Telemetry system for wireless electro-acoustical transmission of data along a wellbore

Abstract

A system for downhole telemetry is provided herein. The system employs a series of communications nodes spaced along a tubular body either above or below ground, such as in a wellbore. The nodes allow for wireless communication between one or more sensors residing at the level of a subsurface formation or along a pipeline, and a receiver at the surface. The communications nodes employ electro-acoustic transducers that provide for node-to-node communication along the tubular body at high data transmission rates. A method of transmitting data in a wellbore is also provided herein. The method uses a plurality of data transmission nodes situated along a tubular body to accomplish a wireless transmission of data along the wellbore using acoustic energy.

Claims

1. An electro-acoustic system for wireless telemetry along a tubular body, comprising: a tubular body fabricated from steel; at least one sensor disposed along the tubular body; a sensor communications node placed along the tubular body and connected to a wall of the tubular body, the sensor communications node being in electrical communication with the at least one sensor and configured to receive signals from the at least one sensor, the signals representing a parameter associated with a subsurface location along the tubular body; a topside communications node placed proximate a surface; a plurality of intermediate communications nodes spaced along the tubular body and attached to an outer wall of the tubular body, the intermediate communications nodes configured to transmit acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement; and a receiver at the surface configured to receive signals from the topside communications node; wherein each of the intermediate communications nodes comprises: a sealed housing; an independent power source residing within the housing; an electro-acoustic transducer and associated transceiver also residing within the housing designed to receive and re-transmit the acoustic waves, thereby providing communications telemetry; wherein each of the acoustic waves represents a packet of information comprising a plurality of separate tones; and wherein at least one of (i) the sensor communications node and (ii) at least one of the plurality of intermediate communications node, is configured to: (a) transmit a first acoustic tone at a selected frequency at a frequency in a range of from 50-500 kHz for a first transmission time, (b) receive the transmitted acoustic tone for a first reverberation listening time that is greater than the first transmission time, (c) transmit another acoustic tone at another selected frequency at a frequency in a range of from 50-500 kHz for at least one of the first transmission time and another transmission time, (d) receive the another transmitted acoustic tone for at least one of the first reverberation listening time and another reverberation listening time, greater than the another transmission time, (e) determine a dominant received frequency based on the received acoustic tone for the first reverberation listening time and the received another acoustic tone for at least one of the first reverberation listening time and the another reverberation listening time, and (f) transmit subsequent acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement using the dominant frequency, wherein each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node.

2. The electro-acoustic system of claim 1, wherein: the surface is an earth surface; and the tubular body is a pipe residing below ground.

3. The electro-acoustic system of claim 1, wherein: the surface is a water surface; and the tubular body is a pipe residing below the water surface.

4. The electro-acoustic system of claim 1, wherein: the tubular body is comprised of pipe joints disposed in a wellbore, with the wellbore penetrating into a subsurface formation; and the at least one sensor and the sensor communications node are disposed along the wellbore proximate a depth of the subsurface formation.

5. The electro-acoustic system of claim 4, wherein the parameter comprises temperature, pressure, fluid flow, strain, or geological information related to a rock matrix of the subsurface formation.

6. The electro-acoustic system of claim 4, wherein the at least one sensor comprises (i) a pressure sensor, (ii) a temperature sensor, (iii) an induction log, (iv) a gamma ray log, (v) a formation density sensor, (vi) a sonic velocity sensor, (vii) a vibration sensor, (viii) a resistivity sensor, (ix) a flow meter, (x) a microphone, (xi) a geophone, or (xii) a set of position sensors.

7. The electro-acoustic system of claim 4, wherein: the tubular body is a drill string; and each of the intermediate communications nodes is removably attached to an outer surface of pipe joints making up the drill string.

8. The electro-acoustic system of claim 4, wherein: the tubular body is a casing string; at least some of the intermediate communications nodes are surrounded by a cement sheath; and each of the intermediate communications nodes is attached to an outer surface of pipe joints making up the casing string.

9. The electro-acoustic system of claim 4, wherein: the tubular body is a production tubing; and each of the intermediate communications nodes is attached to an outer surface of pipe joints making up the production tubing.

10. The electro-acoustic system of claim 9, wherein: a well head is placed above the wellbore; and the topside communications node is clamped (i) on an outer surface of the wellhead, or (ii) on the outer surface of an uppermost joint of the production tubing.

11. The electro-acoustic system of claim 10, wherein: the surface is a land surface or an offshore platform; and the signal from the topside communications node to the receiver is transmitted via a Class I, Division 1 conduit or is a wireless transmission.

12. The electro-acoustic system of claim 1, wherein the at least one sensor: (i) resides in the housing of a sensor communications node, or (ii) resides external to the sensor communications node.

13. The electro-acoustic system of claim 1, wherein the at least one sensor: resides in the housing of a sensor communications node; and comprises an electro-acoustic transducer within the sensor communications node.

14. The electro-acoustic system of claim 1, wherein the acoustic waves provide data that is modulated by (i) a multiple frequency shift keying method, (ii) a frequency shift keying method, (iii) a multi-frequency signaling method, (iv) a phase shift keying method, (v) a pulse position modulation method, or (vi) an on-off keying method.

15. The electro-acoustic system of claim 1, wherein the intermediate communications nodes are spaced apart according to the length of the joints of pipe.

16. The electro-acoustic system of claim 1, wherein the intermediate communications nodes are spaced at about 10 to about 100 foot intervals.

17. The electro-acoustic system of claim 1, wherein the communications nodes transmit data representing the parameter at a rate exceeding about 50 bps.

18. The electro-acoustic system of claim 1, wherein a frequency band for the acoustic wave transmission is about 25 KHz wide.

19. The electro-acoustic system of claim 1, wherein the transceivers listen for tones that are selected to be within a frequency band where the signals are detectable at least two nodes away from a transmitting node.

20. The electro-acoustic system of claim 1, wherein: the acoustic waves provide data that is modulated by (i) a multiple frequency shift keying method where each tone is selected from an alphabet of at least 8 tones, representing four bits of information.

21. A method of transmitting data in a wellbore, comprising: providing a sensor along the wellbore at a depth of a subsurface formation; running joints of pipe into the wellbore, the joints of pipe being connected by threaded couplings; attaching a series of communications nodes to the joints of pipe according to a predesignated spacing, wherein adjacent communications nodes are configured to communicate by acoustic signals transmitted through the joints of pipe, wherein each of the communications nodes comprises: a sealed housing; an electro-acoustic transducer and associated transceiver residing within the housing configured to send and receive acoustic signals between nodes; and an independent power source also residing within the housing for providing power to the transceiver; providing a receiver at a surface; and sending signals from the sensor and to the receiver at the surface via the series of communications nodes, with the signals being indicative of a subsurface condition; and using at least one of (i) the sensor and (ii) at least one of the series of communications nodes to: (a) transmit a first acoustic tone at a selected frequency at a frequency in a range of from 50-500 kHz for a first transmission time, (b) receive the transmitted acoustic tone for a first reverberation listening time that is greater than the first transmission time, (c) transmit another acoustic tone at another selected frequency at a frequency in a range of from 50-500 kHz for at least one of the first transmission time and another transmission time, (d) receive the another transmitted acoustic tone for at least one of the first reverberation listening time and another reverberation listening time, greater than the another transmission time; (e) determine a dominant received frequency based on the received acoustic tone for the first reverberation listening time and the received another acoustic tone for at least one of the first reverberation listening time and the another reverberation listening time, and (f) transmit subsequent acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement using the dominant frequency, and (g) each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node, wherein each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node.

22. The method of claim 21, wherein the surface is an earth surface or a water surface.

23. The method of claim 21, wherein the joints of pipe form a string of drill pipe, a string of casing, or a string of production tubing.

24. The method of claim 21, wherein the sensor is (i) a pressure sensor, (ii) a temperature sensor, (iii) an induction log, (iv) a gamma ray log, (v) a formation density sensor, (vi) a sonic velocity sensor, (vii) a vibration sensor, (viii) a resistivity sensor, (ix) a flow meter, (x) a microphone, (xi) a geophone, or (xii) a set of position sensors.

25. The method of claim 21, wherein each of the communications nodes further comprises at least one clamp for radially attaching the intermediate communications node onto an outer surface of a joint of pipe.

26. The method of claim 25, wherein the at least one clamp comprises: a first arcuate section; a second arcuate section; a hinge for pivotally connecting the first and second arcuate sections; and a fastening mechanism for securing the first and second arcuate sections around an outer surface of the tubular body.

27. The method of claim 21, wherein: the electro-acoustic transceivers receive acoustic waves at a frequency, and re-transmit the acoustic waves at the same frequency; and the electro-acoustic transceivers listen for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous communications node.

28. The method of claim 21, wherein the sensor resides in the housing of a sensor communications node.

29. The method of claim 21, wherein: the joints of pipe form a casing string; at least some of the joints of pipe and the communications nodes are surrounded by a cement sheath.

30. A method of transmitting data in a wellbore, comprising: running a tubular body into the wellbore, the wellbore penetrating into a subsurface formation and the tubular body being comprised of pipe joints; placing at least one sensor along the wellbore at a depth of the subsurface formation; attaching a sensor communications node to a wall of the tubular body proximate the depth of the subsurface formation, the sensor communications node being in electrical communication with the at least one sensor and configured to receive signals from the at least one sensor, the signals representing a subsurface condition; providing a topside communications node proximate a surface of the wellbore; and attaching a plurality of intermediate communications nodes to a wall of the tubular body in spaced-apart relation, the intermediate communications nodes configured to transmit acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement; wherein each of the intermediate communications nodes comprises: a sealed housing; an independent power source residing within the housing; an electro-acoustic transducer and associated transceiver also residing within the housing designed to receive the acoustic waves and re-transmit them after reverberation of the acoustic waves has substantially attenuated, the acoustic waves correlating to the signals generated by the sensor; and at least one clamp for radially attaching the communications node onto an outer surface of the tubular body; and using at least one of (i) the sensor communications node and (ii) at least one of the plurality of communications nodes to: (a) transmit a first acoustic tone at a selected frequency at a frequency in a range of from 50-500 kHz for a first transmission time, (b) receive the transmitted acoustic tone for a first reverberation listening time that is greater than the first transmission time, (c) transmit another acoustic tone at another selected frequency at a frequency in a range of from 50-500 kHz for at least one of the first transmission time and another transmission time, (d) receive the another transmitted acoustic tone for at least one of the first reverberation listening time and a another reverberation listening time, greater than the another transmission time; (e) determine a dominant received frequency based on the received acoustic tone for the first reverberation listening time and the received another acoustic tone for at least one of the first reverberation listening time and the another reverberation listening time, (f) transmit subsequent acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement using the dominant frequency, and (g) each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node.

31. The method of claim 30, wherein the communications nodes transmit data representing the subsurface condition at a rate exceeding about 50 bps.

32. The method of claim 30, wherein the tubular body forms a string of drill pipe, a string of casing, a string of production tubing, or a string of injection tubing.

33. The method of claim 32, further comprising: receiving signals from the topside communications node at a receiver; and analyzing the signals.

34. The method of claim 32, wherein: the tubular body comprises a string of production tubing; a well head is placed above the wellbore; and the topside communications node is attached to (i) an outer surface of the well head, or (ii) the outer surface of an uppermost joint of the production tubing.

35. The method of claim 33, wherein: the surface is a land surface or an offshore platform; and the signal from the topside communications node to the receiver is transmitted via (i) a Class I, Division 1 conduit, or (ii) an electromagnetic (RF) wireless connection.

36. The method of claim 30, wherein the at least one sensor comprises (i) a pressure sensor, (ii) a temperature sensor, (iii) an induction log, (iv) a gamma ray log, (v) a formation density sensor, (vi) a sonic velocity sensor, (vii) a vibration sensor, (viii) a resistivity sensor, (ix) a flow meter, (x) a microphone, (xi) a geophone, or (xii) a set of position sensors.

37. The method of claim 30, wherein a frequency band for the acoustic wave transmission operates from 100 kHz to 125 kHz.

38. The method of claim 37, wherein the electro-acoustic transceiver for each of the intermediate communications nodes receives the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous communications node.

39. The method of claim 30, wherein the step of attaching a plurality of intermediate communications nodes to the tubular body comprises clamping the intermediate communications nodes to an outer surface of the tubular body.

40. A communications node system for downhole telemetry, comprising: a tubular body having a pin end, a box end, and an elongated wall between the pin end and the box end, with the tubular body being fabricated from a steel material having a resonance frequency; and a communications node comprising: a housing also fabricated from a steel material, with the steel material of the housing having a resonance frequency; a sealed bore within the housing; an independent power source residing within the bore; an electro-acoustic transducer and associated transceiver also residing within the bore for receiving and transmitting acoustic waves; and at least one clamp for radially clamping the communications node onto an outer surface of the tubular body; and a sensor communications node; and a plurality of intermediate communications nodes; wherein at least one of the sensor communications node and (ii) at least one of the plurality of intermediate communication nodes, is configured to: (a) transmit a first acoustic tone at a selected frequency at a frequency in a range of from 50-500 kHz for a first transmission time, (b) receive the transmitted acoustic tone for a first reverberation listening time that is greater than the first transmission time, (c) transmit another acoustic tone at another selected frequency at a frequency in a range of from 50-500 kHz for at least one of the first transmission time and another transmission time, (d) receive the another transmitted acoustic tone for at least one of the first reverberation listening time and a another reverberation listening time, greater than the another transmission time, (e) determine a dominant received frequency based on the received acoustic tone for the first reverberation listening time and the received another acoustic tone for at least one of the first reverberation listening time and the another reverberation listening time, and (f) transmit subsequent acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement using the dominant frequency, wherein each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node.

41. The communications node system of claim 40, wherein the tubular body is a joint of drill pipe, a joint of casing, a joint of production tubing, or a joint of a liner string.

42. The communications node system of claim 40, wherein: the housing of the communications node comprises a first end and a second opposite end; and the at least clamp comprises a first clamp secured at the first end of the housing, and a second clamp secured at the second end of the housing.

43. The communications node system of claim 42, wherein the communications node further comprises a first shoe at the first end of the housing and a second shoe at the second end of the housing.

44. The communications node system of claim 43, wherein the first shoe and the second shoe each comprises: a beveled edge designed to face away from the tubular body, a flat surface designed to face towards the tubular body, and a shoulder providing a clearance between the flat surface and the tubular body; and the flat surface of each shoe is welded onto a respective clamp.

45. The communications node system of claim 40, wherein: the transceiver is designed to receive acoustic waves, convert the acoustic waves into an electrical signal, convert the electrical signal into new acoustic waves, and re-transmit the new acoustic waves at the same frequency; and the transceiver is configured to transmit data representing a subsurface condition at a rate exceeding about 50 bps.

46. The communications node system of claim 40, wherein a frequency band for the acoustic wave transmission operates from 50 kHz to 500 kHz.

47. The electro-acoustic system according to claim 1, wherein the wireless telemetry is achieved through transmission of a number of tones including an initial tone and a final tone using a MFSK tonal alphabet with a supplemental tone such that the final tone transmitted is not repeated.

48. An electro-acoustic system for wireless telemetry along a pipeline, comprising: a tubular body fabricated from steel; at least one sensor disposed along the tubular body; a sensor communications node placed along the tubular body and connected to a wall of the tubular body, the sensor communications node being in electrical communication with the at least one sensor and configured to receive signals from the at least one sensor, the signals representing a parameter associated with a location along the tubular body; a proximal communications node placed at a beginning location along the tubular body; a plurality of intermediate communications nodes spaced along the tubular body and attached to an outer wall of the tubular body, the intermediate communications nodes configured to transmit acoustic waves from the sensor communications node to the proximal communications node in node-to-node arrangement; a receiver configured to receive signals from the proximal communications node; wherein each of the intermediate communications nodes comprises: a sealed housing; an independent power source residing within the housing; an electro-acoustic transducer and associated transceiver also residing within the housing designed to receive and re-transmit the acoustic waves, thereby providing communications telemetry; and wherein at least one of (i) the sensor communications node and (ii) at least one of the plurality of intermediate communications node, is configured to: (a) transmit a first acoustic tone at a selected frequency at a frequency in a range of from 50-500 kHz for a first transmission time, (b) receive the transmitted acoustic tone for a first reverberation listening time that is greater than the first transmission time, (c) transmit another acoustic tone at another selected frequency at a frequency in a range of from 50-500 kHz for at least one of the first transmission time and another transmission time, (d) receive the another transmitted acoustic tone for at least one of the first reverberation listening time and a another reverberation listening time, greater than the another transmission time, (e) determine a dominant received frequency based on the received acoustic tone for the first reverberation listening time and the received another acoustic tone for at least one of the first reverberation listening time and the another reverberation listening time, and (f) transmit subsequent acoustic waves from the sensor communications node to the topside communications node in node-to-node arrangement using the dominant frequency, wherein each intermediate communications node listens for the acoustic waves generated for a longer time than the time for which the acoustic waves were generated by a previous intermediate communications node.

49. The electro-acoustic system of claim 48, wherein the at least one sensor comprises (i) a pressure sensor, (ii) a temperature sensor, (iii) a sonic velocity sensor, (iv) a vibration sensor, or (v) a flow meter.

50. The electro-acoustic system of claim 48, wherein each of the intermediate communications nodes further comprises at least one clamp for radially attaching the communications node onto an outer surface of the tubular body.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) So that the present inventions can be better understood, certain drawings, charts, graphs and/or flow charts are appended hereto. It is to be noted, however, that the drawings illustrate only selected embodiments of the inventions and are therefore not to be considered limiting of scope, for the inventions may admit to other equally effective embodiments and applications.

(2) FIG. 1 is a side, cross-sectional view of an illustrative wellbore. The wellbore is being formed using a derrick, a drill string and a bottom hole assembly. A series of communications nodes is placed along the drill string as part of a telemetry system.

(3) FIG. 2 is a cross-sectional view of a wellbore having been completed. The illustrative wellbore has been completed as a cased hole completion. A series of communications nodes is placed along a tubing string as part of a telemetry system.

(4) FIG. 3 is a perspective view of an illustrative pipe joint. A communications node (such as a sensor communications node or an intermediate communications node) of the present invention, in one embodiment, is shown exploded away from the pipe joint.

(5) FIG. 4A is a perspective view of a communications node as may be used in the wireless data transmission system of the present invention, in an alternate embodiment.

(6) FIG. 4B is a cross-sectional view of the communications node of FIG. 4A. The view is taken along the longitudinal axis of the node. Here, a sensor is provided within the communications node.

(7) FIG. 4C is another cross-sectional view of the communications node of FIG. 4A. The view is again taken along the longitudinal axis of the node. Here, a sensor resides along the wellbore external to the communications node.

(8) FIGS. 5A and 5B are perspective views of a shoe as may be used on opposing ends of the communications node of FIG. 4A, in one embodiment. In FIG. 5A, the leading edge, or front, of the shoe is seen. In FIG. 5B, the back of the shoe is seen.

(9) FIG. 6 is a perspective view of a communications node system of the present invention, in one embodiment. The communications node system utilizes a pair of clamps for connecting a communications node onto a tubular body.

(10) FIG. 7 is a flowchart demonstrating steps of a method for transmitting data in a wellbore in accordance with the present inventions, in one embodiment.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

Definitions

(11) As used herein, the term “hydrocarbon” refers to an organic compound that includes primarily, if not exclusively, the elements hydrogen and carbon. Examples of hydrocarbons include any form of natural gas, oil, coal, and bitumen that can be used as a fuel or upgraded into a fuel.

(12) As used herein, the term “hydrocarbon fluids” refers to a hydrocarbon or mixtures of hydrocarbons that are gases or liquids. For example, hydrocarbon fluids may include a hydrocarbon or mixtures of hydrocarbons that are gases or liquids at formation conditions, at processing conditions, or at ambient conditions (20° C. and 1 atm pressure). Hydrocarbon fluids may include, for example, oil, natural gas, gas condensates, coal bed methane, shale oil, shale gas, and other hydrocarbons that are in a gaseous or liquid state.

(13) As used herein, the term “subsurface” refers to regions below the earth's surface.

(14) As used herein, the term “sensor” includes any electrical sensing device or gauge. The sensor may be capable of monitoring or detecting pressure, temperature, fluid flow, vibration, resistivity, or other formation data.

(15) As used herein, the term “formation” refers to any definable subsurface region. The formation may contain one or more hydrocarbon-containing layers, one or more non-hydrocarbon containing layers, an overburden, and/or an underburden of any geologic formation.

(16) The terms “zone” or “zone of interest” refer to a portion of a formation containing hydrocarbons. The term “hydrocarbon-bearing formation” may alternatively be used.

(17) As used herein, the term “wellbore” refers to a hole in the subsurface made by drilling or insertion of a conduit into the subsurface. A wellbore may have a substantially circular cross section, or other cross-sectional shape. As used herein, the term “well,” when referring to an opening in the formation, may be used interchangeably with the term “wellbore.”

(18) The terms “tubular member” or “tubular body” refer to any pipe, such as a joint of casing, a portion of a liner, a drill string, a production tubing, an injection tubing, a pup joint, a buried pipeline, underwater piping, or above-ground pipeline. The tubular body may also be a downhole tubular device such as a joint of sand screen having a base pipe with pre-drilled holes, a slotted liner, or an inflow control device.

Description of Selected Specific Embodiments

(19) The inventions are described herein in connection with certain specific embodiments. However, to the extent that the following detailed description is specific to a particular embodiment or a particular use, such is intended to be illustrative only and is not to be construed as limiting the scope of the inventions.

(20) FIG. 1 is a side, cross-sectional view of an illustrative well site 100. The well site 100 includes a derrick 120 at an earth surface 101, and a wellbore 150 extending from the earth surface 101 into an earth subsurface 155. The wellbore 150 is being formed using the derrick 120, a drill string 160 below the derrick 120, and a bottom hole assembly 170 at a lower end of the drill string 160.

(21) Referring first to the derrick 120, the derrick 120 includes a frame structure 121 that extends up from the earth surface 101 and which supports drilling equipment. The derrick 120 also includes a traveling block 122, a crown block 123 and a swivel 124. A so-called kelly 125 is attached to the swivel 124. The kelly 125 has a longitudinally extending bore (not shown) in fluid communication with a kelly hose 126. The kelly hose 126, also known as a mud hose, is a flexible, steel-reinforced, high-pressure hose that delivers drilling fluid through the bore of the kelly 125 and down into the drill string 160.

(22) The kelly 125 includes a drive section 127. The drive section 127 is non-circular in cross-section and conforms to an opening 128 longitudinally extending through a kelly drive bushing 129. The kelly drive bushing 129 is part of a rotary table. The rotary table is a mechanically driven device that provides clockwise (as viewed from above) rotational force to the kelly 125 and connected drill string 160 to facilitate the process of drilling a borehole 105. Both linear and rotational movement may thus be imparted from the kelly 125 to the drill string 160.

(23) A platform 102 is provided for the derrick 120. The platform 102 extends above the earth surface 101. The platform 102 generally supports rig hands along with various components of drilling equipment such as a pumps, motors, gauges, a dope bucket, pipe lifting equipment and control equipment. The platform 102 also supports the rotary table.

(24) It is understood that the platform 102 shown in FIG. 1 is somewhat schematic. It is also understood that the platform 102 is merely illustrative and that many designs for drilling rigs, both for onshore and for offshore operations, exist. The claims provided herein are not limited by the configuration and features of the drilling rig unless expressly stated in the claims.

(25) Placed below the platform 102 and the kelly drive section 127 but above the earth surface 101 is a blow-out preventer, or BOP 130. The BOP 130 is a large, specialized valve or set of valves used to control pressures during the drilling of oil and gas wells. Specifically, blowout preventers control the fluctuating pressures emanating from subterranean formations during a drilling process. The BOP 130 may include upper 132 and lower 134 rams used to isolate flow on the back side of the drill string 160. Blowout preventers 130 also prevent the pipe joints making up the drill string 160 and the drilling fluid from being blown out of the wellbore 150 when a blowout threatens.

(26) As shown in FIG. 1, the wellbore 150 is being formed down into the subsurface formation 155. In addition, the wellbore 150 is being shown as a deviated wellbore. Of course, this is merely illustrative as the wellbore 150 may be a vertical well or even a horizontal well, as shown later in FIG. 2.

(27) In drilling the wellbore 150, a first string of casing 110 is placed down from the surface 101. This is known as surface casing 110 or, in some instances (particularly offshore), conductor pipe. The surface casing 110 is secured within the formation 155 by a cement sheath. The cement sheath resides within an annular region 115 between the surface casing 110 and the surrounding formation 155.

(28) During the process of drilling and completing the wellbore 150, additional strings of casing (not shown) will be provided. These may include intermediate casing strings and a final production casing string. For the final production casing, a liner may be employed, that is, a string of casing that is not tied back to the surface 101.

(29) As noted, the wellbore 150 is formed by using a bottom hole assembly 170. The bottom-hole assembly 170 allows the operator to control or “steer” the direction or orientation of the wellbore 150 as it is formed. In this instance, the bottom hole assembly 170 is known as a rotary steerable drilling system, or RSS.

(30) The bottom hole assembly 170 will include a drill bit 172. The drill bit 172 may be turned by rotating the drill string 160 from the platform 102. Alternatively, the drill bit 172 may be turned by using so-called mud motors 174. The mud motors 174 are mechanically coupled to and turn the nearby drill bit 172. The mud motors 174 are used with stabilizers or bent subs 176 to impart an angular deviation to the drill bit 172. This, in turn, deviates the well from its previous path in the desired azimuth and inclination.

(31) There are several advantages to directional drilling. These primarily include the ability to complete a wellbore along a substantially horizontal axis of a subsurface formation, thereby exposing a substantially greater formation face. These also include the ability to penetrate into subsurface formations that are not located directly below the wellhead. This is particularly beneficial where an oil reservoir is located under an urban area or under a large body of water. Another benefit of directional drilling is the ability to group multiple wellheads on a single platform, such as for offshore drilling. Finally, directional drilling enables multiple laterals and/or sidetracks to be drilled from a single wellbore in order to maximize reservoir exposure and recovery of hydrocarbons.

(32) The illustrative well site 100 also includes a sensor 178. Here, the sensor 178 is part of the bottom hole assembly 170. The sensor 178 may be, for example, a set of position sensors that is part of the electronics for a RSS. Alternatively or in addition, the sensor 178 may be a temperature sensor, a pressure sensor, or other sensor for detecting a downhole condition during drilling. Alternatively still, the sensor may be an induction log or gamma ray log or other log that detects fluid and/or geology downhole.

(33) The sensor 178 is part of a MWD or a LWD assembly. It is observed that the sensor 178 is located above the mud motors 174. This is a common practice for MWD assemblies. This allows the electronic components of the sensor 178 to be spaced apart from the high vibration and centrifugal forces acting on the bit 172.

(34) Where the sensor 178 is a set of position sensors, the sensors may include three inclinometer sensors and three environmental acceleration sensors. Ideally, a temperature sensor and a wear sensor will also be placed in the drill bit 172. These signals are input into a multiplexer and transmitted.

(35) It is desirable to send signals about the downhole condition back to an operator at the surface 101. To do this, a telemetry system is used. As discussed above, various telemetry systems are known in the industry. However, the well site 100 of FIG. 1 presents a telemetry system that utilizes a series of novel communications nodes 180 placed along the drill string 160. These nodes 180 allow for the high speed transmission of wireless signals based on the in situ generation of acoustic waves.

(36) The nodes first include a topside communications node 182. The topside communications node 182 is placed closest to the surface 101. The topside node 182 is configured to receive and/or transmit acoustic signals. The topside communications node can be below grade as shown above, or above grade.

(37) The nodes may also include a sensor communications node 184. The sensor communications node is placed closest to the sensor 178. The sensor communications node 184 is configured to communicate with the downhole sensor 178, and then send a wireless signal using an acoustic wave.

(38) Finally, the nodes include a plurality of intermediate communications nodes 180. Each of the intermediate communications nodes 180 resides between the sensor node 182 and the topside node 184. The intermediate communications nodes 180 are configured to receive and then relay acoustic signals along the length of the wellbore 150. Preferably, the intermediate communications nodes 180 utilize two-way electro-acoustic transducers to both receive and relay mechanical waves.

(39) In FIG. 1, the nodes 180 are shown schematically. However, FIG. 3 offers an enlarged perspective view of an illustrative pipe joint 300, along with an illustrative intermediate communications node 350. The illustrative communications node 350 is shown exploded away from the pipe joint 300.

(40) In FIG. 3, the pipe joint 300 is intended to represent a joint of drill pipe. However, the pipe joint 300 may be any other tubular body such as a joint of tubing or a portion of pipeline. The pipe joint 300 has an elongated wall 310 defining an internal bore 315. The bore 315 transmits drilling fluids such as an oil based mud, or OBM, during a drilling operation. The pipe joint 300 has a box end 322 having internal threads, and a pin end 324 having external threads.

(41) As noted, an illustrative intermediate communications node 350 is shown exploded away from the pipe joint 300. The communications node 350 is designed to attach to the wall 310 of the pipe joint 300 at a selected location. In one aspect, selected pipe joints 300 will each have an intermediate communications node 350 between the box end 322 and the pin end 324. In one arrangement, the communications node 350 is placed immediately adjacent the box end 322 or, alternatively, immediately adjacent the pin end 324 of every joint of pipe. In another arrangement, the communications node 350 is placed at a selected location along every second or every third pipe joint 300 in a drill string 160. In other aspects, more or less than one intermediate communications node may be placed per joint 300.

(42) The intermediate communications node 350 shown in FIG. 3 is designed to be pre-welded onto the wall 310 of the pipe joint 300. However, it is preferred that the communications node 350 be configured to be selectively attachable to/detachable from a pipe joint 300 by mechanical means at a well site. This may be done, for example, through the use of clamps. Such a clamping system is shown at 600 in FIG. 6, described more fully below. Alternatively, an epoxy or other suitable acoustic couplant may be used for chemical bonding. In any instance, the communications node 350 is an independent wireless communications device that is designed to be attached to an external surface of a well pipe.

(43) There are several benefits to the use of an externally-placed communications node that uses acoustic waves. For example, such a node will not interfere with the flow of fluids within the internal bore 315 of the pipe joint 300. Further, installation and mechanical attachment can be readily assessed or adjusted, as necessary.

(44) In FIG. 3, the intermediate communications node 350 includes an elongated body 351. The body 351 supports one or more batteries, shown schematically at 352. The body 351 also supports an electro-acoustic transducer, shown schematically at 354. In a preferred embodiment, the electro-acoustic transducer 354 may be a two-way transceiver that can both receive and transmit acoustic signals. The communications node 350 is intended to represent the communications nodes 180 of FIG. 1, in one embodiment. The two-way electro-acoustic transducer 354 in each node 180 allows acoustic signals to be sent from node-to-node, either up the wellbore 150 or down the wellbore 150.

(45) Returning to FIG. 1, in operation, the sensor communications node 184 is in electrical communication with the sensor 178. This may be by means of a short wire, or by means of wireless communication such as infrared or radio-frequency communication. The sensor communications node 184 is configured to receive signals from the sensor 178, wherein the signals represent a subsurface condition such as position, temperature, pressure, resistivity, or other formation data. Preferably, the sensor is contained in the same housing as the sensor communications node 184. Indeed, the sensor may be the same electro-acoustic transducer that enables the telemetry communication.

(46) The sensor communications node 184 transmits signals from the sensor 178 as acoustic waves. The acoustic waves are preferably at a frequency of between about 50 kHz and 500 kHz. The signals are received by an intermediate communications node 180 that is closest to the sensor communications node 184. That intermediate communications node 180, in turn, will relay the signal on to a next-closest node 180 so that acoustic waves indicative of the downhole condition are sent from node-to-node. A last intermediate communications node 180 transmits the signals acoustically to the topside communications node 182.

(47) Communication may be between adjacent nodes, or it may occasionally skip a node depending on node spacing or communication range. Preferably, communication is routed around any nodes that are broken. Preferably, the number of nodes which transmit a communication packet is fewer than the total number of nodes between the sensor node and the topside node in order to conserve battery power and extend the operational life of the network.

(48) The well site 100 of FIG. 1 also shows a receiver 190. The receiver 190 comprises a processor 192 that receives signals sent from the topside communications node 182. The signals may be received through a wire (not shown) such as a co-axial cable, a fiber optic cable, a USB cable, or other electrical or optical communications wire. Alternatively, the receiver 190 may receive signals from the topside communications node 182 wirelessly through a modem, a transceiver or other wireless communications link. The receiver 190 preferably receives electrical signals via a so-called Class I, Division 1 conduit, that is, a housing for wiring that is considered acceptably safe in an explosive environment. In some applications, radio, infrared or microwave signals may be utilized.

(49) In any event, the processor 192 may be incorporated into a computer having a screen. The computer may have a separate keyboard 194, as is typical for a desk-top computer, or an integral keyboard as is typical for a laptop or a personal digital assistant. In one aspect, the processor 192 is part of a multi-purpose “smart phone” having specific “apps” and wireless connectivity.

(50) It is noted that data may be sent along the nodes not only from the sensor 178 up to the receiver 190, but also from the receiver 190 down to the sensor 178. This transmission may be of benefit in the event that the operator wishes to make a change in the way the sensor 178 is functioning. This is also of benefit when the sensor 178 is actually another type of device, such as an inflow control device that opens, closes or otherwise actuates in response to a signal from the surface 101.

(51) FIG. 1 demonstrates the use of a wireless data telemetry system in connection with a drilling operation. However, the wireless downhole telemetry system may also be used for a completed well.

(52) FIG. 2 is a cross-sectional view of an illustrative well site 200. The well site 200 includes a wellbore 250 that penetrates into a subsurface formation 255. The wellbore 250 has been completed as a cased-hole completion for producing hydrocarbon fluids. The well site 200 also includes a well head 260. The well head 260 is positioned at an earth surface 201 to control and direct the flow of formation fluids from the subsurface formation 255 to the surface 201.

(53) Referring first to the well head 260, the well head 260 may be any arrangement of pipes or valves that receive reservoir fluids at the top of the well. In the arrangement of FIG. 2, the well head 260 is a so-called Christmas tree. A Christmas tree is typically used when the subsurface formation 255 has enough in situ pressure to drive production fluids from the formation 255, up the wellbore 250, and to the surface 201. The illustrative well head 260 includes a top valve 262 and a bottom valve 264. In some contexts, these valves are referred to as “master fracture valves.” Other valves may also be used.

(54) It is understood that rather than using a Christmas tree, the well head 260 may alternatively include a motor (or prime mover) at the surface 201 that drives a pump. The pump, in turn, reciprocates a set of sucker rods and a connected positive displacement pump (not shown) downhole. The pump may be, for example, a rocking beam unit or a hydraulic piston pumping unit. Alternatively still, the well head 260 may be configured to support a string of production tubing having a downhole electric submersible pump, a gas lift valve, or other means of artificial lift (not shown). The present inventions are not limited by the configuration of operating equipment at the surface unless expressly noted in the claims.

(55) Referring next to the wellbore 250, the wellbore 250 has been completed with a series of pipe strings, referred to as casing. First, a string of surface casing 210 has been cemented into the formation. Cement is shown in an annular bore between the bore wall 215 of the wellbore 250 and the casing 210. The surface casing 210 has an upper end in sealed connection with the lower master valve 264.

(56) Next, at least one intermediate string of casing 220 is cemented into the wellbore 250. The intermediate string of casing 220 is in sealed fluid communication with the upper master valve 262. Cement is again shown in a bore 215 of the wellbore 250. The combination of the casing strings 210, 220 and the cement sheath in the bore 215 strengthens the wellbore 250 and facilitates the isolation of formations behind the casing 210, 220.

(57) It is understood that a wellbore 250 may, and typically will, include more than one string of intermediate casing. Some of the intermediate casing strings may be only partially cemented into place, depending on regulatory requirements and the presence of migratory fluids in any adjacent strata.

(58) Finally, a production liner 230 is provided. The production liner 230 is hung from the intermediate casing string 230 using a liner hanger 232. A portion of the production liner 230 may optionally be cemented in place. The liner is a string of casing that is not tied back to the surface 201.

(59) The production liner 230 has a lower end 234 that extends substantially to an end 254 of the wellbore 250. For this reason, the wellbore 250 is said to be completed as a cased-hole well. Those of ordinary skill in the art will understand that for production purposes, the liner 230 may be perforated or may include sections of slotted liner to create fluid communication between a bore 235 of the liner 230 and the surrounding rock matrix making up the subsurface formation 255.

(60) As an alternative, portions of the liner 230 may include joints of sand screen (not shown). The use of sand screens with gravel packs allows for greater fluid communication between the bore 235 of the liner 230 and the surrounding rock matrix while still providing support for the wellbore 250. The present inventions are not limited by the nature of the completion unless expressly so stated in the claims.

(61) The wellbore 250 also includes a string of production tubing 240. The production tubing 240 extends from the well head 260 down to the subsurface formation 255. In the arrangement of FIG. 2, the production tubing 240 terminates proximate an upper end of the subsurface formation 255. A production packer 242 is provided at a lower end of the production tubing 240 to seal off an annular region 245 between the tubing 240 and the surrounding production liner 230. However, the production tubing 240 may extend closer to the end 234 of the liner 230.

(62) It is also noted that the bottom end 234 of the production liner 230 is completed substantially horizontally within the subsurface formation 255. This is a common orientation for wells that are completed in so-called “tight” or “unconventional” formations. However, the present inventions have equal utility in vertically completed wells or in multi-lateral deviated wells. Further, the communications nodes 280 themselves may be used in other tubular constructions such as above-ground, under-ground, or below water pipelines.

(63) The illustrative well site 200 also includes one or more sensors 290. Here, the sensors 290 are placed at the depth of the subsurface formation 255. The sensors 290 may be, for example, pressure sensors, flow meters, or temperature sensors. A pressure sensor may be, for example, a sapphire gauge or a quartz gauge. Sapphire gauges are preferred as they are considered more rugged for the high-temperature downhole environment. Alternatively, the sensors may be microphones for detecting ambient noise, or geophones (such as a tri-axial geophone) for detecting the presence of micro-seismic activity. Alternatively still, the sensors may be fluid flow measurement devices such as a spinners, or fluid composition sensors.

(64) It is desirable to send signals about the downhole condition back to a receiver at the surface 201. As with the well site 100 of FIG. 1, the well site 200 of FIG. 2 includes a telemetry system that utilizes a series of novel communications nodes. Here, the communications nodes are placed along the outer diameter of the string of production tubing 240. These nodes allow for the high speed transmission of wireless signals based on the in situ generation of acoustic waves.

(65) The nodes first include a topside communications node 282. The topside communications node 282 is placed closest to the surface 201. The topside node 282 is configured to receive and/or transmit signals. The topside communications node 282 should be placed on the wellhead or next to the surface along the uppermost joint of casing 210.

(66) The nodes also include a sensor communications node 284. The sensor communications node 284 is placed closest to the sensors 290. The sensor communications node 284 is configured to communicate with the downhole sensor 290, and then send a wireless signal using acoustic waves.

(67) Finally, the nodes include a plurality of intermediate communications nodes 280. Each of the intermediate communications nodes 280 resides between the sensor communications node 284 and the topside communications node 282. The intermediate communications nodes 280 are configured to receive and then relay acoustic signals along the length of the tubing string 240. Preferably, the intermediate nodes 280 utilize two-way electro-acoustic transducers to receive and relay mechanical waves. The intermediate communications nodes 280 preferably reside along an outer diameter of the casing strings 210, 220, 230.

(68) In operation, the sensor communications node 284 is in electrical communication with the (one or more) sensors 290. This may be by means of a short wire, or by means of wireless communication such as infrared or radio waves. The sensor communications node 284 is configured to receive signals from the sensors 290, wherein the signals represent a subsurface condition such as temperature or pressure. Alternatively, sensor 290 may be contained in the housing of communications node 284.

(69) The sensor communications node 284 transmits signals from the sensors 290 as acoustic waves. The acoustic waves are preferably at a frequency band of about 100 kHz. The signals are received by an intermediate communications node 280. That intermediate communications node 280, in turn, will relay the signal on to another intermediate communications node so that acoustic waves indicative of the downhole condition are sent from node-to-node. A last intermediate communications node 280 transmits the signals to the topside node 282.

(70) The well site 200 of FIG. 2 shows a receiver 270. The receiver 270 comprises a processor 272 that receives signals sent from the topside communications node 284. The receiver 270 may include a screen and a keyboard 274 (either as a keypad or as part of a touch screen). The receiver 270 may also be an embedded controller with neither screen nor keyboard which communicates with a remote computer via cellular modem or telephone lines.

(71) The signals may be received by the processor 272 through a wire (not shown) such as a co-axial cable, a fiber optic cable, a USB cable, or other electrical or optical communications wire. Alternatively, the receiver 270 may receive the final signals from the topside node 282 wirelessly through a modem or transceiver. The receiver 270 preferably receives electrical signals via a so-called Class I, Division 1 conduit, that is, a wiring conduit that is considered acceptably safe in an explosive environment.

(72) FIGS. 1 and 2 present illustrative wellbores 150, 250 having a downhole telemetry system that uses a series of acoustic transducers. In each of FIGS. 1 and 2, the top of the drawing page is intended to be toward the surface and the bottom of the drawing page toward the well bottom. While wells commonly are completed in substantially vertical orientation, it is understood that wells may also be inclined and even horizontally completed. When the descriptive terms “up” and “down” or “upper” and “lower” or similar terms are used in reference to a drawing, they are intended to indicate relative location on the drawing page, and not necessarily orientation in the ground, as the present inventions have utility no matter how the wellbore is orientated.

(73) In each of FIGS. 1 and 2, the communications nodes 180, 280 are specially designed to withstand the same corrosive and environmental conditions (i.e., high temperature, high pressure) of a wellbore 150 or 250 as the casing strings, drill string, or production tubing. To do so, it is preferred that the communications nodes 180, 280 include sealed steel housings for holding the electronics.

(74) FIG. 4A is a perspective view of a communications node 400 as may be used in the wireless data transmission systems of FIG. 1 or FIG. 2 (or other wellbore), in one embodiment. The communications node 400 may be an intermediate communications node that is designed to provide two-way communication using a transceiver within a novel downhole housing assembly. FIG. 4B is a cross-sectional view of the communications node 400 of FIG. 4A. The view is taken along the longitudinal axis of the node 400. The communications node 400 will be discussed with reference to FIGS. 4A and 4B, together.

(75) The communications node 400 first includes a housing 410. The housing 410 is designed to be attached to an outer wall of a joint of wellbore pipe, such as the pipe joint 300 of FIG. 3. Where the wellbore pipe is a carbon steel pipe joint such as drill pipe, casing or liner, the housing is preferably fabricated from carbon steel. This metallurgical match avoids galvanic corrosion at the coupling.

(76) The housing 410 is dimensioned to be strong enough to protect internal electronics. In one aspect, the housing 410 has an outer wall 412 that is about 0.2 inches (0.51 cm) in thickness. A bore 405 is formed within the wall 412. The bore 405 houses the electronics, shown in FIG. 4B as a battery 430, a power supply wire 435, a transceiver 440, and a circuit board 445. The circuit board 445 will preferably include a micro-processor or electronics module that processes acoustic signals. An electro-acoustic transducer 442 is provided to convert acoustical energy to electrical energy (or vice-versa) and is coupled with outer wall 412 on the side attached to the tubular body. The transducer 442 is in electrical communication with at least one sensor 432.

(77) It is noted that in FIG. 4B, the sensor 432 resides within the housing 410 of the communications node 400. However, as noted, the sensor 432 may reside external to the communications node 400, such as above or below the node 400 along the wellbore. In FIG. 4C, a dashed line is provided showing an extended connection between the sensor 432 and the electro-acoustic transducer 442.

(78) The transceiver 440 will receive an acoustic telemetry signal. In one preferred embodiment, the acoustic telemetry data transfer is accomplished using multiple frequency shift keying (MFSK). Any extraneous noise in the signal is moderated by using well-known conventional analog and/or digital signal processing methods. This noise removal and signal enhancement may involve conveying the acoustic signal through a signal conditioning circuit using, for example, a bandpass filter.

(79) The transceiver will also produce acoustic telemetry signals. In one preferred embodiment, an electrical signal is delivered to an electromechanical transducer, such as through a driver circuit. In a preferred embodiment, the transducer is the same electro-acoustic transducer that originally received the MFSK data. The signal generated by the electro-acoustic transducer then passes through the housing 410 to the tubular body (such as production tubing 240), and propagates along the tubular body to other communication nodes. The re-transmitted signal represents the same sensor data originally transmitted by sensor communications node 284. In one aspect, the acoustic signal is generated and received by a magnetostrictive transducer comprising a coil wrapped around a core as the transceiver. In another aspect, the acoustic signal is generated and received by a piezoelectric ceramic transducer. In either case, the electrically encoded data are transformed into a sonic wave that is carried through the wall of the tubular body in the wellbore.

(80) The communications node 400 optionally has a protective outer layer 425. The protective outer layer 425 resides external to the wall 412 and provides an additional thin layer of protection for the electronics. The communications node 400 is also preferably fluid sealed with the housing 410 to protect the internal electronics. Additional protection for the internal electronics is available using an optional potting material.

(81) The communications node 400 also optionally includes a shoe 500. More specifically, the node 400 includes a pair of shoes 500 disposed at opposing ends of the wall 412. Each of the shoes 500 provides a beveled face that helps prevent the node 400 from hanging up on an external tubular body or the surrounding earth formation, as the case may be, during run-in or pull-out. The shoes 500 may have a protective outer layer 422 and an optional cushioning material 424 (shown in FIG. 4A) under the outer layer 422.

(82) FIGS. 5A and 5B are perspective views of an illustrative shoe 500 as may be used on an end of the communications node 400 of FIG. 4A, in one embodiment. In FIG. 5A, the leading edge or front of the shoe 500 is seen, while in FIG. 5B the back of the shoe 500 is seen.

(83) The shoe 500 first includes a body 510. The body 510 includes a flat under-surface 512 that butts up against opposing ends of the wall 412 of the intermediate communications node 400.

(84) Extending from the under-surface 512 is a stem 520. The illustrative stem 520 is circular in profile. The stem 520 is dimensioned to be received within opposing recesses 414 of the wall 412 of the node 400.

(85) Extending in an opposing direction from the body 510 is a beveled surface 530. As noted, the beveled surface 530 is designed to prevent the communications node 400 from hanging up on an object during run-in into a wellbore.

(86) Behind the beveled surface 530 is a flat surface 535. The flat surface 535 is configured to extend along the drill string 160 (or other tubular body) when the communications node 400 is attached along the tubular body. In one aspect, the shoe 500 includes an optional shoulder 515. The shoulder 515 creates a clearance between the flat surface 535 and the tubular body opposite the stem 520.

(87) In one arrangement, the communications nodes 400 with the shoes 500 are welded onto an inner or outer surface of the tubular body, such as wall 310 of the pipe joint 300. More specifically, the body 410 of the respective communications nodes 400 are welded onto the wall of the tubular body. In some cases, it may not be feasible or desirable to pre-weld the communications nodes 400 onto pipe joints before delivery to a well site. Therefore, it is desirable to utilize a clamping system that allows a drilling or service company to mechanically connect/disconnect the communications nodes 400 along a tubular body as the tubular body is being run into a wellbore.

(88) FIG. 6 is a perspective view of a communications node system 600 of the present invention, in one embodiment. The communications node system 600 utilizes a pair of clamps 610 for mechanically connecting an intermediate communications node 400 onto a tubular body 630.

(89) The system 600 first includes at least one clamp 610. In the arrangement of FIG. 6, a pair of clamps 610 is used. Each clamp 610 abuts the shoulder 515 of a respective shoe 500. Further, each clamp 610 receives the base 535 of a shoe 500. In this arrangement, the base 535 of each shoe 500 is welded onto an outer surface of the clamp 610. In this way, the clamps 610 and the communications node 400 become an integral tool.

(90) The illustrative clamps 610 of FIG. 6 include two arcuate sections 612, 614. The two sections 612, 614 pivot relative to one another by means of a hinge. Hinges are shown in phantom at 615. In this way, the clamps 610 may be selectively opened and closed.

(91) Each clamp 610 also includes a fastening mechanism 620. The fastening mechanisms 620 may be any means used for mechanically securing a ring onto a tubular body, such as a hook or a threaded connector. In the arrangement of FIG. 6, the fastening mechanism is a threaded bolt 625. The bolt 625 is received through a pair of rings 622, 624. The first ring 622 resides at an end of the first section 612 of the clamp 610, while the second ring 624 resides at an end of the second section 614 of the clamp 610. The threaded bolt 625 may be tightened by using, for example, one or more washers (not shown) and threaded nuts 627.

(92) In operation, a clamp 610 is placed onto the tubular body 630 by pivoting the first 612 and second 614 arcuate sections of the clamp 610 into an open position. The first 612 and second 614 sections are then closed around the tubular body 630, and the bolt 625 is run through the first 622 and second 624 receiving rings. The bolt 625 is then turned relative to the nut 627 in order to tighten the clamp 610 and connected communications node 400 onto the outer surface of the tubular body 630. Where two clamps 610 are used, this process is repeated.

(93) The tubular body 630 may be, for example, a drill string such as the illustrative drill string 160 of FIG. 1. Alternatively, the tubular body 630 may be a string of production tubing such as the tubing 240 of FIG. 2. In any instance, the tubular body 630 is ideally fabricated from a steel material having a thickness which contributes to broadening a mechanical response of the electro-acoustic transducer in the intermediate communications node 400, where the mechanical resonance is at a frequency contained within the frequency band used for telemetry.

(94) In one aspect, the communications node 400 is about 12 to 20 inches (0.30 to 0.51 meters) in length as it resides along the tubular body 630. Specifically, the housing 410 of the communications node may be 8 to 16 inches (0.20 to 0.41 meters) in length, and each opposing shoe 500 may be 2 to 5 inches (0.05 to 0.13 meters) in length. Further, the communications node 400 may be about 1 inch in width and 1 inch in height. The housing 410 of the communications node 400 may have a concave profile that generally matches the radius of the tubular body 630.

(95) A method for transmitting data in a wellbore is also provided herein. The method preferably employs the communications node 400 and the clamping system 600 of FIG. 6.

(96) FIG. 7 provides a flow chart for a method 700 of transmitting data in a wellbore. The method 700 uses a plurality of communications nodes situated along a tubular body to accomplish a wireless transmission of data along the wellbore. The wellbore penetrates into a subsurface formation, allowing for the communication of a wellbore condition at the level of the subsurface formation up to the surface.

(97) The method 700 first includes running a tubular body into the wellbore. This is shown at Box 710. The tubular body is formed by connecting a series of pipe joints end-to-end. The pipe joints are fabricated from a steel material that is suitable for conducting an acoustical signal.

(98) The method 700 also includes placing at least one sensor along the wellbore at a depth of the subsurface formation. This is provided at Box 720. Here, the sensor may be a pressure sensor, a temperature sensor, an inclinometer, a logging tool, a resistivity sensor, a vibration sensor, a fluid density sensor, a fluid identification sensor, a fluid flow measurement device (such as a so-called “spinner”) or other sensor. The sensor may reside, for example, along a string of drill pipe as part of a rotary steerable drilling system. Alternatively, the sensor may reside along a string of casing within a wellbore. Alternatively still, the sensor may reside along a string of production tubing or a joint of sand screen.

(99) The method 700 further includes attaching a sensor communications node to the tubular body. This is seen at Box 730. The sensor communications node may be placed either inside or outside of a tubular body. The sensor communications node is then placed at the depth of the subsurface formation. The sensor communications node is in communication with the at least one sensor. This is preferably a short wired connection or a connection through a circuit board. Alternatively, the communication could be acoustic or radio frequency (RF), particularly in the case when the sensor and communications nodes are not in the same housing. The sensor communications node is configured to receive signals from the at least one sensor. The signals represent a subsurface condition such as temperature, pressure, pipe strain, fluid flow or fluid composition, or geology.

(100) Preferably, the at least one sensor resides within the housing for the sensor communications node. The sensor communications node may alternatively be configured to use the electro-acoustic transducer as a sensor.

(101) The method 700 also provides for attaching a topside communications node to the tubular body. This is indicated at Box 740. The topside communications node is attached to the tubular body proximate the surface. In one aspect, the topside communications node is connected to the well head, which for purposes of the present disclosure may be considered part of the tubular body.

(102) The method 700 further comprises attaching a plurality of intermediate communications nodes to the tubular body. This is shown at Box 750. The intermediate communications nodes reside in spaced-apart relation along the tubular body between the sensor communications node and the topside communications node. The intermediate communications nodes are configured to receive and transmit acoustic waves from the sensor communications node to the topside node. In one aspect, piezo wafers or other piezoelectric elements are used to receive and transmit acoustic signals. In another aspect, multiple stacks of piezoelectric crystals or magnetostrictive devices are used. Signals are created by applying electrical signals of an appropriate frequency across one or more piezoelectric crystals, causing them to vibrate at a rate corresponding to the frequency of the desired acoustic signal. Each acoustic signal represents a packet of data comprised of a collection of separate tones.

(103) In the method 700, each of the intermediate communications nodes has an independent power source. The independent power source may be, for example, batteries or a fuel cell. In addition, each of the intermediate communications nodes has a transducer. The transducer is preferably an electro-acoustic transducer with an associated transceiver that is designed to receive the acoustic waves and produce acoustic waves.

(104) In one aspect, the data transmitted between the nodes is represented by acoustic waves according to a multiple frequency shift keying (MFSK) modulation method. Although MFSK is well-suited for this application, its use as an example is not intended to be limiting. It is known that various alternative forms of digital data modulation are available, for example, frequency shift keying (FSK), multi-frequency signaling (MF), phase shift keying (PSK), pulse position modulation (PPM), and on-off keying (OOK). In one embodiment, every 4 bits of data are represented by selecting one out of sixteen possible tones for broadcast.

(105) Acoustic telemetry along tubulars is characterized by multi-path or reverberation which persists for a period of milliseconds. As a result, a transmitted tone of a few milliseconds duration determines the dominant received frequency for a time period of additional milliseconds. Preferably, the communication nodes determine the transmitted frequency by receiving or “listening to” the acoustic waves for a time period corresponding to the reverberation time, which is typically much longer than the transmission time. The tone duration should be long enough that the frequency spectrum of the tone burst has negligible energy at the frequencies of neighboring tones, and the listening time must be long enough for the multipath to become substantially reduced in amplitude. In one embodiment, the tone duration is 2 ms, then the transmitter remains silent for 48 milliseconds before sending the next tone. The receiver, however, listens for 2+48=50 ms to determine each transmitted frequency, utilizing the long reverberation time to make the frequency determination more certain. Beneficially, the energy required to transmit data is reduced by transmitting for a short period of time and exploiting the multi-path to extend the listening time during which the transmitted frequency may be detected.

(106) In one embodiment, an MFSK modulation is employed where each tone is selected from an alphabet of 16 tones, so that it represents 4 bits of information. With a listening time of 50 ms, for example, the data rate is 80 bits per second.

(107) The tones are selected to be within a frequency band where the signal is detectable above ambient and electronic noise at least two nodes away from the transmitter node so that if one node fails, it can be bypassed by transmitting data directly between its nearest neighbors above and below. In one example, the tones can be approximately evenly spaced in frequency, but the tones may be spaced within a frequency band from about 50 kHz to about 500 kHz. More preferably, the tones are evenly spaced in a period within a frequency band approximately 25 kHz wide centered around or including 100 kHz.

(108) Preferably, the nodes employ a “frequency hopping” method where the last transmitted tone is not immediately re-used. This prevents extended reverberation from being mistaken for a second transmitted tone at the same frequency. For example, 17 tones are utilized for representing data in an MFSK modulation scheme; however, the last-used tone is excluded so that only 16 tones are actually available for selection at any time.

(109) In one aspect, the tubular body is a drill string. In this instance, each of the intermediate communications nodes is preferably placed along an outer diameter of pipe joints making up the drill string. In another aspect, the tubular body is a casing string. In this instance, each of the intermediate communications nodes is placed along an outer surface of pipe joints making up the casing string. In yet another embodiment, the tubular body is a production string such as tubing. In this instance, each of the intermediate communications nodes may be placed along an outer diameter of pipe joints making up the production string.

(110) In one aspect, the method 700 further includes transmitting a signal from the topside communications node to a receiver. This is shown at Box 760. The topside communications node also comprises an independent power source, meaning that it does not also supply power to any other intermediate or sensor communications node. The independent power source may be either internal to or external to the topside communications node. Further, the topside communications node has an electro-acoustic transducer designed to receive the acoustic waves from one or more of the plurality of intermediate communications nodes, and transmit acoustic waves to the receiver as a new signal. Preferably, the topside communications node includes a magnetically activated reed switch or other means to silence radio transmissions from the node without opening the Class 1 Div 1 housing.

(111) The communication signal between the topside communications node and the receiver may be either a wired electrical signal or a wireless radio transmission. Alternatively, the signal may be an optical signal. In any instance, the signal represents a subsurface condition as transmitted by the sensor in the subsurface formation. The signals are received by the receiver, which has data acquisition capabilities. The receiver may employ either volatile or non-volatile memory. The data may then be analyzed at the surface.

(112) As can be seen, a novel downhole telemetry system is provided, as well as a novel method for the wireless transmission of information using a plurality of data transmission nodes. The re-transmission process that takes place along the nodes not only provides a mechanism to remove signal noise, but also increases the signal amplitude. In the system, the repertoire of frequencies used by the nodes for communication, the amplitude of each frequency, the time duration for which each frequency is transmitted, and the time between signals may be optimized to find a balance between data transmission rate and energy used in data transmission.

(113) In one embodiment, the tubular body is made up of joints of pipe that form a casing string. At least some of the joints of pipe and the connected communications nodes are surrounded by a cement sheath.

(114) While it will be apparent that the inventions herein described are well calculated to achieve the benefits and advantages set forth above, it will be appreciated that the inventions are susceptible to modification, variation and change without departing from the spirit thereof.