Understanding Well Cementing Principles

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.com
August 3, 2022 1

Petroleum Well Design & Completion
Course Code No. 69372
Prepared by Md. Majedur Rahman, E-mail:
majedu1r_ru6871@yahoo.com
August 3, 2022 2

Chapter-07
Understand the Cementing
7.1 Define cementing.
7.2 Describe factors affecting cement slurry design.
7.3 State cement additives.
7.4 Describe floating equipment's.
7.5 Describe primary and secondary cementation.
7.6 Application of liner cementation.
7.7 Define cement plug.
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Part of the process of preparing a well for further drilling, production
or abandonment, cementing a well is the procedure of developing and
pumping cement into place in a wellbore. Most
commonly, cementing is used to permanently shut off water
penetration into the well.
Cement is used to hold casing in place and to prevent fluid migration
between subsurface formations.
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7.1 Define cementing.

Cementing Principle
• To support the vertical and radial loads applied to the casing
• Isolate porous formations from the producing zone formations
• Exclude unwanted sub-surface fluids from the producing interval
• Protect casing from corrosion
• Resist chemical deterioration of cement
• Confine abnormal pore pressure
• To increase the possibility to hit the target
Cement is introduced into the well by means of a cementing head. It
helps in pumping cement between the running of the top and
bottom plugs.
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7.2 Describe factors affecting cement slurry design.
Cement slurry is a mixture of Portland cement, water, and additives. A cement
slurry is forced into the annulus between the outside of the casing that has been
run in the well and the walls of the borehole.
• FACTORS AFFECTING CEMENT SLURRY DESIGN
The factors which influence the slurry design are :
1. Well depth, well diameter and casing size.
2. Bottom hole static temperature (BHST).
3. Bottom hole circulating temperature (BHCT).
4. Mud density/nature of mud in the well bore.
5. Samples of available cement, cement additives and water that is to be used in actual
job.
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The thermal and pressure conditions existing in the bore hole is of fundamental
importance to the planning, designing and execution of cementing operation. Also,
quality of cement, cement additives and mixing water affect the properties of
cement slurry. Slurry design should be carried out under well simulated conditions
with the cementing materials to be used at site. Following major factors have been
found important which need careful consideration in the design of cement slurry.
• DENSITY
Density of cement slurry is adjusted to:
1. Counter-balance the formation pressure,
2. Control the loss of slurry in weak zones,
3. Facilitate the effective mud removal/ displacement.
Normally, slurry density is kept higher than the mud for facilitating the
displacement of drilling fluid from annulus. The density difference of 0.2 to 0.5
gm/cc is normally recommended between mud and cement slurry .However,
formation to be cemented is the controlling factor to decide the extent of increase
over mud density .
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• THICKENING TIME
Thickening time is a function of both temperature and pressure. Thickening time
can also be shortened by interruption of pumping (loss of agitation). Thus,
thickening time of a slurry must be established for realistic conditions to
ensure adequate pumping time for slurry placement. BHCT is used for determining
thickening time. Thickening time of the cement slurry should be sufficient which
should enable the operator to place the slurry to the predetermined depth safely.
Some margin of safety is also included so as to cover up the time of break down
while cementing. However I excessive thickening time over job time should
be avoided to prevent:
1. Delays in resuming drilling operation
2. Formation of free water pockets
3. Settling and separation of cement slurry components
4. Loss of hydrostatic head and gas cutting. Normally, recommended thickening
time is considered to be one hour plus the time required for the job.
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7.3 State cement additives.
The rate at which hydration occurs when water is mixed with cement can be
altered using chemical additives. Additives are chemicals and materials
blended into base cement slurries to change the performance of the cement.
Due to the inherent nature of base cements and because of the demands
placed on the cement sheath throughout the life of the well, the
performance properties of the cementing slurry are modified to address the
specific and unique conditions of each well Anon. Many of the additives
currently used are organic, polymeric materials which have been specifically
formulated for use in well cementing operations Cowan and Eoff. Typical
chemical additives for oil and as well cementing operations include;
accelerator, retarders, extenders, fluid loss and loss circulation additives,
dispersants, and many more.
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There are 8 general categories of additives.
• Accelerators reduce setting time and increases the rate of
compressive strength build up.
• Retarders extend the setting time.
• Extenders lower the density
• Weighting Agents increase density.
• Dispersants reduce viscosity.
• Fluid loss control agents.
• Lost circulation control agents.
• Specialty agents.
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7.4 Describe floating equipment's.
Floating equipment is generally used in the lower section of the well to help:
• Reduce strain on the derrick while guiding casing past ledges and slough zones in
the hole;
• Provide a landing point for bottom and top cementing plugs (pumped ahead of
and behind the slurry as part of cementing operations);
• Provide a backpressure valve to prevent cement from flowing back into the inner
diameter of the casing after the cement has turned the corner into the annulus
and the top plug has been bumped.
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Basic floating equipment includes the float collar and either the guide shoe or float
shoe:
• The guide shoe runs on the first joint of casing to be run into the hole to help
maneuver the casing past annular irregularities. The guide shoe includes side
ports and an open end to enable fluid circulation for mud conditioning, hole
cleaning, and cement placement.
• The float shoe contains a backpressure valve that prevents fluids from entering
the casing while the pipe is lowered into the hole and prevents cement from
flowing back into the casing after placement, while enabling circulation down
through the casing.
• Float collars are placed one to three joints above the guide shoe or float shoe.
They provide a seat for the cement plugs, the bottom plug pumped ahead of the
cement and the top plug behind the full volume of slurry. Once seated, the top
plug shuts off fluid flow and prevents over-displacement of the cement. The
space between the float shoe and the float collar provides a containment area to
entrap the likely-contaminated fluids from the wiping action of the top cementing
plug, securing the contaminated fluid away from the shoe where a strong cement
bond is of primary importance. Float collars include a backpressure valve and
serve basically the same function as the float shoe.
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Advantages of Float Equipment's
• Drillability of plugs and float equipment is easy and fast with either
conventional rotary bits or PDC bits.
• WiperLok system provides a proven anti-rotational mechanism and is
available in both standard as well as Sub-Surface Release plugs (SSR™
Plugs ).
• Withstands long periods of circulation with highly abrasive fluids.
• Top and bottom plugs rated to 80% of burst pressure for most
standard weight and grade casing.
• Polyurethane plug material is resistant to wear, making it ideal for
long casing strings
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Float Equipment's
• Sure-Seal 3™ Float Equipment
• Sure-Seal 3 Float Valves
• Guide Shoes
• Cement Nose Guide Shoe - Model 202
• Downjet Cement Nose Guide Shoe - Model 222
• Composite Nose Guide Shoe - Model 202WM
• Texas Pattern Guide Shoe - Model 112
• Saw Tooth Pattern Guide Shoe - Model 105
• Large Bore Guide Shoe - Model L202
• Sure-Seal 3 Float Shoes
• Sure-Seal 3 Float Shoes
• Sure-Seal 3 Float Collars
• Auto-Fill Float Equipment
• Stab-in Float Equipment
• Insert Float Equipment
• SurgeMaster II
• MudMaster II Filter Shoe ™ and Auto-Fill Float Equipment
• Centralizer Sub and Float Equipment
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7.5 Describe primary and secondary cementation.
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Basic cementing procedure
1. Running Casing
2. Circulating mud by rig pump
3. Pressure testing
4. Pumping wash and spacer
5. Dropping the bottom plug
6. Mixing slurry
7. Pumping lead slurry
8. Pumping tail slurry
9. Dropping the top plug
10. Displacing slurries and plugs with fluid
11. Checking returns
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Running casing
• The first joint of the casing run into the well has a float or guide shoe
attached to the end.
• After the first or second joint, a float collar is installed. The space
between the float collar and the shoe is called a shoe track.
• When the casing string is run to the desired depth, special
connections may need to be made just at the wellhead; this process is
called nippling up.
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Pressure testing
The high-pressure treating lines running from the cement unit to the
well connection must be pressure tested before the cementing process
begins
1. Prime the cement unit and lines with water to fill all the lines
2. Close the valve at the wellhead, and make sure no one is near the
lines
3. Increase the pressure to a predetermined level by having the unit
pump water.
4. Hold the pressure for about 5 minutes, and monitor for leaks.
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Checking returns
• The float collar contains a check valve
• At the end of a cementing job, check to ensure that the float collar or
float shoe is not leaking
• This check is done by allowing fluid to flow back to the cement unit
displacement tanks
• If the float collar or shoe is working correctly, 2 to 5 bbl will flow back
and then stop
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Remedial/Secondary Cementing
When a primary cement job objectives have not been achieved, or
when the cement or casing has failed over time, it may be necessary to
repair the problem.
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Squeeze cementing
Cement slurry is forced through holes or splits in the casing to repair a
primary cement job or a well problem.
Purposes of squeeze cementing
1. Repair improper zonal isolation
2. Eliminate water intrusion
3. Repair casing leaks
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7.6 Application of liner cementation.
A liner is a string of casing that does not extend up to the wellhead. It
is used to case-off the open hole below an existing casing string.
Running such a string at the end of a drilling operation ensures that
the completion will be run in unworn casing.
Application
Cement plug system used in liner applications typically serve two
basic function:
1. They serve as physical barriers between the cement and other
wellbore fluids as they are being pumped, while effectively
wiping the cement from the tabular that its pumped through.
2. They confirm displacement volumes of both the running string
and the liner. Visible pressure indications signal when the
cement has been completely displaced from both the drill pipe
and the liner casing.
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7.7 Define cement plug.
Cement plugs are placed into the casing or the open hole for many purposes:
• Abandoning depleted zones
• Sealing off lost circulation zones
• Sidetracking or directional drilling
• Abandoning the entire well
There are two techniques to place cement plugs: dump bailer and balanced plug.
• Dump bailer: this method requires the use of a bridge plug. The tool which contains the
cement slurry is run with the wireline and it is opened when it touches the bridge plug and
then the cement is dumped while pulling the tool. This method is used for shallow depths.
• Balanced plugs: it is the most common method. It is performed by running drill pipe string or
tubing at the desired depth. The mud contamination is avoided by pumping spacer to provide
proper placement. The volumes should be carefully calculated to obtain equal height of
cement in the annulus and the drill pipe string when completing the displacement and then
the string is slowly pulled with no rotation in order to do not disturb the balanced cement
plug.
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Any Questions
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THANKS TO ALL
August 3, 2022 43

Understanding Well Cementing Principles

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