Casing of oil well

UNIVERSITY OF

TECHNOLOGY &

MANAGEMENT

GROUP MEMBERS

• ANKIT KUMAR• BHANU MITRA• DUSHYANT SHUKLA• GARGI• KUMAR ASHISH

CASING

What is CASING ?

• CASING IS LARGE DIAMETER PIPE THAT IS ASSEMBLED AND INSERTED INTO A RECENTLY DRILLED SECTION OF A BOREHOLE AND TYPICALLY HELD INTO PLACE WITH CEMENT.• CASING IS THE MAIN PART OF THE WELL CONSTRUCTION. ALL

WELLS DRILLED FOR THE PURPOSE OF OIL OR GAS PRODUCTION (OR INJECTING MATERIALS INTO UNDERGROUND FORMATIONS) MUST BE CASED WITH MATERIAL WITH SUFFICIENT STRENGTH AND FUNCTIONALITY.

PURPOSE OF CASING

• CASING THAT IS CEMENTED IN PLACE AIDS THE DRILLING PROCESS IN SEVERAL WAYS:

• PREVENT CONTAMINATION OF FRESH WATER WELL ZONES.• PREVENT UNSTABLE UPPER FORMATIONS FROM CAVING-IN AND STICKING THE DRILL STRING OR

FORMING LARGE CAVERNS.• PROVIDES A STRONG UPPER FOUNDATION TO USE HIGH-DENSITY DRILLING FLUID TO CONTINUE

DRILLING DEEPER.• ISOLATES DIFFERENT ZONES, THAT MAY HAVE DIFFERENT PRESSURES OR FLUIDS - KNOWN AS

ZONAL ISOLATION, IN THE DRILLED FORMATIONS FROM ONE ANOTHER.• SEALS OFF HIGH PRESSURE ZONES FROM THE SURFACE, AVOIDING POTENTIAL FOR A BLOWOUT• PREVENTS FLUID LOSS INTO OR CONTAMINATION OF PRODUCTION ZONES.• PROVIDES A SMOOTH INTERNAL BORE FOR INSTALLING PRODUCTION EQUIPMENT.

Design of casing• Based on subsurface data such as

formation pressures, strengths, makeup and balanced against the cost objectives and desired drilling strategy.

• Strategic depths at which the hole will need to be cased in order for drilling to reach the desired total depth.

DEPTH VS. DIAMETER

• WITH THE CASING SET DEPTHS DETERMINED, HOLE SIZES AND CASING SIZES MUST FOLLOW.

• THE HOLE DRILLED FOR EACH CASING STRING MUST BE LARGE ENOUGH TO EASILY FIT THE CASING INSIDE IT, ALLOWING ROOM FOR CEMENT BETWEEN THE OUTSIDE OF THE CASING AND THE HOLE.

• ALSO, THE INSIDE DIAMETER OF THE FIRST CASING STRING MUST BE LARGE ENOUGH TO FIT THE SECOND BIT THAT WILL CONTINUE DRILLING. THUS, EACH CASING STRING WILL HAVE A SUBSEQUENTLY SMALLER DIAMETER.

• IN DRILLING TECHNOLOGY, CASING STRING IS A LONG SECTION OF CONNECTED OILFIELD PIPE THAT IS LOWERED INTO A WELLBORE AND CEMENTED. THE PIPE SEGMENTS (CALLED "JOINTS") ARE TYPICALLY ABOUT 40 FEET (12 M) IN LENGTH, MALE THREADED ON EACH END AND CONNECTED WITH SHORT LENGTHS OF DOUBLE-FEMALE THREADED PIPE CALLED COUPLINGS.

CASING STRING

INTERVALSTYPICALLY , A WELL CONTAINS MULTIPLE INTERVALS OF CASING SUCCESSIVELY PLACED WITHIN THE PREVIOUS CASING RUN. THE FOLLOWING CASING INTERVALS ARE TYPICALLY USED IN AN OIL OR GAS WELL:-• CONDUCTOR CASING,• SURFACE CASING,• INTERMEDIATE CASING (OPTIONAL),• PRODUCTION CASING,• PRODUCTION LINER.

Casing programs

• SOMETIMES THE WELL IS DRILLED IN STAGES CALLED A CASING PROGRAM.

• HERE, A WELL IS DRILLED TO A CERTAIN DEPTH, CASED AND CEMENTED, AND THEN THE WELL IS DRILLED TO A DEEPER DEPTH, CASED AND CEMENTED AGAIN, AND SO ON.

• EACH TIME THE WELL IS CASED, A SMALLER DIAMETER CASING IS USED.

• THE WIDEST TYPE OF CASING IS CONDUCTOR PIPE (30 TO 42 INCHES FOR OFFSHORE WELLS AND 16 INCHES FOR ONSHORE WELLS).

• THE NEXT SIZE IN CASING STRING IS THE SURFACE CASING, WHICH CAN RUN SEVERAL THOUSANDS FEET IN LENGTH.• IN SOME WELLS, PROTECTION OR INTERMEDIATE CASING IS

RUN TO SEPARATE CHALLENGING AREAS OR PROBLEM ZONES( AREA OF HIGH PRESSURE OR LOST CIRCULATION)• THE LAST TYPE OF CASING STRING RUN INTO THE WELL , AND

SMALLEST IN DIAMETER, IS THE PRODUCTION OR OIL STRING.• THE OIL STRING RUNS DIRECTLY INTO THE PRODUCING

RESERVOIR.

CASING ALTERNATIVES

• IN AN EFFORT TO SAVE MONEY , SOMETIMES A LINER STRING IS RUN INTO THE WELL INSTEAD OF A CASING STRING.• WHILE A LINER STRING IS VERY SIMILAR TO CASING STRING IN

THAT IT IS MADE UP OF SEPARATE JOINTS OF TUBING , THE LINER STRING IS NOT RUN THE COMPLETE LENGTH OF THE WELL.• A LINER STRING IS HUNG IN THE WELL BY A LINER HANGER ,

AND THEN CEMENTED INTO PLACE.

OIL RIG CASING

• AS THE PROCESS OF DRILLING CONTINUES, THEY REACH THE PRE-SET DEPTH (ANYWHERE FROM A FEW HUNDRED TO A COUPLE-THOUSAND FEET),THEY MUST RUN AND CEMENT THE CASING PIPE SECTIONS INTO HOLE TO PREVENT IT FROM COLLAPSING IN ON ITSELF.

THE CASING PIPE HAS SPACERS AROUND THE OUTSIDE TO KEEP IT CENTERED IN THE HOLE.

• CASING IS RUN FROM THE RIG FLOOR, CONNECTED ONE JOINT AT A TIME BY CASING ELEVATORS ON THE TRAVELLING BLOCK AND STABBED INTO PREVIOUS CASING STRING THAT HAS BEEN INSERTED INTO THE WELL.• CASING A RIG ALSO INVOLVES RUNNING STEEL PIPE DOWN THE

INSIDE OF A RECENTLY DRILLED WELL.• THE SMALL SPACE BETWEEN THE CASING AND UNTREATED SIDES

OF THE WELL IS FILLED WITH CEMENT TO PERMANENTLY SET THE CASING IN PLACE.

CASING DRILLING TECHNOLOGY

• CASING DRILLING IS AN ALTERNATIVE OPTION FOR CONVENTIONAL DRILLING AND USES STANDARD OILFIELD CASING INSTEAD OF DRILL STRING.• THIS TECHNOLOGY IS ONE OF THE GREATEST DEVELOPMENT IN

DRILLING OPERATIONS, AND INVOLVES DRILLING AND CASING A WELL SIMULTANEOUSLY.• CASING DRILLING CAN REDUCE DRILLING TIME BY 20 TO 30%,

AND ALSO HAS GREATER BOREHOLE STABILITY AND WELL CONTROL.

THANK YOU….