Patent Description:
Coiled tubing is commonly used as a running string for a wide variety of downhole tools. Coiled tubing is well known in the art and consists of a length of metallic tubing which is capable of being wound onto a coil while at surface and unspooled from the coil to be injected into a wellbore. Telecoil® is sometimes used to transmit power and data through coiled tubing. Telecoil is coiled tubing which includes tubewire within coiled tubing. Tubewire is a tube that contains an insulated cable that is used to provide electrical power and/or data to a bottom hole assembly (BHA) or to transmit data from the BHA to the surface. Tube-wire is available commercially from manufacturers such as Canada Tech Corporation of Calgary, Canada. <CIT> describes a dual telemetric coiled tubing running string for disposing a bottom hole assembly into a wellbore. The dual telemetric coiled tubing running string includes a string of coiled tubing which defines a flowbore along its length, an electrical wire conduit disposed within the flowbore, and an optic fiber disposed within the flowbore.

The invention provides systems and methods for transmitting electrical power and/or signals as well as optical signals within coiled tubing and along a wellbore. A coiled tubing system is described which includes a string of coiled tubing which defines a central flowbore along its length. The invention provides a coiled tubing-based telemetry system incorporating a hybrid cable which includes at least one electrical conduit and at least one optic fiber which permits two-way communication and two-way power transmission.

The systems and methods of the present invention are useful for communication and control for various bottom hole assemblies. When interconnected with a variety of wellbore sensors, hybrid cabling can provide real-time information to operators at surface. In described embodiments, electrical conduits transmit signals to surface in real-time and supply power to downhole sensors and/or tools. In accordance with described embodiments, the systems and methods of the present invention provide dual wellbore telemetry to surface in real-time during downhole operations. A first set of telemetry is provided via sensors within the bottom hole assembly. The sensors are preferably single point sensors. A second set of telemetry is provided via optic fiber sensing techniques, such as distributed temperature sensing (DTS).

In described embodiments, a connector is used to interconnect the coiled tubing and cabling with a bottom hole assembly. An exemplary connector is described which includes a housing with threaded connections at each axial end. The connector includes a termination for finishing the optic fiber above the bottom hole assembly while the electrical conduit passes through the connector to the bottom hole assembly below it.

In described embodiments, the telemetry system includes a bus system which allows the bottom hole assembly to be made up of a number of interchangeable modules. The bus system allows power and data to be transmitted between the modules of the bottom hole assembly. This feature allows for custom construction of a bottom hole assembly having a desired mix of sensors and/or tools.

For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:.

The invention features a telemetry system for a wellbore work string having running string and a bottom hole assembly which is secured to the running string by a connector. The telemetry system includes an optical sensing system which monitors a wellbore parameter along a length of the running string using at least one optic fiber which extends along a flowbore of the running string and which terminates within the connector. The telemetry system also includes an electrical telemetry system which includes at least one sensor within the bottom hole assembly and an electrical conductor which transmits data from the sensor to a controller.

<FIG> illustrates an exemplary wellbore <NUM> which has been drilled from the surface <NUM> through the earth <NUM>. Although the depicted wellbore <NUM> is shown as being vertically oriented within the earth <NUM>, it should be understood that the wellbore, or portions thereof, may be inclined or horizontal.

A coiled tubing injector (not shown) of a type known in the art is located at surface <NUM> and is used to inject coiled tubing into the wellbore <NUM>. A controller <NUM> is also located at surface <NUM>. The controller <NUM> is preferably a programmable device, such as a computer, which is capable of receiving data in the form of electrical signals from a downhole sensor arrangement for display to a user and/or for storage. Additionally, an electrical power source <NUM> is located at surface <NUM> and may be in the form of a generator or battery. The electrical power source <NUM> should be suitable for transmitting power downhole to a sensor or tool. Also located at surface <NUM> is an OTDR (optical time-domain reflectometer) <NUM>.

A coiled tubing-based work string <NUM>, is shown being injected into the wellbore <NUM>. The work string includes a running string <NUM> made up of coiled tubing, of a type known in the art, and which defines a central flowbore <NUM> along its length. Generally, the work string <NUM> is useful for conducting one or more of several types of downhole operations within the wellbore <NUM>, as dictated by the variety of bottom hole assembly which is installed on the work string <NUM>. A connector <NUM> and a bottom hole assembly (BHA) <NUM> are located at the distal end of the running string <NUM>. The bottom hole assembly <NUM> may be a fishing BHA, an acidizing/fracturing BHA, or a cleanout BHA. Alternatively, the bottom hole assembly <NUM> could be any electrically powered tool, such as an electric submersible pump, a tool for opening and closing sliding sleeves or a drilling/milling arrangement. The connector <NUM> connects the bottom hole assembly <NUM> with the running string <NUM>.

A hybrid cable <NUM> extends along the flowbore <NUM> of the running string <NUM> to the connector <NUM>. At surface <NUM>, elements of the hybrid cable <NUM> are operably associated with the controller <NUM>, electrical power source <NUM> and OTDR <NUM>. <FIG> illustrates an exemplary hybrid cable <NUM> which permits two-way data communication and two-way power through electrical conductors. The cable <NUM> includes a plurality of electrical conductors or wires <NUM> which are surrounded by a layer of insulation <NUM>. A plurality of optic fibers <NUM> are located radially outside of the insulation layer <NUM>. An outer metallic tubing <NUM> surrounds the optic fibers <NUM>. The electrical conductors or wires <NUM> are associated at surface <NUM> with the electrical power source <NUM> to provide power to one or more sensors, such as sensor <NUM>, or other tools of the bottom hole assembly <NUM>. The electrical conductors or wires <NUM> are also interconnected with the controller <NUM> and can transmit data from sensor(s) <NUM> or other tools to the controller <NUM> so that a first operating parameter or first set of parameters are provided to the controller <NUM>. The sensor(s) <NUM> preferably single point sensors which are capable of detecting wellbore parameters associated with the bottom hole assembly <NUM> and its proximate location. These parameters can include temperature, pressure, gamma, casing collar location, azimuth, tension, compression and torque.

The optic fibers <NUM> are interconnected at surface <NUM> with the OTDR <NUM>. The optic fibers <NUM> will each typically include a transparent central core with outer cladding which has a lower index of refraction than that of the core. One or more of the optic fibers <NUM> will include a number of Bragg gratings, as known in the art, along their lengths. In accordance with preferred embodiments, the Bragg gratings are formed within the core of the optic fiber(s) <NUM> at spaced intervals along the length of the fiber(s) <NUM>. The OTDR <NUM> is used to both generate optical pulses into the optic fiber <NUM> as well as receive backscattered light from the optical fiber <NUM>.

During operation of the work string <NUM>, the optic fibers <NUM> provide optical telemetry to the OTDR <NUM> which is indicative of at least one second operating parameter within the wellbore <NUM>. In certain embodiments, the optic fibers <NUM> and OTDR <NUM> are configured to perform distributed temperature sensing (DTS) or distributed acoustic sensing (DAS) and provide telemetry to the OTDR <NUM>. The optic fibers <NUM> and OTDR <NUM> can provide information regarding sensed temperature or acoustics along the length of the optic fiber <NUM>.

An exemplary connector <NUM> is illustrated in <FIG> apart from other components of the work string <NUM>. In preferred embodiments, the connector <NUM> includes a housing <NUM> having axial ends <NUM> and <NUM> which are threaded for attachment of the bottom hole assembly <NUM> and the running string <NUM>. It is noted that, while threading is depicted, the connector <NUM> might also be a dimple or roll-on style connector sub. The connector <NUM> defines a flowbore <NUM> along its length. The connector <NUM> also preferably includes a termination channel <NUM> for each optic fiber <NUM>. Each optic fiber <NUM> is terminated within the connector <NUM> by disposing the distal end of the fiber <NUM> within a termination channel <NUM> which contains a gel <NUM> which is solidified to secure the end within. The electrical conductors <NUM> and insulation layer <NUM> extend through the connector <NUM> down to the bottom hole assembly <NUM>.

In preferred embodiments, the bottom hole assembly <NUM> includes a bus system and electrical connectors which permit assembly of separate subs within the bottom hole assembly in a modular fashion. The bus is preferably a multiconductor line which has a ground, +24VDC and +<NUM>. 5VDC are well as a two communication lines: signal A and signal B. The communication architecture may be based off of the RS-<NUM> standard with a speed of <NUM> bits/second. Subs may be interchanged or added to allow construction of a bottom hole assembly <NUM> having a desired mix of sensors and/or tools. <FIG> illustrates an exemplary bottom hole assembly <NUM> which is made up of a plurality of interconnected subs <NUM>, <NUM>, <NUM>, <NUM> and which is useful for conducting a downhole coiled tubing operation. In the illustrated embodiment, the bottom hole assembly <NUM> is useful for conducting a coiled tubing fishing operation. However, it should be understood that this is by way of example only and that the bottom hole assembly <NUM> might be used to conduct any and all types of coiled tubing operations. A flow through passageway <NUM> is defined along the length of the bottom hole assembly <NUM>. The electrical conductor(s) <NUM> extend along the length of the passageway <NUM> of the bottom hole assembly <NUM>. Sub <NUM> includes a fishing tool <NUM> of a type known in the art for removal of a stuck tool or object within the wellbore <NUM>. Sub <NUM> contains sensors <NUM> for detection of tool and annulus pressure as well as temperature. Sub <NUM> contains sensors for detection of gamma. The electrical conductor(s) <NUM> is/are preferably provided with detachable connection points <NUM> which allow the subs <NUM>, <NUM>, <NUM>, <NUM> to be electrically interconnected in a reversible manner. The connection points <NUM> may comprise USB-type connectors or similar connectors which allow for transmission of power and data. The electrical conductor(s) <NUM> incorporate a modem <NUM> for transmission of data uphole to the controller <NUM>. Individual sensor(s) <NUM> communicate with the modem <NUM> which packages the data provided from the sensor(s) <NUM> and transmits it uphole to the controller <NUM>.

Each of the subs <NUM>, <NUM>, <NUM>, <NUM> includes an electronics package, generally indicated at <NUM> which can include sensors, such as sensor(s) <NUM>, as well as other wellbore electronics, such as those which drive or operate valve actuators or other actuators as well as a processor, logic controller or digitizer and data storage, if desired. Electronics packages for various sensor and tool functions may be implemented using printed circuit boards or other methods known in the art.

Modules in the form of additional sensor and/or tool subs may be added or interchanged with the subs <NUM>, <NUM>, <NUM>, <NUM>, as desired to provide a combination of desired functionality for the bottom hole assembly <NUM>. For example, the sub <NUM> might be replaced by a sub having sensors for detection of tension, compression and torque. In this way, the bottom hole assembly <NUM> may be customized to have a desired mix of subs with a corresponding mix of functionality. When modules are disassembled from one another, the connection points <NUM> are disconnected and these are reassembled as modules are reassembled.

Claim 1:
A work string (<NUM>) for conducting a downhole operation within a wellbore, the work string (<NUM>) comprising:
a running string (<NUM>) which defines a flowbore (<NUM>);
a bottom hole assembly (<NUM>) having at least one electrically powered sensor (<NUM>) or tool;
a hybrid cable (<NUM>) within the flowbore (<NUM>), the hybrid cable (<NUM>) including at least one electrical conductor (<NUM>) and at least one optic fiber (<NUM>);
a connector (<NUM>) which interconnects the bottom hole assembly (<NUM>) with the running string (<NUM>);
wherein the electrical conductor (<NUM>) passes through the connector (<NUM>) and is interconnected with the electrically powered sensor (<NUM>) or tool within the bottom hole assembly (<NUM>); and
the optic fiber (<NUM>) terminates within the connector (<NUM>).