PNG 451

LAB REPORT 12 – Spring 2015

CEMENT HEAD LABORATORY

Cement a Casing String

Department of Energy and Mineral Engineering

Pennsylvania State University

Date of experiment : April 14, 2015

Section : 009

Group Member :

Christian Smith (ces5477)

Edward Korkollie Jr (etk5065)

Thishaanthan Samynathan (tys5343)

TABLE OF CONTENT

Summary ------------------------------------------------------------------------------- 2

Objectives ------------------------------------------------------------------------------- 2

Theory ------------------------------------------------------------------------------ 3

Materials ------------------------------------------------------------------------------ 4

Procedure ----------------------------------------------------------------------------- 7

Discussion ---------------------------------------------------------------------------- 8

1

SUMMARY

The purpose of this lab was to familiarize us with the cement displacement method

technique of wellbore-cementing through computer simulated program. After finding the

volumes of the annulus and the drillpipe, the strokes of cement slurry, water, and mud were

calculated using a pump factor of 0.0432 bbl/stroke. The number of strokes of cement slurry

was 2,704 strokes while the strokes of mud were 665 strokes. In this experiment, 10 barrels

(232 strokes) of water was pumped at the first stage instead of mud to create a water column

ahead of the cement. Cement was pumped next, then mud followed until the cementing was

successful. The cementing process concluded when a spike in pump pressure occurred as a

result of the diaphragm rupturing. In the field, however, another way of knowing when to

shut off the cement pump is when the volume of the water flow back from the water column

is close to the initial volume of water initially pumped in, or simply when the calculated

cement volume is finished.

OBJECTIVE

The main purpose of this lab was to learn how to evaluate the techniques of

cementing a casing in a well. Specific and systematic steps were taught in order to prevent

any disaster in the well which eventually would delay the oil or gas production. Each member

of our group has to have a full understanding on how to calculate the amount of cement slurry

needed for the well and the simulator operations. The casing cementing procedure was later

shown first by the lab instructor for better understanding before we cement by ourselves.

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THEORY

Different cementing equipment and placement techniques are used for cementing

casing strings, cementing liner strings, setting cement plugs, and squeeze cementing. A

casing string is different from a liner string in the fact that the casing extends to the surface,

while the liner is attached to the subsurface casing previously cemented in the hole. Cement

plugs are placed in open hole or in casing before abandoning a lower portion of the well.

Cement is squeezed into lost-circulation zones, abandoned casing perforation, or a leaking

cemented zone to stop undesired fluid movement.

Cementing Casing

When the casing string is ready to be cemented the cement slurry is prepared in a

special cementing unit for the type of the job (truck mounted for land jobs, skid mounted for

offshore).

The cement slurry is pumped from the unit to a special cementing head screwed into

the top joint of casing. When cementing begins, the bottom rubber wiper plug is released

from the plug container ahead of the cement slurry. The plug wipes the mud from the casing

ahead of the slurry to minimize contamination of the cement with the mud. The plug reaches

the float collar and stops. Continuing to pump cement causes a diaphragm in the plug to

rupture (a spike will occur in the pump pressure). This allows the cement slurry to be

displaced through the plug and into the annulus. After the desired volume of cement slurry is

pumped into the casing, the top wiper plug is released from the plug container. The top plug

displaces the cement plug by pumping drilling mud into the casing behind the top plug. When

the top plug reaches the bottom plug a pressure increase will be encountered which signifies

the end of the displacement operation.

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MATERIALS

Draw works console:

This helps to control the hoisting machinery of the drilling rig and allows the

traveling blocks be raised and lowered. The long handle next to the draw works

console is the main brake; this acts similar to a parking brake. It is the main lifting

control equipment of the rotary drilling rig. Contains five clutches and rheostat

controls that control the drum, rotary, table and pumps. Draw work brake enhances a

mechanism for controlling the weight on bit, penetration rate and the lifting of the

drill string.

Cement pump switch: a rotary switch that engages power to cement pump blower.

Mud pump 1 switch: a rotary switch that engages power to mud pump 1

Mud pump 2 switch: a rotary switch that engages power to mud pump 2

Rotary table switch forward/reverse: a rotary switch that applies power to the rotary

table.

R.T. Limit: rotating control that allows the operator to adjust the maximum power

applied to the rotary table.

Draw works forward/reverse: a forward and reverse switch that applies power to the

draw works.

Draw works: clutch used in engaging or disengaging mud pump.

Emergency Off: shuts power on the draw works in case of emergency.

Make Up: adds water to dilute or maintain the water-mud system.

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Breakout: controls the breakout tongs, which are large self-locking wrenches used to

grip the components of the drill string and apply force.

Rotary Table: the revolving section of the drill floor which provides power to turn the

drill string.

Draw Works: transmits the torque which is required for hoisting and braking. This

also stores the drilling live which is required to move the traveling block the length of

the derrick. It is the primary hoisting component of a rotary drilling rig.

Drilling console

Contains the analog and digital gauges used to monitor the key parameters

required for efficient drilling and effective well control. It also had four chart

recorders for monitoring pit level, drill pipe, penetration rate and casing pressures.

Rotary torque: a circular 4" face gauge that measures rotary torque with a scale of 0 to

1,000 amps.

Tong torque: a circular 4" face gauge that measures make up or break out torque.

Return mud flow: a circular 6" face gauge that measures the return in the flow line

from the well with a scale of 0 to 100%.

Rotary speed: a circular 4" gauge that measures the rotary rpm with a scale of 0 to 300

rpm.

Stroke counter: a digital readout of total elapsed strokes with rest and run/hold

control.

Drill pipe pressure: a circular 6" gauge that measures drill pipe pressure.

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Mud weight indicator: a digital indicator that measures return mud weight.

Casing pressure: a circular 6" gauge that measures casing pressure.

Deviation mud volume: a circular 6" gauge that measures the increase or decrease in

mud volume. It consists of high and low level set controls with two visual alarms.

Mud volume totalizer: a circular 6" gauge that measures the total mud in the system

with a scale of 0 to 1,000. A power on/off switch and four mud tank switches are

provided so the student can add or subtract mug from the system.

Trip tank: 4" circular tank that measures the total number of barrels of mud in the trip

tank.

On/off switch: a switch allowing the geolograph to be turned on or off.

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PROCEDURE

For this experiment, we were provided with the depth, hole diameter, and casing

size in order to find the volumes of the annulus and drillpipe. Afterwards, we were able to

calculate the total strokes of cement slurry and water.

First, the volume of the required cement slurry is calculated using the outer dimensions

of the casing. The volume of the slurry should be the same as the volume of the annulus

in this case.

With the calculated volume of slurry, the number of strokes required can be calculated.

Water is pumped down the wellbore first in order to create a leading water column.

After 10 barrels of water is pumped (equal to 232 strokes), pumps are switched off and

the bottom plug-wiper is lowered down the hole to remove any remaining mud or water

that may contaminate the cement slurry. The bottom wiper drops till it reaches the float

collar.

Pumping the cement

Before pumping the cement, we switched from the bottom head valve to the top one.

Now, the calculated cement volume is to be pumped from the cementing unit through

the casing to the annulus.

The pump is switched on, which allows the cement slurry to flow. At the beginning of

this process the pump pressure is expected to rapidly increase as a result of the cement

rupturing the diaphragm in the plug.

The pumping is continued until 2,704 strokes are reached then the cement pump was

shut off and the top wiper plug is released.

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After switching back to the bottom head valve, mud is pumped into the casing until the

top plug has reaches the float collar and the number of strokes achieves 665 strokes; a

spike in the pump pressure is usually a good indicator for the end of the cementing

process.

DISCUSSION

1) Describe the method of cementing the casing.

The cement slurry is pumped from the unit to a special cementing head screwed into

the top joint of casing. When cementing begins, the bottom rubber wiper plug is

released from the plug container ahead of the cement slurry. The plug reaches the float

collar and stops. Continuing to pump cement a spike will occur in the pump pressure.

After the desired volume of cement slurry is pumped into the casing, the top wiper plug

is released from the plug container. When the top plug reaches the bottom plug a

pressure increase will be encountered. Thus, this signifies the end of the displacement

operation.

2) Compare the method completed in the lab with other methods used in the industry.

Modified techniques from cementing casing are used in special situations. The

techniques include: Stage Cementing, Inner-String Cementing, and Annular Cementing

through Tubing, Multiple-String Cementing, Reverse-Circulation Cementing, and

Delayed-Setting Cementing. Stage Cementing allows the use of a cement column height

in the annulus that usually causes surface formations to fracture, and it can reduce

potential gas flow after cementing. The inner- String Cementing can reduce cementing

time. It uses float collar or shoe with sealing adapters that allows tubing or drillpipe to

be landed and hydraulically closed. Cement is displaced in the inner drillpipe or string

tubing instead of the casing. The Annular Cementing through Tubing allows pumping

cement through tubing in the annulus between two casing strings or between the casing

and the open hole. The Multiple-String Cementing involves cementing several strings of

tubing in the hole without the use of an outer casing string and it is a multiple

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completion method. The Reverse-Circulation Cementing allows pumping the slurry down

the annulus and displaces mud back through the casing. It is used when extremely low-

strength formations could be found near the bottom of the hole. It needs a special float

collar or shoe and it requires a special wellhead assembly. This method presents

difficulty in finding the end of the cement displacement because of the absence of wiper

plugs. The Delayed-Setting Cementing is used to achieve consistent mud displacement in

the annulus. It places retarded cement slurry with good filtration properties in the

wellbore before the casing.

3) Describe other uses of cementing.

a) Use to prevent the movement of fluids through the annular space outside the casing.

b) To stop the movement of fluid into fractured formations.

c) To close an abandoned well or a portion of a well.

d) To prevent casing corrosion - cementing a water bearing zone will help reduce the

corrosion of the casing and will also help protect it from shocks during drilling

operations.

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