of merit, U, such that: U = k^Q_lQ₁ > 3 , wherein

2π ∑, 2π ₂∑2

Q_l = and Q₂ = and Q l and Q2 are the quality factors associated with

^Ri ^R2

the respective coils, /; and / are the frequencies in Hertz of the respective coils, Lj and L₂ are the self-inductances of the respective coils, and Ri and ¾ are the resistances of the respective coils.