INTRODUCTION
CASING IS LARGE DIAMETER PIPE THAT IS INSERTED INTO A RECENTLY DRILLED SECTION TO PROTECT THAT BARE HOLE.CASING IS DONE AFTER EVERY INTERVAL OF DRILLING IS COMPLETED.AFTER EACH CASING CEMENTING IS DONE TO HOLD CASING FIRMLY IN HOLE.
TYPES OF CASING
- CONDUCTOR CASING
- SURFACE CASING
- INTERMEDIATE CASING
- PRODUCTION CASING
CONDUCTOR CASING
THIS IS THE FIRST CASING DONE AFTER A SECTION OF HOLE IS DRILLED.IT IS INSTALLED GENERALLY BEFORE RIG ARRIVES ON LOCATION.THE SIZE OF CASING DEPEND ON DEPTH OF HOLE AND DIAMETER OF THE HOLE.THE CONDUCTOR PIPE SIZE RANGES FROM MIN 16 “TO MAX 24 “. IT CAN BE DRIVES UPTO A LENGTH OF 250 FT.
SURFACE CASING
THIS IS THE SECOND STAGE OF CASING DONE AFTER A SECTION OF HOLE IS DRILLED.THIS IS SMALLER AS COMPARED TO CONDUCTOR CASING .THE MAIN PURPOSE OF THIS CASING IS TO PROTECT WELL FROM FRESH WATER DEPOSIT.THEY ARE RUN INTO HOLE & CEMENTED BACK TO SURFACE. THE SURFACE CASING PIPE SIZE RANGES FROM MIN 7 5/8 “TO MAX 20”.IT CAN DRIVES UPTO A DEPTH OF 3000 FT+.
INTERMEDIATE CASING
THIS IS THIRD STAGE OF CASING DONE AFTER A SECTION OF HOLE IS DRILLED.THIS IS SMALLER AS COMPARED TO SURFACE CASING .THE MAIN PURPOSE OF THIS CASING IS TO PROTECT WELL FROM MUD FALL & WATER FLOW TO WELL. THE INTERMEDIATE CASING PIPE SIZE OF 13 3/8”. IT CAN DRIVE UPTO A DEPTH OF 6000 FT+.
PRODUCTION CASING
THIS IS FINAL STAGE OF CASING DONE AFTER A SECTION OF HOLE IS DRILLED.THIS IS SMALLER AS COMPARED TO INTERMEDIATE CASING .THE MAIN PURPOSE OF THIS CASING IS TO PROTECT THE PRODUCTION ZONE. THE PRODUCTION CASING PIPE SIZE IS OF 9 5/8”. IT CAN DRIVE UPTO A DEPTH OF 21000 FT+.
ADVANTAGES OF CASING
- MAINTAIN HOLE INTEGRITY
- SUPPORT UNSOLIDATED SEDIMENTS
- PROTECT SHALLOW WEAK FORMATION FROM HEAVIER MUD WEIGHTS.
- PREVENT CONTAMINATION OF FRESH WATER
- ISOLATE UBNORMALLY PRESSURED ZONE
- PROVIDES CONTROL FOR FORMATION PRESSURE & FLUIDS.
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