Work-over F.j.p.b
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WORK-OVER
Work-over F.J.P.B
WORK-OVER
A WORK-OVER IS, AFTER NEUTRALIZING THE WELL THE REMOVAL AND CHANGE OUT OF THE TUBING.
WHEN DO WE REQUIRE A WORK-OVER?
TUBING MIGHT BE CORRODED
RE-PERFORATION
DEEPENING THE WELL
CHANGE OUT THE TRSCSSSV
SIDE TRACK
© 2012 - IFP Training
Work-over F.J.P.B
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WORK-OVER
EQUIPMENT REQUIRED FOR A WORK-OVER
A WORK-OVER RIG (A LIGHT DRILLING RIG)
WELL NEUTRALIZING EQUIPMENT
SAFETY EQUIPMENT (BOP, MUD PUMPS, ETC)
© 2012 - IFP Training
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WELL KILLING / NEUTRALIZING
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MEANS OF ACTING ON KILLED WELLS
PREAMBLE: • NECESSITY TO "KILL THE WELL" BEFOREHAND, OR, MORE EXACTLY TO "NEUTRALISE THE WELL"
MEANS OF ACTING ON KILLED WELLS: • DEPEND MAINLY ON: DEPTH OF THE WELL, EQUIPMENT INSTALLED IN THE WELL, JOB THAT NEEDS TO BE DONE • TYPES OF UNITS: CRANE, PULLING OR SERVICING UNITS, WORKOVER RIG • CRITERIA OF CHOICE: HOISTING CAPACITY, PUMPING CAPACITY & SAFETY EQUIPMENT, POSSIBILITY OF ROTATION, ANCILLARY EQUIPMENT, DAILY COST, GEOGRAPHICAL AVAILABILITY • BEWARE, NECESSITY OF AN APPROPRIATE SPECIALISED EQUIPMENT: SPECIFIC SAFETY EQUIPMENT (BPV, GRAY VALVE, ETC.); HOISTING, PIPE MAKE UP & FISHING EQUIPMENT SUITABLE FOR SMALL DIAMETER DRILL PIPE AND TUBING; WIRELINE EQUIPMENT; ETC
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
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WELL KILLING / NEUTRALIZING
A WELL KILL IS THE OPERATION OF PLACING A COLUMN OF HEAVY FLUID INTO A WELL BORE IN ORDER TO PREVENT THE FLOW OF THE RESERVOIR FLUIDS WITHOUT THE NEED FOR PRESSURE CONTROL EQUIPMENT AT THE SURFACE.
IT WORKS ON THE PRINCIPLE THAT THE HYDROSTATIC HEAD OF THE “KILL FLUID” OR “KILL MUD” WILL BE ENOUGH TO SUPPRESS THE PRESSURE OF THE FORMATION FLUID.
WELL KILLS MAY BE PLANNED IN THE CASE OF ADVANCED INTERVENTIONS SUCH AS WORK-OVERS, OR BE CONTINGENCY OPERATIONS.
© IFP Training
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WELL KILLING / NEUTRALIZING
THE PRINCIPLE OF A WELL KILL REVOLVES AROUND THE WEIGHT OF A COLUMN OF FLUID AND HENCE THE PRESSURE EXERTED AT THE BOTTOM
P=HXGX P IS THE PRESSURE AT DEPTH H IN THE COLUMN G IS THE ACCELERATION OF GRAVITY
IS THE DENSITY OF THE FLUID (IT IS COMMON IN THE OIL INDUSTRY TO USE WEIGHT DENSITY, WHICH IS THE PRODUCT OF MASS DENSITY AND THE ACCELERATION OF GRAVITY. THIS REDUCES THE EQUATION TO: P=HX
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© IFP Training
WHERE IS THE WEIGHT OF THE DENSITY.
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 1.
REVERSE CIRCULATION:
THIS IS OFTEN THE “TIDIEST” WAY OF MAKING A PRE-PLANNED WELL KILL. IT INVOLVES PUMPING KILL FLUID DOWN THE ANNULUS OF THE WELL, THROUGH THE POINT OF COMMUNICATION BETWEEN THE IT AND THE PRODUCTION TUBING JUST ABOVE THE PRODUCTION PACKER AND UP THE TUBING, DISPLACING THE LIGHTER WELL BORE FLUIDS, WHICH ARE ALLOWED TO FLOW TO PRODUCTION. THE POINT OF COMMUNICATION WAS TRADITIONALLY CALLED A SLIDING SLEEVE, OR SLIDING DOOR, WHICH IS MECHANICALLY OPERATED BY MEANS OF WIRELINE, BUILD INTO THE PRODUCTION TUBING. AFTER A CERTAIN TIME IN THE WELL THE SSD IF HARD TO OPEN, AND THEREFOR IT IS COMMON TO PUNCH A HOLE IN THE TUBING FOR CIRCULATION PURPOSES. © IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL REVERSE CIRCULATION
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 3.
FORWARD CIRCULATION
THIS IS SIMILAR TO REVERSE CIRCULATION, EXCEPT THE KILL FLUID IS PUMPED INTO THE PRODUCTION TUBING AND CIRCULATED OUT THROUGH THE ANNULUS. THOUGH EFFECTIVE, IT IS NOT AS DESIRABLE SINCE IT IS PREFERRED THAT THE WELL BORE FLUIDS BE DISPLACED OUT OF THE PRODUCTION, RATHER THAN THE ANNULUS.
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL FORWARD CIRCULATION
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 2.
BULL-HEADING
THIS IS THE MOST COMMON METHOD OF A CONTINGENCY WELL KILL. IF THERE IS A SUDDEN NEED TO KILL A WELL QUICKLY, WITHOUT THE TIME FOR RIGGING UP FOR CIRCULATION, THE MORE BLUNT INSTRUMENT OF BULL HEADING MAY BE USED. THIS INVOLVES SIMPLY PUMPING THE KILL FLUID DIRECTLY DOWN THE WELL BORE, FORCING THE WELL BORE FLUIDS BACK INTO THE RESERVOIR. HOWEVER, IT CAN BE LIMITED BY THE BURST-PRESSURE CAPABILITIES OF THE TUBING OR CASING, AND CAN RISK DAMAGING THE RESERVOIR BY FORCING UNDESIRED MATERIALS INTO IT. (MUD, BRINE, ETC..)
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL BULL HEADING
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 4.
LUBRICATE AND BLEED
THIS IS THE MOST TIME CONSUMING FORM OF A WELL KILL. IT INVOLVES REPEATEDLY PUMPING IN SMALL QUANTITIES OF KILL MUD INTO THE WELL BORE AND THEN BLEEDING OFF EXCESS PRESSURE. IT WORKS ON THE PRINCIPLE THAT THE HEAVIER KILL MUD WILL SINK BELOW THE LIGHTER WELL BORE FLUIDS AND SO BLEEDING OFF THE PRESSURE WILL REMOVE THE LATTER LEAVING AN INCREASING QUANTITY OF KILL MUD IN THE WELL BORE WITH SUCCESSIVE STEPS.
© IFP Training
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METHODS FOR KILLING OR NEUTRALISING A WELL: "WELL KILLING"
Kill method Bullheading
Reverse Circulation
Direct Circulation Lubricate & bleed pumping&purge
Description - Kill fluid force pumped from the surface - Effluent in tubing squeezed into the formation - Kill fluid pumped from annulus - Completion fluid in annulus moved to tubing through a circulation system (SSD, GL mandrel…) - Effluent in tubing sent to stock tank at surface - Kill fluid pumped in tubing at surface - Tubing fluid moved to annulus through circulation system - Annulus fluide sent to stock tank at surface - pumping of kill fluid - surface purge of gas pressure equal to hydrostatic weight of fluid pumped after deducting gas weight
© IFP Training
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Work-Over principles & procedures Hydrostatics-hydrodynamics
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General procedure of an operation: Preamble
Note: possibly, inversion between: - steps (b, c) and step (d) - step (j) and step (k) EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
General procedure mainly function of: • Equipment installed & its condition • What needs to be done & how the operation is actually going on However, the main steps involved are: • (a): Preparing the well (before the servicing or workover unit arrives) • (b): Putting the well under provisional safe conditions • (c): Installing the servicing or workover unit • (d): Neutralising the well • (e): Replacing the Christmas tree with the BOPs • (f): Removing completion equipment • (g): Downhole operations • (h): Running in completion equipment • (i): Replacing BOPs by the Christmas tree • (j): Well start-up • (k): Moving out the servicing or workover unit
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More tricky operations (from a safety point of view) • • • •
Installing the servicing or workover unit Neutralising the well Replacing the Christmas tree with the BOPs "Unsetting" the packer
And: • Perforating or reperforating • High pressure (…) pumping • Replacing BOPs by the Christmas tree • Well start-up • Moving out the servicing unit © 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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General procedure of an operation
Preparing the well (before the servicing or workover unit arrives) : • Wireline checking • Pressure testing Possibly: • Circulating device opening
Putting the well(s) under provisional safe conditions: • Wells involved function of the installation configuration (cluster) • Placing "plugs" (downhole plug, SCSSV, BPV, etc.) & Isolating the well
Installing the servicing or workover unit:
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
• Followed by the set up and testing of pumping and return lines • Christmas tree not yet removed to be replaced by the BOPs
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General procedure of an operation (cont.)
Neutralising the well: • Volume concerned = global volume* • Workover fluid: − Brine, etc. − Safety margin
• Displacing the fluid by circulating or squeezing • Observing the well • Final neutralisation phase
Replacing the Christmas tree with the BOPs:
Volume concerned
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
• After installation of safety barriers • As quickly as possible • Followed by a BOPs test
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General procedure of an operation (cont.)
Removing completion equipment: • • • • •
Tubing safety device on the rig floor Procedure function of the type of equipment & its condition In the program, provide alternatives in case of operating difficulties Circulate as soon as possible the volume trapped under the packer Check the well's stability during all the job (take care to avoid swabbing, keep the well full & compare the filling volume with the pulled out steel volume)
Downhole operations
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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General procedure of an operation (cont.)
Recompleting the well: • • • •
Running in completion equipment Replacing BOPs by the Christmas tree Well start up Moving out the servicing or workover unit: − After (or before) the well start-up − Safety barriers in place
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Workover on depleted reservoirs
Losses and formation damage: main solutions: • • • • •
"Light" workover fluid "Temporary" blocking agents "Lost" level Suited downhole equipment* Work on a live well : coiled tubing, snubbing
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Downhole equipment suited to depleted reservoir: Example of equipment & Procedure for pulling out the tubing
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
1. A plug is set in the landing nipple of the fixed part of the disconnectable joint (beforehand a plug can also be set in the top no-go landing nipple) 2. The circulating device is opened or the production string is perforated just above the disonnectable joint 3. The workover fluid is circulated into the well 4. A BPV is set in the tubing hanger 5. The Christmas tree is removed 6. The BOPs are installed 7. The BPV is replaced by a TWCV 8. The BOPs are tested (between the TWCV and the blind rams) ; a tubing is screwed into the tubing hanger and the pipe-ram BOPs are tested against on the tubing 9. The tubing hanger is unlocked (tie-down screws) 10. The upper part of the production string is pulled out
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Workover on depleted reservoirs (cont.)
Kick-off after the workover: • No problem if an artificial lift system is in place • Coiled tubing & nitrogen, (swabbing, rocking, etc.)
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Fishing tools
Causes of fishing operation: Retrievable packer which cannot be unset, Stuck packer, Broken tubing, Unscrew string, Stuck string, Cemented string, etc.
Main tools*: • • • • •
External catch tools: Die collar, Overshot, Junk catcher Internal catch tools: releasing spear, taper tap Jarring tools: bumper sub, hydraulic jar, jar accelerator or intensifier Milling or washover milling tools Tools to unscrew the tubing: reversing tool, left-hand threading tap, back-off
• Tools to cut the tubing: section mill, jetting tool, explosive cutter,
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
chemical cutter (acid) • Safety joints (allowing the workover string to be disconnected)
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Fishing and jarring tools
Overshot
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
Releasing spear
Taper tap Bumper sub
© 2010 - IFP Training
Die collar
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Milling tools & safety joint
Milling tools
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
Section mill
Safety joints
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HYDROSTATICS
FLUIDS AT REST SUBJECTED ONLY TO GRAVITY
THE HYDROSTATIC PRESSURE BETWEEN A AND B IS DIRECTLY PROPORTIONAL TO THE VERTICAL HEIGHT Z
IN A HOMOGENOUS FLUID, IF THE TWO POINTS B AND C ARE ON THE SAME HORIZONTAL PLANE, THEN: PB=PC
Fluid of density r
© IFP Training
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HYDROSTATICS
- Fluids at rest subjected only to gravity - SI system: PHB - PHA= ρ×g × Z PHB,PHA: hydrostatic pressure in Pascal (N/m2) ρ:density of the fluid in kg/m3 g=9.81 m/s2(earth’s gravitational acceleration) Z:vertical height between A and B in metres
- Metric system:
PHB PHA
Zd 10.2
PHB,PHA: hydrostatic pressure in bar
d: density of the fluid in relation to water 10.2:conversion factor
Z: vertical height between A and B in metres
- Anglo-Saxon system: PHB - PHA= 0.052 × Z ×
PHB,PHA: hydrostatic pressure in psi
: density of the fluid in ppg (pounds/gallon) 0.052: conversion factor
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© IFP Training
Z: vertical height between A and B in feet
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HYDROSTATICS
WITH A AT THE SURFACE OF THE LIQUID WITH A DENSITY OF Ρ:PHA = 0
(IN REALITY 1ATM)
TO CALCULATE PH BETWEEN TWO POINTS, WE MUST KNOW: • THE HYDROSTATIC PRESSURE AT 1 POINT • THE VERTICAL HEIGHT BETWEEN THE TWO POINTS • THE DENSITY OF THE FLUID BETWEEN THESE TWO POINTS • IF THERE ARE SEVERAL FLUIDS OF DIFFERENT DENSITY, WE MUST KNOW THE RESPECTIVE HEIGHT OF EACH FLUID AND CALCULATE THE PRESSURE PART BY PART
HYDROSTATIC PRESSURE INCREASES WITH DEPTH (VERTICAL)
THE LIQUIDS EXERT PRESSURE. THEY WILL BE CONSIDERED AS INCOMPRESSIBLE FLUIDS. © IFP Training
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PRACTICAL CALCULATION FORMULAS
(FLUIDLIQUID WITH NO COMPRESSIBILITY)
METRIC SYSTEM
Z d Phyd (bar ) 10.2
Z: vertical depth, in metres d: fluid specific gravity / water = (fluid)/(water)
FIELD UNITS
Phyd ( psi ) fluid density ( ppg ) 0.052 vert .depth ( ft ) NB: for pressure calculations, always use vertical depths © IFP Training
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WELL KILLING / NEUTRALIZING REVERSING A WELL KILL (PUT BACK ON PRODUCTION) THE INTENTION OF A WELL KILL (OR THE REALITY OF AN UNINTENTIONAL WELL KILL) IS TO STOP THE RESERVOIR FLUIDS FLOWING TO SURFACE. THIS OF COURSE CREATES PROBLEMS WHEN IT IS DESIRABLE TO GET THE WELL FLOWING AGAIN. IN ORDER TO REVERSE THE WELL KILL, THE KILL FLUID MUST BE DISPLACED FROM THE WELL BORE.
Work-over F.J.P.B
© IFP Training
THIS INVOLVES INJECTING GAS AT HIGH PRESSURE, USUALLY N2. THE GAS CAN BE PUT UNDER SUFFICIENT PRESSURE TO ALLOW IT TO PUSH THE HEAVY KILL FLUID, BUT WILL THAN EXPAND AND BECOME LIGHT ONCE PRESSURE IS REMOVED. THIS MEANS THAT HAVING DISPLACED THE KILL FLUID, IT WILL NOT ITSELF KILL THE WELL. THE RESERVOIR FLUIDS SHOULD BE ABLE TO FLOW TO SURFACE, DISPLACING THE GAS
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WELL KILLING / NEUTRALIZING REVERSING A WELL KILL (PUT BACK ON PRODUCTION) ANOTHER WAY IS TO RUN INTO THE TUBING A COILED TUBING. ONCE AT THE BOTTOM OF THE WELL WE INJECT THE N2 INTO THE WELL BORE AND PUSHES UP THE KILL FLUID. THE KILL FLUID COLUMN BECOMES LIGHTER. IN AN OIL WELL WE MIGHT CONSIDER THE USE OF “SWABBING” EQUIPMENT. IN THIS CASE WE ARE LIFTING UP THE KILL FLUID IN ORDER THE DECREASE THE HYDROSTATIC PRESSURE. THIS METHOD SHOULD NOT BE USED IN GAS WELL, DUE TO SAFETY REASONS. AN OTHER METHOD IS BY WIRE LINE WE OPEN THE SSD BY WIRE LINE AND DISPLACE THE KILL FLUID BY A LIGHTER FLUID. (DIESEL, OR DEPENDING ON THE FORMATION PRESSURE, BRINE OR WATER) © IFP Training
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WORK-OVER PROCEDURES GENERAL GUIDE-LINES
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PHASES AND SEQUENCE OF AN OPERATION VARIES FROM ONE JOB TO ANOTHER.
IT MAINLY DEPENDS ON THE EQUIPMENT ALREADY INSTALLED IN THE WELL AND THE CONDITION IT IS IN.
IT ALSO DEPENDS ON WHAT NEEDS TO BE DONE AND HOW THE OPERATION IS GOING TO PROCEED IN PRACTICAL TERMS.
WE DISCUSS BELOW THE DETAILED STEPS WHICH ARE GENERALLY INVOLVED IN ALL THE WORK-OVER OPERATIONS © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
1.
PREPARATION OF THE WELL PRIOR TO THE ARRIVAL OF THE WORK-OVER UNIT
THIS MAINLY MEANS :
CHECKING THE STATUS OF THE WELL BY WIRELINE TECHNIQUES (CHECKING THE TUBING, PROVING THE HOLES, TAGGING SEDIMENTS, TO CHECKING THE PERFORATIONS WHETHER THEY ARE OPEN OR NOT).
CHECKING THE WELL INTEGRITY (PRESSURE TESTS OF CASINGS)
OPENING A CIRCULATING DEVICE DOWN-HOLE (SLIDING SLEEVE, BLANKING PLUG OR DUMMY FROM SIDE POCKET MANDREL) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
CHECKING THE INTEGRITY OF VALVES OF THE X-MAS TREE (PRESSURE TESTING OF VALVES)
CHECKING AND PREPARING THE APPROACH ROAD TO WELLS FOR MOVEMENT OF THE WORK-OVER RIG.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
2.
PUTTING THE WELL UNDER SAFE CONDITIONS (BEFORE RIGGING UP THE SERVICE/WORK-OVER UNITS)
THIS SAFETY PRECAUTION-CUM-OPERATION, IN FACT, SHOULD ALSO INVOLVE ALL THE NEARBY WELLS THAT MIGHT BE AFFECTED WHEN THE SERVICE/WORK-OVER UNIT IS BEING SET UP.
THE OPERATION CONSISTS ESSENTIALLY IN ISOLATING THE SURROUNDINGS FROM THE WELL PRESSURES AND KEEPING THEM UNDER OPTIMUM SAFE CONDITIONS WHILE INSTALLING THE SERVICE/WORK-OVER UNITS OVER THE WELLHEAD.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THERE ARE 3 BASIC WAYS OF ACHIEVING THIS:
BY INSTALLING PLUGS IN THE LANDING NIPPLES IN THE TUBING, WHICH ARE GENERALLY AT THE BOTTOM OF THE WELL, BELOW THE PACKER.
BY CLOSING THE SUBSURFACE SAFETY VALVE, IF THERE IS ONE.
BY SETTING A BACK PRESSURE VALVE IN THE TUBING HANGER
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
AT LEAST, 2 OUT OF THESE 3 BARRIERS SHOULD NORMALLY BE IN PLACE.
THE VARIOUS LINES CONNECTED TO THE WELLHEAD ON THE SURFACE SHOULD BE BLED OFF ANY PRESSURES AND/OR ISOLATED.
IF NEED BE, THEY CAN BE DISMANTLED.
NEARBY EQUIPMENT, THAT MIGHT BE DAMAGED, SHOULD BE COMPLETELY DEPRESSURIZED.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
3.
INSTALLING THE SERVICING OR WORK-OVER UNITS
ONCE THE WELL AND IT’S SURROUNDINGS HAVE BEEN SAFELY SECURED, THE SERVICE/WORK-OVER UNIT AND IT’S ACCESSORY EQUIPMENT LIKE TANKS, PUMPS, WORKSHOPS ETC. CAN BE SET UP .
THE EQUIPMENT IN THE SITE SHOULD BE SET UP IN ACCORDANCE WITH THE SAFETY RULES AND REGULATIONS OF THE REGULATORY BODY.
HOWEVER, THE X-MAS TREE IS NOT YET REMOVED TO BE REPLACED BY THE BOP’S © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
4.
KILLING THE WELL
A WELL IS CONSIDERED TO BE PERFECTLY KILLED WHEN THE WORK-OVER FLUID, WHOSE SP.GR. IS APPROPRIATE FOR THE RESERVOIR PRESSURE, TOTALLY FILLS UP THE WELL .
THIS MEANS THAT THE INSIDE OF THE TUBING, THE TUBING-CASING ANNULUS AND THE SPACE BELOW THE PACKER IS FILLED WITH THE WORKOVER FLUID.
THE WORK-OVER FLUID IS PREPARED IN SUFFICIENT AMOUNTS. THIS IS GENERALLY 3 TIMES THE TOTAL VOLUME OF THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PROPERTIES REQUIRED OF A WORK-OVER FLUID IS AS FOLLOWS:
TO KEEP THE WELL UNDER CONTROL BY IT’S HYDROSTATIC PRESSURE.
TO CARRY UP CUTTINGS IF DRILLING OR MILLING IS PLANNED.
NOT TO DAMAGE THE FORMATION.
NO FLUID LOSS IN THE FORMATION © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WITH THE SERVICE/WORK-OVER RIG IN PLACE AND THE WORK-OVER FLUID READY, THE NEXT SET OF OPERATIONS ARE PERFORMED AS BELOW:
THE PLUGS THAT WERE SET IN THE TUBING PRIOR TO THE MOVEMENT OF THE SERVICE/WORK-OVER RIGS, HAVE TO BE PULLED OUT.
THE WORK-OVER FLUID IS PUMPED INTO THE WELL TO DISPLACE THE TUBING CONTENTS.
THIS IS DONE EITHER BY CIRCULATION OR BY SQUEEZING.
THE WELL IS THEN PUT UNDER OBSERVATION FOR STABILITY.
KILLING OF WELL, SOMETIMES, IS CARRIED OUT BEFORE THE RIG IS INSTALLED. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
CONSIDERATIONS ON KILLING THE WELL
THE WORK-OVER FLUID USED TO KILL THE WELL, USUALLY, DISPLACES THE WELL CONTENTS BY EITHER CIRCULATION OR BY SQUEEZING.
KILLING BY CIRCULATION
EXCEPT IN SPECIAL CASES, CIRCULATION IS THE PREFERRED WAY TO KILL THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE FLUID IS CIRCULATED AS DEEP AS POSSIBLE IN THE TUBING, BUT ABOVE THE PACKER, EITHER: THROUGH A CIRCULATING DEVICE OPERATED BY WIRELINE, VIZ. BY PULLING OUT A DUMMY FROM THE SIDE POCKET MANDREL OR BY OPENING THE PORTS OF A SLIDING SLEEVE. OR THROUGH PUNCTURED HOLES IN THE TUBING OPENED UP BY ELECTRIC CABLE SHAPED CHARGES.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
A REVERSE CIRCULATION IS USUALLY THE OPTION CHOSEN FOR GAS WELLS OR HIGH GOR OIL WELLS. IN OTHER WORDS, FLUID IS PUMPED INTO THE ANNULUS WITH RETURNS THROUGH THE TUBING.
THIS METHOD ENSURES THAT OIL AND GAS ARE THOROUGHLY DISPLACED.
WITH DIRECT CIRCULATION, THE LIGHTER OIL AND GAS TEND TO MIGRATE IN THE HEAVIER WORK-OVER FLUID WHICH IS LOCATED ABOVE THEM.
ACCORDINGLY, THEIR IS NO CERTAINTY AS TO THE SPECIFIC GRAVITY OF THE WORK-OVER FLUID THAT IS LEFT IN PLACE IN THE WELL AND AS SUCH, THERE IS NO CERTAINTY REGARDING KILLING OF THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
HOWEVER, AFTER A VOLUME CORRESPONDING TO THE TUBING VOLUME HAS BEEN PUMPED IN THROUGH THE ANNULUS – AND THEREFORE AFTER OIL AND GAS HAVE BEEN PUMPED OUT OF THE WELL – DIRECT CIRCULATION IS USED TO HOMOGENIZE THE FLUIDS PRESENT IN THE TUBING AND ANNULUS.
IN CONTRAST, SINCE ANNULAR PRESSURE LOSSES ARE GENERALLY LOWER THAN TUBING PRESSURE LOSSES, WITH DIRECT CIRCULATION THE OVERPRESSURE EXERTED ON THE PAY ZONE BY PRESSURE LOSSES IS MINIMIZED.
HENCE PROBLEMS OF LOST CIRCULATION AND PLUGGING ARE ALSO MINIMIZED. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WHETHER CIRCULATION IS REVERSE OR TOTALLY DIRECT, THE CHOKE IS APPLIED ON THE RETURNS TO KEEP THE BOTTOM-HOLE PRESSURE HIGHER THAN THE RESERVOIR PRESSURE ALL THROUGHOUT THE OPERATION, THEREBY PREVENTING ANY KICKS.
WHEN THE CIRCULATION IS FINISHED, NOT ALL THE FLUIDS LOCATED BELOW THE CIRCULATION DEVICES HAVE BEEN REPLACED BY THE KILLING FLUID – SO, KILLING IS ONLY PARTIAL.
IF INJECTIVITY IS FAIR, KILLING CAN BE IMPROVED, AFTER CIRCULATION, BY SQUEEZING THE OIL AND GAS STILL REMAINING BELOW THE CIRCULATION DEVICE INTO THE FORMATION.
HOWEVER, SOME OIL & GAS IS EXPECTED TO REMAIN TRAPPED IN THE ANNULUS UNDER THE PACKER AND THE TAILPIPE.
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© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
SOMETIMES, THE WORK-OVER FLUID IS CIRCULATED AFTER SETTING A PLUG IN THE LOWER END OF THE TUBING.
AS A RESULT THERE IS NO RISK OF LOST CIRCULATION INTO THE FORMATION DURING CIRCULATION.
HOWEVER THERE IS UNCERTAINTY REGARDING WHETHER THE PLUG CAN BE PULLED OUT, ESPECIALLY IF IT GETS COVERED WITH DEPOSITS.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
KILLING BY SQUEEZING
THE SQUEEZE TECHNIQUE IS USED:
WHEN THE CIRCULATION METHOD CANNOT BE USED - FOR EXAMPLE, WHEN THERE IS A HOLE IN THE TUBING NEAR THE SURFACE; WIRELINE IS IMPOSSIBLE BECAUSE OF A COLLAPSED TUBING OR BECAUSE OF A FISH; VOLUME BELOW THE TUBING SHOE IS VERY LARGE ETC.
WHEN INJECTIVITY IS VERY GOOD – THIS IS TRUE ESPECIALLY FOR GAS WELLS.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
SQUEEZING IS DONE ONLY AFTER AN INJECTIVITY TEST – JUST TO BE SURE THAT INJECTIVITY IS SUFFICIENT.
THIS IS BECAUSE OF THE SAME DRAWBACK AS WITH DIRECT CIRCULATION – THAT IS, MIGRATION OF OIL AND GAS IN THE KILLING FLUID – GREATLY COMPOUNDED BY THE FACT THAT THE FLOW RATES WITH A SQUEEZE JOB IS OFTEN MUCH LOWER THAN WITH CIRCULATION.
IF THE INJECTIVITY TEST IS UNSATISFACTORY, IT IS NECESSARY TO MODIFY THE SQUEEZE CONDITIONS.
FOR EXAMPLE, SQUEEZE AT A LOWER FLOW RATE, PROVIDED THE TOTAL INJECTED VOLUME IS INCREASED.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FOR A GAS WELL, PERFORM A SERIES OF SQUEEZES AND BLEED OFFS AT CONSTANT BOTTOM-HOLE PRESSURE TO ALLOW THE GAS TO MIGRATE UP TO THE SURFACE WITHOUT FRACTURING THE FORMATION.
SOMETIMES, IT MAY BE NECESSARY TO ACCEPT TO SQUEEZE AT A FRACTURING RATE OR
REVISE THE PROGRAM THOROUGHLY AND USE A TECHNIQUE SUCH AS COIL TUBING OR SNUBBING JUST TO KILL THE WELL OR TO CARRY OUT THE COMPLETE OPERATION. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THIS IMPLIES THAT THE INJECTIVITY TEST HAS TO BE PERFORMED LONG BEFORE THE WORK-OVER IS DONE.
THE CHOICE OF MEANS TO BE UTILIZED AND THE WORK-OVER PROGRAMM DESIGN BOTH DEPEND ON THE INJECTIVITY TEST.
JUST AS FOR CIRCULATION, KILLING IS NOT COMPLETE WHEN THE SQUEEZE OPERATION IS OVER, AS OIL AND GAS STILL REMAINS TRAPPED IN THE ANNULUS UNDER THE PACKER AND ALL OF THE ANNULAR FLUID.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
OBSERVING THE WELL
AFTER KILLING BY CIRCULATION OR SQUEEZING, THE WELL MUST BE OBSERVED TO CHECK THAT : THERE IS NO PRESSURE IN THE WELLHEAD; THE LEVELS ARE STABLE; THERE IS NO GAS CUTTING ON THE SURFACE.
WHATEVER THE OBSERVATION TIME, THERE IS NO ABSOLUTE GUARANTEE THAT THE WELL IS STABLE.
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IT CAN VARY FROM ONE TO SEVERAL HOURS.
© IFP Training
THE TIME DEPENDS ON THE METHOD USED TO KILL THE WELL, THE WAY THE OPERATION ACTUALLY PROCEEDED AND ON OUTSIDE SIGNS OF PHENOMENA SUCH AS THERMAL EXPANSION.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
IF THE WELL SHOULD PROVE UNSTABLE, KILLING MUST BE STARTED ALL OVER AGAIN EITHER WITH THE SAME METHOD OR WITH ANOTHER METHOD.
MODIFYING THE CHARACTERISTICS OF THE CONTROL FLUID OR USE OF SPACE FLUIDS, SOMETIMES, IS QUITE EFFECTIVE.
THE WELL WILL BE UNDER OBSERVATION ONCE AGAIN FOR STABILITY.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FINAL KILLING PHASE
WHATEVER THE METHOD USED, THERE IS ALWAYS A CERTAIN VOLUME LEFT IN THE WELL WHERE IT IS IMPOSSIBLE TO PLACE THE WORK-OVER FLUID.
THIS VOLUME MUST BE CIRCULATED AS SOON AS THE COMPLETION EQUIPMENT REMOVAL OPERATIONS ALLOW.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
REPLACING X-MAS TREE WITH BOP
SINCE THE WORK-OVER FLUID IS KEEPING THE WELL STABLE, ONLY ONE MECHANICAL SAFETY BARRIER IS DEEMED NECESSARY – EITHER THE DOWNHOLE PLUG AND/OR THE SCSSV AND/OR THE BPV
THE X-MAS TREE CAN THEN BE DISMANTLED AT THE TUBING HEAD SPOOL AND REPLACED BY THE BOP, WHICH WILL BE THEN TESTED.
THIS OPERATION SHOULD BE COMPLETED AS QUICKLY AS POSSIBLE.
IT IS IMPERATIVE THEREFORE THAT ALL REQUIRED PERSONNEL SHOULD BE MOBILIZED, REQUIRED EQUIPMENT SHOULD BE IN STATE OF READINESS, APPROPRIATE HANDLING AND HOISTING EQUIPMENT AVAILABLE AND THE WELLHEAD CHECKED ETC. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
REMOVING COMPLETION EQUIPMENT
THE INSTALLED BPV OR PLUG HAS TO BE RETRIEVED BEFORE THE PULLING OUT OF THE DOWN-HOLE EQUIPMENT CAN COMMENCE.
IF THERE IS A KICK WHILE TRIPPING, IT IS NECESSARY TO BE ABLE TO CLOSE QUICKLY NOT ONLY THE ANNULUS WITH THE BOP TUBING RAMS, BUT ALSO THE TUBING ITSELF.
THE CORRESPONDING SAFETY DEVICE (KELLY COCK VALVE/ TUBING SAFETY VALVE) MUST BE ON THE WORK-OVER RIG FLOOR READY FOR USE (THREADS TO BE COMPATIBLE WITH TUBING THREADS) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PROCEDURE FOR REMOVING THE DOWN-HOLE EQUIPMENT DEPENDS ON THE TYPE OF EQUIPMENT AND IT’S CONDITION.
PARTICULARLY IMPORTANT IS THE TYPE OF PACKER –RETRIEVABLE OR PERMANENT – TYPE OF CONNECTION BETWEEN THE TUBING AND THE PACKER (SEAL ALONE OR SEAL PLUS ANCHOR).
WITH A RETRIEVABLE PACKER, AND ESPECIALLY IF THE WORK-OVER IS BEING DONE SEVERAL YEARS AFTER IT’S SETTING, IT IS OFTEN WISE TO CUT OFF THE TUBING A FEW METERS ABOVE THE PACKER BY CHEMICAL CUTTERS.
THEN, RUN IN DRILL PIPE WITH OVERSHOT, LATCH ONTO THE TUBING AND UNSEAT THE PACKER.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FURTHERMORE, WHATEVER THE KILLING METHOD, THERE IS ALWAYS A VOLUME OF OIL AND/OR GAS TRAPPED UNDER THE PACKER.
IT IS IMPORTANT TO CIRCULATE IT OUT AS SOON AS POSSIBLE – AFTER UNSEATING THE RETRIEVABLE PACKER OR AFTER STABBING OUT OF A PERMANENT PACKER.
WHENEVER TRIPPING OUT, CARE MUST BE TAKEN TO AVOID SWABBING – PARTICULARLY WHEN THE PACKER IS BEING PULLED OUT.
SECONDLY, THE WELL MUST ALWAYS BE KEPT FULL WITH WORK-OVER FLUID.
LASTLY, THE WELL’S STABILITY MUST FREQUENTLY BE CHECKED.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WORK-OVER PLAN WELLS COMPLETED WITH RETRIEVABLE HYDRAULIC PACKER
OPEN SLIDING SLEEVE OR PULL OUT DUMMY FROM THE SIDE POCKET MANDREL OR MAKE A HOLE ABOVE PACKER WITH ELECTRIC CABLE.
LOCK OPEN SUB SURFACE SAFETY VALVES
KILL THE WELL BY CIRCULATING WORK-OVER FLUID
INSTALL BPV IN THE TUBING HANGER.
REMOVE X-MAS TREE
INSTALL BOP.
REPLACE BPV WITH TWCV.(Two Way Check Valve) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
TEST THE BOP BETWEEN THE TWCV AND THE BLIND RAM; CONNECT A TUBING IN THE TUBING HANGER, CLOSE THE PIPE RAM AGAINST THE TUBING AND TEST THE PIPE RAM.
REMOVE THE TWCV.
CONNECT TUBING HANGER WITH TUBING STRING.
UNLOCK TUBING HANGER BY UNSCREWING ANCHOR BOLTS.
RELEASE PACKER BY STRAIGHT PULL/ROTATION.
CIRCULATE WORK-OVER FLUID (AT LEAST ONE CYCLE).
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GENERAL PROCEDURE OF WORK-OVER OPERATION
RECIPROCATE THE STRING TO BREAK THE SEAL TO AVOID SWABBING ACTION.
PULL OUT COMPLETION STRING.
IF IT IS NOT POSSIBLE TO RELEASE THE PACKER, CUT THE TUBING ABOVE THE PACKER, PULL OUT THE COMPLETION STRING.
RUN IN OVERSHOT WITH BUMPER SUB ON TUBING/DRILL PIPE, CATCH THE FISH AND PULL OUT. © IFP Training
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GENERAL PROCEDURE OF WOR-KOVER OPERATION
WELLS COMPLETED WITH RETAINER PRODUCTION PACKER
OPEN SLIDING SLEEVE OR PULL OUT DUMMY FROM THE SIDE POCKET MANDREL OR MAKE A HOLE ABOVE PACKER WITH THE ELECTRIC CABLE
LOCK OPEN SUBSURFACE SAFETY VALVE
KILL WELL BY CIRCULATING WORKOVER FLUID
INSTALL BPV IN THE TUBING HANGER.
REMOVE X-MAS TREE.
INSTALL BOP.
REPLACE BPV WITH TWCV.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
TEST THE BOP BETWEEN THE TWCV AND THE BLIND RAM; CONNECT A TUBING IN THE TUBING HANGER, CLOSE THE PIPE RAM AGAINST THE TUBING AND TEST THE PIPE RAM
REMOVE THE TWCV
CONNECT TUBING HANGER WITH TUBING STRING
INSTALL BPV IN THE TUBING HANGER.
UNLOCK TUBING HANGER BY UNSCREWING ANCHOR BOLTS.
DISCONNECT TUBING SEAL FROM PACKER.
CIRCULATE WORKOVER FLUID (AT LEAST ONE CYCLE) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
PULL OUT PRODUCTION STRING
RUN IN MILLING TOOL WITH CATCHER SUB, MILL THE PACKER AND PULL OUT THE PACKER OR
RUN IN MILLING TOOL WITHOUT CATCHER SUB, MILL THE PACKER AND PUSH DOWN UP TO THE BOTTOM.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
DOWNHOLE OPERATION, RECOMPLETION, REPLACING BOP BY THE X-MAS TREE AND START UP
THE TECHNIQUES ARE THE SAME AS THOSE USED WHEN THE WELL WAS ORIGINALLY COMPLETED.
HOWEVER, THE BOTTOMHOLE IS USUALLY CHECKED BEFOREHAND BY RUNNING IN A DRILL STRING EQUIPPED WITH A DRILL BIT AND SCRAPER
MOVING OUT THE SERVICING OR WORKOVER UNIT
IN THE SAME WAY AS FOR INITIAL COMPLETION, THE RIG CAN BE MOVED OUT BEFORE OR AFTER THE WELL IS BROUGHT BACK ON STREAM.
THE SAME SAFETY RULES AND REGULATIONS ARE COMPLIED WITH (ESPECIALLY SETTING PLUGS)
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GENERAL PROCEDURE OF WORK-OVER OPERATION
DEPLETED RESERVOIRS
DEPLETED RESERVOIRS POSE PARTICULAR PROBLEMS AS SOON AS THEIR RESERVOIR PRESSURE IS SUCH THAT CONVENTIONAL WORKOVER FLUIDS (BRINE, OIL BASE FLUID) EXERT A CONSIDERABLE OVERPRESSURE.
THEN THE FOLLOWING PROBLEMS ARE POSED: • LOSES MUD/ OR FORMATION DAMAGE. • WELL KICK OFF AFTER OPERATIONS.
LOSSES AND FORMATION DAMAGE
THE FIRST SOLUTION IS TO USE SPECIAL LIGHT FLUIDS, BUT BESIDES FOAM (SP.GR. FROM 0.1 TO 0.2) THERE IS YET NO FLUID READILY AVAILABLE IN THE MARKET IN THE NEIGHBOURHOOD OF THE 0.2 TO 0.8 RANGE (BETWEEN FOAM TO OIL BASE FLUIDS) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
LOSSES AND FORMATION DAMAGE
THE SECOND SOLUTION IS TO PROTECT THE FORMATION WITH “TEMPORARY” BLOCKING AGENTS.
THESE ARE USUALLY PRODUCTS THAT ARE UNSTABLE WITH TEMPERATURE OR HIGHLY SOLUBLE IN ACID.
THE PROBLEM WITH THEM IS THAT THEY ARE NEVER 100% TEMPORARY.
THE THIRD SOLUTION CONSISTS IN ACCEPTING TO WORK WITH A “LOST” LEVEL. THAT IS, WITH THE LEVEL SOMEWHERE IN THE WELL AND NOT ON THE SURFACE.
HOWEVER, THIS CAUSES SAFETY PROBLEMS AS IT IS HARD TO CHECK WELL STABILITY CONSTANTLY AND IS INCOMPATIBLE WITH OPERATIONS THAT REQUIRE CIRCULATION. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE FOURTH SOLUTION, WHEN ONLY THE PRODUCTION STRING ABOVE THE PACKER IS INVOLVED, CONSISTS IN PULLING OUT THE TUBING STRING ONLY LEAVING THE PACKER WITH A PLUG IN THE TAILPIPE INSIDE THE WELL.
THE FIFTH SOLUTION MIGHT BE TO USE A UNIT ALLOWING WORK ON A PRESSURISED WELL, SUCH AS COIL TUBING OR SNUBBING IF THEY ARE APPROPRIATE FOR THE JOB (CLEANING THE BOTTOM OF THE WELL ETC.)
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GENERAL PROCEDURE OF WORK-OVER OPERATION
START UP PROBLEMS •
THE TECHNIQUES DESCRIBED IN INITIAL COMPLETION ARE APPLICABLE AT THIS STAGE EXCEPT THAT THERE IS USUALLY NO AVAILABLE KICKOFF FLUID THAT IS LIGHT ENOUGH.
•
IN SOME CASES THE PROBLEM DOES NOT CROP UP BECAUSE THE PURPOSE OF THE OPERATION WAS TO INSTALL AN ARTIFICIAL LIFT SYSTEM OR READAPT THE OLD ONE.
•
IN OTHER CASES, IT IS VERY COMMON TO USE A COILED TUBING FOR NITROGEN START UP OR TEMPORARY GAS LIFT.
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WORK-OVER
A WORK-OVER IS, AFTER NEUTRALIZING THE WELL THE REMOVAL AND CHANGE OUT OF THE TUBING.
WHEN DO WE REQUIRE A WORK-OVER?
TUBING MIGHT BE CORRODED
RE-PERFORATION
DEEPENING THE WELL
CHANGE OUT THE TRSCSSSV
SIDE TRACK
© 2012 - IFP Training
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WORK-OVER
EQUIPMENT REQUIRED FOR A WORK-OVER
A WORK-OVER RIG (A LIGHT DRILLING RIG)
WELL NEUTRALIZING EQUIPMENT
SAFETY EQUIPMENT (BOP, MUD PUMPS, ETC)
© 2012 - IFP Training
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WELL KILLING / NEUTRALIZING
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MEANS OF ACTING ON KILLED WELLS
PREAMBLE: • NECESSITY TO "KILL THE WELL" BEFOREHAND, OR, MORE EXACTLY TO "NEUTRALISE THE WELL"
MEANS OF ACTING ON KILLED WELLS: • DEPEND MAINLY ON: DEPTH OF THE WELL, EQUIPMENT INSTALLED IN THE WELL, JOB THAT NEEDS TO BE DONE • TYPES OF UNITS: CRANE, PULLING OR SERVICING UNITS, WORKOVER RIG • CRITERIA OF CHOICE: HOISTING CAPACITY, PUMPING CAPACITY & SAFETY EQUIPMENT, POSSIBILITY OF ROTATION, ANCILLARY EQUIPMENT, DAILY COST, GEOGRAPHICAL AVAILABILITY • BEWARE, NECESSITY OF AN APPROPRIATE SPECIALISED EQUIPMENT: SPECIFIC SAFETY EQUIPMENT (BPV, GRAY VALVE, ETC.); HOISTING, PIPE MAKE UP & FISHING EQUIPMENT SUITABLE FOR SMALL DIAMETER DRILL PIPE AND TUBING; WIRELINE EQUIPMENT; ETC
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
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WELL KILLING / NEUTRALIZING
A WELL KILL IS THE OPERATION OF PLACING A COLUMN OF HEAVY FLUID INTO A WELL BORE IN ORDER TO PREVENT THE FLOW OF THE RESERVOIR FLUIDS WITHOUT THE NEED FOR PRESSURE CONTROL EQUIPMENT AT THE SURFACE.
IT WORKS ON THE PRINCIPLE THAT THE HYDROSTATIC HEAD OF THE “KILL FLUID” OR “KILL MUD” WILL BE ENOUGH TO SUPPRESS THE PRESSURE OF THE FORMATION FLUID.
WELL KILLS MAY BE PLANNED IN THE CASE OF ADVANCED INTERVENTIONS SUCH AS WORK-OVERS, OR BE CONTINGENCY OPERATIONS.
© IFP Training
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WELL KILLING / NEUTRALIZING
THE PRINCIPLE OF A WELL KILL REVOLVES AROUND THE WEIGHT OF A COLUMN OF FLUID AND HENCE THE PRESSURE EXERTED AT THE BOTTOM
P=HXGX P IS THE PRESSURE AT DEPTH H IN THE COLUMN G IS THE ACCELERATION OF GRAVITY
IS THE DENSITY OF THE FLUID (IT IS COMMON IN THE OIL INDUSTRY TO USE WEIGHT DENSITY, WHICH IS THE PRODUCT OF MASS DENSITY AND THE ACCELERATION OF GRAVITY. THIS REDUCES THE EQUATION TO: P=HX
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© IFP Training
WHERE IS THE WEIGHT OF THE DENSITY.
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 1.
REVERSE CIRCULATION:
THIS IS OFTEN THE “TIDIEST” WAY OF MAKING A PRE-PLANNED WELL KILL. IT INVOLVES PUMPING KILL FLUID DOWN THE ANNULUS OF THE WELL, THROUGH THE POINT OF COMMUNICATION BETWEEN THE IT AND THE PRODUCTION TUBING JUST ABOVE THE PRODUCTION PACKER AND UP THE TUBING, DISPLACING THE LIGHTER WELL BORE FLUIDS, WHICH ARE ALLOWED TO FLOW TO PRODUCTION. THE POINT OF COMMUNICATION WAS TRADITIONALLY CALLED A SLIDING SLEEVE, OR SLIDING DOOR, WHICH IS MECHANICALLY OPERATED BY MEANS OF WIRELINE, BUILD INTO THE PRODUCTION TUBING. AFTER A CERTAIN TIME IN THE WELL THE SSD IF HARD TO OPEN, AND THEREFOR IT IS COMMON TO PUNCH A HOLE IN THE TUBING FOR CIRCULATION PURPOSES. © IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL REVERSE CIRCULATION
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 3.
FORWARD CIRCULATION
THIS IS SIMILAR TO REVERSE CIRCULATION, EXCEPT THE KILL FLUID IS PUMPED INTO THE PRODUCTION TUBING AND CIRCULATED OUT THROUGH THE ANNULUS. THOUGH EFFECTIVE, IT IS NOT AS DESIRABLE SINCE IT IS PREFERRED THAT THE WELL BORE FLUIDS BE DISPLACED OUT OF THE PRODUCTION, RATHER THAN THE ANNULUS.
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL FORWARD CIRCULATION
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 2.
BULL-HEADING
THIS IS THE MOST COMMON METHOD OF A CONTINGENCY WELL KILL. IF THERE IS A SUDDEN NEED TO KILL A WELL QUICKLY, WITHOUT THE TIME FOR RIGGING UP FOR CIRCULATION, THE MORE BLUNT INSTRUMENT OF BULL HEADING MAY BE USED. THIS INVOLVES SIMPLY PUMPING THE KILL FLUID DIRECTLY DOWN THE WELL BORE, FORCING THE WELL BORE FLUIDS BACK INTO THE RESERVOIR. HOWEVER, IT CAN BE LIMITED BY THE BURST-PRESSURE CAPABILITIES OF THE TUBING OR CASING, AND CAN RISK DAMAGING THE RESERVOIR BY FORCING UNDESIRED MATERIALS INTO IT. (MUD, BRINE, ETC..)
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL BULL HEADING
© IFP Training
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WELL KILLING / NEUTRALIZING METHODS OF WELL KILL 4.
LUBRICATE AND BLEED
THIS IS THE MOST TIME CONSUMING FORM OF A WELL KILL. IT INVOLVES REPEATEDLY PUMPING IN SMALL QUANTITIES OF KILL MUD INTO THE WELL BORE AND THEN BLEEDING OFF EXCESS PRESSURE. IT WORKS ON THE PRINCIPLE THAT THE HEAVIER KILL MUD WILL SINK BELOW THE LIGHTER WELL BORE FLUIDS AND SO BLEEDING OFF THE PRESSURE WILL REMOVE THE LATTER LEAVING AN INCREASING QUANTITY OF KILL MUD IN THE WELL BORE WITH SUCCESSIVE STEPS.
© IFP Training
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METHODS FOR KILLING OR NEUTRALISING A WELL: "WELL KILLING"
Kill method Bullheading
Reverse Circulation
Direct Circulation Lubricate & bleed pumping&purge
Description - Kill fluid force pumped from the surface - Effluent in tubing squeezed into the formation - Kill fluid pumped from annulus - Completion fluid in annulus moved to tubing through a circulation system (SSD, GL mandrel…) - Effluent in tubing sent to stock tank at surface - Kill fluid pumped in tubing at surface - Tubing fluid moved to annulus through circulation system - Annulus fluide sent to stock tank at surface - pumping of kill fluid - surface purge of gas pressure equal to hydrostatic weight of fluid pumped after deducting gas weight
© IFP Training
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Work-Over principles & procedures Hydrostatics-hydrodynamics
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General procedure of an operation: Preamble
Note: possibly, inversion between: - steps (b, c) and step (d) - step (j) and step (k) EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
General procedure mainly function of: • Equipment installed & its condition • What needs to be done & how the operation is actually going on However, the main steps involved are: • (a): Preparing the well (before the servicing or workover unit arrives) • (b): Putting the well under provisional safe conditions • (c): Installing the servicing or workover unit • (d): Neutralising the well • (e): Replacing the Christmas tree with the BOPs • (f): Removing completion equipment • (g): Downhole operations • (h): Running in completion equipment • (i): Replacing BOPs by the Christmas tree • (j): Well start-up • (k): Moving out the servicing or workover unit
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More tricky operations (from a safety point of view) • • • •
Installing the servicing or workover unit Neutralising the well Replacing the Christmas tree with the BOPs "Unsetting" the packer
And: • Perforating or reperforating • High pressure (…) pumping • Replacing BOPs by the Christmas tree • Well start-up • Moving out the servicing unit © 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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General procedure of an operation
Preparing the well (before the servicing or workover unit arrives) : • Wireline checking • Pressure testing Possibly: • Circulating device opening
Putting the well(s) under provisional safe conditions: • Wells involved function of the installation configuration (cluster) • Placing "plugs" (downhole plug, SCSSV, BPV, etc.) & Isolating the well
Installing the servicing or workover unit:
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
• Followed by the set up and testing of pumping and return lines • Christmas tree not yet removed to be replaced by the BOPs
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General procedure of an operation (cont.)
Neutralising the well: • Volume concerned = global volume* • Workover fluid: − Brine, etc. − Safety margin
• Displacing the fluid by circulating or squeezing • Observing the well • Final neutralisation phase
Replacing the Christmas tree with the BOPs:
Volume concerned
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
• After installation of safety barriers • As quickly as possible • Followed by a BOPs test
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General procedure of an operation (cont.)
Removing completion equipment: • • • • •
Tubing safety device on the rig floor Procedure function of the type of equipment & its condition In the program, provide alternatives in case of operating difficulties Circulate as soon as possible the volume trapped under the packer Check the well's stability during all the job (take care to avoid swabbing, keep the well full & compare the filling volume with the pulled out steel volume)
Downhole operations
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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General procedure of an operation (cont.)
Recompleting the well: • • • •
Running in completion equipment Replacing BOPs by the Christmas tree Well start up Moving out the servicing or workover unit: − After (or before) the well start-up − Safety barriers in place
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Workover on depleted reservoirs
Losses and formation damage: main solutions: • • • • •
"Light" workover fluid "Temporary" blocking agents "Lost" level Suited downhole equipment* Work on a live well : coiled tubing, snubbing
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Downhole equipment suited to depleted reservoir: Example of equipment & Procedure for pulling out the tubing
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
1. A plug is set in the landing nipple of the fixed part of the disconnectable joint (beforehand a plug can also be set in the top no-go landing nipple) 2. The circulating device is opened or the production string is perforated just above the disonnectable joint 3. The workover fluid is circulated into the well 4. A BPV is set in the tubing hanger 5. The Christmas tree is removed 6. The BOPs are installed 7. The BPV is replaced by a TWCV 8. The BOPs are tested (between the TWCV and the blind rams) ; a tubing is screwed into the tubing hanger and the pipe-ram BOPs are tested against on the tubing 9. The tubing hanger is unlocked (tie-down screws) 10. The upper part of the production string is pulled out
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Workover on depleted reservoirs (cont.)
Kick-off after the workover: • No problem if an artificial lift system is in place • Coiled tubing & nitrogen, (swabbing, rocking, etc.)
© 2010 - IFP Training
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
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Fishing tools
Causes of fishing operation: Retrievable packer which cannot be unset, Stuck packer, Broken tubing, Unscrew string, Stuck string, Cemented string, etc.
Main tools*: • • • • •
External catch tools: Die collar, Overshot, Junk catcher Internal catch tools: releasing spear, taper tap Jarring tools: bumper sub, hydraulic jar, jar accelerator or intensifier Milling or washover milling tools Tools to unscrew the tubing: reversing tool, left-hand threading tap, back-off
• Tools to cut the tubing: section mill, jetting tool, explosive cutter,
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
chemical cutter (acid) • Safety joints (allowing the workover string to be disconnected)
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Fishing and jarring tools
Overshot
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
Releasing spear
Taper tap Bumper sub
© 2010 - IFP Training
Die collar
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Milling tools & safety joint
Milling tools
EP 21471_b_A_for_00 Well servicing & workover (WC&S version_Lecturer)
© 2010 - IFP Training
Section mill
Safety joints
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HYDROSTATICS
FLUIDS AT REST SUBJECTED ONLY TO GRAVITY
THE HYDROSTATIC PRESSURE BETWEEN A AND B IS DIRECTLY PROPORTIONAL TO THE VERTICAL HEIGHT Z
IN A HOMOGENOUS FLUID, IF THE TWO POINTS B AND C ARE ON THE SAME HORIZONTAL PLANE, THEN: PB=PC
Fluid of density r
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HYDROSTATICS
- Fluids at rest subjected only to gravity - SI system: PHB - PHA= ρ×g × Z PHB,PHA: hydrostatic pressure in Pascal (N/m2) ρ:density of the fluid in kg/m3 g=9.81 m/s2(earth’s gravitational acceleration) Z:vertical height between A and B in metres
- Metric system:
PHB PHA
Zd 10.2
PHB,PHA: hydrostatic pressure in bar
d: density of the fluid in relation to water 10.2:conversion factor
Z: vertical height between A and B in metres
- Anglo-Saxon system: PHB - PHA= 0.052 × Z ×
PHB,PHA: hydrostatic pressure in psi
: density of the fluid in ppg (pounds/gallon) 0.052: conversion factor
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© IFP Training
Z: vertical height between A and B in feet
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HYDROSTATICS
WITH A AT THE SURFACE OF THE LIQUID WITH A DENSITY OF Ρ:PHA = 0
(IN REALITY 1ATM)
TO CALCULATE PH BETWEEN TWO POINTS, WE MUST KNOW: • THE HYDROSTATIC PRESSURE AT 1 POINT • THE VERTICAL HEIGHT BETWEEN THE TWO POINTS • THE DENSITY OF THE FLUID BETWEEN THESE TWO POINTS • IF THERE ARE SEVERAL FLUIDS OF DIFFERENT DENSITY, WE MUST KNOW THE RESPECTIVE HEIGHT OF EACH FLUID AND CALCULATE THE PRESSURE PART BY PART
HYDROSTATIC PRESSURE INCREASES WITH DEPTH (VERTICAL)
THE LIQUIDS EXERT PRESSURE. THEY WILL BE CONSIDERED AS INCOMPRESSIBLE FLUIDS. © IFP Training
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PRACTICAL CALCULATION FORMULAS
(FLUIDLIQUID WITH NO COMPRESSIBILITY)
METRIC SYSTEM
Z d Phyd (bar ) 10.2
Z: vertical depth, in metres d: fluid specific gravity / water = (fluid)/(water)
FIELD UNITS
Phyd ( psi ) fluid density ( ppg ) 0.052 vert .depth ( ft ) NB: for pressure calculations, always use vertical depths © IFP Training
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WELL KILLING / NEUTRALIZING REVERSING A WELL KILL (PUT BACK ON PRODUCTION) THE INTENTION OF A WELL KILL (OR THE REALITY OF AN UNINTENTIONAL WELL KILL) IS TO STOP THE RESERVOIR FLUIDS FLOWING TO SURFACE. THIS OF COURSE CREATES PROBLEMS WHEN IT IS DESIRABLE TO GET THE WELL FLOWING AGAIN. IN ORDER TO REVERSE THE WELL KILL, THE KILL FLUID MUST BE DISPLACED FROM THE WELL BORE.
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© IFP Training
THIS INVOLVES INJECTING GAS AT HIGH PRESSURE, USUALLY N2. THE GAS CAN BE PUT UNDER SUFFICIENT PRESSURE TO ALLOW IT TO PUSH THE HEAVY KILL FLUID, BUT WILL THAN EXPAND AND BECOME LIGHT ONCE PRESSURE IS REMOVED. THIS MEANS THAT HAVING DISPLACED THE KILL FLUID, IT WILL NOT ITSELF KILL THE WELL. THE RESERVOIR FLUIDS SHOULD BE ABLE TO FLOW TO SURFACE, DISPLACING THE GAS
33
WELL KILLING / NEUTRALIZING REVERSING A WELL KILL (PUT BACK ON PRODUCTION) ANOTHER WAY IS TO RUN INTO THE TUBING A COILED TUBING. ONCE AT THE BOTTOM OF THE WELL WE INJECT THE N2 INTO THE WELL BORE AND PUSHES UP THE KILL FLUID. THE KILL FLUID COLUMN BECOMES LIGHTER. IN AN OIL WELL WE MIGHT CONSIDER THE USE OF “SWABBING” EQUIPMENT. IN THIS CASE WE ARE LIFTING UP THE KILL FLUID IN ORDER THE DECREASE THE HYDROSTATIC PRESSURE. THIS METHOD SHOULD NOT BE USED IN GAS WELL, DUE TO SAFETY REASONS. AN OTHER METHOD IS BY WIRE LINE WE OPEN THE SSD BY WIRE LINE AND DISPLACE THE KILL FLUID BY A LIGHTER FLUID. (DIESEL, OR DEPENDING ON THE FORMATION PRESSURE, BRINE OR WATER) © IFP Training
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WORK-OVER PROCEDURES GENERAL GUIDE-LINES
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PHASES AND SEQUENCE OF AN OPERATION VARIES FROM ONE JOB TO ANOTHER.
IT MAINLY DEPENDS ON THE EQUIPMENT ALREADY INSTALLED IN THE WELL AND THE CONDITION IT IS IN.
IT ALSO DEPENDS ON WHAT NEEDS TO BE DONE AND HOW THE OPERATION IS GOING TO PROCEED IN PRACTICAL TERMS.
WE DISCUSS BELOW THE DETAILED STEPS WHICH ARE GENERALLY INVOLVED IN ALL THE WORK-OVER OPERATIONS © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
1.
PREPARATION OF THE WELL PRIOR TO THE ARRIVAL OF THE WORK-OVER UNIT
THIS MAINLY MEANS :
CHECKING THE STATUS OF THE WELL BY WIRELINE TECHNIQUES (CHECKING THE TUBING, PROVING THE HOLES, TAGGING SEDIMENTS, TO CHECKING THE PERFORATIONS WHETHER THEY ARE OPEN OR NOT).
CHECKING THE WELL INTEGRITY (PRESSURE TESTS OF CASINGS)
OPENING A CIRCULATING DEVICE DOWN-HOLE (SLIDING SLEEVE, BLANKING PLUG OR DUMMY FROM SIDE POCKET MANDREL) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
CHECKING THE INTEGRITY OF VALVES OF THE X-MAS TREE (PRESSURE TESTING OF VALVES)
CHECKING AND PREPARING THE APPROACH ROAD TO WELLS FOR MOVEMENT OF THE WORK-OVER RIG.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
2.
PUTTING THE WELL UNDER SAFE CONDITIONS (BEFORE RIGGING UP THE SERVICE/WORK-OVER UNITS)
THIS SAFETY PRECAUTION-CUM-OPERATION, IN FACT, SHOULD ALSO INVOLVE ALL THE NEARBY WELLS THAT MIGHT BE AFFECTED WHEN THE SERVICE/WORK-OVER UNIT IS BEING SET UP.
THE OPERATION CONSISTS ESSENTIALLY IN ISOLATING THE SURROUNDINGS FROM THE WELL PRESSURES AND KEEPING THEM UNDER OPTIMUM SAFE CONDITIONS WHILE INSTALLING THE SERVICE/WORK-OVER UNITS OVER THE WELLHEAD.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THERE ARE 3 BASIC WAYS OF ACHIEVING THIS:
BY INSTALLING PLUGS IN THE LANDING NIPPLES IN THE TUBING, WHICH ARE GENERALLY AT THE BOTTOM OF THE WELL, BELOW THE PACKER.
BY CLOSING THE SUBSURFACE SAFETY VALVE, IF THERE IS ONE.
BY SETTING A BACK PRESSURE VALVE IN THE TUBING HANGER
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
AT LEAST, 2 OUT OF THESE 3 BARRIERS SHOULD NORMALLY BE IN PLACE.
THE VARIOUS LINES CONNECTED TO THE WELLHEAD ON THE SURFACE SHOULD BE BLED OFF ANY PRESSURES AND/OR ISOLATED.
IF NEED BE, THEY CAN BE DISMANTLED.
NEARBY EQUIPMENT, THAT MIGHT BE DAMAGED, SHOULD BE COMPLETELY DEPRESSURIZED.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
3.
INSTALLING THE SERVICING OR WORK-OVER UNITS
ONCE THE WELL AND IT’S SURROUNDINGS HAVE BEEN SAFELY SECURED, THE SERVICE/WORK-OVER UNIT AND IT’S ACCESSORY EQUIPMENT LIKE TANKS, PUMPS, WORKSHOPS ETC. CAN BE SET UP .
THE EQUIPMENT IN THE SITE SHOULD BE SET UP IN ACCORDANCE WITH THE SAFETY RULES AND REGULATIONS OF THE REGULATORY BODY.
HOWEVER, THE X-MAS TREE IS NOT YET REMOVED TO BE REPLACED BY THE BOP’S © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
4.
KILLING THE WELL
A WELL IS CONSIDERED TO BE PERFECTLY KILLED WHEN THE WORK-OVER FLUID, WHOSE SP.GR. IS APPROPRIATE FOR THE RESERVOIR PRESSURE, TOTALLY FILLS UP THE WELL .
THIS MEANS THAT THE INSIDE OF THE TUBING, THE TUBING-CASING ANNULUS AND THE SPACE BELOW THE PACKER IS FILLED WITH THE WORKOVER FLUID.
THE WORK-OVER FLUID IS PREPARED IN SUFFICIENT AMOUNTS. THIS IS GENERALLY 3 TIMES THE TOTAL VOLUME OF THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PROPERTIES REQUIRED OF A WORK-OVER FLUID IS AS FOLLOWS:
TO KEEP THE WELL UNDER CONTROL BY IT’S HYDROSTATIC PRESSURE.
TO CARRY UP CUTTINGS IF DRILLING OR MILLING IS PLANNED.
NOT TO DAMAGE THE FORMATION.
NO FLUID LOSS IN THE FORMATION © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WITH THE SERVICE/WORK-OVER RIG IN PLACE AND THE WORK-OVER FLUID READY, THE NEXT SET OF OPERATIONS ARE PERFORMED AS BELOW:
THE PLUGS THAT WERE SET IN THE TUBING PRIOR TO THE MOVEMENT OF THE SERVICE/WORK-OVER RIGS, HAVE TO BE PULLED OUT.
THE WORK-OVER FLUID IS PUMPED INTO THE WELL TO DISPLACE THE TUBING CONTENTS.
THIS IS DONE EITHER BY CIRCULATION OR BY SQUEEZING.
THE WELL IS THEN PUT UNDER OBSERVATION FOR STABILITY.
KILLING OF WELL, SOMETIMES, IS CARRIED OUT BEFORE THE RIG IS INSTALLED. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
CONSIDERATIONS ON KILLING THE WELL
THE WORK-OVER FLUID USED TO KILL THE WELL, USUALLY, DISPLACES THE WELL CONTENTS BY EITHER CIRCULATION OR BY SQUEEZING.
KILLING BY CIRCULATION
EXCEPT IN SPECIAL CASES, CIRCULATION IS THE PREFERRED WAY TO KILL THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE FLUID IS CIRCULATED AS DEEP AS POSSIBLE IN THE TUBING, BUT ABOVE THE PACKER, EITHER: THROUGH A CIRCULATING DEVICE OPERATED BY WIRELINE, VIZ. BY PULLING OUT A DUMMY FROM THE SIDE POCKET MANDREL OR BY OPENING THE PORTS OF A SLIDING SLEEVE. OR THROUGH PUNCTURED HOLES IN THE TUBING OPENED UP BY ELECTRIC CABLE SHAPED CHARGES.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
A REVERSE CIRCULATION IS USUALLY THE OPTION CHOSEN FOR GAS WELLS OR HIGH GOR OIL WELLS. IN OTHER WORDS, FLUID IS PUMPED INTO THE ANNULUS WITH RETURNS THROUGH THE TUBING.
THIS METHOD ENSURES THAT OIL AND GAS ARE THOROUGHLY DISPLACED.
WITH DIRECT CIRCULATION, THE LIGHTER OIL AND GAS TEND TO MIGRATE IN THE HEAVIER WORK-OVER FLUID WHICH IS LOCATED ABOVE THEM.
ACCORDINGLY, THEIR IS NO CERTAINTY AS TO THE SPECIFIC GRAVITY OF THE WORK-OVER FLUID THAT IS LEFT IN PLACE IN THE WELL AND AS SUCH, THERE IS NO CERTAINTY REGARDING KILLING OF THE WELL. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
HOWEVER, AFTER A VOLUME CORRESPONDING TO THE TUBING VOLUME HAS BEEN PUMPED IN THROUGH THE ANNULUS – AND THEREFORE AFTER OIL AND GAS HAVE BEEN PUMPED OUT OF THE WELL – DIRECT CIRCULATION IS USED TO HOMOGENIZE THE FLUIDS PRESENT IN THE TUBING AND ANNULUS.
IN CONTRAST, SINCE ANNULAR PRESSURE LOSSES ARE GENERALLY LOWER THAN TUBING PRESSURE LOSSES, WITH DIRECT CIRCULATION THE OVERPRESSURE EXERTED ON THE PAY ZONE BY PRESSURE LOSSES IS MINIMIZED.
HENCE PROBLEMS OF LOST CIRCULATION AND PLUGGING ARE ALSO MINIMIZED. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WHETHER CIRCULATION IS REVERSE OR TOTALLY DIRECT, THE CHOKE IS APPLIED ON THE RETURNS TO KEEP THE BOTTOM-HOLE PRESSURE HIGHER THAN THE RESERVOIR PRESSURE ALL THROUGHOUT THE OPERATION, THEREBY PREVENTING ANY KICKS.
WHEN THE CIRCULATION IS FINISHED, NOT ALL THE FLUIDS LOCATED BELOW THE CIRCULATION DEVICES HAVE BEEN REPLACED BY THE KILLING FLUID – SO, KILLING IS ONLY PARTIAL.
IF INJECTIVITY IS FAIR, KILLING CAN BE IMPROVED, AFTER CIRCULATION, BY SQUEEZING THE OIL AND GAS STILL REMAINING BELOW THE CIRCULATION DEVICE INTO THE FORMATION.
HOWEVER, SOME OIL & GAS IS EXPECTED TO REMAIN TRAPPED IN THE ANNULUS UNDER THE PACKER AND THE TAILPIPE.
Work-over F.J.P.B
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
SOMETIMES, THE WORK-OVER FLUID IS CIRCULATED AFTER SETTING A PLUG IN THE LOWER END OF THE TUBING.
AS A RESULT THERE IS NO RISK OF LOST CIRCULATION INTO THE FORMATION DURING CIRCULATION.
HOWEVER THERE IS UNCERTAINTY REGARDING WHETHER THE PLUG CAN BE PULLED OUT, ESPECIALLY IF IT GETS COVERED WITH DEPOSITS.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
KILLING BY SQUEEZING
THE SQUEEZE TECHNIQUE IS USED:
WHEN THE CIRCULATION METHOD CANNOT BE USED - FOR EXAMPLE, WHEN THERE IS A HOLE IN THE TUBING NEAR THE SURFACE; WIRELINE IS IMPOSSIBLE BECAUSE OF A COLLAPSED TUBING OR BECAUSE OF A FISH; VOLUME BELOW THE TUBING SHOE IS VERY LARGE ETC.
WHEN INJECTIVITY IS VERY GOOD – THIS IS TRUE ESPECIALLY FOR GAS WELLS.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
SQUEEZING IS DONE ONLY AFTER AN INJECTIVITY TEST – JUST TO BE SURE THAT INJECTIVITY IS SUFFICIENT.
THIS IS BECAUSE OF THE SAME DRAWBACK AS WITH DIRECT CIRCULATION – THAT IS, MIGRATION OF OIL AND GAS IN THE KILLING FLUID – GREATLY COMPOUNDED BY THE FACT THAT THE FLOW RATES WITH A SQUEEZE JOB IS OFTEN MUCH LOWER THAN WITH CIRCULATION.
IF THE INJECTIVITY TEST IS UNSATISFACTORY, IT IS NECESSARY TO MODIFY THE SQUEEZE CONDITIONS.
FOR EXAMPLE, SQUEEZE AT A LOWER FLOW RATE, PROVIDED THE TOTAL INJECTED VOLUME IS INCREASED.
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© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FOR A GAS WELL, PERFORM A SERIES OF SQUEEZES AND BLEED OFFS AT CONSTANT BOTTOM-HOLE PRESSURE TO ALLOW THE GAS TO MIGRATE UP TO THE SURFACE WITHOUT FRACTURING THE FORMATION.
SOMETIMES, IT MAY BE NECESSARY TO ACCEPT TO SQUEEZE AT A FRACTURING RATE OR
REVISE THE PROGRAM THOROUGHLY AND USE A TECHNIQUE SUCH AS COIL TUBING OR SNUBBING JUST TO KILL THE WELL OR TO CARRY OUT THE COMPLETE OPERATION. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THIS IMPLIES THAT THE INJECTIVITY TEST HAS TO BE PERFORMED LONG BEFORE THE WORK-OVER IS DONE.
THE CHOICE OF MEANS TO BE UTILIZED AND THE WORK-OVER PROGRAMM DESIGN BOTH DEPEND ON THE INJECTIVITY TEST.
JUST AS FOR CIRCULATION, KILLING IS NOT COMPLETE WHEN THE SQUEEZE OPERATION IS OVER, AS OIL AND GAS STILL REMAINS TRAPPED IN THE ANNULUS UNDER THE PACKER AND ALL OF THE ANNULAR FLUID.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
OBSERVING THE WELL
AFTER KILLING BY CIRCULATION OR SQUEEZING, THE WELL MUST BE OBSERVED TO CHECK THAT : THERE IS NO PRESSURE IN THE WELLHEAD; THE LEVELS ARE STABLE; THERE IS NO GAS CUTTING ON THE SURFACE.
WHATEVER THE OBSERVATION TIME, THERE IS NO ABSOLUTE GUARANTEE THAT THE WELL IS STABLE.
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IT CAN VARY FROM ONE TO SEVERAL HOURS.
© IFP Training
THE TIME DEPENDS ON THE METHOD USED TO KILL THE WELL, THE WAY THE OPERATION ACTUALLY PROCEEDED AND ON OUTSIDE SIGNS OF PHENOMENA SUCH AS THERMAL EXPANSION.
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GENERAL PROCEDURE OF WORK-OVER OPERATION
IF THE WELL SHOULD PROVE UNSTABLE, KILLING MUST BE STARTED ALL OVER AGAIN EITHER WITH THE SAME METHOD OR WITH ANOTHER METHOD.
MODIFYING THE CHARACTERISTICS OF THE CONTROL FLUID OR USE OF SPACE FLUIDS, SOMETIMES, IS QUITE EFFECTIVE.
THE WELL WILL BE UNDER OBSERVATION ONCE AGAIN FOR STABILITY.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FINAL KILLING PHASE
WHATEVER THE METHOD USED, THERE IS ALWAYS A CERTAIN VOLUME LEFT IN THE WELL WHERE IT IS IMPOSSIBLE TO PLACE THE WORK-OVER FLUID.
THIS VOLUME MUST BE CIRCULATED AS SOON AS THE COMPLETION EQUIPMENT REMOVAL OPERATIONS ALLOW.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
REPLACING X-MAS TREE WITH BOP
SINCE THE WORK-OVER FLUID IS KEEPING THE WELL STABLE, ONLY ONE MECHANICAL SAFETY BARRIER IS DEEMED NECESSARY – EITHER THE DOWNHOLE PLUG AND/OR THE SCSSV AND/OR THE BPV
THE X-MAS TREE CAN THEN BE DISMANTLED AT THE TUBING HEAD SPOOL AND REPLACED BY THE BOP, WHICH WILL BE THEN TESTED.
THIS OPERATION SHOULD BE COMPLETED AS QUICKLY AS POSSIBLE.
IT IS IMPERATIVE THEREFORE THAT ALL REQUIRED PERSONNEL SHOULD BE MOBILIZED, REQUIRED EQUIPMENT SHOULD BE IN STATE OF READINESS, APPROPRIATE HANDLING AND HOISTING EQUIPMENT AVAILABLE AND THE WELLHEAD CHECKED ETC. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
REMOVING COMPLETION EQUIPMENT
THE INSTALLED BPV OR PLUG HAS TO BE RETRIEVED BEFORE THE PULLING OUT OF THE DOWN-HOLE EQUIPMENT CAN COMMENCE.
IF THERE IS A KICK WHILE TRIPPING, IT IS NECESSARY TO BE ABLE TO CLOSE QUICKLY NOT ONLY THE ANNULUS WITH THE BOP TUBING RAMS, BUT ALSO THE TUBING ITSELF.
THE CORRESPONDING SAFETY DEVICE (KELLY COCK VALVE/ TUBING SAFETY VALVE) MUST BE ON THE WORK-OVER RIG FLOOR READY FOR USE (THREADS TO BE COMPATIBLE WITH TUBING THREADS) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE PROCEDURE FOR REMOVING THE DOWN-HOLE EQUIPMENT DEPENDS ON THE TYPE OF EQUIPMENT AND IT’S CONDITION.
PARTICULARLY IMPORTANT IS THE TYPE OF PACKER –RETRIEVABLE OR PERMANENT – TYPE OF CONNECTION BETWEEN THE TUBING AND THE PACKER (SEAL ALONE OR SEAL PLUS ANCHOR).
WITH A RETRIEVABLE PACKER, AND ESPECIALLY IF THE WORK-OVER IS BEING DONE SEVERAL YEARS AFTER IT’S SETTING, IT IS OFTEN WISE TO CUT OFF THE TUBING A FEW METERS ABOVE THE PACKER BY CHEMICAL CUTTERS.
THEN, RUN IN DRILL PIPE WITH OVERSHOT, LATCH ONTO THE TUBING AND UNSEAT THE PACKER.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
FURTHERMORE, WHATEVER THE KILLING METHOD, THERE IS ALWAYS A VOLUME OF OIL AND/OR GAS TRAPPED UNDER THE PACKER.
IT IS IMPORTANT TO CIRCULATE IT OUT AS SOON AS POSSIBLE – AFTER UNSEATING THE RETRIEVABLE PACKER OR AFTER STABBING OUT OF A PERMANENT PACKER.
WHENEVER TRIPPING OUT, CARE MUST BE TAKEN TO AVOID SWABBING – PARTICULARLY WHEN THE PACKER IS BEING PULLED OUT.
SECONDLY, THE WELL MUST ALWAYS BE KEPT FULL WITH WORK-OVER FLUID.
LASTLY, THE WELL’S STABILITY MUST FREQUENTLY BE CHECKED.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
WORK-OVER PLAN WELLS COMPLETED WITH RETRIEVABLE HYDRAULIC PACKER
OPEN SLIDING SLEEVE OR PULL OUT DUMMY FROM THE SIDE POCKET MANDREL OR MAKE A HOLE ABOVE PACKER WITH ELECTRIC CABLE.
LOCK OPEN SUB SURFACE SAFETY VALVES
KILL THE WELL BY CIRCULATING WORK-OVER FLUID
INSTALL BPV IN THE TUBING HANGER.
REMOVE X-MAS TREE
INSTALL BOP.
REPLACE BPV WITH TWCV.(Two Way Check Valve) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
TEST THE BOP BETWEEN THE TWCV AND THE BLIND RAM; CONNECT A TUBING IN THE TUBING HANGER, CLOSE THE PIPE RAM AGAINST THE TUBING AND TEST THE PIPE RAM.
REMOVE THE TWCV.
CONNECT TUBING HANGER WITH TUBING STRING.
UNLOCK TUBING HANGER BY UNSCREWING ANCHOR BOLTS.
RELEASE PACKER BY STRAIGHT PULL/ROTATION.
CIRCULATE WORK-OVER FLUID (AT LEAST ONE CYCLE).
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
RECIPROCATE THE STRING TO BREAK THE SEAL TO AVOID SWABBING ACTION.
PULL OUT COMPLETION STRING.
IF IT IS NOT POSSIBLE TO RELEASE THE PACKER, CUT THE TUBING ABOVE THE PACKER, PULL OUT THE COMPLETION STRING.
RUN IN OVERSHOT WITH BUMPER SUB ON TUBING/DRILL PIPE, CATCH THE FISH AND PULL OUT. © IFP Training
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GENERAL PROCEDURE OF WOR-KOVER OPERATION
WELLS COMPLETED WITH RETAINER PRODUCTION PACKER
OPEN SLIDING SLEEVE OR PULL OUT DUMMY FROM THE SIDE POCKET MANDREL OR MAKE A HOLE ABOVE PACKER WITH THE ELECTRIC CABLE
LOCK OPEN SUBSURFACE SAFETY VALVE
KILL WELL BY CIRCULATING WORKOVER FLUID
INSTALL BPV IN THE TUBING HANGER.
REMOVE X-MAS TREE.
INSTALL BOP.
REPLACE BPV WITH TWCV.
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© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
TEST THE BOP BETWEEN THE TWCV AND THE BLIND RAM; CONNECT A TUBING IN THE TUBING HANGER, CLOSE THE PIPE RAM AGAINST THE TUBING AND TEST THE PIPE RAM
REMOVE THE TWCV
CONNECT TUBING HANGER WITH TUBING STRING
INSTALL BPV IN THE TUBING HANGER.
UNLOCK TUBING HANGER BY UNSCREWING ANCHOR BOLTS.
DISCONNECT TUBING SEAL FROM PACKER.
CIRCULATE WORKOVER FLUID (AT LEAST ONE CYCLE) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
PULL OUT PRODUCTION STRING
RUN IN MILLING TOOL WITH CATCHER SUB, MILL THE PACKER AND PULL OUT THE PACKER OR
RUN IN MILLING TOOL WITHOUT CATCHER SUB, MILL THE PACKER AND PUSH DOWN UP TO THE BOTTOM.
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
DOWNHOLE OPERATION, RECOMPLETION, REPLACING BOP BY THE X-MAS TREE AND START UP
THE TECHNIQUES ARE THE SAME AS THOSE USED WHEN THE WELL WAS ORIGINALLY COMPLETED.
HOWEVER, THE BOTTOMHOLE IS USUALLY CHECKED BEFOREHAND BY RUNNING IN A DRILL STRING EQUIPPED WITH A DRILL BIT AND SCRAPER
MOVING OUT THE SERVICING OR WORKOVER UNIT
IN THE SAME WAY AS FOR INITIAL COMPLETION, THE RIG CAN BE MOVED OUT BEFORE OR AFTER THE WELL IS BROUGHT BACK ON STREAM.
THE SAME SAFETY RULES AND REGULATIONS ARE COMPLIED WITH (ESPECIALLY SETTING PLUGS)
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
DEPLETED RESERVOIRS
DEPLETED RESERVOIRS POSE PARTICULAR PROBLEMS AS SOON AS THEIR RESERVOIR PRESSURE IS SUCH THAT CONVENTIONAL WORKOVER FLUIDS (BRINE, OIL BASE FLUID) EXERT A CONSIDERABLE OVERPRESSURE.
THEN THE FOLLOWING PROBLEMS ARE POSED: • LOSES MUD/ OR FORMATION DAMAGE. • WELL KICK OFF AFTER OPERATIONS.
LOSSES AND FORMATION DAMAGE
THE FIRST SOLUTION IS TO USE SPECIAL LIGHT FLUIDS, BUT BESIDES FOAM (SP.GR. FROM 0.1 TO 0.2) THERE IS YET NO FLUID READILY AVAILABLE IN THE MARKET IN THE NEIGHBOURHOOD OF THE 0.2 TO 0.8 RANGE (BETWEEN FOAM TO OIL BASE FLUIDS) © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
LOSSES AND FORMATION DAMAGE
THE SECOND SOLUTION IS TO PROTECT THE FORMATION WITH “TEMPORARY” BLOCKING AGENTS.
THESE ARE USUALLY PRODUCTS THAT ARE UNSTABLE WITH TEMPERATURE OR HIGHLY SOLUBLE IN ACID.
THE PROBLEM WITH THEM IS THAT THEY ARE NEVER 100% TEMPORARY.
THE THIRD SOLUTION CONSISTS IN ACCEPTING TO WORK WITH A “LOST” LEVEL. THAT IS, WITH THE LEVEL SOMEWHERE IN THE WELL AND NOT ON THE SURFACE.
HOWEVER, THIS CAUSES SAFETY PROBLEMS AS IT IS HARD TO CHECK WELL STABILITY CONSTANTLY AND IS INCOMPATIBLE WITH OPERATIONS THAT REQUIRE CIRCULATION. © IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
THE FOURTH SOLUTION, WHEN ONLY THE PRODUCTION STRING ABOVE THE PACKER IS INVOLVED, CONSISTS IN PULLING OUT THE TUBING STRING ONLY LEAVING THE PACKER WITH A PLUG IN THE TAILPIPE INSIDE THE WELL.
THE FIFTH SOLUTION MIGHT BE TO USE A UNIT ALLOWING WORK ON A PRESSURISED WELL, SUCH AS COIL TUBING OR SNUBBING IF THEY ARE APPROPRIATE FOR THE JOB (CLEANING THE BOTTOM OF THE WELL ETC.)
© IFP Training
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GENERAL PROCEDURE OF WORK-OVER OPERATION
START UP PROBLEMS •
THE TECHNIQUES DESCRIBED IN INITIAL COMPLETION ARE APPLICABLE AT THIS STAGE EXCEPT THAT THERE IS USUALLY NO AVAILABLE KICKOFF FLUID THAT IS LIGHT ENOUGH.
•
IN SOME CASES THE PROBLEM DOES NOT CROP UP BECAUSE THE PURPOSE OF THE OPERATION WAS TO INSTALL AN ARTIFICIAL LIFT SYSTEM OR READAPT THE OLD ONE.
•
IN OTHER CASES, IT IS VERY COMMON TO USE A COILED TUBING FOR NITROGEN START UP OR TEMPORARY GAS LIFT.
© IFP Training
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