Sonatrach_Well Intervention and Workovers

8/11/2019 Sonatrach_Well Intervention and Workovers

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September October 2005abalt solutions limited - 2005

INTRODUCTION TO HYDROCARBON EXPLOITATION

WellInterventio

n&Workovers

2005 Abalt Solutions Limited. All rights reserved

Well Servicing & Workovers

Potential Well Problems

Well Servicing and Workover Techniques

Intervention Techniques

Wireline

Coiled Tubing

Hydraulic Snubbing Units

Surface Well Intervention Technique

WellIntervention&Workovers


Well Servicing & Workovers

During the conceptual design stage it is important toidentify any potential reasons for workovers and theapplicable techniques.

When reviewing the impact of well problems andWorkover techniques on the initial completion design, itis important to recognise the risk associated with that

problem and the potential consequences.

Optimising the completion design around potential wellproblems and Workover techniques is, like many otherissues, a question ofbalancing riskagainstlikelyconsequence.


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Types of Operations

Measurements

Maintenances

Workover



Types of Operations

Measurements

May involve the status of equipment

Quality of pay zones-borehole connections

Status of reservoir and well equipments etc.

Maintenances

Simple operations that can be done on a well duringproduction operations

Workovers

Heavier operations that might require the well to bekilled

Sometimes carried out with the well under pressure


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Measurement Operations

At the Wellhead

Pressure and temperatures, variation would meanmodification in production conditions.

Pressures or loss in pressures in the annulus to checkintegrity of packers, casing and production strings.

In artificial lift operations to monitor stress on rods,pumps or gas lift valves.

Safety valve testing etc.

At the Tubing

Calibrations and checks

Corrosion or deposit problems etc.

At the Bottom hole

Checking top of sediments

Production logs density, flow rate or temperature



Maintenance Operations

At the Wellhead

Routine operations such as adjusting flow rates

Opening and shutting in well.

Replacing faulty parts downstream

Periodic verification of safety valves etc

At the Tubing

Operations connected with problems of deposits,corrosions etc

Injection of inhibitors, chemicals, de-emulsifiers, antifoaming agents etc.

Operations for exchange of equipments downhole etc.

At the Bottom hole

Sand control, further perforations etc

Pumping chemicals etc.


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Workover Operations

At the Wellhead Leaks in lower master valves, tubing hanger.

Problems with SSSV control lines etc

Damaged back pressure valves and other wellhead components.

At the Tubing Casing or tubing problems/leaks

Collapsed, burst or broken pipe

Tubing partially or totally plugged.

At the Bottom hole Leaks in equipments that has seals such as packers, locators, slip

joints etc.

Gas lift valves, fish, broken rod, pumping problems

Miscellaneous faulty downhole equipment such as sensors, control

lines etc. Modification in production conditions

Restoration to pay zone bore hole conditions

Change in purpose of well

Fishing




Low Reservoir Pressure:

The reduction in reservoir pressure and hence flowratesis particularly acute in dissolved gas drive reservoirs. Ingas cap and water drive reservoirs, pressuremaintenance techniques can often offset the reduction inpressure due to depletion.

How to Solve it:

Recomplete the well with either smaller tubing orsome form of artificial lift.

Injection


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Control of Water Production:

Excessive water production can lead to a number ofproduction problems including

loss of production and eventual well death

expensive treatment and disposal costs,

corrosion and scaling.

Recovery from water drive reservoirs

Significant increase in water production

rise in water/oil contact as a result of reservoirdepletion

How to solve it:

Squeeze cementing

plugging back and re-completion




Fingering

Water migrating along a highpermeability streak.

Water Conning

water is drawn up from the

aquifer either across beddingplanes leading to coning.

How to solve it:

Reduce off take from wells

plugging back and re-completion


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Control of Gas Production:

Excessive gas production from a well can result from solution gas in theoil evolving as the pressure declines, or as a result of gas encroachmentfrom the gas cap.

With pressure decline in saturated oil reservoirs, the gas evolved acrossthe reservoir may migrate to the gas cap.

However, the gas evolved near the wellbore as the oil is produced causesan increase in gas saturation and allows the gas to be produced with theoil.

How to solve it:

High gas/oil ratios (GORs) in this case are a function of the reservoirdrive mechanism and cannot usually be remedied by a workover.

An increase in GOR can also occur from a lowering of the gas capinto the producing zone and through channels in the cement orcasing leaks. This increase in GOR can be temporarily remedied bysqueeze cementing and lowering the perforated interval.




Mechanical Failures:

Mechanical failures of tubing, casing and downholeequipment often require a workover to rectify theproblem.

Typical problems would include

casing leaks, either as a result of corrosion orcollapse,

tubing failures, packer failures and downholesafety valve failures.

How to solve it:

Replacement of downhole components by work overunits

Expandable tubular


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Primary Cement Failures:

A poor primary cement job which leaves channels behindthe casing can lead to the influx of unwanted fluids andin certain instances casing collapse.

How to solve it:

Squeeze cementing

Scab liners

Expandables




Sand Production: Failure of reservoir formations and subsequent sand

production from wellbore can cause

Erosion of tubular and components

Productivity impairment

Clogging of separators

How to solve it:

Mechanical sand control

Screens

Gravel pack

Frac pack

Expandables

Sand Management-

reservoir pressure maintenance


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Well Servicing & Workover Techniques

The most commonly utilised workovertechniques include: Wireline operations;

slickline, braided line and electric line.

Coiled tubing operations.

Hydraulic workover operations.

Remedial cementing.

Concentric workover operations.

Full rig workovers.



Wireline Operations

Technique used to operate in a producing and

injecting well by means of a steel cable, toenter, run. set and retrieve measurement tools

and instruments needed for production.


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Wireline Operations

Advantages

Work can be done inside tubing without killingthe well.

Operations performed quickly due to lightweightand mobile units.

Pay zone not damaged during operation

Relatively easy to handle, saving money andnumber of resources to operate.

Limitations

Highly skilled personal required to operate.

Risky to work in highly deviated wells

Can work in tension and moderate loads, no

rotation and circulation possible.



Wireline Operations

Classification

Checking and cleaning tubing or bottom hole

(checking corrosion, clogging, top of sedimentetc.

Carrying out measurements (BHT and Pressure,

locating surfaces, production logging etc) Running & retrieving operations (setting and

pulling SSSV, plugs, chokes, gas lift valves etc)


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Wireline Operations

Slickline. This is a solid single strand of wire, the commonest

size being 0.108in

Braided line. This wireline consists of stranded wire resulting in a

higher load capacity than slickline. Commonly usedsizes are 3/16 and 5/16in

commonly used in fishing operations where slicklinehas insufficient strength to impart the required loads.

Electric line. This consists of stranded wire and a conductor

capable of transmitting an electrical signal to thesurface.

any application where an electrical signal needs to betransmitted up or down the well.



Wireline Operations

The main functions of slickline are as follows:

Installation and retrieval of flow control equipment.

Running of pressure, temperature and flow monitoringdevices.

Cleaning the tubing.

Bailing fill.

Swabbing the well.

Fishing equipment.

Wireline units are installed on various means of transportincluding trailers, trucks, boats and barges. Units used onoffshore platforms are typically skid mounted. Thewireline is spooled on to a reel that is usuallyhydraulically driven.


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Wireline Equipment



Wireline Equipment

The minimum surface equipment required to performwireline operations is:

Wireline winch unit.

Measuring device.

Weight indicator.

Hay pulley and wireline clamp.

Stuffing box. Lubricator.

Blowout preventer (BOP).

Wireline.


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Wireline Equipment

The weight indicator displays the total load or line tension and is

critical to jarring operations to avoidbreaking the wire.

Types Hydraulic

electric

The device will also indicate restrictions in the tubing,

changes in fluid density

losses or increases in weight when setting orretrieving downhole equipment.

The hay pulley guides the wire down from the lubricator

and out parallel to the floor to the winchdrum.

The hay pulley is attached to the Xmas treevia the load cell for the weight indicator.



Wireline Equipment

Lubricator

Placed on top of the x-mas tree to allow tools to

be run into pressurized well.

Serves as intermediary between surface and

well. Lower part has quick union on end.

Common sections are 8ft long and depend uponlength of string that is going to be run.

Widespread diameters are 2 to 4and series

from 3000 to 10,000 psi.

At the base there is a bleed off valve, used

when BOP is closed


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Wireline Equipment

The wireline clamp is usedto secure the wire whenrequired e.g. when removingthe lubricator.

The stuffing box providesthe pressure seal on the wireand consists of a packing glandthat can be adjusted by meansof an external nut.

In the event that the wirebreaks and is forced out of

the packing, there is a aninternal BOP plunger that isdesigned to seal off thestuffing box.

Source:www.uniteddrilling.com



Wireline Equipment

BOP or wireline valve Located between lubricator and top of wellhead.

provides a means of well control in emergency situations. BOPscan either be single or double.

The BOP can isolate pressure with or without wire in the well. TheBOP rams have resilient seals which can close and seal around awire, without damaging or cutting the wire.

Dual BOPs are normally employed for braided line or fishingoperations.

Source: Well completions-Perrin


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Wireline Tool String

All equipment placed abovespecialized tools and run in holealong with them.

It is connected to the wire byspecial socket.

Rope Socket Threaded on its lower end and

connected to the wire by a knot Spring placed in machine cavity

acts as shock absorber.

Used to connect the tools towireline.



Wireline Tool String

Knuckle Joint Provides flexibility to the tool string in deviated

holes etc.

Prevents wire from twisting around due to toolstring dragging against wall

Jars Makes it possible to hammer with stems at end

of stroke to shear pin. Use for maintenance and fishing operations.

Mechanical jars can move upwards/downwardsby sudden pulling

Hydraulic jars allow only upward pulling

Wireline stem or sinker bars Heavy bars that allow string to be run into well

despite wellhead pressure and friction.

Aids in the jarring of tools.

Available in sizes of 2,3 or 5 feet.

Knuckle

JointMechanical Jar


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Wireline Tools

Wireline tools fall into 4 categories-

Checking and maintenance tools

Running and pulling tools

Lock mandrels, downhole tools and others

Fishing tools



Wireline Tools

Checking and maintenance tools Tools screwed directly on the bottom of

wireline tool string.

Checking and cleaning inside of tubing &bottom of well

Swaging tools Straighten tubing walls that have been

slightly deformed allowing free passage ofwireline tools

Gage Cutters Run prior to wireline operations to check the

way is clear.

Allows some deposits to be cleared. Remove corrosion, paraffin etc.

Source:

www.rebcooiltools.com


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Wireline Tools

Sand Bailers

Used to take sediment fillat the bottom of the wellor even clean the bottom

Equipped with a checkvalve

Mechanical orhydraulically activated.

Scratchers

Used to clean the insideof tubing.

Source:

www.rebcooiltools.com



Wireline Tools

Running and Pulling tools Specialized tools for pulling and retrieving downhole tools.

Downhole tools are attached to the tool string by means of thestandard landing and fishing heads located in the upper partof each tool

Running tools

Run and set downhole tools in well. Holding on to them by retainer pins and gripping dogs

Allow downhole tools to be landed and locked, then to freethem by jarring

Pulling tools Gripping and retrieving downhole tools from well to surface.

Gripping dogs latch onto fishing head that can be unseatedand pulled up by jarring.

Combination tools


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Wireline Tools

Source: D PERRIN



Wireline Tools

Other Tools

Locking Mandrel Carry tools screwed on under them.

Landed and locked into landing nipples integrated in thetubing or sometimes directly on tubing walls.

Equalizing subs Inserted between mandrel and plug and allows pressure

differential to be equalized across assembly before it isunseated.

Kick over tools for installing side pocket mandrels in gaslift operations

Swabbing tools to start and kick off well


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Wireline Tools

Fishing Tools Wireline cutters

Designed to cut the wire flush with ropesocket when string is stuck.

Wireline finders To find upper end of a broken wireline and

tamp it down to make it into a nest.

Bell shaped and very close to tubingdiameters

Wireline grabs Serve to catch wire and bring it to surface.

Consist of 2 or 3 branches with teeth anddiameter corresponding to inside tubing.

Impression blocks Identify shape and condition of the head

of fish Bell shaped and filled with lead

Overshot Allows broken equipment to be fished. Bowl equipped with a grapple (basket)

that latches onto head of fish.

Wireline

grab

Impression

block

Overshot



Electric Line

The primary use is

Cased-hole Formation Evaluation

Production Logging.

Perforating, setting bridge plugs and packers etc.

Production logging is the term used for any surveywhich is run to evaluate the nature and behaviour offluids in the well during production or injection.

The applications of production logging include:

Well test evaluation.

Determining reservoir characteristics.

Evaluating completion efficiency.

Identifying unwanted fluid flow eg thief zones.

Reviewing stimulation treatments, before andafter.


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Coiled Tubing Equipment




Safety Assembly Stripper with sealing

elements and stack ofsafety rams.

Stripper located above BOP,sealing element actuated

hydraulically at a pressurethat depends on wellheadpressure.

BOP Stack consists of

Pipe Rams-close and seal ontubing

Slip rams-hold the tubing

Shear rams-cut the tubing

Blind rams-total closureover cut tubing


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Surface equipment Power pack consisting of diesel engine driving

hydraulic pump required for all equipment.

Control cab with control unit, gages and warninglights needed to operate and monitor.

Hydraulic crane or mast to retrieve safetyassembly and injector head.



Standard Coiled Tubing Operations

Coiled tubing units are routinely used for the followingoperations:

Nitrogen lifting.

Sand lifting.

Cleaning out the wellbore utilising a downhole motor.

Circulating fluids.

Drill stem testing (DST).

Sand control.

Corrosion inhibitor placement.

Spotting acid, Spotting cement.

Coiled tubing conveyed electric line services.

Inflatable bridge plugs.

Fishing operations.


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Nitrogen Lifting

Pumping nitrogen down coiled tubing to reduce thehydrostatic head of the well fluids is utilised in a numberof well operations.

Lifting unstable wells and circulating out completionfluids following a workover are common applications.

The injection rate required to bring on the well is afunction of the pipe size, depth, fluid characteristics andreservoir performance.

Coiled tubing can also be used to provide the requiredunderbalance prior to perforating.



Sand Lifting

Coiled tubing can be used to clean out sand fill

from sumps that has occurred duringproduction or as a result of hydraulic fracturing

operations.

Coiled tubings ability to maintain circulation

while running in or pulling out of hole make itideally suited for this application. If possiblesand lifting should be performed with the wellflowing.

This may alleviate the need for injecting gel,although cross linked polymer is usuallyinjected.


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Cleaning Out with DH Motors

This technique is utilised when the deposits inthe well are compacted or cemented and is

particularly useful in the removal of insolublescale deposits.

A downhole motor is used to drill out the

deposit which is then washed to the surface.

The downhole motor operates on the Moineauprinciple which utilises fluid being forced

through a progressive cavity to supply therotational power.



Clean Out


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Circulating Fluids

Coiled tubing obviously provides a convenientand economic means of circulating fluids and is

used for such varied purposes as circulating killfluid, washing drilling mud, and removingparaffin and salt using hot oil or water.



Drill Stem Testing

Coiled tubing is often used as a means of artificial lift toassist wells which will not flow naturally during DSTs.

Two methods are used, downhole jet pumping andnitrogen gas lift.

The jet pumping method utilises the coiled tubing toboth locate the jet pump module in a landing nipple

and subsequently convey the power fluid. The powerfluid is usually water, although a combination of waterand nitrogen can be used for low GOR crudes. Heavycrude oils may also benefit from applying heat to thepower fluid.

The jet pumping technique is most appropriate forcrudes with an API gravity of 12 or less.

Nitrogen gas lifting is more suitable for the higher APIcrudes.


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Sand Control

Limitations on pump pressure and rates limit thisapplication to shallow wells less than 6000 ft.

Both resin coated sand and water activated plastic can bepumped with coiled tubing.

To place water activated plastic:

CT is run in the hole to the interval to be treated, andthe well fluids are circulated out to diesel. With thewellbore free of water, the plastic is pumped throughthe coiled tubing with the annulus shut off.

After the plastic is squeezed into the formation, the

coiled tubing is shut in for 12 to 24 hours withsufficient wellhead pressure to prevent backflow ofthe plastic from the formation.



Corrosion Inhibitor Placement

Coiled tubing has been used in conjunction with

an inhibitor valve to atomise corrosion inhibitorand coat the tubular on low rate gas wells with

potential carbon dioxide corrosion.

However, in many cases the use of inhibitor to

prevent corrosion has not proven to be cost-effective.


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Stimulation

Coiled tubing is ideally suited for the selective placement(spotting) of acid and can be used in a number ofapplications, including opening perforations anddissolving acid soluble scale deposits.

Using coiled tubing in this manner avoids having tobullhead the well. Coiled tubing allows acid to becirculated across the perforations and take the returnsback up the tubing.

In this way smaller amounts of acid can be used at lowerpressures and the contact time with the productiontubing is reduced.



CT Conveyed Electric Line Services

Coiled tubing provides a convenient means of

obtaining the functionality of electric line inhighly deviated and horizontal wells.

The system can be adopted in both cased and

open hole. Coiled tubing has certain

advantages over other systems in that nodownhole wet connections are required and thetools are less prone to damage.


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Inflatable Bridge Plugs

Inflatable bridge plugs can be run through on coiledtubing, set in production liner and subsequentlyretrieved.

The bridge plugs, manufactured by Lynes and Baker OilTools, consist of an inflatable element that is set bypumping down the tubing and a hydraulic disconnectwhich is activated by dropping a ball down the tubingand pressuring up.

The tool has the advantage of being able to pass throughrestrictions in the tubing and set in relatively largediameters.



Fishing Operations

Coiled tubing fishing techniques are provensuccessful, especially in the recovery of fishburied under sand, cement or scale.

Fishing with coiled tubing allows fill to becleaned out and the fish washed over andlatched during the same operation.

Application of this technology has potential inremote or offshore locations where rigavailability is a problem or in cases where theCTU is already available on site.


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Remedial Cementing

Remedial cementing uses various techniques toplace small volumes in specific targets. The

type of operations fall into two categories:

Cement squeezes, where cement is squeezedunder pressure to seal perforations or defects inthe primary cement sheath.

Cement plugs, which are set to isolate part or allof the wellbore.



Remedial Cementing

Remedial cementing is usually performedduring the production phase to control thefluids entering the wellbore, or to restorepressure integrity.

Common applications include:

Recompletion or perforation squeeze.

Repairing of channels.

Repair of casing leaks.

Supplementing top of cement.

Plug and abandonment.


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Rig Workovers

Conventional rig workovers are usuallyemployed to perform the following:

Retrieving and running completion strings.

Repairing or modifying the permanent downholeequipment e.g running scab liners etc.

Changing the completion interval.



Concentric Workovers

Concentric workovers involve the use of a

smaller diameter workstring which is run insidethe permanent completion.

Concentric workover methods include coiled

tubing, HWUs and small workover rigs.

Coiled tubing and HWUs have the advantage ofbeing able to be run in the well without killing

the well.


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Hydraulic Workover Units (HWU)

A hydraulic workover or snubbing operates onthe principle that pipe can be inserted or

withdrawn from a well under pressure.

The process utilises jointed tubing or drill pipewith a hydraulic snubbing unit to run the tubing

string without killing the well, and allows smalldiameter tubing to be run through the

completion.



(HWU)

The unit has to performthree basic functions:

Feed the pipe into andout of the well in acontrolled manneragainst wellheadpressure.

Provide a seal whichmaintains integrity whileat the same timeallowing the pipe to beinserted or removedfrom the well.

Provide a means ofplugging the inside of thepipe.


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Hydraulic workover units have several advantages overconventional workover rigs and greater capability thancoiled tubing:

The workover operation can be performed underpressure and in certain cases with the well stillflowing. This eliminates the risk of formation damagein sensitive formations resulting from killing the wellprior to a conventional workover.

Mobilisation and demobilisation are shorter reducingthe overall time a well is off production.

The hydraulic workover unit is flexible, with a lifting

capacity up to 340 000 lbs, allowing it to handlerelatively large tools. The ability to rotate the pipeenables light drilling and milling work to beperformed.




The primary use for HWU was for emergency and non-routine well interventions.

This use has to some extent tarnished the reputation ofHWU, in that most of the experience has been gainedunder difficult or emergency situations.

Indeed, in many cases HWU was the only appropriate

technique to control the well. However, for some of thereasons outlined above, the HWU is now becoming thepreferred well servicing technique for certain situations.


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Current applications include:

Fishing or milling in casing.

Cleaning out cemented solids in the tubing, liner orcasing.

Drilling out bridge plugs.

Washing out frac materials.

Pressure control/well killing.

Circulating out heavy fluids.

Acidising and washing.

Running macaroni tubing to pump nitrogen in wells

where depth and pressure preclude the use of coiledtubing.

Running completions under pressure.

Sand consolidation.

Squeeze cementing or plugging back.



Hydraulic Snubbing Unit

Hydraulic snubbing units are made up from modularunits which can be easily transported and rigged up.

When locating the unit, care should be taken to ensurethat the structure or wellhead can support the weight ofthe unit together with any forces generated during thesnubbing operation. A hydraulic workover unit (HWU)

consists of the following components The hydraulic jack assembly, guide tube, window,

travelling and stationary slips, rotary table and powertongs.

The work basket and control panel.

Hydraulic power pack and accessories.

Circulating swivel, kelly hose and pumps.

BOP stack.


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BOP Stack Configuration




The main components of the BOP system areas follows:

stripper rubber is located immediately below the window and is

used for running pipe in and out of the holewithout using the stripper rams.

The stripper rubber is a solid synthetic rubberelement that can stretch as couplings etc passthrough, and maintain pressure integrity.

Allows pipe to be stripped through the rubberunder pressure.

stripper rams Should always be incorporated in a snubbing BOP.

The stripper rams provide pressure integrity atpressures above 3000 psi

Facilitates the running of downhole tools.


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Equalizing loop This loop runs from below the lower stripper ram to

below the upper ram and is used to equalize thepressure above the lower ram before opening it.

choke included in the loop to regulate the rate of

equalisation.

These chokes are changed out to suit the fluid in thewell.

Vent line ties in below the upper stripping ram and is run to

safe point away from the snubbing unit. This line is used to bleed down the pressure between

each stripper ram.




Safety Rams located below the stripper rams and are used to contain the

well pressure in the event of a stripper ram failure orchange in the stack.

Safety rams are pipe rams and the number used in thestack will depend on the well conditions and plannedoperations.

At least one set of safety rams must be controlled from thebasket.

These are the same asblind ramsused in a drilling BOP andare used to shut in the well when there is no pipe in thestack.


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