well cementing

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Well design & completionwww.utp.edu.my

By: Dr. Syahrir Ridha

WELL CEMENTING

Describe the principal functions of cement. Describe the major properties of cement slurry and the

additives used in the cement slurries. Calculate the volume of: slurry, cement, mixwater, displacing

fluid required for a single stage and two-stage cementing operation.

Describe the reasons for setting cement plugs. Describe the principal methods for placing a cement plug in

casing or open hole. Describe the principles involved and the tools and

techniques used to evaluate the quality of a cementing operation.


Lesson Outcome

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Cementing Illustration


Objectives

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Objectives


Objectives

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Cementing Operation

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These practices are called single stage cementing

Single-Stage Cementing Operation


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Multi-Stage Cementing Operation

The idea is to split the cement sheath in the annulus into two, which are:• From the casing shoe to some point above

potentially troublesome formations at the bottom of the hole;

• The cement covering shallower troublesome formations.

Why?1. Long pumping times2. High pump pressures3. Excessive hydrostatic pressure on

weak formations due to the relatively high density of cement slurries.

How its work????


Inner String Cementing

It is also known as Stinger Cement Job to cement the casing through a tubing or drillpipestring, rather than trough the casing itself.

Why we need this ???

For LARGE diameter casing, such as conductor and surface casing, conventional cementing techniques result in: The potential for cement contamination during pumping nad

displacement Large displacement volume Long pumping times Large volume of cement left inside the casing between float

collar and shoe.


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Stinger String Operation


A special float shoe is run rather than conventional one.

Once the surface casing (or others) has been run, the string (generally tubing) with the seal adapter attached is run and stabbed into the float shoe.

Drilling mud is then circulated to ensure the annulus clear of any debris.

The cement slurry is pump with spaces ahead and behind.

No plugs are used in this operation since diameter of stinger is so small.

Conventional cementing techniques cannot be used for cementing a liner.

Special equipment must be used for cementing these liners.

The liner has a float collar and shoe installed. There is also a landing collar, positioned about

two joints above the float collar. A wiper plug is held on the end of the tailpipe

of the running string by shear pins. The liner is run on drillpipe and the hanger is set

inside the previous casing string. Mud is circulated to ensure the liner and

annulus free from debris.

Liner Cementing


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http://www.linertools.com/Publications/how_to_run_and_cement_liners_part_1.pdfFurther reading

1. Pump spacer/wash2. Pump slurry3. Release pump down plug (dart)4. Displace cement down the running string, to the

liner and into the annulus5. Continue pumping until the pump down plug

lands on the wiper plug6. Bleed off pressure and check for back pressure.7. Setting tools release

Procedures as follow:

Liner Cementing


QUESTIONS


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Cementing Equipment Evolution




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Properties of Cement




API fluid-loss rate less than 50 mL/30 min is often required

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Classes of Oilwell Cement


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API Cement Classification



Cement System


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Cement Additives



Cement Additives

A chemical agent used to increase the thickening time of cement slurries to enable proper placement.

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Cement Additives


Cement Additives

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Cement Additives

Remedial Cementing

Remedial cementing is usually done to correct problems associated with the primary cement job.

The most successful and economical approach to remedial cementing is to avoid it by: thoroughly planning, designing, and executing all

drilling, primary cementing, and completion operations.

Remedial cementing needed to restore a well’s operation indicates that primary operational planning and execution were ineffective resulting in costly repair operations.

Remedial cementing operations consist of two broad categories:1. Squeeze Cementing2. Plug Cementing


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It is the process by which hydraulic pressure is used to force cement slurry through holes in the casing and into the annulus and/or the formation.

This jobs are often used to carry out remedial operations during a workover on the well.

Squeeze Cementing Application

i. To seal off gas or water producing zones for maximizing oil production;

ii. To repair casing failures by squeezing cement through leaking joints or corrosion hole;

iii. To seal off lost circulation zones;iv. To carry out remedial work on a poor primary cement job;v. To prevent vertical reservoir fluid migration into producing zones;vi. To prevent fluids escaping from abandoned zones.

Squeeze Cementing


Methods

High Pressure SqueezeThis method require the formation to be fractured, which then allows the cement slurry to be pumped into the fractured zone.

Low Pressure SqueezeIn this method , the fracture gradient of the formation is not exceeded during squeezing.

Cement slurry is placed against the formation, and when pressure is applied the fluid content (filtrate) of the cement is squeezed into the rock, while the solid cement material (filter cake) builds up on the face of the formation.

Squeeze Cementing


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Testing the Squeeze JobAfter the cement has hardened it must be pressure test.It should include both positive and negative differential pressure.

Positive pressure test can be performed by closing the BOPs and pressuring up on the casing (Do not exceed formation fracture gradient).

Negative pressure test (inflow test) can be performed by reducing the hydrostatic pressure inside the casing. This can be done using a DST tool. This test is more meaningful since mud filled perforations

may hold pressure from the casing, but may become unblocked when pressure from the formation is applied.

Squeeze Cementing


A cement plug is designed to fill a length of casing or open hole to prevent vertical fluid movement.

Cement plugs may be used for:i. Abandoning depleted zonesii. Seal off lost circulation zonesiii. Isolating a zone for formation testingiv. Abandoning an entire well

Plug Cementing


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Balanced plugThis method is aimed to achieve equal level of cement in the drillpipe and annulus.

Preflush, cement slurry and spacer fluid are pumped down the drillpipe and displaced with mud.

The displacement continues until the level of cement inside and outside the drillpipe is the same (balanced).

If the levels are not the same then a U-tube effect will take place.

The drillpipe can then be retrieved leaving the plug in place.

Plug Cementing


Techniques for placing cement plug

Dump bailer This is an electrically operated device which

is run on wireline. A permanent bridge plug is set below the

required plug back depth. A cement bailer containing the slurry is then

lowered down the well on wireline. When the bailer reached the bringe plug the

slurry is released and sits on top of the bridge plug.

Advantages over Balanced PlugHigh accuracy of depth controlReduced risk of contamination of the cement

Plug Cementing


Techniques for placing cement plug

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Cementing Evaluation

A primary cement job can be considered a failure if the cement does not isolate undesirable zones

Why ?? The cement does not fill the annulus completely; The cement does not provide a good seal between the casing and the

borehole; The cement does not provide a good seal at the casing shoe and a poor

leak off test is achieve.

>>Before these problems are existed, cementing evaluation is performed<<

Temperature survey detecting Top of Cement Cement Bond Log (CBL) detecting the Quality of cement bond

(between casing and cement) Variable Density Log (VDL) detecting the Quality of cement bond

(between casing and cement and also between cement and formation)


Temperature surveyInvolves running a thermometer inside the casing just after cement job.It responds to the heat generated by the cement hydration can be used to detect the top of cement

Radioactive surveyRadioactive tracers (carnolite) can be added to the cement slurry before pumped.A logging tool is rub after the cement job is completed.



Detecting Top of Cement

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Cement Bond Logs (CBL) This tools become the standard method of evaluating cement jobs,

since they not only detect the top of cement but also indicate how good the cement bond is.

It is a sonic tool which is rub on wireline. The distance between transmitter and receiver is about 3 ft. The logging tool must be centralized in the hole to give accurate results. Both the time taken for the signal and amplitude to reach the receiver

give an indication of the cement bond. The sound speed in casing > that formation or mud, then the first

signals received at receiver are casing. If the applitude is large (strong signal), this indicates that the pipe is

free (poor bond). When cement is firmly bonded to the casing and the formation, the

signal is attenuated.

Measuring quality of cement Bond



“Amplitude” low. Good cement. No

need for squeeze

GOOD CEMENT

“Amplitude” low. Poor cement.

Squeeze cement needed

POOR CEMENT

CBL interpretationCementing Evaluation


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Variable Density Logs (VDL) CBL only provide bond between casing and cement. VDL can indicate the quality between casing-cement and cement –

formation. A good bond between the casing and cement and cement and

formation is shown by wavy lines to the right of the VDL plot. The wavy lines correspond to those signal which have passed into

formation. If bonding is poor the signal will not reach the formation and parallel

line will be recorded all across the VDL plot.



Measuring quality of cement Bond

Example of VDL



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>>Be careful with CEMENT<<

Failure to do so…..

• Data gathering• Lab verification• Cement job simulation

• Cement placement• Flow rate control• Density monitoring• Enough slurry volume

• Hydraulic isolation• Bonding quality• Cement physical properties

Summary


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THANKYOU

well cementing

Documents

cement plugs

cement contamination

cement sheath

casing shoe

myobjectiveswell design

liner cementingwell

principal functions

stinger cement job