CASING FAILURE & REPAIR

CASING FAILURE AND REPAIR:

• FAILURE OF CASING IS AN AREA OF INCREASING CONCERN.

• THE EXTENT OF CASING FAILURE COVERS WELLS OFFSHORE AND ONSHORE VARYING IN SIZE FROM 20” TO 5 ½”.

FAILURE OF CASING OCCURS MAINLY DUE TO:

1. LEAKAGE FROM JOINTS DUE TO IMPROPER MAKE UP.

2. WEAR OUT OF INTERMEDIATE CASING DUE TO TOOL JOINT OF DRILL STRING / JUNK INSIDE CASING.

3. COLLAPSE & BURST CASING.

4. IMPROPER DESIGN.

5. STRUCTURAL DEFECTS.

LEAKS:

CASING LEAKS ARE THE MOST COMMON FAILURES AND OFTEN OCCUR IN ASSOCIATION WITH MOST OTHER FAILURES. THE MAJOR CAUSES FOR LEAKS ARE:

1. IMPROPER MAKE UP DURING RUNNING IN.

2. DRILLPIPE WEAR DURING DRILLING.

3. WEAR DUE TO RUNNING STABILIZERS IN CASED HOLE.

4. MECHANICAL WEAR DURING FISHING AND SPECIALLY MILLING.

5. CORROSION AND TO A LESSER EXTENT EROSION AND MECHANICAL WEAR DURING PRODUCTION LIFE OF THE WELL.

SPLIT OR BURST:

SPLIT OR BURST CASING OCCURS FROM MANY CAUSES:

1. BUMPING THE PLUG TOO HARD DURING CEMENTING.

2. APPLYING EXCESS INTERNAL PRESSURE SOMETIMES IN COMBINATION WITH HIGH TENSILE LOADING. EXCESS INTERNAL PRESSURE MAY OCCUR WHILE TESTING LINER TOP OR TESTING CASING BEFORE DRILL OUT.

3. SOME FAILURES THAT CAUSE CASING LEAKS MAY ALSO CAUSE SPLIT OR BURST CASING.

4. CASING MAY SPLIT WHILE HANGING LONG, HEAVY LINERS.

5. GENERAL CAUSES INCLUDE INADEQUATE STRENGTH DUE TO IMPROPER DESIGN, OR WORN CASING AT THE POINT WHERE LINER SETTING TOOL SLIPS ENGAGE THE CASING.

6. CASINGS CAN ALSO SPLIT DUE TO HIGH DENSITY PERFORATION SPECIALLY IN THE HIGHER STRENGTH STEELS.

7. CASINGS CAN ALSO SPLIT DUE TO HIGH DENSITY PERFORATION SPECIALLY IN THE HIGHER STRENGTH STEELS.

8. CASING MAY ALSO SPLIT DUE TO STRUCTURAL DEFECTS.

PARTED CASING: THESE TYPE OF FAILURES ARE CAUSED MAINLY DUE TO:

1. IMPROPER DESIGN.

2. OPERATIONS OR MECHANICAL FAILURES DUE TO IMPROPER CONSTRUCTION. PARTED CASING USUALLY OCCURS AT THE CONNECTIONS SPECIALLY IN LESSER STRONG CONNECTIONS.

4. CASING THAT HAS SPLIT OR BURST CASING MAY ALSO PART DUE LOSS OF STRUCTURAL INTEGRITY.

5. CASING MAY PART DURING RUNNING IN DUE TO IMPROPER HANDLING, SUCH AS BEING LOWERED RAPIDLY, LOWERED AND STOPPED ABRUPTLY, ESPECIALLY WITH LONG, HEAVY CASING STRINGS.

6. OTHER CAUSES CAN INCLUDE EXCESS WEAR AND RESULTING LOSS OF TENSILE STRENGTH, PULLING HARD WHILE WORKING STUCK CASING AND BUMPING THE PLUG TOO HARD DURING CEMENTATION.

COLLAPSED CASING: CASING COLLAPSE DUE TO VARIOUS REASONS SOME OF WHICH ARE THE SAME WHICH CAUSE CASING LEAKS.

SOME OF THEM ARE:

1. IMPROPER DESIGN.

2. FAILURE TO FILL THE CASING DURING RUNNING IN HOLE.

3. WEAR REDUCES BODY STRENGTH SO THE EXTERNAL PRESSURE MAY CAUSE THE CASING TO COLLAPSE.

4. ANYTHING THAT REDUCES WALL THICKNESS, INCLUDING WEAR OR CORROSION INCREASES SUSCEPTIBILITY TO COLLAPSE.

5. CASING MAY COLLAPSE DUE TO SQUEEZING OR TREATING BELOW A PACKER SET IN THE CASING.

6. WORN OR POORLY DESIGNED PRODUCTION CASING MAY COLLAPSE WHEN THE HYDROSTATIC HEAD IS REDUCED BY COMPRESSOR / NITROGEN APPLICATION.

7. AN INFREQUENT CAUSE OF COLLAPSE MAY BE DUE TO SHIFTING OR FLOWING FORMATIONS LIKE MASSIVE SALT SECTIONS.

FACTORS AFFECTING CASING REPAIRS:

1. CASING TYPE, SIZE & DEPTH OF FAILURES.

2. WHETHER THE PROBLEM IS IN CEMENTED OR UNCEMENTED SECTION.

3. WHETHER THE OPTION OF USING EXTRA STRING OF CASING IS AVAILABLE.

4. FORMATION TYPE, PRESSURE, FLUID IN THE FORMATION & TRANSITION ZONE.

5. AGE OF THE WELL.

6. CURRENT STATUS OF THE WELL (DRILLING OR PROD).

7. PRODUCTIVITY FROM THE WELL.

8. SEVERITY OF FAILURE.

COLLAPSED LEAK, SPLIT OR BURST

PARTED

SWAGEORROLLOUT

MILL OR REAMOUT

PACK OFFDAMAGED SECTION

SET INTERNAL CASINGPATCH

REPAIR CASING IN PLACE

CUT, MILL AND FISH OUT THROUGH THE PARTED SECTION. WASH OVER CASING

BACK OFF BELOW DAMAGED SECTION AND REPLACE

MILL A TOP CLEAN

BACK OFF LEAVE THREAD UP

RUN CASINGWITH EXTERNAL PATCH

RUN CASING WITH ALIGNMENT TOOL AND MAKE UPSQUEEZE, CLEAN OUT

TEST

RESUME OPERATIONS

LAND CASINGNIPPLE UP

CAUSES

& HANDLING

COLLAPSED CASING

LEAKED CASING

PARTED CASING

CORRODED CASING

CASING ROLLER

MANDREL

UPPER ROLLER

MIDDLE ROLLER

LOWER ROLLER

BALL BEARING

NOSE CONE

CASING REPAIR TOOLS – CASING ROLLER

1. DESIGNED TO RESTORE & RECONDITION COLLAPSED, BUCKLED OR DENTED CASING.

2. ENTERS SMALLER ID OF CASING & WITH ROTATION IT EXERTS LATERAL PR. TO RESTORE ID.

3. THE MANDREL IS ECCENTRIC AND ON IT ARE MOUNTED STEEL ROLLERS AND NOSE CONE

4. THE NOSE LOCKS ALL THE ROLLERS.

5. THE CASING ROLLERS IS MADE UP WITH DRILL COLLAR OR HWDP WITH A FISHING UP JAR

6. ON CONTACT WITH THE DAMAGED PORTION INCREASE RPM TO 50-100 RPM , START CIRCULATION.

7. AS THE TOOL IS LOWERED THE ECCENTRICITY FORCES THE ROLLERS AGAINST THE WALL OF CASING RESTORING THE NORMAL ID.

8. USE MODERATE TO HEAVY LOADS.

9. TOO LITTLE WEIGHT WITH HIGH RPM WILL CAUSE ROLLERS TO WEAR OUT.

10. USE EXPERIENCE FOR WEIGHT AND RPM COMBINATION, AS LONG AS STEADY PROGRESS IS ACHIEVED THE COMBINATION IS RIGHT.

11. BADLY DAMAGED CASING WILL REQUIRE THE MAXIMUM WEIGHT.

12. CIRCULATION SHOULD ALWAYS BE MAINTAINED.

CASING REPAIR TOOLS – CASING SWAGE

SWAGE

1. THESE ARE HEAVY TAPERED CONES.

2. THEY ARE DRIVEN DOWN THRU. THE COLLAPSED SECTION AND JARRED OUT.

3. THEY ARE RUN IN DIFFERENT SIZES AS THE CASING IS SWAGED IN SMALL INCREMENTS SOMETIMES AS LITTLE AS ¼” AT A TIME.

4. CASING CAN BE SWAGED OUT TO WITHIN 1/8” BELOW DRIFT DIAMETER.

CASING RETRIEVAL TOOLS – CASING SPEAR

• IS USED FOR POSITIVE ENGAGEMENT WITH CASING

• CAN WITHSTAND HEAVY JARRING AND PULLING STRAIN. EASILY TO ENGAGE AND DISENGAGE.

• SINCE ENGAGEMENT IS OVER A LARGE AREA NO DISTORTION OF THE FISH TAKES PLACE.

• DRESS THE SPEAR ACCORDING TO THE SIZE OF FISH.

• THE GRAPPLE SHOULD BE IN THE RELEASED POSITION ( BOTTOM MOST POSITION).

• RUN IT TO THE DESIRED DEPTH, ROTATE IT ONE FULL TURN TO THE LEFT.( IN DEEP, CROOKED WELLS MORE THAN ONE TURN MAY BE REQ.)

• ROTATION TURNS THE MANDREL DOWN THROUGH THE GRAPPLE IN ENGAGING POSITION.

• A STRAIGHT PULL WILL WEDGE THE GRAPPLE IN POSITIVE ENGAGEMENT WITH THE FISH.

• TO RELEASE THE GRAPPLE BUMP DOWN THE WT. OF FISHING STRING, ROTATE TWO OR THREE TURNS TO THE RIGHT, ELEVATE THE STRING.

CASING CUTTING TOOLS – INTERNAL CASING CUTTER

• PRIOR TO RUNNING IN HOLE, ENSURE THAT THE AUTOMATIC BOTTOM IS FULL ENGAGED.

• THIS HOLDS THE CUTTER IN DIS-ENGAGED POSITION.

• AVOID RIGHT ROTATION AS THE CUTTER IS LOWERED. RIGHT HAND ROTATION WILL DISENGAGE THE AUTOMATIC BOTTOM AND SET THE CUTTER IN OPERATING POSITION.

• AFTER REACHING THE DESIRED CUTTING DEPTH THE CUTTER IS ANCHORED BY SLOWLY ROTATING TO THE RIGHT WHILE SLOWLY LOWERING THE STRING.

• THE WIPER BLOCKS RESIST ROTATION AND LOWERING.

• THIS DISENGAGES THE AUTOMATIC BOTTOM FROM THE GRIP IN JAWS.

• CONTINUED LOWERING WILL CAUSE THE CONE TO MOVE THE SLIPS TO MOVE UPWARDS AND OUTWARD TO ANCHOR THE CUTTER.

• THE MANDREL IS NOW FREE TO TRAVEL DOWN UNDER THE KNIFE BLOCKS FORCING THE KNIVES OUT TO START THE CUT.

• SLIGHT ADDITIONAL WT. IS APPLIED WITH ROTATION.

• THE MAIN SPRING IN THE UPPER PART OF THE CUTTER IS COMPRESSED AND ASSIST IN A UNIFORM FEED TO THE KNIVES.

• RPM IS 10-18 WITH VERY CAREFUL APPLICATION OF WT.( JUST ENOUGH TO FEED THE KNIVES).

• LOWERING OF STRING IS IN 1/16” INTERVALS AND A FEED OF 1 ¼” WILL COMPLETE THE CUT.

•FREE ROTATION AND NO REVERSE TORQUE MEANS CUT IS COMPLETE. RAISE THE TOOL BY 1’, NOW THE KNIVES ARE RETRACTED AND THE TOOL IS READY TO BE RAISED OR LOWERED AS DESIRED.

CASING CUTTING AND MILLING TOOLS – SECTION MILL

1. USED TO MILL A SECTION OF CASING FOR A SIDE-TRACKING OPERATION GENERALLY FROM 20M TO 30M.

2. SECTION MILL BLADES ARE OPERATED BY PUMP PRESSURE

3. THE BLADES ARE OF SINTERED TUNGSTEN CARBIDE AND CAN MILL A 50M SECTION IN ONE TRIP.

4. THE PUMP PR. ACTING ON THE PISTON ASSEMBLY KEEPS THE BLADES OPEN AND MAKE THE INITIAL CUT THROUGH THE CASING.

5. THE BLADES EXTEND THROUGH THE GAP IN THE CUT CASING AND AS WEIGHT IS APPLIED THE CASING IS MILLED.

6. DRILL COLLARS ARE RUN ABOVE THE MILL TO STABILISE IT.

7. SPECIAL MUD HAVING VISC. 90-100 AND YIELD 50-60 IS USED TO LIFT THE CUTTINGS FROM THE WELL BORE.

CASING REPAIR TOOL –LEAD SEAL CEMENTING TYPE CASING PATCH

• THIS IS RUN AT THE LOWER END OF THE CASING AND MADE TO THE CASING LEFT IN THE HOLE.

• IT PERMANENTLY SEALS AND CEMENTS TO THE LOWER END OF THE CASING.

• IT HAS COMPRESSION TYPE MULTIPLE LEAD SEAL WITH CEMENTING VALVING FEATURE.

• THIS ALLOWS CEMENTING IN PLACE IMMEDIATELY AFTER THE PATCH IS SET.

• THIS BECOMES A PERMANENT PART OF THE WELL CASING.

• THE MAIN PARTS ARE THE TOP SUB, BOWL, CARRIER AND GUIDE. INSIDE THE CARRIER ARE ASSEMBLED THE GRAPPLE, GRAPPLE CONTROL WITH SET SCREW, STINGER AND STINGER RETAINER AND INTEGRAL LEAD SEALS.

OPERATION:

• PRIOR TO LOWERING THE PATCH, THE FISH (CASING) TO BE MADE UP MUST BE WASHED OVER IF IT IS IN THE OPEN HOLE.

• A BRIDGE PLUG OR PACKER SHOULD BE SET INSIDE THE FISH AT ITS UPPER END TO STOP THE CEMENT.

• LOWER THE TOOL TILL THE FISH TOP IS REACHED.

• WITH SIMULTANEOUS ROTATION THE TOOL SHOULD BE LOWERED SLOWLY.

• THIS IS CONTINUED TILL THE FISH CONTACTS THE SHOULDER AT THE UPPER END OF THE CARRIER AND PUSHES IT TILL IT BOTTOMS UP AGAINST THE TOP SUB.

• SLACK OFF ABOUT 5-10T ON THE PATCH TO INSURE COMPLETE ENGAGEMENT.

• PICK UP THE STRING TO REMOVE THE WT. SLACKED OFF.

• SET THE LEAD SEALS BY PICKING UP THE STRING. THE LOAD REQ. VARIES FROM 5T TO 50T.

• THE PATCH CAN NOW BE PR. TESTED WITH MUD PUMPS.

• USE ONLY VERY LESS PR. (500 TO 1000) PSI.

• ONCE THE PATCH IS SET AND PR. TESTED, THE PATCH IS OPENED TO CIRCULATION BY LOWERING THE STRING TILL 5 TO 10 T IS RESTING ON THE PATCH.

• THIS WILL TELESCOPE THE CARRIER UP AGAINST THE TOP SUB AND AT THE SAME PULL THE STRINGER UP OFF THE SEALS AT THE FACE THE GUIDE.

• CIRCULATION THRU. THE PATCH IS DONE AND MUD IS CONDITIONED.

• CARRY OUT CEMENTATION.

• ESTABLISH THE SEALS BY ELEVATING THE STRING AND KEEP UNDER TENSION AT A WT. WHICH WAS REQ. TO SET THE SEALS (5 – 50T).

• THE PATCH CAN TAKE AS MUCH AND SOME TIMES MORE PRESSURE THAN THE CASING ON WHICH IT IS RUN. DO NOT PRES. THE PATCH UNNECESSARILY TILL THE CEMENT IS SET

ONE TRIP WINDOW MILLING AND EXIT SYSTEM

ONE TRIP WINDOW MILLING AND EXIT SYSTEM

1. IS USED TO EXIT CASING AND PROVIDE A WINDOW FOR RUNNING DRILLING BHA’S CASING AND COMPLETION EQ.

2. THIS IS DONE IN ONE ROUND TRIP OF DRILL STRING.3. THE CUT IS MADE, WINDOW MILLED AND PILOT HOLE

DRILLED FOR SUBSEQUENT DRILLING.4. IF A WHIP STOCK PACKER IS RUN AND WHIP STOCK FACE

ORIENTATION IS REQUIRED, TWO ELECTRIC WIRE LINES RUNS ARE MADE.

5. ONE IS TO SET THE PACKER AND THE OTHER IS TO DETERMINE THE DIRECTION OF THE ORIENTATION KEY INSIDE THE PACKER.

6. WHEN USING A BOTTOM TRIP ANCHOR IF MWD IS AVAILABLE, LINE UP THE TOOL FACE OF THE MWD WITH THE PACKER. WHILE PUMPING THROUGH THE STRING THE MWD TOOL WILL PROVIDE THE WHIP STOCK FACE DIRECTION AT THE SURFACE.

7. IN THIS CASE ONLY ONE DRILLPIPE TRIP IS REQ. TO RUN IN, ORIENT AND ANCHOR THE TOOL; MILL THE WINDOW AND DRILL THE PILOT HOLE.

CASING FAILURE:Sl. No. Description Details

1. Well Name XX

2. Project YY

3. Rig E-2000-6

4. Target depth 4765M

5. Drilled depth 2505M

6. Complication depth 190M

7. Previous casing shoe 18 5/8”- 197M

8. Spud date 06.06.2002

9. Complication date 02.11.2002

10. Cumulative complication days 12

11. Nature of complication CASING FAILURE

Complication brief: R/I 17 ½” bit to 190m. tried to clear below 190m, but failed. P/O. R/I 15” swage & cleared held up portion. P/O. R/I 17 ½” stabiliser and observed held up at 190m. Tried to clear, but failed. P/O. Built up swage and R/I to 190.44m. Tried to clear but failed. P/O. R/I 17 ½” frazer and milled from 190.44m to 193.5m. P/O. R/I swage to 192m. Held up. Tried to clear but failed. P/O. R/I 17 ½” stabiliser to 192m. Tried to clear by hammering, but failed. P/O. R/I 17 ½” frazer and milled from 193m to 197m.

CASING FAILURE:

Sl. No. Description Details

1. Well Name XX

2. Project YY

3. Rig E-3000-1

4. Target depth 5000M

5. Drilled depth 5010M

6. Complication depth

7. Previous casing shoe 5 ½”- 5010M

8. Spud date

9. Complication date 06.09.2002

10. Cum. Complication days 8

11. Nature of complication CASING FAILURE

Complication brief: Tested casing hermetically. Found holding. Made up casing spear and backed off casing. P/O 109 joints casing. R/I new casing with centering device. Made up casing and tested hermetically OK.

CASING FAILURE:

Sl. No. Description Details

1. Well Name XX

2. Project YY

3. Rig E-760-2

4. Target depth 3300M

5. Drilled depth 3353M

6. Complication depth

7. Previous casing shoe 51/2”- 3333M

8. Spud date 05.10.2002

9. Complication date 20.12.2002

10. Cumulative complication days 19

11. Nature of complication CASING FAILURE

Complication brief: During hermetical testing of 5 ½” casing, observed pressure drop and communication with the annulus. R/I RTTS packer and set at 700m. Observed communication with the annulus. Made up casing and backed off. P/O casing (75 singles). Observed casing fractured at 675m. Lowered casing and made up. Tested, observed leakage. This operation had to repeated 3 more times as the casing was found to leaking at different depths. Finally retrieved 119 joints of casing. R/I again with guide and made up. Tested OK.

PRESENT WELL CONSTRUCTION OF TK#1 AFTER TUBING FAILURE

20” 133/8”

275M

1550M

95/8” - 2691M

7” LINER - 3507M

5” LINER - 3701M

PACKER 3083M

FISH TOP – TUBING 1994.43M

CEMENT PLUG TOP1882M

CUT CASING AT 1725M. 1715.7M & 1602M FAILED TO RETRIEVE AS CASING WAS STUCK.

CUT CASING FROM 1540M & RECOVERED THE SAME.

MILLED 95/8” CASING FROM 1540M TO 1592.37M

OBJ– 1(3587M- 82M) TESTED DRY

OBJ– 2 (3175-73) TESTED DRY

OBJ– 3 (3104-3100 & 3095- 3093M)DRY

OBJECT 4 (3065-3052) , OBJECT 5 (2843-33, 2830-28, 2825-23M) & OBJECT 6 (2413 – 2402M) ARE COVERED BY THE FISH