In one aspect of the invention, a swivel for use in a drilling operation comprises a body with a central bore adapted for threaded connection to a tool string component. At least one electrically conductive medium is rotationally supported within the bore and adapted to rotate with respect to an electrically conductive receiver that is rotationally fixed to and disposed within the body. The electrically conductive medium and the receiver are in electrical communication through an electrically conductive arm that is rotationally fixed to the electrically conductive medium and at least partially disposed within an electrically conductive fluid disposed within a reservoir. The reservoir comprises a rigid shape that is partially filled by the conductive fluid. At least one rotary seal is disposed intermediate the reservoir and the electrically conductive medium. The rigid shape of the reservoir is adapted to prevent the conductive fluid from accumulating around the rotary seal.

BACKGROUND OF THE INVENTION

The present invention relates to the field of data and/or power transmission. More specifically, it relates to apparatus for transmitting data and/or power from downhole tool strings to stationary equipment, such as surface equipment.

Downhole tool strings, such as drill strings, have become increasingly versatile in the last half century. In addition to traditional oil, gas, and geothermic exploration and production purposes, tubular tool strings are often used for what is known as horizontal directional drilling to install underground power lines, communication lines, water lines, sewer lines, utility lines, and gas lines. This sort of downhole drilling is particularly useful for boring underneath roadways, waterways, populated areas, and environmentally protected areas.

The increased versatility of downhole drilling with tool strings has led to a higher demand for apparatus that are able to transmit a power signal to downhole equipment as well as transmit data and/or power between downhole tools and surface equipment. Hence, several different approaches to solving the problem of transmitting an electrical signal across the joints of a tool string have been developed and are known in the art.

U.S. Pat. Nos. 6,670,880 and 6,717,501 to Hall et al., both of which are incorporated herein by reference for all that they disclose, teach of a system wherein tubular components are coupled at threaded joints and comprises a signal transmission system in the tool string. Other downhole telemetry systems are disclosed in U.S. Pat. No. 6,688,396 to Floerke et al and U.S. Pat. No. 6,641,434 to Boyle et al, which are also herein incorporated by reference for all that they contain.

Optimally, a system for transmitting power or data between surface equipment and downhole tools in a tool string should be transparent to the tool string operator or crew, as time delays introduced by a complicated telemetry system may represent a significant amount of money.

The use of data swivels for transmitting real-time data to stationary equipment has been disclosed in the art. Some examples of Mercury-type rotating electrical contacts that may be used in data swivels are found in U.S. Pat. No. 2,702,890 to Hildebrandt; U.S. Pat. No. 3,021,496 to Kenyon; U.S. Pat. No. 3,022,479 to Rohrbach; and U.S. Pat. No. 3,957,330 to Roscoe et al. Examples of inductive swivels for use in downhole applications are disclosed in U.S. Pat. Nos. 7,098,802 and 7,193,527 both to Hall et al. Each of the above listed patents is herein incorporated by reference.

BRIEF SUMMARY OF THE INVENTION

A swivel for use in a downhole drilling operation comprises a body with a central bore adapted for threaded connection to a tool string component. At least one electrically conductive medium is rotationally supported within the bore and adapted to rotate with respect to an electrically conductive receiver that is rotationally fixed to and disposed within the body. The electrically conductive medium and the receiver are in electrical communication through an electrically conductive arm that is rotationally fixed to the electrically conductive medium and at least partially disposed within an electrically conductive fluid disposed within a reservoir. The reservoir comprises a rigid shape that is partially filled by the electrically conductive fluid. At least one rotary seal is disposed intermediate the reservoir and the electrically conductive medium. The rigid shape of the reservoir is adapted to prevent the conductive fluid from accumulating around the rotary seal.

The swivel may comprise a plurality of reservoirs, electrically conductive arms, or electrically conductive media. The reservoir may be disposed circumferentially around at least a portion of the electrically conductive medium. The electrically conductive medium may comprise and electrically conductive core that may be surrounded by a dielectric material selected from the group consisting of alumina, ferrite, polycrystalline diamond, carbon, polymers, plastics, rubber, latex, and/or oxides of Mg, Al, Si, Yb, Ca, Be, Sr, Ns, Sm, Er, Eu, Sc, La, Gd, Dy, Tm, ceramics and combinations thereof. The electrically conductive medium may comprise a coaxial cable, a pair of twisted wires, a biaxial cable, a triaxial cable, insulated copper wires, or combinations thereof. An electrically conductive shield of a coaxial cable may be in electrical communication with a first reservoir and an electrically conductive core of the coaxial cable may be in communication with a second reservoir. A channel may extend from a first reservoir to second reservoir or to a second end of the first reservoir.

The receiver may be an electrically conductive portion of the body or may be in electrical communication with an electrical device. The electrical device may be a computer, a data processing unit, a data storage unit, or combinations thereof. The swivel may be in electronic communication with a downhole telemetry system. The electrically conductive fluid may comprise mercury, indium, an aqueous solution, liquid metal, gallium, eutectic mixtures, mixtures thereof, compositions thereof, or a combination thereof.

The rigid shape of the reservoir may be adapted to retain the conductive fluid within the reservoir between the receiver and the electrically conductive arm and away from the at least one rotary seal when a central axis of the reservoir is parallel to the ground and when it is not parallel to the ground. The rigid shape may comprise a generally cylindrical geometry that is coaxial with the body and comprises inner and outer diameters. The rotary seal may comprise at least one o-ring, gasket, adhesive, washer, fastener, back-up or combinations thereof. The reservoir may comprise a flow restrictor proximate the rotary seal. A volume of the reservoir may be less than 50% filled by the electrically conductive fluid. In some embodiments of the invention the reservoir may comprise an internal separator wall.

A tool string may be a drill string100. The drill string100may drill a bore hole101in subterranean formation102in a horizontal direction105such as those used to install utility lines or for coal methane drilling. In other applications of the present invention, the tool string may be for use in deep oil and gas drilling, geothermal drilling, or various types of exploration. In the embodiment ofFIG. 1, a rig103is placed at the ground or surface405and is angled such that the drill string100penetrates the ground or surface405at a non-perpendicular angle. As the drill string100advances, the bore hole101gradually becomes generally parallel to the ground or surface405and then eventually returns to the ground or surface405at a predetermined location. At the predetermined location, a back reamer may be attached to the drill string100and pulled back through the bore hole101in order to widen the hole for pipe and to insert other tools to be inserted. Cables such as fiber optic or metal cables may also be attached to the drill string100as it is pulled back through the bore hole101.

To accomplish horizontal directional drilling, the drill string100may include a steering mechanism. The steering mechanism may allow the drill string100to change direction while drilling, which may allow the drill string100to avoid obstacles such as bodies of water or paved surfaces. Surface equipment, which may be part of the rig103, may allow drill string operators to observe and manually control the direction of the bore hole101.

Downhole tool string components may include drill pipes, jars, shock absorbers, mud hammers, air hammers, mud motors, turbines, reamers, under-reamers, fishing tools, steering elements, MWD tools, LWD tools, seismic sources, seismic receivers, pumps, perforators, packers, other tools with an explosive charge, mud-pulse sirens, or combinations thereof Downhole LWD tools may be located in a bottom hole assembly or along the length of the downhole tool string100. The tools may be inductive resistivity tools, sensors, drill bits, motors, hammers, steering elements, links, jars, seismic sources, seismic receivers, and other tools that aid in the operations of the downhole tool string100.

In order to provide power to downhole tools while drilling, the drill string100may include an electrical transmission system. An example of an electrical transmission system that may be compatible with the present invention is disclosed in U.S. patent application Ser. Nos. 11/428,445 which is now U.S. Pat. No. 7,488,194 that issued on Feb. 10, 2009; 11/559,461 which is now U.S. Pat. No. 7,527,105 that issued on May 5, 2009; 11/737,178 which is now U.S. Pat. No. 7,572,134 that issued on Oct. 11, 2009; and 11/693,909 to Hall et al., which is now U.S. Pat. No. 7,404,725 all of which are herein incorporated by reference. Also in some embodiments, the telemetry system disclosed in U.S. Pat. No. 6,670,880, which is also inhere incorporated by reference for all that it contains, may also be compatible with the present invention. Sensors may sense gamma rays, radioactive energy, resistivity, torque, pressure, temperature, or other drilling dynamics measurements or combinations thereof from the formation being drilled. Other sensors may be useful downhole such as, inclinometers, thermocouplers, accelerometers, and imaging devices. To transmit data in real-time from the tool string to surface equipment or data and/or power to downhole equipment swivel may be employed.

Referring now toFIG. 2, a data swivel201may facilitate the transfer of data power and/or electricity between a rotating drill string100A and the stationary rig103(FIG. 1) on the surface. In some embodiments the swivel201may be disposed downhole. The swivel201may be in electronic communication with a downhole telemetry system such as the systems discloses in U.S. Pat. Nos. 6,670,880 and 6,717,501 to Hall et al.

InFIG. 2, the data swivel201is electrically connected to the drill string100A by a tool string component202via an NPT connector207. In the present embodiment the tool string component202connects with the drill string100and with a drilling fluid supply pipe203. The swivel201also includes a SubMiniature version A (SMA) connector204connected to a data cable205, which may connect to an electrical device such as a computer, data processing unit, data storage unit, or combinations thereof. A rotary rod206may be attached to the swivel201and may assist in connecting the swivel201to the NPT connector207. The tool string component202and the drill string100A may be connected such that the drill string100A may rotate while being rotatably connected to the component202.

FIG. 3discloses a cross-sectional diagram of a data swivel201B in accordance with the present invention. Data swivel201B includes a body301that is adapted for threaded connection with tool string component202(FIG. 2) via an NPT connector207B and a swivel nut302. The body301comprises a central bore303in which an electrically conductive medium304is rotationally supported. The electrically conductive medium304is adapted to rotate with respect to an electrically conductive receiver305that is fixed to and disposed within the body301. In the current embodiment, the electrically conductive medium304is a coaxial cable, but the electrically conductive medium304may be a coaxial cable, a pair of twisted wires, a biaxial cable, a triaxial cable, insulated copper wires, or combinations thereof. The electrically conductive medium304in the present embodiment has an electrically conductive core306that is surrounded by a dielectric material307. The dielectric material307may be selected from the group consisting of alumina, ferrite, polycrystalline diamond, carbon, polymers, plastics, rubber, latex, and/or oxides of Mg, AI, Si, Yb, Ca, Be, Sr, Ns, Sm, Er, Eu, Sc, La, Gd, Dy, Tm, and combinations thereof.

The dielectric material307may be surrounded by a shield308and by a stainless steel conduit309. The shield308and conduit309may help to form electrical connections between adjacent components at downhole junctions of the components. The shield308and conduit309may also protect the electrical signal as it passes from one component to another. This may provide the advantage of keeping the power and/or data signals undistorted Mile they are traveling from component to component. In some embodiments of the invention electrical power may be transferred downhole via the core306and data may be transferred back uphole via the conduit309or shield308. Alternatively, power may be transferred downhole via one electrically conductive medium like electrically conductive medium304and data may return uphole via a separate electrically conductive medium like electrically conductive medium304.

An electrically conductive hollow cylinder310is rotationally fixed to the conduit309by an electrically conductive arm318. The electrically conductive arm318with the hollow cylinder310extends from the electrically conductive medium304into an electrically conductive fluid311disposed within a reservoir312. In the present embodiment, the reservoir312is disposed circumferentially around a portion of the electrically conductive medium304. Whenever the electrically conductive arm318is at least partially disposed within the electrically conductive fluid311, the electrically conductive medium304and the electrically conductive receiver305may be in electrical communication. The reservoir312is partially filled by the electrically conductive fluid311.

In some embodiments, the reservoir312has a total volume; and the total volume of the reservoir312may be less than 50% filled by the electrically conductive fluid311. In some embodiments a non-conductive pressurized lubricant may fill some or all of the reservoir's volume that is not filled by the electrically conductive fluid311.

A plurality of rotary seals313are disposed between the reservoir312and the electrically conductive medium304. The rotary seals313are designed to prevent the electrically conductive fluid311from going between the reservoir312and the electrically conductive medium304. The rigid shape of the reservoir312is adapted to prevent the electrically conductive fluid311from accumulating around the rotary seals313.

The swivel201B may have a plurality of reservoirs like reservoir312or a plurality of electrically conductive arms like electrically conductive arms318. InFIG. 3, the swivel201B has two reservoirs312and316shown disposed within the body301. Separate electrically conductive arms318and319are disposed within each reservoir312and316, respectively. Each electrically conductive arm318and319is attached to the same electrically conductive medium304. In some embodiments of the invention, each electrically conductive arm318and319may be attached to separate electrically conductive cylinders310and315which extend in part into electrically conductive fluid311in reservoir312and electrically conductive fluid330in reservoir316from the electrically conductive medium304.

In some embodiments, first electrically conductive arm319electrically connects to the electrically conductive cylinder315via the fluid311B to the reservoir316to place an electrically conductive receiver317into electrical communication directly with the core306of the electrically conductive medium. The other electrically conductive arm318is connected to the electrically conductive cylinder310and position to contact the electrically conductive fluid311in the other reservoir312to place the electrically conductive receiver305into electrical communication with the conduit309. This may allow for power to be sent down the core306and return via the conduit309or vice versa. The electrically conductive fluids311and330may be mercury, indium, an aqueous solution, liquid metal, gallium, eutectic mixtures, mixtures thereof, compositions thereof, or a combination thereof.

Referring now toFIGS. 3-5, as the swivel201B is rotated the electrically conductive fluid311, which is retained within the reservoir312between the electrically conductive receiver305and the electrically conductive arm310. The electrically conductive fluid311is also kept away from contact with the rotary seals313. This is accomplished by the rigidity and the shape314of the reservoir312. In the present embodiment, the reservoir312is generally cylindrical and is coaxial with the body301. Both the reservoir312and the body301share a common central axis321. The reservoir312is a cylinder314that has inner diameters401and outer diameter402. The electrically conductive fluid311may flow along a length403of the reservoir312between the inner and outer diameters401,402.

InFIG. 4the swivel201B is rotated 45 degrees from the position of the swivel201B seen enlarged inFIG. 3. InFIG. 3, the central axis321of the reservoir312and the central axis of the electrically conductive medium304are the same. The upper surface404B of the fluid311are generally parallel to the ground405(seeFIG. 1). InFIG. 4, the upper surface404B is parallel to the ground405, but the axis321is not parallel with the ground405. The fluid311is retained within the reservoir312between the electrically conductive receiver305and the electrically conductive arm310. The electrically conductive fluid311is retained spaced away from the seals313both when the central axis321of the reservoir312is parallel with the ground405and when it is not parallel. Pooling contact of electrically conductive fluids with the seals313may lead to some electrically conductive fluid5escape from the swivel201or faster degradation of the seals313.

InFIG. 5, the swivel201B is rotated 90 degrees from the position of the swivel201B inFIG. 3. The upper surface404C of the electrically conductive fluid311is still parallel to the ground405, but the central axis321of the reservoir312is now perpendicular to the ground405. The fluid311is still retained within the reservoir312between the electrically conductive receiver305and the electrically conductive arm310and away from the seals313.

Also as seen inFIG. 5, the rotary seals313may be O-rings501A and501B. O-rings501A and501B may help to hold the seals313in place during rotation of the electrically conductive medium304within the swivel201B. In some embodiments, at least one rotary seal313may comprise at least one O-ring, gasket, adhesive, washer, fastener, or combinations thereof. Springs or bearings502may be disposed within the body301. Bearings502may assist with the connection of the body301with the NPT connector207(FIG. 2). Springs may include wave springs, Belleville springs, coiled springs or combinations thereof.

Referring now toFIG. 6, a partial cross-sectional diagram of swivel201B shows electrically conductive arm319connected to electrically conductive structure315that is positioned in the reservoir316. The electrically conductive receiver317is in electrical communication with the core306via the electrically conductive fluid311B and the electrically conductive structure315and the electrically conductive arm319. The electrically conductive medium304is connected to surface equipment (not shown) by a conductor body601which contacts the SMA connector204. In some embodiments, the electrically conductive receiver317may receive a first signal carried up the electrically conductive medium304, and the receiver305may receive a second signal carried up the same electrically conductive medium304. In such embodiments, one signal may be carried through the core306and the other signal may be carried through the conduit309.

FIGS. 7-8disclose alternative shapes314for reservoirs312D and312E for use in swivels201D and201E. The reservoir312D inFIG. 7is generally cylindrical that is coaxial with the body301. The reservoir312has an outer diameter402D along its entire length403D; but it only has an inner diameter401D along a distal portion702of length403D. The electrically conductive structure318D is connected to electrically conductive310D, which extends radially outward from the electrically conductive medium304D. The electrically conductive structure318D has a central axis321D that is roughly parallel with and is here shown to be the same as the central axis321D of the electrically conductive medium304.FIG. 7also shows an end701of the electrically conductive structure318to have a generally circular cross-section radially.

InFIG. 8, the swivel201E has a reservoir312E which is shown having a generally curved or barrel shape. The reservoir312E is closed on opposite ends801and802. The electrically conductive structure318E extends from electrically conductive310E and is similarly is generally curved or barrel shaped. The curved shape may increase the amount of contact surface area between the electrically conductive structure318E and the fluid311E regardless of the orientation of the swivel201E. A portion802of the body301may be electrically conductive material. This portion802may be part of the receiver305E.

FIG. 9shows a portion of a swivel201F having a reservoir312F and flow restrictors901A-F proximate the rotary seal313F. The reservoir312F also has a reservoir branch902that extends from the main volume903of the reservoir312F towards the electrically conductive medium304. Electrically conductive fluid311F may be restricted from greater contact with the rotary seals313by pooling the electrically conductive fluid311F in the branch902and by placing the flow restrictors901A-F proximate the seals313.

Referring now toFIG. 10, the swivel201G has a reservoir312with an internal separator wall201001. The internal separator wall1001may be attached to the reservoir312G at a center point1002and taper outward to extend along most of the length403G of the reservoir312G. A portion of the electrically conductive fluid311G is disposed on an inner side1003of the wall1001and a portion of the fluid311G is disposed on an outer side1004of the wall1001. When the swivel201G is rotated, the fluid311G on the outer side may be retained from contact with the rotary seals313(FIG. 3) by the wall1001. The electrically conductive arm310supports the electrically conductive structure318G which is a hollow cylinder. A radial extension1005of the electrically conductive structure318G may increase contact surface area between the electrically conductive structure318G and the fluid311G. The extension1005may also ensure electrical communication of the electrically conductive receiver305G and the electrically conductive medium304G when the swivel201G is orthogonal to the diagram disclosed inFIG. 10. One or more channels1006may extend from a first end1007of the reservoir312G to a second end1008of the reservoir312G. This may direct fluid311G away from the rotary seals like rotary seals313(FIG. 3) and discourage overflow of the fluid311G onto the seals.

In some embodiments of the invention a channel1006may extend from a first reservoir316to a second reservoir319.