Casing deign

WELCOME TO THE STUDENTS
7th Semester (Mining)
Bogura Polytechnic Institute, Bogura.
Md. Majedur Rahman
B. Sc (Hon’s), M. Sc in Geology & Mining, RU
Instructor (Tech)
Mining and Mine Survey Technology
Bogura Polytechnic Institute, BOGURA.
Presented By
Prepared by Md. Majedur Rahman, E-mail: majedu1r_ru6871@yahoo.comMay 29, 2020 1

Petroleum Well Design & Completion
Course Code No. 69372
Prepared by Md. Majedur Rahman, E-mail:
majedu1r_ru6871@yahoo.com
May 29, 2020 2

Chapter-06
Understand the casing deign
6.1 Define casing.
6.2 Describe casing types.
6.3 Mention the function of casing.
6.4 Illustrate casing specification.
6.5 Explain the strength properties of casing.
6.6 Illustrate the factors influencing casing design.
6.7 Describe the guideline for casing design.
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Casing is large diameter pipe that
is assembled and inserted into a
recently drilled section of a
borehole. Similar to the bones of a
spine protecting the spinal cord,
casing is set inside the drilled
borehole to protect and support
the well stream.
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6.1 Define casing.

6.2 Describe casing types.
There are five different types of casing pipe:
• Conductor Casing
• Surface Casing
• Intermediate Casing
• Production Casing.
• Liner String
Casing pipe is an integral part of the oil drilling and completion process.
Careful planning is required so that the proper casing for each well is
installed.
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6.3 Mention the function of casing.
Casing has many functions and can be summarized as follows:
• Provide a support for fractured, weak and vulnerable formations.
• Prevent contamination of fresh water zones
• Isolate abnormal pressure zones and also lost circulation zones
• Provide passage for production fluids. In general, production operations are
performed through tubing which is run inside the casing.
• Provide support for surface equipment (blow out preventer and production
tree)
• Allow an adequate means for installing artificial lift equipment for
production
• Offer a known borehole diameter in order to perform further operations
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6.4 Illustrate casing specification.
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Once the casing size and setting depth are selected, the loads which are
exerted on the casing string will be calculated. According to these loads the
casing properties are selected. Casing is classified in terms of outer diameter
or size, weight, grade and the type of the connection.
• Casing size
The size of the casing or also called the outer diameter of the casing joint
varies from 4.5'' to 36''. The string which has less than 4.5'' is called the
tubing rather than casing. The casing sizes are limited to standard sizes which
can be available in the market.
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Explain the physical properties of casing.

• Casing Weight
The casing joint is characterized by the casing weight which is given as
weight per foot. The API has designed and limited the internal diameter of a
casing joint, but this diameter can vary slightly when manufacturing the joint
of casing. A minimum guaranteed internal diameter is called drift diameter
which is important when planning for further operations (ex: the drilling bit
which will be run to drill the next section has to be less than the drift
diameter).
• Casing joint length
The casing length is standardized by the API into three ranges:
• - Range 1: 22ft
• - Range 2: 31ft
• - Range 3: 42ft
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6.5 Explain the strength properties of casing.
For casing design, there are three main loads which have to be considered:
• The yield strength
• Collapse pressure
• Burst pressure
Many scenarios have to be imagined to design the casing in realistic way
for risk assessment, integrity and also for costing.
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• The yield strength
The yield strength is defined as tensile stress which produces the 0.5% elongation per unit length of
casing specimen. This value varies according to the steel alloy used to make the casing joint.
Couplings have also their yield strength which can be higher or lower than the main body yield
strength. The manufacturer supplies data for both: main body and the coupling.
• Collapse Strength
It is defined as the maximum external force which crushes the casing. This can happens when the
pressure behind the casing is higher than the pressure inside the casing. The external pressure
tends to crush the joint of casing inwards.
• Burst strength
The casing can rupture when internal pressure is higher than the external pressure. The resultant
pressure tends to deform the joint of casing outwards. The burst pressure is higher if gas comes
from high pressurized formation. If the gas is allowed to migrate to surface in a closed well, the
pressure will be higher because gas cannot expend and the pressure will not decrease which adds
more hydrostatic pressure.
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6.6 Illustrate the factors influencing casing design.
General requirement/factors:
• To design a casing string, one must have knowledge of:
• Purpose of the well
• Geological cross section
• Available casing and bit sizes
• Cementing and drilling practices
• Rig performance
• Safety and environmental regulations
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6.7 Describe the guideline for casing design.
• After cleaning and preparing the rig floor, the first joint with casing shoe
made up on it is picked up. The casing joints have to be transferred
carefully to catwalk. Installing the Klampon protector can be used to
protect the pin end of the joint.
• The shoe track is composed of the casing shoe, two casing joints and float
shoe. The shoe track components should be made up using pipe lock
compound. The pipe lock has to be put on the pin part. The float collar pin
is stabbed in the second joint carefully and made up using the chain tong,
then the next join pin is stub in the float collar and made up using the
power tong. The pipe lock is used to avoid backing off the casing shoe and
float collar while drilling them with the next BHA.
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• The casing shoe and the float collar should be tested, the shoe track is
filled with mud then lifted at least 30 ft above the rotary table, then
lowered again, the level into the shoe track should decrease and the floats
should not allow the back flow. In the case when the floats fail, make the
circulating head and circulate to remove any debris which can affect the
floats, then re-test again.
• The next joints are doped with casing thread compound to all boxes and
seal areas. The dope is applied when the joint is in the V door not when the
joint is on the rotary. Extra joints should be on site, cleaned, calibrated and
measured which can be used when damaging joints.
• Safety clamps or single joints elevator is used above the slips before
removing the elevator to avoid losing the casing into the well. They are
used till getting the weight of 25000 lbs.
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• For buttress couplings, the casing is made up to more or less than 3/8 inch
from the base of the triangle. Make up several joints to triangle, then use
that average torque to make up the remaining joints. The coupling can be
warm up but should not get hot, if this is the case may be it indicates the
over-torquing or galling. The connection should be made up with the high
gear of the power tong, then low gear is engaged prior to shouldering.
• Fill each joint with mud and monitor the correct amount of mud returned
to the mud pit while running in the hole to record any losses or gain.
• Change to spider elevator before running in the open hole
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Any Questions
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THANKS TO ALL
May 29, 2020 22

Casing deign

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