It is to be understood that the various embodiments of the present invention described herein may be utilized in various orientations, such as inclined, inverted, horizontal, vertical, etc., and in various configurations, without departing from the principles of the present invention. The embodiments are described merely as examples of useful applications of the principles of the invention, which is not limited to any specific details of these embodiments.
In the following description of the representative embodiments of the invention, directional terms, such as “above”, “below”, “upper”, “lower”, etc., are used for convenience in referring to the accompanying drawings. In general, “above”, “upper”, “upward” and similar terms refer to a direction toward the earth's surface along a wellbore, and “below”, “lower”, “downward” and similar terms refer to a direction away from the earth's surface along the wellbore.
Representatively illustrated in
The telemetry system 12 includes a downhole transmitter assembly 14 and a surface receiver assembly 16. However, it should be clearly understood that the transmitter assembly 14 may also include a receiver, and the receiver assembly 16 may also include a transmitter, so that either one of these is in effect a transceiver.
Furthermore, the telemetry system 12 could include other or different components not illustrated in
The transmitter assembly 14 is preferably connected to a downhole device 18. The connection between the device 18 and the transmitter assembly 14 may be hardwired as depicted in
The device 18 may be, for example, a sensor for sensing a downhole parameter (such as temperature, pressure, water cut, resistivity, capacitance, radioactivity, acceleration, displacement, etc.), an actuator for a well tool, or any other type of device for which data and/or control signals would be useful for communication with the receiver assembly 16. The device 18 may be incorporated into the transmitter assembly 14.
A tubular string 20 extends between the transmitter assembly 14 and the receiver assembly 16. The telemetry system 12 provides for communication between the transmitter and receiver assemblies 14, 16 by transmission of stress waves through a pressure-bearing wall 22 of the tubular string 20.
Although the tubular string 20 is depicted in
Although the transmitter assembly 14 and downhole device 18 are depicted in
The receiver assembly 16 is preferably positioned at a surface location, but other locations are possible in keeping with the principles of the invention. For example, if the receiver assembly 16 is incorporated into a repeater or other type of well tool, then the receiver assembly may be positioned downhole, in a subsea wellhead, internal or external to the tubular string 20 (as described herein for the transmitter assembly 14), etc.
The receiver assembly 16 as depicted in
Referring additionally now to
Instead, the transmitter assembly 14 is shear coupled to the wall 22, as described more fully below. This unique positioning of the transmitter assembly 14 provides many advantages. For example, the transmitter assembly 14 is not limited to the available cross-sectional area of the wall 22, the transmitter assembly can be used with various sizes of tubular strings, the transmitter assembly can effectively transmit acoustic signal modes other than axial (such as flexural, which is particularly useful for short distance communication), etc.
As depicted in
The electronic circuitry 32 is used for communicating with the device 18 and operating the transmitter 34. The power source 36 is used for supplying electrical power to operate the circuitry 32 and the transmitter 34.
The acoustic transmitter 34 is preferably of the type which includes a stack of piezoceramic or other electromagnetically active elements, as described more fully below. Note that the transmitter 34 is external to the wall 22 of the tubular string 20, and is not concentric with the tubular string.
Referring additionally now to
In this view it may again be seen that the transmitter assembly 14 is external to both the wall 22 and an internal flow passage 42 of the tubular string 20. The transmitter assembly 14 could, however, be positioned within the flow passage 42 and remain external to the wall 22.
We can also see from this view that there is a reduced contact area between the transmitter assembly 14 and the wall 22. Acoustic energy travels from the transmitter assembly 14 to the wall 22 through this reduced contact area.
As used herein, the term “reduced contact area” is used to indicate a line contact or a point contact. A line contact is contact between surfaces wherein a ratio of length to width of the contact is greater than or equal to four. A point contact exists when the area of the contact is less than or equal to half of the total cross-sectional area (taken transverse to the longitudinal axis) of the smaller component, in this case the housing 38 of the transmitter assembly 14.
Referring additionally now to
Referring additionally now to
Preferably, a spherical load transfer device 50 is used between the elements 44 and one or both of the preload nuts 46, 48. The construction and advantages of the load transfer device 50 are more fully described in U.S. application Ser. No. ______, filed concurrently herewith, entitled THERMAL EXPANSION MATCHING FOR ACOUSTIC TELEMETRY SYSTEM, attorney docket no. 2006-IP-019940 U1 USA, and the entire disclosure of which is incorporated herein by this reference. The transmitter 34 may also utilize the thermal expansion matching and acoustic impedance matching techniques described in the incorporated application.
To enhance the shear coupling between the housing 38 and the wall 22 of the tubular string 20, external mating surfaces 52, 54 of the housing and wall may be roughened, serrated, etc. to provide increased “grip” therebetween. This enhanced shear coupling may be provided in addition to attachment of the housing 38 to the wall 22 using adhesive bonding, fasteners, clamps, etc.
Referring additionally now to
Electrically insulating layers may also be used within the transmitter assembly 14 itself, either in addition or as an alternative to the layer 56. For example, the elements 34 could be isolated from the housing 38 using an insulating layer within the housing.
It should be understood, however, that there could be metal-to-metal contact between the housing 38 and the wall 22, if desired. For example, in the configuration depicted in
Referring additionally now to
The structure 58 may perform any of several functions. For example, the structure 58 may protect the transmitter assembly 14 from damage during conveyance in the wellbore 26, the structure may provide a passage 60 for pressure or wired communication with the device 18, the flow passage 42, etc., and may in some embodiments provide some axial acoustic transmission to the wall 22 of the tubular string 20.
However, preferably the main acoustic coupling between the housing 38 and the wall 22 of the tubular string 20 is via shear coupling. Depicted in
It may now be fully appreciated that the acoustic telemetry system 12 described above provides a variety of benefits, including cost-effective and convenient use of the transmitter 34 with various sizes of tubular strings, ability to effectively transmit acoustic stress waves other than or in addition to axial (such as flexural, surface, torsional, multi-mode, etc.), modular construction, volume unlimited by tubular string wall, etc. The transmitter 34 is advantageously not concentric with the tubular string 20, but is instead positioned external to the wall 22 of the tubular string.
As discussed above, the transmitter assembly 14 could include a receiver, so that the transmitter assembly could alternatively be described as a transceiver. In that case, the elements 44 (or other electromagnetically active elements, other types of sensors, etc.) could be used to receive or otherwise sense stress waves transmitted through the tubular string 20 from another location. In this manner, signals could be either transmitted to or from the transmitter assembly 14. The term “acoustic telemetry assembly” is used herein to indicate a transmitter assembly (such as the transmitter assembly 14), a receiver assembly (such as the receiver assembly 16) or a combination thereof.
Although several specific embodiments of the invention have been separately described above, it should be clearly understood that any, or any combination, of the features of any of these embodiments may be incorporated into any of the other embodiments in keeping with the principles of the invention.
Of course, a person skilled in the art would, upon a careful consideration of the above description of representative embodiments of the invention, readily appreciate that many modifications, additions, substitutions, deletions, and other changes may be made to these specific embodiments, and such changes are within the scope of the principles of the present invention. Accordingly, the foregoing detailed description is to be clearly understood as being given by way of illustration and example only, the spirit and scope of the present invention being limited solely by the appended claims and their equivalents.