spe-25499-ms fishing with coiled tubing

Society of Petroleum Engineers

SPE 25499

Fishing With Coiled TubingR.L. Hilts, Otis Engineering Corp.; S.H. Fowler Jr., Halliburton Manufacturing & Services Ltd.;and C.W. Pleasants, Otis Engineering Corp.

SPE Members

Copyright 1993, Society of Petroleum Engineers, Inc.

This paper was prepared for presentation at the Production Operations Symposium held in Oklahoma City, OK, U.S.A., March 21-23, 1993.

This paper was selected for presentation by an SPE Program Committee foliowing review of information contained in an abstract submitted by the author(s). Contents of the paper,as presented, have not been reviewed by the Society of Petroleum Engineers and are subject to correction by the author(s). The material, as presented, does not necessarily reflectany position of the Society of Petroleum Engineers, its officers, or members. Papers presented at SPE meetings are sUbject to publication review by Editorial Committees of the Societyof Petroleum Engineers. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copied. The abstract should contain conspicuous acknowledgmentof where and by whom the paper is presented. Write Librarian, SPE, P.O. Box 833836, Richardson, TX 75083-3836, U.S.A. Telex, 163245 SPEUT.

ABSTRACT

Improved coiled tubing (CT) technology, development ofspecially-designed hydraulically-actuated service tools, andincreased emphasis on cost efficiency have made coiledtubing a viable option for many fishing jobs. Before theemergence of coiled tubing fishing technology, traditionalservice procedures included use of wireline to retrieve fishfrom oil and gas wells. If wireline was unsuccessful, a rigor hydraulic workover (snubbing) unit had to work overthe well and remove the fish.

This paper addresses the successful use of CT in fishingoperations. The capability of CT to circulate fluids at thefish and generate high downhole forces enables theretrieval of fish in situations that would not be possible orcost effective by other service options. CT fishing can beperformed under pressure on live, highly-deviated orhorizontal wells; the job can be completed and the wellreturned to production within 1 to 3 days for only afraction of the cost of a workover.

The paper will describe the tools, their capabilities, andservice techniques currently in use for CT fishingoperations as well as new equipment being developed.Data from several case histories will be used to provideconsiderations, surface rig-up, and job limitations.

References and illustrations at end of paper.

INTRODUCTION

An oilfield definition of fishing might be: "an attempt toengage and retrieve unwanted, unservicable, or oftendamaged equipment from a wellbore." The term "fishing"is generally used when downhole equipment cannot beretrieved from the well using the tools or method designedto operate or retrieve that piece of equipment. Generally,fish fall into two categories -- some are simplynuisances, causing decreased production or increasedoperating difficulties and costs, but some must be removedfor safety or mechanical reasons if the' well is to continueproduction.

In production operations, fish might include:

• Stuck, damaged, or inaccessible subsurface flowcontrols, plugs or subsurface safety equipment thatcannot be pulled by wireline.

• Lengths of wireline or logging (E-line) cable.

• Service tool strings.

• Other foreign objects.

Before 1980, the quality of the CT, particularly the weldjoints, was relatively low, and tubing failures resulted infishing jobs to remove the dropped pipe. In spite of these

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2 FISHING WITH COILED TUBING SPE 25499

problems, the benefits of CT could not be ignored,particularly since falling oil prices during the 80's createdthe need for operators to seek cost-efficient alternatives inproduction operations. CT could offer the benefits ofmobility, relatively low cost, and brief job times combinedwith some of the advantages of jointed pipe, such ascirculation, utilization of pressure-activated tools, andcapability to work on live wells.

As the quality and reliability of CT and related equipmentimproved, changes such as increased tensile strength,improved welds, and larger tubing sizes further expandedthe range of jobs that could be performed with CT. CTcould be considered for services that used downhole toolssuch as inflatable packers, downhole drilling motors, andservice tools on the end of the tubing string for installingand removing downhole flow controls.

The expanding number of horizontal and highly-deviatedwells has increased the number of jobs for CT sincewireline and electric-line services rely on gravity for tooldeployment and, therefore, are not effective in highlydeviated wellbore configurations.'

Large diameter, more-reliable CT enabled tool designersto develop specialized heavy-duty, coiled-tubingworkstrings to service downhole flow controls. Thesetoolstrings form the basis for fishing-with-coiled-tubingoperations. The availability of CT services and suitablefishing tools has expanded the number of fish that can beretrieved from live wells, often eliminating the need for aworkover with a rig or hydraulic workover unit.

COMPARISON OF WIRELINE VERSUS CT

Wireline service is readily available and is the most costeffective means of performing many well servicingoperations. In addition, numerous tools and techniqueshave been developed for wireline fishing operations, andwireline operators with invaluable experience in fishingprocedures are available. However, wireline is limited bywell configurations that must either be straight or deviatedless than 60 degrees from vertical. Increased well deviationlimits the ability to jar effectively and can create problemswith tool transport.

Sand and debris on top of a fish can prevent a wirelineconveyed service tool from effectively reaching and

latching the fish; in addition, there is a practical limit tothe amount of sand that bailers can remove since trips toempty the bailer may allow more debris to settle on top ofthe fish.2 If a CT unit is needed to circulate debris off thefish, the unit should be used for the fish retrieval operationalso since these operations can be performed concurrently.

CT has three major advantages over wireline for fishingoperations:

• It has the capability to circulate various washfluids, including nitrogen and acid, at highpressures to wash, jet, or dissolve sand, mud,scale, and other debris off the top of the fish.

• It has the capability to generate large axial forcesin straight or highly-deviated wells for jarringand/or pulling a fish that is too heavy for wireline.

• It can perform the above operations concurrently.

The breaking strength difference of wireline and CT isillustrated in Figure 1.

CT AND WIRELINE ENERGY COMPARISONS

One method used to compare the efficiency of fishing withCT to wireline is to approximate the available energy ineach system that can be utilized to deliver impact forcesdownhole. This can be done by applying the internalenergy and strain equations in the Appendix.

Tables 1 and 2 list the appropriate information to comparethe internal strain energy of CT and wireline at depths of500 ft. A graphical representation of the internal energyis shown in Figure 2.

Examination of the tables and bar graph of Figure 2 showsthat the internal strain energy, D, of CT at 500 ft is 8.32times that of wireline. Upon further review, these resultsare not surprising, considering the hangoff weight of theCT at such a shallow depth is rather insignificantcompared to the surface load applied. It should also benoted that the spring rate of the CT system is 1,723 Ib/in.This implies that the jarring force in the system willdecrease rapidly as the tubing contracts, but the initialforce or surface load is so large that the overall effect onthe internal strain energy is positive.

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SPE 25499 ROBERT L. HILTS, S. HAMPTON FOWLER, CHARLES W. PLEASANTS 3

Tables 3 and 4 list the appropriate information to comparethe internal strain energy of CT and wireline at a depth of10,000 ft. A graphical representation is also included inFigure 2.

The internal strain energy, U, for CT is again impressive,but this time it is 2.20 times that of wireline. Why thelower energy ratio as compared to both systems at 500 ft1It should be noted that the hangoff weight of the CT isconsiderable, almost 12,000 lbs. The usable force is,therefore, decreased considerably but is balancedsomewhat by the greater amount of deflection, 0, of thelonger length of tubing in the hole.

When examining the data of the wireline system, thedeflection, 0, is enormous at 300.8 inches. This, alongwith the extremely low mass and weight of the wire,explains the large increase in internal energy of this systemas compared to the wireline system of 500 ft. This, inturn, also explains how the energy level of the wirelinesystem has gained on that of the CT system but overall isstill considerably less. With such a large deflection, thespring rate, k, would be expected to decrease significantly,and this is indeed the case.

This data is an indication of the maximum amount ofenergy available in a particular system; how this energytranslates into jarring force will depend upon such factorsas the jar stroke, stem weight, and whether an acceleratoris introduced to the system. This data, however, alongwith the benefits of downhole circulation and ability to usethe tubing as a transportation medium for downhole toolsin highly-deviated and horizontal wells does help supportthe fact that CT provides an excellent option forperformance of fishing operations and deserves highconsideration.

SERVICE TOOLS

CT requires a specialized toolstring designed to takeadvantage of the tubing's flow and pressure capabilities.While wireline relies on speed or wire strain to createimpact forces, CT can also utilize large axial forcesbecause of its high tensile strength.

The toolstring used for CT fishing may vary byapplication; however, a typical toolstring is shown in

Figure 3, and a discussion of the various componentsfollows. 3,4

CT Connector - This component is the crossover betweenthe CT and toolstring. The CT connector must bedesigned to withstand the working pressure and tensileloading capabilities of the tubing string. A thread-onconnector, appropriate for small diameter tubing, is shownin Figure 4. New higher-strength slip-type connectordesigns are now available for 2-inch and larger 0.0.tubing that eliminate the need for threading of the CT.S

This type of connector is also shown in Figure 4.

Emergency Disconnect Sub - The emergencydisconnect sub is used in the event the toolstring becomesstuck and cannot be released. A ball is circulated throughthe tubing string to the disconnect sub, and activates therelease mechanism. This feature may also be used torelease a fish suspended in a blowout preventer (BOP) atthe surface in order to rig down the CT injector and rig upthe additional lubricator and wireline for recovery(Figure 5).

Back Pressure Valve - This is basically a check valvethat allows flow through the CT and into the well but willnot allow back flow into the tubing. In the event of asurface leak in the tubing string, this valve will prevent theuncontrolled release of well fluids at the surface above theBOP stack (Figure 6).

Ported Knuckle Joint - Because of the curvature in theCT, the ported knuckle joint is needed to allow thetoolstring to flex without the influence of side loadings.This curvature is especially prominent near the end of thetubing string, where there is insufficient hanging weight tostraighten the tubing string. When fishing in largerdiameter wellbores, the ported knuckle joint will alsoenable the fishing tools to follow the low side of the holewhere the fish is most likely to be located (Figure 7).

Accelerators - Accelerators that employ a helical springto store the energy necessary to activate the jars are usedto accelerate the weighted stem to a high velocity to createimpact loads at the fishing or service tool. It is notuncommon for jar 'up' and 'down' accelerators to beincluded in the CT fishing toolstrings, particularly whenused in shallow-depth, highly-deviated or horizontalapplications (Figure 8).

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Weighted Stem - The weighted stem provides the massrequired to impart high impact loads to the fish when usedin conjunction with the jars and accelerators (Figure 9).

Hydraulic Jars - The hydraulic jars are the time-delaydevices that allow the up or down accelerators to fullyextend or contract before releasing. The jars also containthe necessary stroke to allow the weighted stem toaccelerate to a high velocity to insure a high impact forceis transmitted to the fish. It is not uncommon for 'up' and'down' jars to be made up into fishing toolstrings(Figure 10).

Fishing or Service Tools - The appropriate tool for thedesired operation is attached below the jars. These toolscan be overshots, tapertaps, spears, wireline pulling tools,junk baskets, and custom-designed hydraulically-actuatedrunning and pulling tools (Figures 11 & 12).

SERVICE TOOLS UNDER DEVELOPMENT

New systems are now being developed that will allow thedeployment of video equipment on CT.6

•7 Downhole video

technology is not new to the petroleum industry in electricline applications; however, restrictions posed by cabledeployment prevent the camera from being transported intohighly-deviated and horizontal wells. CT-deployed videoequipment will further facilitate fishing operations inapplications with deviated well configurations.

Another tool undergoing development is the downholeforce generator.8 This device takes advantage of theinternal pressure capabilities of CT to deliver large tensileand compressive forces downhole. These forces can beused to shift sleeves and to set and retrieve downhole flowcontrols. The downhole force generator will beparticularly advantageous in highly deviated and horizontalapplications where friction limits the amount of force thatcan be delivered to the end of the tubing string.

PRE-JOB PLANNING

The following steps should be taken in pre-job planning tomaximize the economic benefits of CT in fishingoperations:

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• Obtain an Accurate Description and Historyof the Fish

It is important for the operator to assess jobrequirements by thoroughly reviewing the joblogs, impression blocks, mating parts, and similarequipment. Access to well schematics anddimensional data for a known fish can save timeon the well site; knowledge of conditions orreasons the fish remained in the wellbore can alsofacilitate planning. For example, if scale in theproduction tubing caused the loss of wireline tools,removal of the scale prior to actual fishing wouldoptimize operational efficiency.

• Obtain Follow-Up Information Based on InitialFindings

Wireline drift runs and impression block runsprovide additional information necessary to finalizefishing strategy. Downhole video cameras canprovide an invaluable source of informationconcerning location, condition, and orientation ofthe fish that can save days of fishing time on thewell site. 6

• Take Advantage of the Benefits of Wireline

In certain fishing jobs, wireline used inconjunction with CT can shorten the overall jobtime. Wireline's fast rig-up and trip speeds allowdrifts, impression blocks, and wire retrieval toolsto be run quickly and efficiently. Wireline runs tobait the fish (gripping the fish with a service toolthat can be purposely left in the well andsubsequently engaged) can be accomplished morequickly than those done with CT. Wireline issensitive to small changes in weight indicatorreadings; thus, it is useful in locating the top ofwire, tight spots, or tubing leaks that cannot bedetected with CT.

It is preferable to consider CT unit personnel withprior wireline and wireline fishing experience foractual operation of these procedures as theirknowledge of the tools and techniques in variousfishing situations can maximize the efficiency ofthe operation.


• Prepare a Contingency Plan

It is important to plan for those situations in whichthe first fishing attempts are unsuccessful or thefish separates. If possible, have a part similar.tothe one being fished available on location. Also,have adequate spare parts on hand for thedownhole tools that will be utilized, and if possibleand practical, keep a backup set of tools available.

• Test Tools and Methods Prior to Well Entry

The trial testing of special tools and/or operationson the surface prior to commencing the job on thewell site is highly advised. CT generatessignificantly higher forces than many wirelinetools are capable of withstanding. Broken tools ontop of the original fish can be harder to retrievethan the original fish.

• Safety

Safety is the primary concern in all oilfieldoperations, and CT fishing, as with any live wellintervention, must be performed with caution.9

The toolstring should include a hydraulicdisconnect and a minimum of one back pressurevalve. The CT BOP stack should be thoroughlyinspected, tested, and redressed as required priorto arriving on the well site. The injector must beanchored securely to prevent movement orswaying during the jarring operation as movementcan place undesirable bending loads on thewellhead equipment. It is advisable to flange allsurface connections.

SURFACE RIG-UP

The primary considerations are safety and the removal ofthe fish (once it has been pulled to the surface) in planningthe surface rig-up for CT fishing. As previously stated, allwellhead connections should be flanged, and the injectormust be firmly anchored with guy wires.

Surface equipment rig-ups will vary from job to job as willthe fish they are attempting to retrieve. Following is abrief description of a typical rig-up that has been used

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successfully for removing long fish from the wellbore ofkeeping the rig-up height at a minimum.

A flanged wireline BOP is connected directly to the tree.This wireline BOP is used to hold the fish that has beenbrought to the surface if it is too long for the availableriser. Above the wireline BOP is a four-foot flanged riserwith a gate valve. Above the gate valve is sufficientflanged lubricator to cover the fishing tool workstring,followed by the CT BOP stack, and injector (Figure 13).

The advantage of this rig-up lies in how the fish isretrieved at the surface. A typical fish retrieval sequencewould be as follows:

• Hold the fish with the wireline BOP

• Use the CT hydraulic disconnect to release the fishbelow the gate valve

• Lift the CT and close the gate valve

• Rig down CT, and rig-up wireline with alubricator long enough to cover the entire fish

An alternative to using the above sequence uses aspecially-sized hanger sub below the CT hydraulicdisconnect sub, which can be held and sealed by acombination pipe and slip ram BOP. The fish can then belocated across the combination BOP, followed by theclosing of the pipe and slip rams; the pressure above theBOP is then bled off. After insuring that the rams havesealed, the hydraulic disconnect is used to release the CTfrom the fish. In the event that the fish cannot be fullysealed off, or if it is extremely long, the well must bekilled before the fish can be removed.

On some offshore rig-ups, the distance from the tree to theplatform deck or rig floor will provide enough distance tocover the toolstring and fish with a riser as shown inFigure 14.

ADDITIONAL JOB CONSIDERATIONS

Pulling Tools

Any pulling tool run on CT should be designed to releaseeasily in the event the fish cannot be retrieved. It may be


difficult to shear the pins in a "d9wn~to-release" pullingtool using CT, particularly if "down" type accelerators andjars are not employed. However, there are several typesof pulling tools designed for use on CT that can easily bereleased by using the available pressure in the tubing string(Figure 11) or by simply slacking off the tubing weight.

The pressure-release-type tools are disengaged bycirculating a ball to the tool via the tubing string or bypumping fluid at a high enough flow rate to create thenecessary pressure differential to activate the pulling tool'srelease mechanism. Mechanical-type pulling tools, such asovershots and spears, can be released by slacking offtubing weight, which activates the tool's ratchetmechanism. This allows the pulling tool to cycle betweenthe "catch" and "release" modes.

CT Fatigue

Low-cycle fatigue can result from the CT passingrepeatedly over the injector tubing guide (gooseneck)during the jarring operations. The effects of low-cyclefatigue are well known and are a function of the internalpressure of the tubing, the radius of the tubing guide, andthe radius of the pipe on the reel. 10 The higher the internalpressure of the tubing and the smaller the radius of thetubing guide or reel, the shorter the predicted life of theCT will be.

When jarring for an extended period of time, it may benecessary to increase the bend radius to reduce the effectof low-cycle fatigue. The radius can be increased byopening the tubing guide, spooling additional tubing fromthe reel, setting the reel brake, and using a crane tosupport the free arch formed by the additional CT.

Depending upon the equipment and internal tubingpressure, attempts to retrieve the fish are normally limitedto 50 to 150 jarring cycles. If the fish has not beenreleased, the CT should be removed from the wellbore,and several hundred feet of tubing removed prior toresuming the fish retrieval operation. The removal of asegment of tubing limits the number of jarring cycles thatone section of CT receives; this, in turn, limits the fatigueof the tubing. If severe swelling of the CT has occurred,the entire reel of tubing should be replaced.

Large Debris

When the top of the fish is expected to have large debrissuch as metal cuttings, cement, or scale that cannot beeasily circulated to surface, a junk basket may be run aspart of the bottomhole assembly. A junk basket has alsobeen effective in picking up segments of broken pullingtools.

Pulling Methods

Prior to latching the fish, circulation of a high-viscositypill may be used to assist in cleaning debris that couldhinder the fishing operation from the hole. When the holehas been swept clean, accurate pick-up and slack-offweights can be performed and recorded. Once the fish hasbeen engaged, overpull should be limited to 80% of thetubing yield strength. This limit should be downrated iffatigue of the CT string is expected because of extensiveand repetitive service.

In a fluid-filled well, one method to increase the overpullavailable at the fish is to displace the CT with nitrogen,which provides the maximum buoyancy effects. However,displacing the tubing with nitrogen will also increase theCT internal pressure at the surface, thereby decreasing thefatigue life of the tubing. Because of compressibility ofthe nitrogen, this method can also cause potential problemsat the surface in the event of a tubing failure above theBOP stack.

Severelv-Stuck Fish

Malfunctioned lock mandrels, corrosion, sand, and finescan result in stuck fish that can require nearly the physicallimits of the CT string to release. In addition, repeatedjarring in one section of the coil weakens the tubing bycausing low-cycle fatigue as it passes back and forth acrossthe gooseneck of the injector.

The development of 100,000 psi high-strength CTincreases the tensile force available for pulling and/orjarring. The cycle life of high-strength CT is longer thanthat of typical 70,000 psi CT and, accordingly, can beadvantageous in jarring operations. 10 The use of highstrength tubing is also beneficial when fishing in wells thatare deep, have long horizontal sections, or require highpressure circulation.

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Junk Baskets and Plugs in Horizontal Wells

In vertical wells, wireline is often used to run a gauge ringand junk basket below the production-packer setting depthto insure the wellbore is to size and relatively free fromdebris. Wireline may also be used to set a plug in thetailpipe below the packer prior to landing the tubing forcirculating the packer fluid into the well. In applicationswhere the production packer is set in the highly-deviatedor horizontal section of the wellbore, CT can be used forrunning the gauge ring and junk basket or setting andretrieving plugs in the tailpipe.

Openhole Fishing

Retrieving fish that have been dropped into the openholecan be particularly difficult when considering washouts,doglegs, and fill that can make locating and latching thefish nearly impossible in some cases. The situation isaggravated by the fact that the toolstring usually must passthrough smaller ID tubing above the openhole.

Use of a downhole video camera can facilitate preplanningfor this type of job by determining the location andorientation of the fish as well as the ability of a wireline-or CT-conveyed fishing tool to latch the fish.? .

CASE HISTORIES

The following case histories provide data concerning usageof specific fishing techniques and how their usageaccomplished successful retrieval in actual applications.

Ten-Year-Old Plug Stuck in a Landing Nipple

The operator needed to log a well below a wireline plug,which had been stuck in the tailpipe landing nipple for 10years. The well was producing through perforations in thetubing above the plug. The plug was covered with fill,and previous wireline attempts to retrieve the plug hadbeen unsuccessful.

CT washed down to the plug and latched the equalizingprong. Repeated heavy jarring did not successfully freethe prong. Acid was spotted on top of the plug, andcontinued jarring resulted in damage to the pulling tool.The tool was replaced, and the CT was displaced withnitrogen to increase the jarring force available at the fish.

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Jarring continued, and the prong was successfully releasedand retrieved. The plug mandrel was also released andretrieved, thereby completing the fishing job.

In this case, the success of this fishing job can beattributed to the ability of CT to wash debris and generatehigh impact loads.

CT & Wireline Utilized to Recover Lost Wire

While attempting to set a plug below the packer in the nogo nipple at 9,700 ft, the wireline operator lost jarringaction and parted the wire, resulting in 7000 ft of .108inch wire being left in the well. It was determined thatiron oxide and iron sulfide, which were present in thewellbore, could have contributed to the loss of the wireand tools.

The .108 wire was fished using 3/16" braide<:i line towithin 200 feet of the plug where scale had settled out intoa solid bridge. CT was rigged up with a small 0.0.bottomhole assembly and a high pressure jetting nozzle towash down past the top of the wire and remove the scalefill. On the first pass, 100 feet of progress was made pastthe last known top of the wire. Wireline was subsequentlyable to recover the exposed wire.

A second CT pass was made which cleaned down to theplug, and the last of the wire was recovered with wireline.A pressure test determined that the plug was set andholding. A final cleaning trip was made to clear thetubing, and the well was turned over to operations.

In this case, CT was successfully used in conjunction withwireline to recover lost wire.

Electric Line Tooistring With Bridge Plug and SettingTool Stuck in Production Tubing

A bridge plug was being run below the packer on a subseawell to perform a workover when the toolstring becamestuck in the 3 1/2" tubing at 10,000 ft due to iron oxideand iron sulfide scale. Attempts to free the plug resultedin the electric line being pulled out of the rope socket.Wireline fishing attempts were unsuccessful.

CT and high pressure jetting techniques were used toremove the scale down to the top of the fish. A CT


fishing toolstring with an on-off overshot were run butcould not latch the fish. A wireline impression block wasutilized and showed a clean fishing neck. Wireline wasrerun and engaged the fish but could not release the plug.The overshot was modified. for a larger catch and run onCT, which successfully latched the fish, jarred it free, andtransported it to the surface.

In this case, CT jet cleaning removed the scale that keptwireline from locating the fish. The high impact andpulling capabilities of CT were attributed with the successof this job.

Drift Bar Stuck in the 1.0. of a Wireline RetrievableSubsurface Safety Valve

During wireline drifting of a well, a fluted drift bar, toolarge to pass through the I.D. of the wireline retrievablesubsurface safety valve, became stuck in the valve andlock mandrel. Wireline attempts using both wire and3/16" braided line to retrieve the drift bar wereunsuccessful.

An overshot was used to engage the stuck drift bar, sincethe original fishing neck had been damaged by previouswireline jarring. Pulling tools, used to engage the externalfishing neck on the top of the overshot, broke upon heavyjarring by the CT. An additional overshot was modifiedto include an internal fishing neck on top, and was plantedon the fish using wireline. A pulling tool was used tolatch the overshot, and subsequent heavy jarring by CTbroke the skirt on the overshot. A heavy wall skirt wasdesigned for the overshot, which was rerun and latched thestuck drift bar. Repeated heavy jarring pulled the stuckdrift free from the subsurface safety valve.

This job illustrates the need to have spare parts and toolsas well as alternative plans available if the primaryapproach should fail.

Five Wireline Toolstrings and 300 Ft of Wireline inthe Wellbore

Improper assembly of wireline pulling tools would notallow the tools to release as designed, resulting in fivetoolstrings and 300 ft of wireline abandoned on top of asubsurface safety valve. The fish included the followingtoolstrings:

• 1.875 inch slickline running tool and toolstringstuck in the safety valve

• 2-inch pulling tool and toolstring latched to firstfish

• 2-inch wiregrab and toolstring hooked into a ballof wire above the second fish.

• Pulling tool and toolstring latched to the third fish

• 2-inch pulling tool and toolstring latched to thefourth fish

The total job took five days of fishing with CT andwireline. Extensive CT jarring was employed until thepulling tool of toolstring number 4 parted. Wireline wasused for drifting and to remove wire as necessary.Continued jarring with CT and wire removal by sIickiineresulted in all of the fish being removed from the well andsubsequent installation of a new safety valve.This case history again demonstrates the advantages ofwireline used in conjunction with CT to provide the mosteffective means for a successful fishing operation.

Drift Runs and Plug Setting in Highly-Deviated Wells

Using the CT workstring and a specially designed junkbasket, highly-deviated wells were drifted to the packersetting depths. The junk basket was designed with a barrelsection and, therefore, can pass casing and cementingcollars. CT-conveyed plugs were set and retrieved usingthe hydraulically-actuated service tools in well deviationsbetween 60 and 85 degrees.

Wireline Toolstring Dropped in the Rathole Belowthe Packer

A twenty-foot long, I-II2-inch wireline toolstring wasdropped into the cased rathole below the packer. With thefish in place, the well could not be logged below thepacker. The well was deviated 28 degrees at the fish,which was covered with fill. Wireline was unable tolocate the fish due to the fill.

CT washed down to the toolstring and latched the fish.After the latching operation, gel was pumped through theCT to circulate the sand out of the bottom of the well.

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The fish was pulled to the surface, and the well wassuccessfully logged.

The success of this job can be attributed to CT's ability towash and circulate, which allowed well c1eanout to beperformed in conjunction with a fishing job.

Wireline Plug Covered With Drilling Mud

After a drilling rig successfully set a production packer, aplug was set in the tailpipe by wireline. While circulatingout the hole, diesel mud had settled out above the plug.Wireline attempts to latch the plug and bail the mud wereunsuccessful. A CT unit was then brought on site andpositioned on the drilling rig. A specially-ported pullingtool was used to successfully wash away the mud, allowingthe plug to be released and retrieved.

CT's fast rig-up and trip speed saved a considerableamount of drilling-rig time, which would have entailedpulling the production tubing, washing down to the plug,retrieving the plug by wireline, and re-running theproduction tubing.

CONCLUSION

CT can be used to effectively remove fish from live wellswhere wireline alone has failed. Previously, a workoverwould have been required to clean the well and retrieve thedownhole tool. The use of preplanning, wireline, and CToperators that are experienced in fishing can reduce jobtime and increase the chance of success when utilizing CTfor jarring and retrieving.

The use of downhole video cameras, high strength tubing,and downhole force generators will enhance the capabilitesof CT systems when used in fishing operations,particularly in highly deviated and horizontal wellapplications. The development of new state-of-the-artservice tools such as these will promote expansion of CTtechnology and further enhance its ability to support fieldservice needs.

ACKNOWLEDGEMENTS

The authors with to thank the management of OtisEngineering Corporation for their permission to publishthis paper. The authors also wish to thank A. Keith

McNeilly of Otis Engineering Corporation and A. KarimHedjazi, Nazzeer M. Gazaq, and Amin H. Nasser ofSaudi-Aramco for their valuable contributions to coiledtubing fishing.

REFERENCES

1. Moore, S.D.: "The Coiled Tubing Boom," PetroleumEngineer International (April 1991) 16-20.

2. Mullin, M.A., McCarty, S.H., and Plante, M.E.:"Fishing With 1.5 and 1.75 Inch Coiled Tubing at WesternPrudhoe Bay, Alaska," paper SPE 20679, presented at theInternational Arctic Technology Conference, Anchorage,AK, May 29-31, 1991.

3. Fowler Jr., S.H., and Pleasants, C.W.: "Operationand Utilization of Hydraulic-Actuated Service Tools forReeled Tubing," paper SPE 20678 presented at the 199065th Annual Technical Conference & Exhibition of SPE,New Orleans, LA, September 23-26.

4. Walker, E.J., and Schmohr, D.R.: "The Role ofCoiled Tubing in the Western Operating Area of thePrudhoe Bay Unit," paper SPE 22959, presented at theSPE Asia-Pacific Conference, Perth, Western Australia,November 4-7, 1991.

5. Robison, C.E., and Cox, D.C.: "Alternate Methodsfor Installing ESP's," paper OTC 7035, presented at the24th Annual Offshore Technology Conference, Houston,TX, May 4-7, 1992.

6. Cobb, C.C., and Schultz, P.K.: "A Real-Time FiberOptic Downhole Video System," paper OTC 7046,presented at the 1992 24th Annual Offshore TechnologyConference, Houston, TX, May 4-7, 1992.

7. Rademaker, R.A., Olszewski, K.K., Goiffon, J.1.,and Maddox, S.D.: "A Coiled-Tubing-Deployed DownholeVideo System," paper SPE 24794, presented at the 199267th Annual Technical Conference & Exhibition of SPE,Washington, DC, October 4-7.

8. Kilgore, M.D.: "New Muscle for Coiled Tubing,"paper OTC 7034, presented at the 1992 24th AnnualOffshore Technology Conference, Houston, TX, May 4-7,1992.

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9. Sas-Jaworsky, Alexander II: "Coiled Tubing:Operations and Services, Part 2: Workover Safety," WorldOil (December 1991) 71-78.

10. Chitwood, G.B., Lewis, P.C., Fowler, S.H., andZernick, W.M.: "High Strength Coiled Tubing ExpandsService Capabilities," paper OTC 7032, presented at the1992 24th Annual Offshore Technology Conference,Houston, TX, May 4-7, 1992.

11. Shigley, J.E., and Mitchell, L.D.: MechanicalEngineering Design, McGraw-Hill Inc., New York, NY(1983) 110, 111, 132-135.

12. Blake, A.: Practical Stress Analysis in EngineeringDesign, Marcel Dekker Inc., New York, NY(l982) 52-58.

APPENDIX

INTERNAL STRAIN ENERGY, DEFLECTION, ANDSPRING RATE EQUATIONS

One way to compare the efficiency of fishing withCoiled Tubing versus wireline is to approximate theavailable energy in each system. This can be done byinvestigating the internal strain energy equation, U, foran elastic member of uniform cross section: 1I

(1) U = Fo/2

Equations (1)-(3) can be combined, which resultsin the following: II

•12

(4) U = PL/2AE = F2/[2(AE/L)] = P/2k

Where: 0F

is the axial deflection of the memberis the tensile load on the member

Deflection, 0, of an elastic member of uniform crosssection is defined by the following equation: 11

(2) 0 = FL/AE

Where: A is the cross sectional areaE is the modulus of elasticityL is the unloaded length of the elastic

member

Also of interest is the spring rate, k, of an elasticmember of uniform cross section which is defined bythe following equation: 12

(3) k = Flo = AE/L

836

SPE25499

TABLE 11.25 IN 0.0. x .095 IN W.T. CT - 500 FT

Modulus of Elasticity: 30E06 psi Maximum Surface Load: 18,OOOIbs

Tubing Weight: 5861bs Deflection, 6: 10.1 in

Internal Energy, U: 7,331 ft-Ib Spring Rate, k: 1,7231bs/in

TABLE 2.108 IN 0.0. WIRELINE - 500 FT

Modulus of Elasticity: 30E06 psi Maximum Surface Load: 1,0001bs

Wireline Weight: 15.61bs Deflection, 6: 21.5 in

Internal Energy, U: 881 ft-Ib Spring Rate, k: 45.8lbs/in

TABLE 31.25 IN 0.0. x .095 IN W.T. CT - 10k FT

Modulus of Elasticity: 30E06 psi Max. Surface Load: 18,0001bs

Tubing Weight: 11,7201bs Deflection, 6: 72.9 in

Internal Energy, U: 19,068 ft-Ib Spring Rate, k: 86.2lbs/in

TABLE 4.108 IN 0.0. WIRELINE - 10k FT

Modulus of Elasticity: 30E06 psi Max. Surface Load: 1,OOOIbs

Wireline Weight: 311.1 Ibs Deflection, 6: 300.8 in

Internal Energy, U: 8,634 ft-Ib Spring Rate, k: 2.29lbs/in

837

SPE25499

TENSILE STRENGTH COMPARISONSWIRELINE AND COILED TUBING

.092 IN WL

.108 IN WL

1.25 X .095 IN CT

1.50 X .109 IN CT

1.75 X .1251N CT

I. I

I II ., II

o 5 10 15 20 25 30 35 40 45 50TENSILE STRENGTH, LBS

(Thousands)

FIGURE 1 • TENSILE STRENGTH OF COILED TUBING & WIRELINE

INTERNAL ENERGY COMPARISONS1.25 X .095 INCH CT & .108 INCH WL

.108 WL, 500 FT

1.25 CT, 500 FT

.108 WL, 10k FT

1.25 CT, 10k FT

o 2 4 6 8 10 12 14 16 18 20ENERGY, FT·LBS

(Thousands)

FIGURE 2 • INTERNAL ENERGY COMPARISONS OF COILED TUBING & WIRELINE

838

SPE25499Ht---t+-- COILED TUBING·

Figure 5Coiled Tubing

Emergency Disconnect

THREAD-ON SLIP-TYPE

TYPE

Figure 4Coiled Tubing

Connectors

COILED TUBINGHr--++--- BACK PRESSURE

VALVE

Hl--I+--- COILED TUBINGCONNECTOR SUB

I.- .....

COILED TUBINGHf---H--- PORTED KNUCKLE

JOINT

COILED TUBING::::::>--H----+t--- ACCELERATOR

Hl--I+--- COILED TUBINGSTEM

COILED TUBINGH+----++---JARS

COILED TUBINGPULLING TOOL

JI+---+!---- FOR FLOW

CONTROLSFigure 6

Back Pressure ValveFigure 7

Coiled TubingPorted Knuckle Joint

Figure 3Coiled.Tubing

Tool String Schematic

839

Figure 8Coiled Tubing Accelerator

Figure 9Coiled Tubing Stem

840

SPE25499

@

Figure 10Coiled Tubing Jars

F==

e

G0

0

I ~T r

=

/

®

@

@

0

00

E>

a~

~@l

0

Figure 11 Figure 12Coiled Tubing Pulling Coiled Tubing RunningTool fOr Flow Controls Tool for Flow Controls

841

~- TUBING INJECTOR

r----I+---- STRIPPER

.-- BLIND RAMSL-.JJ----..Jfll""~ SHEA~ RAMS

g~~2j~- SLIP RAMSu;r---<L....iJ..--,U...-----JI--w"-- PIPE RAMS

RISER AS REQUIRED~--- TO COVER FISHING

TOOL STRING

J~~-- GATE VALVE

~--- 4" FLANGED RISER

n-r----nit=:J£11..,.f-- WIRELINE BOP

U~---- TREE CONNECTION

Fig. 13Land Well Coiled Tubing

Fishing Job Rig Up Configuration

~-- TUBING INJECTOR

~--- STRIPPE~

...- BLIND RAMS",":'_":=d='t---t=b:=--':",fl...-- SHEAR RAMS

r>.'"_.:=d=1----t=b:=--':",fl...- SLIP RAMS...-- PIPE RAMS

RISER AS REQUIREDj+---- TO COVER TOOLS

AND FISH

~=fJCD=~~- SHEAR/SEAL BOP

1.....--- TREE CONNECTION

Fig. 14Offshore Well Coiled Tubing

Fishing Job Rig Up Configuration

842

spe-25499-ms fishing with coiled tubing

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