Slack management

1 . A wellbore system, comprising:

coiled tubing extending into a wellbore from a surface location;

a downhole tool coupled to a downhole end of the coiled tubing;

a cable extending through the coiled tubing and operably coupled to the downhole tool within the wellbore; and

an insert disposed within the coiled tubing and engaging the cable, the insert including:

a plurality of elongated rods radially spaced around the cable and defining a longitudinal axis of the insert; and

a plurality of retractable bars pivotally coupled to the elongated rods by a flexible hinge defined between the plurality of retractable bars and the elongated rods, the retractable bars extending radially inwardly from the elongated rods and biased radially inward to an extended position wherein the retractable bars collectively engage the cable from differing radial directions at longitudinal intervals,

wherein each retractable bar flexes the cable into an undulating configuration with respect to the longitudinal axis,

wherein the undulating configuration retains at least 10 percent of a length of the coiled tubing as slack in the cable, and

wherein each retractable bar is responsive to an increased tension in the cable to move radially outward to a retracted configuration.

2 . The wellbore system of claim 1 , wherein the plurality of retractable bars is coupled to the elongated rods with a threaded fastener at the flexible hinge, and wherein the threaded fastener is operable to adjust a force required to move the plurality of retractable bars from the extended configuration to the retracted configuration.

3 . The wellbore system of claim 2 , wherein each retractable bar defines a curved radially inner surface that is curved in a longitudinal direction, and wherein the curved radially inner surface is engaged with the cable when the cable and rolls against the cable when each retractable bar is moved between the extended and retracted configurations.

4 . The wellbore system of claim 1 , wherein the insert further comprises one or more ring connectors circumscribing the cable and affixed to each of the elongated rods to maintain a circumferential spacing of the elongated rods about the cable.

5 . The wellbore system of claim 1 , wherein the elongated rods are constructed of a thermoplastic material including at least one of polyether ether ketones (PEEK) or acrylonitrile butadiene styrene (ABS).

6 . The wellbore system of claim 5 , wherein the plurality of retractable bars is formed monolithically with the elongated rods of the thermoplastic material.

7 . The wellbore system of claim 1 , wherein the retractable bars are substantially more rigid than the cable.

8 . The wellbore system of claim 1 , wherein the insert is sized such that at least one of the elongated rods is spaced radially from the coiled tubing.

9 . A method of deploying a downhole tool on coiled tubing, the method comprising:

installing an insert on a cable to bias the cable into an undulating configuration that retains at least 10 percent of a length of the coiled tubing as slack in the cable, the insert including a plurality of elongated rods radially spaced around the cable and a plurality of retractable bars pivotally coupled to the elongated rods by a flexible hinge defined between the plurality of retractable bars and the elongated rods, the retractable bars extending radially inwardly from the elongated rods and biased radially inward to an extended position wherein the retractable bars collectively engage the cable from differing radial directions at longitudinal intervals;

inserting the insert and the cable through the coiled tubing;

coupling the downhole tool to a downhole end of the coiled tubing and a downhole end of the cable; and

deploying the downhole tool into the wellbore on the coiled tubing such that operational forces apply a tensile force to the cable within the coiled tubing such that the cable imparts a radial outward force on the plurality of retractable bars and such that the plurality of retractable bars pivot radially outward to a retracted configuration by rolling a curved radially inner surface of the plurality of retractable bars against the cable.

10 . The method of claim 9 , further comprising adjusting a retraction force of the plurality of retractable bars prior to installing the insert on the cable.

11 . The method of claim 10 , wherein adjusting the retraction force includes tightening or loosening a threaded fastener extending between the plurality of retractable bars and the elongated rods at a hinge defined between the plurality of retractable bars and the elongated rods.

12 . The method of claim 9 , further comprising releasing tension from the cable and thereby returning the plurality of retractable bars to the extended configuration and the cable to the undulating configuration.

13 . The method of claim 9 , further comprising determining an amount of slack required for the cable based on an observed or predicted shape of the coiled tubing in the wellbore and a tortuosity of the wellbore.

14 . The method of claim 9 , wherein inserting the insert and the cable through the coiled tubing includes pumping a fluid through the coiled tubing to propel the insert and the cable through the coiled tubing.

15 . A tubing assembly for deploying a downhole too in a wellbore, the tubing assembly comprising:

coiled tubing;

a cable extending through the coiled tubing and operable to transmit electrical and/or hydraulic signals therethrough;

a plurality of elongated rods disposed within the coiled tubing and radially spaced around the cable; and

a plurality of retractable bars pivotally coupled to the elongated rods by a flexible hinge defined between the plurality of retractable bars and the elongated rods, the retractable bars extending radially inwardly from the elongated rods and biased radially inward to an extended position wherein the retractable bars collectively engage the cable from differing radial directions at longitudinal intervals,

wherein the plurality of retractable bars flexes the cable into an undulating configuration,

wherein the undulating configuration retains at least 10 percent of a length of the coiled tubing as slack in the cable, and

wherein the plurality of retractable bars is responsive to an increased tension in the cable to move radially outward to a retracted configuration.

16 . The assembly of claim 15 , further comprising a threaded fastener disposed at the flexible hinge defined between the elongated rods and the plurality of retractable bars, and wherein the threaded fastener is operable to adjust a force required to pivot the plurality of retractable bars from the extended configuration to the retracted configuration about the flexible hinge.

17 . The assembly of claim 15 , wherein the retractable bars define a curved radially inner surface engaged with the cable to roll against the cable as the plurality of retractable bars pivot about the flexible hinge.

18 . The assembly of claim 15 , further comprising one or more ring connectors circumscribing the cable and affixed to each of the elongated rods to maintain a circumferential spacing of the elongated rods about the cable.

19 . The assembly of claim 15 , wherein the plurality of retractable bars are formed monolithically with the elongated rods with the flexible hinge defined between the plurality of retractable bars and the elongated rods.

20 . The assembly of claim 19 , wherein the elongated rods, the plurality of retractable bars and the flexible hinge are each constructed of a thermoplastic material including at least one of polyether ether ketones (PEEK) or acrylonitrile butadiene styrene (ABS).