The present disclosure generally relates to downhole communications and, more particularly, to a system and method using Stoneley waves for downhole telemetry.
Illustrative embodiments and related methods of the present disclosure are described below as they might be employed in a well system and method for Stoneley wave based pipe telemetry. In the interest of clarity, not all features of an actual implementation or method are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. Further aspects and advantages of the various embodiments and related methodologies of the disclosure will become apparent from consideration of the following description and drawings.
As described herein, the present disclosure is directed to systems and methods for conducting downhole telemetry operations using Stoneley wave carrier signals. In a generalized embodiment, a plurality of Stoneley wave telemetry devices are positioned along a tubular string. The Stoneley wave telemetry devices may be implemented as a transmitter, receiver, or repeater. Each Stoneley wave telemetry device includes a plurality of transducers used to transmit and/or receive the Stoneley waves. During a telemetry operation, the Stoneley wave transducers perform an uplink or downlink communication of Stoneley waves between one another.
In this illustrative embodiment, Stoneley wave telemetry device 12 is implemented in short pipe joints (e.g., drill collars) inserted at various intervals between the tubular/pipe joints. Each Stoneley wave telemetry device 12 may act as a transmitter, receiver, or transceiver to achieve uplink or downlink communications. However, for the following description, telemetry device will be described as a transmitter or receiver (not a transceiver). When acting as a transceiver, telemetry device 12 is referred to herein as a “repeater.” Stoneley wave telemetry devices 12 are axially separated from one another. In certain embodiments, the distance between the Stoneley wave telemetry devices may be a distance of 10-40 meters, thus qualifying the system as a short hop telemetry system.
Each Stoneley wave telemetry device 12 includes a tubular housing 14, and transducers 16a-d acting as Stoneley wave transmitters or receivers spatially separated from each other radially in symmetrical pairs orthogonal to the axis of repeater 12, thus forming a transmitter-receiver pair. Stoneley wave telemetry device 12 may also include elements to attenuate, reflect or direct the Stoneley waves. As will be described in more detail below, the Stoneley wave transmitter/receiver pairs can also be repeater pairs that are spatially separated along the axis of the tubular 10, so as to extend the distance over which signals can be telemetered and/or to provide bimodal communication capability. Stoneley telemetry device (s) 12 transmit(s) and receive(s) the Stoneley waves making up the carrier of the signal. Stoneley telemetry device 12 may be powered by on-board batteries or via some remote power source (not shown).
In certain illustrative embodiments, Stoneley telemetry device 12 is made of a plurality of transducers 16a-d, which may be azimuthally distributed piezo-electric or magnetostrictive (consisting of a material such as terfenol) elements mounted on inner wall 4 of tubular housing 14. In other words, transducers 16a-d are radially separated from one another in symmetrical pairs orthogonal to the axis of telemetry device 12. Although four transducers are shown, more or less transducers may be utilized in any of the embodiments described herein. During operation of certain embodiments, transducer elements 16a-d are fired in a synchronized fashion (to transmit) or receive the Stoneley signals in a synchronized fashion.
After firing, the Stoneley wave(s) travel inside tubular 10 to the next Stoneley wave telemetry device 12 where it is detected and re-launched. One advantage of the Stoneley telemetry device 12 is that any lateral noise 18 will be automatically cancelled by subtracting signals from opposing transducers 16a-d, which is why they are positioned in opposite orientation with respect to one another, as previously described. One advantage of using Stoneley waves, as compared to other sonic modes, is that Stoneley waves typically have the least attenuation of the acoustic modes, especially in steel pipe. Another advantage is that Stoneley waves can readily be generated that have amplitudes that are higher than the amplitudes of other acoustic modes.
Referring now to
Still referring to
A suitable arrangement for transmitting Stoneley waves is shown in
Adaptable to standard suites of tubulars/pipe, the illustrate embodiments described herein require less dedicated capital investment and less logistics than wired pipes. The illustrative telemetry systems rely on Stoneley waves which are stronger and carry further than compressional or shear waves in the same range of frequencies. As shown in
A modeling study was conducted to determine how Stoneley waves inside a mandrel attenuate with mud properties. In the study, the attenuation and dispersion of low frequency (between 5 Hz to 100 Hz) Stoneley waves propagating in a borehole with viscous fluid (drilling mud) and a steel mandrel were analyzed.
During the study, a coefficient matrix M (12×12) was generated with boundary conditions at three different boundaries. The boundaries were between the inner fluid 24 and inner surface of steel mandrel 20 (1); between the outer surface of steel mandrel 20 and outer fluid 24 (2); and between outer fluid 24 and the formation (3), as shown in
After the coefficient matrix is generated, the axial wavenumber was calculated. The fluid sound velocity and density were 1500 m/s and 1000 kg/m̂3, respectively. The compressional (p), shear velocity (s) and density of steel mandrel were 5600 m/s, 3000 m/s and 7800 kg/m̂3. The compressional (p), shear velocity (s) and density of formation were 3670 m/s, 2170 m/s and 2400 kg/m̂3. The inner and outer diameters of steel mandrel 20 were 4.276 and 7 inch, respectively. The radius of borehole 22 was 9 inches. The dynamic viscosity of the drilling fluid was then calculated.
ki[ω]=kr[ω]/(2*Q[ω]), Eq. (1),
Alternatively, the imaginary part of the wave number is related to the velocity by:
ki[ω]=ω/(2*Q[ω]*v[ω]), Eq. (2).
In Equations 1-2, ω is the frequency (radian frequency), kr is the real part of the wave number, ki is the imaginary part of the wave number, v is velocity, [ω] is used to indicate that a variable is a function of ω. The attenuation provides an indication of how far a signal can be propagated. The Q is defined as:
Q[ω]=−(1/π)(ΔA[ω]/A[ω]), Eq. (3)
where A[ω] is the amplitude of the wave at frequency ω, and AA[ω] is the change in amplitude as the wave propagates one cycle. Once kr and ki are known, wave propagation characteristics with various types of reflectors may be calculated, as will be needed to model propagation in a drillstring since there is a change in diameter at every tool joint. In general, one would need to know kr and ki not only as a function of frequency, but as a function of the inner diameter of the pipe, the outer diameter of the pipe, the diameter of the borehole, the speed of sound in the pipe and the speed of sound in the drilling mud. However, there is little variation in the propagation properties for a system with any range of inner and outer pipe diameters and borehole sizes realizable in the drilling environment as long as the pipe is uniform.
The studies reported above were useful for obtaining a preliminary understanding of the capabilities of a Stoneley wave telemetry system, in accordance to the illustrative embodiments of the present disclosure. A deeper understanding was obtained when a similar analysis was carried out to a frequency of 20 KHz, and detailed calculations were made of transmission and reflection when pipe joints or other disturbances in the cross-section of the pipe were included.
The plots of
Wave properties from
where Tf1 is the transmission coefficient from a pipe having an internal area of a1 to a pipe having an internal area of a2; Tf2 is the transmission coefficient from a pipe having an internal area of a2 to a pipe having an internal area of a1; Rf1 is the reflection coefficient for a wave traveling in a pipe of internal area a1 being reflected off of a pipe having an internal area of a2; and Rf2 is the reflection coefficient for a wave traveling in a pipe of internal area a2 being reflected off of a pipe having an internal area of a1. The term f in Tf1, Tf2, Rf1 and Rf2 refers to “forward” traveling waves, that is waves traveling in a specified direction. Similar relations can be written for waves traveling in the opposite direction. “b” will be used for these terms.
When these results are combined, and propagation is taken into account, the effect of multiple reflections when propagating across a tool joint (i.e. a connection between one span of pipe and another) can be calculated, and it can be shown that for sequential nodes i and i+1, the composite properties are given by:
with j=√{square root over (−1)},
and it is assumed that z is the drift coordinate along the system, and that diameter changes occur at locations zi and zi+1. It was also assumed that the pipe is sufficiently thick that the outer diameter of the pipe has little effect on the propagation of Stoneley waves, which is a good approximation for any embodiment of a Stoneley wave telemetry system in a drillstring.
These relations make it possible to compare the effects of reflections at pipe joints with those simply due to propagation. Since Stoneley waves propagating along a borehole are promptly attenuated by a crack in the borehole, it might be supposed that Stoneley waves propagating within a drill pipe would be severely attenuated at pipe joints due to the change in internal diameter at pipe joints. This turns out not to be the case. Referring to
In this case, a Stoneley wave would be attenuated by a factor of between about 0.3 and 0.5 with the overall attenuation increasing noticeably with the length of the pipe joint. Further study reveals that the increase in overall attenuation has little to do with the fact that there is a pipe joint and instead is due to the overall increase of the system as the pipe joint length is increased. This is even evident at 1 KHz, as shown in
Therefore, in certain illustrative embodiments of the present disclosure, a short hop telemetry system may be used, for example, to telemeter information from a point within or above a drill bit past a mud motor or rotary steerable device to a module above the mud motor or rotary steerable device. It may also be used to pass information gathered within a mud motor or rotary steerable device to a module above the mud motor or rotary steerable device. The type of information that may be telemetered pertains to, for example, the condition of the mud motor or rotary steerable device, the condition of the drill bit, drilling vibration, torque, weight on bit, bending, mud properties or formation properties.
Elements of one illustrative embodiment of a tubular used in a short hop telemetry system according to the present disclosure are shown in
As was noted above, a Stoneley wave telemetry system cannot be operated over long distances without making use of repeaters. An inherent property of most, if not all other telemetry systems making use of a large number of repeaters is high latency, that is a large delay in the transmission of data, even if a suitable data rate is obtained for continuous transmission. This is due to the need at each repeater to receive packets of information and retransmit them from a location near the receiver. Even if retransmission is somehow effected in real time in a different frequency band from the band of the received signal, it is very difficult to obtain suitable isolation between the transmitter and receiver to allow simultaneous operation of both.
In certain illustrative embodiments of the present disclosure, one solution is to receive a packet of information, decode it and then retransmit it. This has the advantage of removing noise that was introduced into the received signal, but it is achieved at the cost of system latency. Although this might be tolerable in certain applications, others may require more speed. Therefore, alternate embodiments of the present disclosure are described below.
Stoneley waves have a property that can be exploited in order to work around the system latency problem. As will be understood by those ordinarily skilled in the art having the benefit of this disclosure, Stoneley waves are absorbed by porous media. This effect is typically observed in acoustic logging, as discussed in “Stoneley-wave attenuation and dispersion in permeable formations,” Andrew N. Norris, Geophysics, Vol. 54, No. 3 (March 1989): P. 330-341. Thus, in certain embodiments described herein, this same effect is exploited to isolate the transmitter and receiver in a Stoneley wave telemetry repeater. An embodiment of such a repeater is illustrated in
Repeater 1300 includes a tubular housing 1302 having a first and second end. In certain embodiments, repeater 1302 may be housed in a section of drill collar. Transducers 1304a-d are mounted on both ends of repeater 1300 along its inner wall 1306. Transducers 1304a-d may be arranged for synchronous operation, as described earlier. For bi-directional capability, transducers 1304a-d can be transceivers, such as piezoelectric or magnetostrictive devices, or separate elements may be dedicated to up-link and down-link operation. Transducers 1304a-d are communicably coupled to one another using, for example, wiring 1310. As will be described in greater detail below, electronics and power module 1312 is also coupled along wiring 1310 in order to provide various functions, such as, for example, amplification, filtering, and/or processing of Stoneley wave signals.
In certain illustrative embodiments of the present disclosure, inner wall 1306 is lined with a Stoneley wave absorber 1308, such as, for example, a compliant and porous material. The porous and compliant properties of Stoneley wave absorber 1308 makes it possible to receive a Stoneley wave telemetry signal, boost its amplitude and perform simple filtering or processing in real time, and retransmit the signal in the same direction without saturating the receiver. Stoneley wave absorber 1308 is positioned between transducers 1304a,b at the first end and transducers 1304c,d at the second end of tubular 1302. Stoneley wave absorber 1308 may be bonded to inner wall 1306 of tubular 1302 or hung from a sleeve within tubular 1302.
In certain embodiments, the porous material is also permeable, that is the porosity is connected. It may consist of a substance such as Viton, carboxylated nitrile, neoprene, or a large number of other rubbers including silicon rubbers. It should be fabricated such that it is porous, such that the porosity is connected throughout most of the material, and with pores of sufficient size that packing off by lost circulation material or mud particulates is minimal. An illustrative mean diameter of porous inclusions would be in the range of about 0.1 mm to about 0.5 mm. A porous material can be fabricated by starting with a distribution of spheres, ellipsoids or similarly shaped objects made of the rubber and fusing them. The very low Young's modulus of the rubber in comparison to the Young's modulus of the drill collar material, coupled with the porosity should make it a good absorber of Stoneley waves. For example, the Young's modulus of Viton is about 4.6 M Pa, while that of typical drill collar material is on the order of 300,000 m Pa (e.g. 6140 steel).
In
In
As shown, logging tools 1746 may be integrated into a bottom-hole assembly near drill bit 1740. As drill bit 1740 extends the borehole 1736 through formation 1748, logging tools 1746 may collect measurements relating to various formation properties, as well as the tool orientation and various other drilling conditions. Each of logging tools 1746 may take the form of a drill collar, i.e., a thick-walled tubular that provides weight and rigidity to aid the drilling process.
Moreover, as described herein, a plurality of Stoneley wave telemetry devices 1738a-e may positioned along drill string 1732 in order to conduct downhole telemetry operations. In the illustrated embodiment, telemetry devices 1738a-e are repeaters. Stoneley wave repeaters 1738a-e may be housed in drill collars that join sections of drill string 1732 together. During telemetry operations, logging or other measurements may be transferred in an uplink or downlink direction using Stoneley wave repeaters 1738a-e, as previously described herein. As an example, the Stoneley wave-based techniques described herein may communicate logging measurements to a surface receiver 1730 and/or receive commands from the surface. Moreover, in other embodiments, telemetry devices 1738a-e may be a transmitter or receiver only, thereby allowing uni-directional communication between transmitter-receiver pairs.
Embodiments described herein further relate to any one or more of the following paragraphs:
1. A well system for downhole telemetry, the well system comprising a tubular string adapted to be positioned along a borehole extending within a formation; and a plurality of Stoneley wave telemetry devices positioned along the tubular string to communicate Stoneley waves between each other.
2. A well system as defined in paragraph 1, wherein the Stoneley wave telemetry devices are positioned within drill collars along the tubular string.
3. A well system as defined in any of paragraphs 1 or 2, wherein the Stoneley wave telemetry devices are receivers, transmitters or repeaters.
4. A well system as defined in any of paragraphs 1-3, wherein the Stoneley wave repeaters each comprise: a tubular housing; at least one transducer at a first end of the tubular housing; and at least one transducer at a second end of the tubular housing opposite the first end.
5. A well system as defined in any of paragraphs 1-4, wherein the transducers at the first and second end of the tubular housing each comprise two radially opposed transducers.
6. A well system as defined in any of paragraphs 1-5, wherein the two transducers are synchronized.
7. A well system as defined in any of paragraphs 1-6, wherein the transducers are piezo-electric or magnetostrictive elements.
8. A well system as defined in any of paragraphs 1-7, wherein the Stoneley wave telemetry devices are repeaters; and the well system is a short hop telemetry system.
9. A well system as defined in any of paragraphs 1-8, wherein the Stoneley wave repeaters are separated from each other by a distance 10-40 meters.
10. A well system as defined in any of paragraphs 1-9, further comprising a Stoneley wave absorber positioned between the at least one transducer at the first end and the at least one transducer at the second end of the tubular housing.
11. A well system as defined in any of paragraphs 1-10, wherein the Stoneley wave absorber is bonded to an inner wall of the tubular housing.
12. A well system as defined in any of paragraphs 1-11, wherein the Stoneley wave absorber is sleeve positioned along an inner wall of the tubular housing.
13. A well system as defined in any of paragraphs 1-12, wherein the Stoneley wave absorber comprises a porous material.
14. A well system as defined in any of paragraphs 1-13, further comprising a signal conditioner communicably coupled between the at least one transducer at the first end and the at least one transducer at the second end of the tubular housing, wherein the signal conditioner is configured to perform at least one of an amplification, filtering or processing of Stoneley wave signals.
15. A well system as defined in any of paragraphs 1-14, wherein the well system is a full duplex telemetry system.
16. A well system as defined in any of paragraphs 1-15, wherein the well system is a half duplex telemetry system; and the well system further comprises a control module communicably coupled between the at least one transducer at the first end and the at least one transducer at the second end of the tubular housing, to thereby switch the Stoneley wave repeaters between an uplink and downlink mode.
17. A method for downhole telemetry, the method comprising using a first telemetry device to transmit Stoneley waves along a tubular string extending inside a borehole positioned in a formation; and receiving the Stoneley waves at a second telemetry device positioned along the tubular string, thereby conducting a telemetry operation using the first and second telemetry devices.
18. A method as defined in paragraph 17, wherein the telemetry devices are transmitters, receivers, or repeaters.
19. A method as defined in paragraphs 17 or 18, wherein the first and second repeaters each comprise a plurality of transducers; and the method further comprising synchronously transmitting or receiving the Stoneley waves using the transducers.
20. A method as defined in any of paragraphs 17-19, wherein receiving the Stoneley waves further comprises cancelling noise from the received Stoneley waves.
21. A method as defined in any of paragraphs 17-20, wherein cancelling the noise comprises subtracting signals from radially opposing transducers which form part of the second telemetry device.
22. A method as defined in any of paragraphs 17-21, wherein receiving the Stoneley waves further comprises amplifying the received Stoneley waves.
23. A method for downhole telemetry, comprising using Stoneley waves as carrier signals for a downhole telemetry operation.
24. A method as defined in paragraph 23, further comprising performing a short hop telemetry operation using the Stoneley carrier signals.
25. A method as defined in paragraphs 23 or 24, wherein a full duplex telemetry operation is conducted.
26. A method as defined in any of paragraphs 23-25, wherein a half duplex telemetry operation is conducted.
Although various embodiments and methodologies have been shown and described, the disclosure is not limited to such embodiments and methodologies and will be understood to include all modifications and variations as would be apparent to one skilled in the art. Therefore, it should be understood that embodiments of the disclosure are not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.
Filing Document | Filing Date | Country | Kind |
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PCT/US2015/015200 | 2/10/2015 | WO | 00 |