Patent Application
20050092499
1. Field of the Invention
This invention relates to oil and gas drilling, and more particularly to apparatus and methods for reliably transmitting information along downhole drilling strings.
2. Background
In the downhole drilling industry, MWD and LWD tools are used to take measurements and gather information concerning downhole geological formations, status of downhole tools, and other conditions located downhole. Such data is useful to drill operators, geologists, engineers, and other personnel located at the surface. This data may be used to adjust drilling parameters, such as drilling direction, penetration speed, and the like, to effectively tap into an oil, gas, or other mineral bearing reservoir. Data may be gathered at various points along the drill string, such as from a bottom hole assembly or from sensors distributed along the drill string.
Nevertheless, data gathering and analysis represent only certain aspects of the overall process. Once gathered, apparatus and methods are needed to rapidly and reliably transmit the data to the earth's surface. Traditionally, technologies such as mud pulse telemetry have been used to transmit data to the surface. However, most traditional methods are limited to very slow data rates and are inadequate for transmitting large quantities of data at high speeds.
In order to overcome these limitations, various efforts have been made to transmit data along electrical and other types of cable integrated directly into drill string components, such as sections of drill pipe. In such systems, electrical contacts or other transmission elements are used to transmit data across tool joints or connection points in the drill string. Nevertheless, many of these efforts have been largely abandoned or frustrated due to unreliability and complexity.
For example, one challenge is effectively integrating a transmission line into a downhole tool, such as a section of tool. Due to the inherent nature of drilling, most downhole tools have an elongated cylindrical shape defining a central bore. The wall thickness surrounding the central bore is typically designed in accordance with weight, strength, and other constraints needed to operate in a downhole environment. In some cases, the wall thickness may not be sufficient to allow for direct integration of a transmission line into the wall without significantly weakening the wall. Thus, in certain instances, the transmission line may be routed through the internal bore of the downhole tool.
Nevertheless, routing the transmission line through the internal bore may create interference between the transmission line and drilling fluids, cements, wireline tools, or other substances or objects passing through the central bore. Moreover, in directional drilling applications, drill tools may bend slightly as a drill string deviates from a straight path. In these circumstances, the transmission line may actually deviate away from the internal surface of the central bore, thereby worsening the obstruction within the internal bore of the downhole tool. The operation of drilling fluids, cement, wireline tools, or other components may be adversely affected by interference with the transmission line or, in other instances, the transmission line itself may be damaged.
Thus, what are needed are apparatus and methods to route a transmission line though the central bore of a downhole tool, without interfering with drilling fluids, cement, wireline tools, or other components that may be present in the central bore.
What are further needed are apparatus and methods to keep a transmission line firmly pressed against the inside surface of the central bore even when the downhole tool bends or deviates from a linear path.
What are further needed are apparatus and methods to protect a transmission line from components or substances located or traveling through the central bore of a downhole tool.
In view of the foregoing, it is a primary object of the present invention to provide apparatus and methods for routing a transmission line though the central bore of a downhole tool, without interfering with drilling fluids, cement, wireline tools, or other components or substances present in the central bore. It is a further object of the invention to provide apparatus and methods to keep a transmission line firmly positioned against the inside surface of the central bore even when the downhole tool bends or deviates from a linear path. It is yet a further object of the invention to provide apparatus and methods to protect a transmission line from components or substances passing through the central bore of a downhole tool.
Consistent with the foregoing objects, and in accordance with the invention as embodied and broadly described herein, a transmission line assembly for transmitting information along a downhole tool comprising a pin end, a box end, and a central bore traveling between the pin end and the box end, is disclosed in one embodiment of the invention as including a protective conduit. A transmission line is routed through the protective conduit. The protective conduit is routed through the central bore and the ends of the protective conduit are routed through channels formed in the pin end and box end of the downhole tool. The protective conduit is elastically forced into a spiral or other non-linear path along the interior surface of the central bore by compressing the protective conduit to fit within a length of the downhole tool shorter than the protective conduit.
In selected embodiments, the protective conduit is narrowed to provide improved contact between the protective conduit and the transmission line. In certain embodiments, this narrowing provides additional stiffness to the protective conduit, thereby keeping the conduit more firmly pressed against the internal surface of the central bore. In selected embodiments, the narrowing makes the conduit less subject to deformation in the presence of cement, wireline or logging tools, drilling fluids, or other components or substances in the central bore.
In certain embodiments, the protective conduit is configured to stay pressed against the inside surface of the central bore even when the downhole tool bends in directional drilling applications. The transmission line may be a coaxial cable, conductive wires, optical fibers, waveguides, or like transmission media. In selected embodiments, the ends of the protective conduit are fixed at the pin end and box end of the downhole tool to retain the protective conduit.
In another aspect of the present invention, a method for routing a transmission line assembly through a drill tool having a pin end, a box end, and a central bore traveling between the pin end and the box end, includes providing a protective conduit and routing a transmission line through the protective conduit. The method further includes routing the protective conduit through the central bore, and routing the ends of the protective conduit through channels formed in the pin end and box end of the downhole tool. The method further includes compelling the protective conduit to a spiral or non-linear path along the interior surface of the central bore by constraining the protective conduit to fit within a length of the drill tool shorter than the protective conduit.
In selected embodiments, the method includes narrowing the protective conduit to provide improved contact between the protective conduit and the transmission line. This narrowing may provide additional stiffness to the protective conduit, thereby making the protective conduit less subject to deformation in the presence of downhole cement, wireline or logging tools, drilling fluids, or other downhole tools or substances. The added stiffness may also be effective to more firmly urge the protective conduit against the interior surface of the central bore.
In selected embodiments, the spiral or non-linear path the conduit takes through the central bore may be effective to maintain contact between the protective conduit and the internal bore when the downhole tool bends in directional drilling applications. In certain embodiments, the transmission line may be coaxial cable, conductive wire, optical fiber, waveguides, or like transmission media. In other embodiments, a method in accordance with the invention includes fixing the ends of the protective conduit proximate the pin end and the box end of the downhole tool, respectively.
In another aspect of the present invention, a method for forming a transmission line assembly for routing through a drill tool having a pin end, a box end, and a central bore traveling between the pin end and the box end, includes providing a protective conduit and routing a transmission line through the protective conduit. The method further includes narrowing the protective conduit to provide improved contact between the protective conduit and the transmission line, and routing the protective conduit through the drill tool such that it spirals or takes a non-linear path along the interior surface of the central bore. The ends of the protective conduit are routed through channels formed in the pin end and box end of the downhole tool.
The foregoing and other features of the present invention will become more fully apparent from the following description, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments in accordance with the invention and are, therefore, not to be considered limiting of its scope, the invention will be described with additional specificity and detail through use of the accompanying drawings.
It will be readily understood that the components of the present invention, as generally described and illustrated in the Figures herein, could be arranged and designed in a wide variety of different configurations. Thus, the following more detailed description of embodiments of apparatus and methods of the present invention, as represented in the Figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of various selected embodiments of the invention.
The illustrated embodiments of the invention will be best understood by reference to the drawings, wherein like parts are designated by like numerals throughout. Those of ordinary skill in the art will, of course, appreciate that various modifications to the apparatus and methods described herein may easily be made without departing from the essential characteristics of the invention, as described in connection with the Figures. Thus, the following description of the Figures is intended only by way of example, and simply illustrates certain selected embodiments consistent with the invention as claimed herein.
Referring now to
As was previously mentioned, in order to transmit data up and down the drill string 104, a transmission line 14 may be integrated into a drill tool 10. If the transmission line 14 is routed straight along the central bore 15 of the drill tool 10, the transmission line 14 may separate or detach from the inside surface of the central bore 15 when the drill tool 10 bends or curves. This may be undesirable since the transmission line 14 may obstruct or interfere with fluids, wireline tools, concrete, or other objects or substances traveling through the central bore. In fact, in some cases, when a drill tool 10, such as a section of drill pipe 10, bends significantly, the transmission line 14 may actually come into contact with the opposite side 17 of the central bore 15. Thus, apparatus and methods are needed to route a transmission line 14 through the central bore 15 such that the transmission line 14 stays in relatively constant contact with the inside surface of the central bore 15.
Referring to
When in a spiral configuration, the transmission line 14 may have relatively few coils. For example, in selected embodiments, there may be between 3 and 5 coils 26a-c. Since drill tools 10, such as sections of drill pipe 10, may reach lengths of more than 30 feet, each coil 26 may span approximately 6 to 10 feet of the drill tool. Nevertheless, any number of coils 26 may be used as desired.
The transmission line 14 is not pre-formed into a spiral or other non-linear shape, but simply takes on a spiral shape because it is elastically forced or compelled to fit within the central bore 15 of the downhole tool 10. Thus, if the transmission line 14 were removed from the drill tool 10, the transmission line 14 may substantially revert to the shape it had before insertion into the downhole tool 10. The transmission 14 remains in the elastic mode and is not yielded. Thus, the transmission line 14 may be constructed of resilient materials capable of taking on a spiral or other non-linear shape. This resiliency assists in keeping the transmission line 14 pressed or biased against the inside surface of the central bore 15, as it is elastically loaded against the wall. Were the transmission line 14 pre-formed into a spiral, the yielding associated with forming the spiral not only significantly reduces the available loading against the wall, but also may change the electrical characteristics of the transmission line 14 or worse, damage it.
Another reason for not pre-forming the transmission line 14 into a spiral or other non-linear shape is that doing so may be difficult. As was previously described, in selected embodiments, the coils 26a-c may be spaced every 6 to 10 feet. This relatively “lazy”spacing of the coils 26 may be difficult to pre-form into a transmission line 14. As stated earlier, by not pre-forming the coils 26, the transmission line 14 may be urged with greater force against the inside diameter of the central bore 15 since the tendency of the transmission line 14 may be to uncoil itself.
As illustrated, the ends of the transmission line 14 may be routed through channels 22, 24 formed in the pin end 18 and box end 16 of a drill tool 10. The channels 22, 24 may keep the ends of the transmission line 14 rigidly fixed. This enables the coiled or spiral shape of the transmission line 14 to be maintained since, together with the central bore 15, the channels 22, 24 hold the transmission line 14 in its spiral or non-linear shape.
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In certain cases, a conduit 38 used to protect or cover a transmission cable 40 may have an inside diameter larger than the outside diameter of the transmission cable 40. Thus, in certain embodiments, it may be desirable to improve the bond between the conduit 38 and the cable 40. This may provide several advantages. For example, an improved bond may keep the transmission cable 14 from moving with respect to the conduit, thereby reducing wear or chafing that may occur between the two. An improved bond may also keep unwanted fluids or other substances from being introduced between the conduit 14 and the cable 40.
In selected embodiments, the diameter of the conduit may be reduced to more closely bond with or contact the cable 40. For example, the conduit 38 may be narrowed by passage through a tool 46. This narrowing process may actually thicken the walls of the conduit, thereby providing additional stiffness or resiliency to the conduit 38. This may be desirable because the added stiffness or resiliency may keep the conduit 38 more firmly pressed against the inside surface of the central bore 15. In selected embodiments, stainless steel may provide a suitable material for the conduit 38 since it is resistant to corrosion and wear, and is also sufficiently resilient. Nevertheless, other materials may also be used and provide similar qualities.
Referring to
As was mentioned, the channels 22, 24 may provide a convenient location to fix the ends of the transmission line 14. For example, in selected embodiments, the conduit 38 may be flared (not shown) to keep the transmission line 14 fixed with respect to the channels 22, 24. In other embodiments, keys, wedges, or other components (not shown) may be inserted in the channel 22, 24 between the transmission line 14 and the channel 22, 24 to keep the transmission line 14 from moving with respect to the channel 22, 24. In reality, any other suitable method of fixing the transmission line 14 with respect to the channels 22, 24 may be used and is within the scope of the present invention.
As illustrated, transmission elements 52a, 52b may be installed in the box end 16 and pin end 18 of the drill tool 10, respectively. Recesses may be milled or otherwise formed in the box and pin end 16, 18 to accommodate the transmission elements 52a, 52b. In certain embodiments, the transmission elements 52a, 52b may be installed in the secondary shoulders 54a, 54b, rather than the primary shoulders 56a, 56b, since the secondary shoulders 54a, 54b may be more protected from external elements and may also be less subject to stress incident on the primary shoulders 56a, 56b.
Referring to
In selected embodiments, the transmission elements 52 may communicate by direct electrical contact with one another. A conductor 60 of one transmission element 52 may contact a corresponding conductor 60 located in a corresponding transmission element 52. In other embodiments, the transmission elements 52 may communicate inductively. That is, the transmission elements 52 may convert electrical signals transmitted along the transmission line 14 to magnetic fields for transmission from one transmission element 52a to another 52c. This may be advantageous in cases where direct electrical contacts are unreliable.
The present invention may be embodied in other specific forms without departing from its essence or essential characteristics. The described embodiments are to be considered in all respects only as illustrative, and not restrictive. The scope of the invention is, therefore, indicated by the appended claims, rather than by the foregoing description. All changes within the meaning and range of equivalency of the claims are to be embraced within their scope.
This invention was made with government support under Contract No. DE-FC26-97FT343656 awarded by the U.S. Department of Energy. The government has certain rights in the invention.
