IADC Drilling Manual Part 13 pot

Class A This product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as

A well cement which has been manufactured and supplied according to this specification may be mixed and placed

in the field using water ratios or additives at the user's discretion It is not intended that manufacturing ance with this specification be based on such field conditions

compli-Classes and Grades.

Well cement shall be specified in the following Classes (A, B, C, D, E, F, G and H) and Grades (O, MSR andHSR)

Class A

This product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have been shown to meet the requirements of ASTM C 465 This product is intended for use whenspecial properties are not required Available only in ordinary (O) Grade (similar to ASTM C 150, Type I)

Class B

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have been shown to meet the requirements of ASTM C 465 This product is intended for use whenconditions require moderate or high sulfate-resistance Available in both moderate (MSR) and high sulfate-

resistance (HSR) Grades (similar to ASTM C 150, Type II)

Class C

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as in interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have been shown to meet the requirements of ASTM C 465 This product is intended for use whenconditions require early strength Available in ordinary (O), moderate sulfate-resistance (MSR) and high sulfate-resistant (HSR) Grades (similar to ASTM C 150, Type III)

Class D

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have shown to meet the requirements of ASTM C 465 Further, at the option of the manufacturer,

suitable set modifying agents* may be interground or blended during manufacture This product is intended for useunder conditions of high temperatures and pressures Available in moderate sulfate-resistant (MSR) and highsulfate-resistant (HSR) Grades.

Class E

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have been shown to meet the requirements of ASTM C 465 Further, at the option of the manufac-turer, suitable set modifying agents* may be interground or blended during manufacture This product is intendedfor use under conditions of high temperatures and high pressures Available in moderate sulfate-resistance (MSR)and high sulfate-resistant (HRS) Grades

Class F

The product obtained by grinding Portland cement clinker, consisting of essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition At the option of themanufacturer, processing additions* may be used in the manufacture of the cement, provided such materials in theamounts used have been shown to meet the requirements of ASTM C 465 Further, at the option of the manufac-turer, suitable set-modifying agents* may be interground or blended during manufacture This product is intendedfor use under conditions of extremely high temperatures and pressures Available in moderate sulfate-resistant(MSR) and high sulfate-resistant (MSR) Grades

Class G

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicatesusually containing one or more of the forms of calcium sulfate as an interground addition No additions other thancalcium sulfate or water, or both, shall be interground or blended with clinker during manufacture of Class G wellcement This product is intended for use as a basic well cement Available in moderate sulfate-resistant (MSR)and high sulfate-resistant (HRS) Grades

Class H

The product obtained by grinding Portland cement clinker, consisting essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulfate as an interground addition No additions other thancalcium sulfate or water, or both, shall be interground or blended with the clinker during manufacture of Class Hwell cement This product is intended for use as a basic well cement Available in moderate sulfate-resistant(MSR) and high sulfate-resistant (HSR) Grades

The placement of any cement composition depends primarily on temperature rather than depth The API testingschedules for standardization purposes have been developed after many years of study and industry cooperation.This is an average and extrapolative data should be used with caution as it may not meet your well conditions.Instrumentation is available to measure bottom hole circulating temperature very easily in today's field operationsbefore each cement job These schedules in Table T1-1 represent average temperatures at various depths alongthe Gulf Coast and may not correspond to temperatures at the same depths in other areas

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Chapter T: Cementing

Table T1-1 Basis For API Well-Simulation Test Schedules

Values in parenthesis represent the time for the first sack of cement to reach bottom hole conditions

D Testing and Blending

In recent years, major advancements have been made in oil well cements, admixtures for cements and equipmentfor testing cements The development of the Pan American thickening time tester makes possible the testing of oilwell cements under simulated temperature and pressure conditions encountered in actual well operations SeeFigure T1-1

Figure T1-1 The Pressure-Temperature Thickening Time Tester

It should be used with samples of actual cement and mixing water where placement conditions are critical

Tests such as these give accurate data as to the thickening time of a cement under prescribed well conditions

The cements used in oil wells are usually referred to as portland, high early strength and retarded However, withthe tremendous number of admixtures available, the cementing of an oil well has developed into what may beregarded as a chemical service Cementing compositions are now being tailormade for specific well conditions.The inauguration of bulk cement blends are then delivered to the well site in specially designed carriers wherecementing units complete the job of mixing and pumping the cement into the well.

E Yield of Cements

Due to the ease of making calculations, it is becoming more common to estimate the amount of cement required interms of cubic feet of cement in cementing oil wells Overseas operations often require the quantity of cementreported in cubic meters and the weight of the slurry in specific gravity, instead of pounds per gallon or pounds percubic foot This change has been due to the fact that more cement is brought to the job in bulk trucks rather thansacks Table T1-2 gives the relations of the yield of cement slurry in cubic feet per standard sack and cubic metersper standard sack

Table T1-2 Yield of Cements

Density is expressed in pounds per gallon, pounds per cubic foot and specific gravity

A General Types of Casing and Reasons for Cementing

1 Conductor casing or pipe: set to prevent caving around the mouth of the bore and conduct drilling fluid to asufficient height while drilling surface hole

2 Surface casing or pipe: set to protect fresh water zones, to guard against possible cave-in of the near-surfaceformations and to provide a position for the initial well control devices

3 Intermediate or protection string: run inside the surface pipe to protect the hole for various reasons One ormore such strings may be set

4 Oil string: set to isolate and protect the prospective producing formations; to test for production and for purposes

of completing the well as a producer With respect to the above general types of easing, it is only when it is

cemented and a strong tight seal is formed between the casing and wall of the hole, does casing do the job forwhich it is intended

B Reasons for Cementing

The cementing of oilwells accomplishes the following:

1 Bonds the casing to the formation, thus supporting and strengthening it

2 Protects the oil producing zones

3 Seals against contamination to fresh water zones that may be used for domestic supply and protects otherpossibly useful strata such as coal, potash, and other oil and gas zones not being used

4 Helps prevent blowouts from high pressure zones behind the casing

5 Protects the casing from excluded corrosive waters and lowers electrolytic currents

6 Seals off "lost circulations" zones and other troublesome formations in order to drill ahead

7 Protects surface pipe and intermediate casing strings while drilling additional hole Uncemented pipe is severelyshock loaded

8 Prevents the vertical migration of formation fluids between the casing and hole wall

9 Provides a base for fracturing, squeeze cementing and future workover during the life of the well

C Casing Running Equipment and Accessories

The surface equipment usually required for running of casing in a well consists of a spinning line, or power tongs,conventional power tongs, special slips, or spiders The subsurface equipment attached to the casing are centraliz-ers, casing shoe or float shoe and/or float collar, and wall cleaners The type of each piece of subsurface equip-ment varies with the requirements peculiar to the well to be cemented, the type and design of the casing stringused The subsurface equipment may be described briefly as:

1 The guide shoe usually used with a float collar in the casing string; it is placed on the bottom joint of casing andhas a rounded nose to prevent digging into the side of the hole wall

2 Float shoes can be divided into two classifications:

a Seal type shoe that allows the casing to be floated down filling the casing at the top from a hose connected tothe standpipe.

b The differential type shoe that allows the drilling fluid to enter the casing at the bottom as it is being lowered butonly allows the fluid level in the easing to reach 91% of the fluid level in the annulus Designed to eliminate orreduce high pressure surges against the formation as casing is lowered

3 The float collar is usually made up in the easing string about one joint above the casing shoe essentially servesthe same purpose as the float shoe but for different application of the cement

4 Centralizers are attached to the casing to center the casing in the bore of the hole thus securing a uniformdeposit of cement around the casing

5 Scratchers or wall cleaners are attached to the casing to remove the mud cake from the hole wall thus assuring

a better bond between the wall and the cement Wall cleaners are generally cable or spring wire devices and are

of two types:

a The rotating wall cleaner which removes the mud cake by simply rotating the casing while circulating the drillingfluid Often preferred because it does not require the movement of the casing once it is set at the desired depth

b The reciprocating wall cleaner which requires the raising and lowering of the entire casing string

i.e.,reciprocation, to remove the mud cake

6 Cement Baskets attached to casing are commonly used to isolate the troublesome zones or coal, mineral, orpotable water strata above the production zones A packer is set inside the casing opposite the basket on theoutside The casing is perforated at the point and cement is squeezed through the perforations into the basket

As the weight of the cement builds up, the basket is forced against the hole wall to prevent the heavier cementslurry from slipping down in the annulus

D Types of Cementing Jobs

Most cementing jobs fall under three general classifications:

1 cementing through pipe and casing;

2 cementing through drill pipe;

3 cementing through tubing

1 Cementing through pipe and casing.

a Conductor pipe cementing job

b Surface casing cementing job

c Protection or intermediate string job single stage

d Protection or intermediate string job two stage

1) Placing two batches of cement with continuous cementing operations overlapping;

2) Bell hole job with two stages:

a) Gel, water or petroleum base compounds placed through top stage, this string being placed through a very largestring casing to allow for shilling of formations; modifications of this same job being used to combat corrosion, then;b) Bottom stage is cemented

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Chapter T: Cementing

f Production string job single stage

g Production string job two stage

h Production string job three stage

i Split pipe or split easing job

1) Locating split or leak in casing using plug method and measuring line

2) Locating split or leak using hook wall packer

j Liner or short string job

k Bull head squeeze job

2 Cementing through drill pipe or tubing.

a Placing cementitious materials for lost circulation problems

b Open hole plug back job

c Straight plug back job

d Bradenhead squeeze job

3 Cementing through tubing and, in some cases, drill pipe.

a Retainer (drillable) squeeze job

b Packer (retrievable) squeeze job

c Scabbing methods

1) Placing cement through perforated liner using straddle took, dump bailer, open ended tubing or drill pipe, downswab assumable, retainer and drillable tailpipe

2) Drillable sleeve cemented in place

d Liner or short string squeeze job using bradenhead

e Liner or short string squeeze job using packer type setting tool

4 Combination of various jobs and new developments.

a Top outside job, between easing or between casing and hole, using tubing or small diameter pipe

b Cementing annulus between string through casing head surface connection

c Combination job

1) Two sections of casing bottom section liner job

2) Top section single stage job using special Tool to joint two strings together

d Full hole job (in some areas called combination string), placing cement through tool above a liner which is thesame size as the casing

e Permanent-type completions (PWC)

f Concentric tubing

g Multiple tubingless completions

h Casing patch.

i Wireline squeeze jobs

II Plug Back Cementing

A Reasons for Placing a Cement Plug

Figure T2-1: There are several reasons for setting a cement plug

1 ZONE ISOLATION

In a well with two or more producing zones, it is sometimes beneficial to abandon a depleted or unprofitableproducing zone by placing a permanent cement plug above it, thus helping to prevent possible production loss into,

or fluid migration from, the lower interval

2 LOST CIRCULATION CONTROL

During the drilling operation, if mud circulation is lost, it is sometimes possible to restore circulation by spotting acement plug across the thief zone and drilling back through the plug Generally, this operation is less expensive than

a squeeze cementing job

3 DIRECTIONAL DRILLING

In an operation designed to sidetrack the hole around a non-retrievable fish, such as a broken drill string which hasbecome stuck in the hole, it is necessary to place a cement plug at a specific depth to help support the whipstockfor directing the bit into the desired area Another example of a controlled change in the drilling direction to helpreach a specific target area is in shoreline drilling operations for offshore production

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Chapter T: Cementing

4 FORMATION TESTING

A cement plug is sometimes placed below a zone to be tested which is considerable distance from the bottom, and

a straddle packer with a side wall anchor or a bridge plug is not possible or practical

5 ABANDONMENT

To seal off a dry hole or depleted well, a cement plug placed at the required depth, helps prevent zone tion and any migration of fluids that might infiltrate underground fresh water sources or cause undesirable surfaceconditions

communica-B Common Plug Back Techniques

1 THE BALANCE METHOD

Using this technique, Figure T2-2, the desired quantity of cement slurry is usually placed in the drill pipe or tubingand displaced from the bottom of the string until the level of cement outside is equal to that inside the string

Figure T2-2: Balance plug method

The pipe or tubing is then pulled slowly from the slurry, leaving the plug in place See T-3 Balancing a Plug forcalculations

ADVANTAGES: This method is simple and requires no special equipment other than a cementing service unit.OTHER CONSIDERATIONS:

A) When it is difficult to establish the top of a cement plug, it may be necessary for the well owner to run anexcess of cement, then pull the running-in string to the desired plug top and reverse out the excess cement abovethat point A loss of fluid to the formation below this point may cause a movement in the plug

B) Contamination of the cement with mud is possible, especially when using small volumes of cement

C) If the drilling mud is of low viscosity it may be necessary to place a viscous pill to keep the cement slurry fromfalling downhole

2 THE DUMP BAILER METHOD

This technique is usually employed at shallow depths, but with the availability of new materials it has been used todepths of over 20,000 feet The dump bailer, containing a measured quantity of cement, is lowered on a wire line

A Limit Plug, Cement Basket, permanent type bridge plug, or gravel pack is usually placed below the desiredplugging location The bailer is dumped and raised to place cement above the plug or basket, Figure T2-3

Figure T2-3: Dump bailer method

Method may include limit plug* (b), or a basket (c)

ADVANTAGES:

A) Since the tool is run on wire line, depth of plug is easily controlled

B) The cost of a dump bailer is usually low

OTHER CONSIDERATIONS:

A) Not as readily adaptable for setting deep plugs

B) Mud Contamination of cement may occur unless the well operator circulates the hole prior to dumping.C) Limited on the quantity of slurry that can be placed per run and initial set must be attained before the next runcan me made and the bailer dumped

3 THE TWO PLUG METHOD

This method, Figure T2-4, involves running top and bottom cementing plugs to isolate the cement from the welldisplacement fluids (similar to standard primary cementing practices)

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IADC Drilling Manual - Eleventh Edition

B Applications and Benefits of Squeeze Cementing

1 HIGH GAS/OIL RATIOS

Where an oil zone can be isolated from an adjacent gas zone, the gas/oil ratio can usually be improved to helpincrease oil production

2 EXCESSIVE WATER

Water sands can be squeezed off below the oil sand to help improve water/oil ratios Independent water zones canusually be squeezed to eliminate water intrusion

3 CASING LEAK REPAIR

A casing leak may be repaired by squeezing cement through the leak

7 DEFECTIVE PRIMARY CEMENTING JOB

Channeling or insufficient fill-up of the primary cementing job can usually be overcome by squeeze cementing

8 ABANDONMENT

Squeeze cementing is sometimes employed to seal old perforations or plug a depleted producing zone completed inopen hole This helps prevent fluid migration from the abandoned zone or well

C Common Squeeze Cementing Techniques

1 BRADENHEAD SQUEEZE METHOD

In this method, Figure T2-5, cement is pumped into the cased hole through tubing (or drill pipe), displacing wellfluids into the annulus

Figure T2-6: Squeeze Packer Method

The interval to be squeezed is isolated from the surface by a packer run on tubing Many types of packers areavailable, each designed for use when specific well conditions are anticipated Both retrievable and permanent(drillable) packers can be used It is recommended practice to pressure-test the tubing and casing prior to placingcement

In certain instances it is necessary to isolate the section below the perforations to be squeezed A drillable orretrievable bridge plug is placed below the perforations for this purpose The perforations above are then squeezedand the remaining slurry reversed out

ADVANTAGES:

A) Permits high squeeze pressures The squeeze packer isolates the zone to be squeezed

B) Closer control of the entire operation than with the bradenhead method

C) Permits more efficient placement of the slurry by the hesitation squeeze method

D) It is possible to get an effective squeeze job without having to drill out

3 HESITATION SQUEEZE METHOD

In general, modern cements with low fluid loss characteristics and the availability of retrievable packers and bridgeplugs have made this the most effective squeeze cementing method The hesitation method, Figure T2-7, involvesthe placement of cement in a single stage, but divided the placement into alternate pumping and waiting periods

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IADC Drilling Manual - Eleventh Edition

Pressure is held momentarily on the formation to verify static conditions and then released to determine if cementwill stay in place The excess slurry above the perforations is then reversed out

5 STAGE METHOD

The stage method is often employed in cases where continuous pumping fails to result in a pressure build-upbecause of thief zones in the formation This method involves mixing one batch of cement (30 to 100 sacks),displacing this into the formation, waiting at least until initial set, and repeating the operation as many times asrequired

D Squeeze Cementing Materials

The ideal squeeze cement slurry is designed to permit adequate thickening time, yet produce sufficient sive strength with minimum waiting-on-cement time Most slurries are designed with neat or retarded cements Inaddition, there are a wide variety of special cements and additives to cope with specific well problems

compres-E Special Cements

1 Diesel Oil Cement (DOC)

A mixture of cement, Diesel oil, and a dispersing surfactant This slurry is for water control; it has an indefinitepumping time and sets only when contacted by water

2 Radioactive Cement

Formulated with special tracer particles to aid in located squeezed cement sections with tools

3 Cal Seal (Fast Setting Plaster of Paris)

An extremely fast-setting materials They are often used in lost-circulation control and Low-temperature squeezecementing

4 Non-Cementitious

Chemical solutions used in water control operations

F Additives

1 LOW FLUID LOSS ADDITIVES

These additives help prevent rapid fluid loss (dehydration) under high-pressure squeeze conditions Adding smallquantities of certain low fluid loss additives builds up a filter cake which controls filtration rates and retards theslurry so setting of the cement against the formation and perforations can be accomplished, yet sufficient time isallowed to reverse the parent slurry form the casing Each of the additives in common use have been developedfor specific hole and temperature conditions They can be effective in formations containing shales or bentoniticsands that are sensitive to fresh water

2 OTHER ADDITIVES

Lost Circulation Materials, LCM, are sometimes helpful in partially bridging-off permeable formations in order topermit squeezing the thief zone with a minimum of slurry volume Retarders help extend cement pumping time athigh bottom hole temperatures Accelerators are often employed in squeezing shallow zones to shorten waiting-on-cement time, and to aid in obtaining an initial set of the slurry

There is a complete selection of these and other additives to help improve squeeze cementing results

IV Horizontal Well Completions

Oil and gas wells are drilled horizontally for a variety of reason, mostly to improve production with drilling multiplevertical wells and to prevent water or gas coning

Where the productive zone may be thin and of large areal extent, a horizontal well can help provide increasedexposure to the production area, rather than drilling multiple vertical wells

Parameters such as cement free water and solids suspension capability, spacer composition, wetting tics, pipe movement and mud properties, have been demonstrated by full scale laboratory testing and field experi-ence to be important in horizontal cementing

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IADC Drilling Manual - Eleventh Edition

When running a plug, the column of fluid in the tubing must balance the column of fluid in the annulus If the fluid

in the tubing is heaviest, then the fluid in the tubing will continue flowing down out of the end of the tubing and upinto the annulus after pumping is stopped If the annulus fluid is heaviest, then flow will be in the opposite directiondown the annulus and up the tubing after the pumping is stopped

In any case, the cement is liable to become contaminated with mud during such movement To avoid these ties, an effort is made to balance the column of fluid in the tubing with the column of fluid in the annulus Sincesome water is pumped ahead of the cement into the annulus, it is necessary to put some water behind the cement

difficul-in the tubdifficul-ing difficul-in order to keep the columns balanced

Also, displacement by the tubing or drill pipe in the cement slurry will cause the slurry to rise higher than the filluprequired until the tubing is pulled out of it

The term, "balancing a plug" refers to simply putting the right amount of water behind to balance that put ahead ofthe cement and pumping the right amount of mud to balance the two columns of fluid

B To Calculate Amount of Water to Follow Cement

The easiest way to do this is use Tables in Chapter V General Information to obtain the volume per linear foot ofthe annulus and the tubing Then, after it is decided how much water to pump ahead of the cement, take thatvolume of water times the ratio of tubing volume per foot over annular volume per foot For instance, with 2-3/8''4.7 lb/ft., EUE tubing in 6-1/2" open hole, it has been decided to run 10 barrels of water ahead of the cement in theannulus How much water must be run behind the cement to balance the plug?

H = Height of balanced cement column (in ft)

V = Volume of cement slurry used (in cu ft)

A = Annular volume between tubing or drill pipe and open hole or casing (in cu ft per ft)

CP = Capacity of tubing or drill pipe (in cu ft per ft)

D Amount of Mud Needed to Displace Cement and Water to Bottom

The cement fillup has been calculated and the water fillup has been calculated so the amount of mud to use topump the cement to the proper point will be:

[Total length of tubing - (Cement fillup + water fillup)] x bbls capacity per ft of tubing

E Example 1

Balance 100 sack cement plug in 6-1/2" open hole with 2 3/8" 4.7 lb/ft, EUE tubing at 8000 ft

Run 10 bbl water ahead of plug

Determine:

1) Depth to top of plug if common (Class A) neat cement is used

2) Amount of water to run behind cement to balance the 10 bbl of water run ahead

3) Amount of mud to pump to balance plug

100 sacks neat common cement will yield 100 x 1.18* = 118 cu ft of slurry

Annular Volume = 0.0356 bbls OR 0.1997 cu ft/ft**

Tubing Volume = 0.0039 bbls OR 0.0217 cu ft/ft**

* Yield in cu ft per sack from Table T1-2 Yield of Cements

**From Chapter V

Height of Plug = V/(A + Cp) = 117/(0.1997 + 0.0217) = 528 ft

Depth of Top of Plug = 8000 - 528 = 7472 ft

Amount of water behind plug to balance 10 bbl ahead of cement:

= {(Tbj Vol per ft)/(Annulus Vol per ft)} x 10 bbls = (0.0039/0.0356) x 10 = 1.1 bbls

Feet of Water in tubing = 1.1/(bbl/ft) = 1.1/0.0039 = 282 ft

Amount of mud needed to pump a balanced plug:

= [(8000 ft total depth) - (528 ft of cement + 282 ft of water)] x (.0039 bbls mud per ft) = 28 bbls

It is advisable, after balancing the plug as above, to under displace the cement down the tubing by a small amount,say 1/4 to 1/2 bbl, in order that the fluid column in the tubing will be slightly heavier than the fluid column in theannulus due to the added small amount of cement in the tubing This practice will help the tubing fluid to fall whenthe tubing is pulled to the top of the plug for reverse circulating The cement tends to hang in the tubing and

sometimes requires a little added weight to move it out of the tubing The added cement left in the tubing by underdisplacement will generally give the needed additional weight

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IADC Drilling Manual - Eleventh Edition

II Calculating Fillup

It is necessary in all cementing operations, except squeeze work, to have a pretty good idea of the fillup to beobtained from a certain amount of cement in a certain size hole or annular space These figures are available incubic foot per barrels per foot in Section VI Calculation is then worked as follows:

First, decide fillup desired (number of feet cement is to come up hole) and get the figure for cubic feet per foot offillup for that particular hole or annular space Second, then find the yield per sack in cubic feet for the particularslurry to be used from Section 1 Third, next divided the fillup desired in cubic feet by the slurry yield in cubic feetper sack This will give the number of sacks of cement needed per 100% fillup to the desired level

It is usually necessary to add to the cement volume calculated as above, because the hole is oversize or uneven orperhaps because cement may be lost into some formations The amount to be added varies from area to area, butoften runs between 10 and 50%

A Example 1

It is desired to cement 5-1/2-inch OD casing in 7-3/4-inch open hole to a height of 500 feet Operator wants to use50% safety factor because this has been found necessary in this area The cement to be used is neat Class Acement, with a yield of 1.18 cubic feet per sack How many sacks of cement are needed to get desired fillup?From Section IV Estimating Cement Required For Various Cementing Jobs

Annular volume between 5-1/2" OD casing and 7-3/4" OH = 0.1626 cubic feet per foot

Total Calculated Volume = 500 ft fillip x 0.1626 cu ft/ft

Total Calculated Volume = 81.3 cu ft

Sacks needed:

Total Calculated Volume = 81.3 cu ft / 1.18 cu ft/sk = 69.5 sacks

50% Safety Factor = 69.5 sacks x 1.5 = 104 sacks

B Example 2

It is desired to plug to abandon a 6-3/4" hole (no casing set) Plug to cover bottom 200 feet of hole Operatorwants to use Class A cement with 4% gel and it is common practice in area to allow a 20% safety factor, so hewishes to do that also

Volume of Hole (from Handbook) = 2485 cu ft/ft

200 ft x 2485 = 49.70 cu ft

Yield Class A Cement in 4% gel = 1.55 cu ft/sack

= (49.70 cu ft/155 cu ft/sack) = 32.1 sacks

Total Sacks to be Used = (safety factor = 20%, so) 1.20 x 32.1 sacks = 38.5 sacks

III Pumping Large Diameter Surface-string Up The Hole

Pumping the pipe up the hole may occur when attempting to start (break) circulation is preparation for the ing job on large diameter surface or conductor strings The usual cause is the accumulation of cuttings and cavingsaround the outside of the pipe If the rig pump is started to fast and the annulus is bridged, the pipe may be raisedfrom the hole The pipe should be chained down in any case where there is a possibility of pumping it out of thehole Good hole conditioning just before pulling the drill pipe, and breaking circulation at intermediate points while

cement-running the casing are two good practices to minimize the likelihood of this problem developing The formula forcalculating the pressure required to pump the pipe up the hole, if the same fluid is in the pipe and the annulus, is asfollows:

P = (Weight of Pipe/Area of Pipe OD)

With cement in the annulus and water in the pipe, the difference in the weights of the two materials will cause a lift

on the pipe also

That lift may be calculated as follows:

Lift = Pipe L x [(Hd of cmt/ft) - (Hd water/ft)] x (Area Pipe ID)

Note: some manuals call Hd of fluid/ft the Fluid Gradient and express it in psi/ft

If such lift exceeds or approaches the pipe weight, then the pipe should be anchored in some manner

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IADC Drilling Manual - Eleventh Edition

T-4 Estimating Cement Required For Various Cementing Jobs

To estimate the quantity of cement required to set a given string of casing in a give size hole, use the Volume andHeight Tables, Chapter V

Example: To determine the amount of cement to set 535 feet of 10.75 inch surface pipe to the top The surfacehole was drilled and reamed to 13.5 inches to 542 feet From Chapter V it requires 0.3637 cubic feet of cementslurry to fill one foot of the annulus between the casing and the hole wall

Therefore: 535 x 0.3637 = 194.6 cu ft of cement slurry

Open Hole: 542 - 535 = 7 ft of 13.5 inch hole

From table in Chapter V Capacity of Hole":

It requires 0.9940 cu ft of cement slurry for each foot of 13.5 inch hole

Therefore: 7 x 0.9940 = 6.96 cu ft of cement slurry

Hence the theoretical total required:

(Annulus = 194.6 cu ft) + (Open Hole = 6.9 cu ft) = 201.5 cu ft cement slurry

To estimate the number of sacks of cement required, use Table T1-2 Yield of Cements for yield of type of cement

to be used

Then: Total Slurry Required (cu ft) = {(No sxs dry cement)/(Yield(cu ft/sack)}

Hence, for Class D or Class E Cement: (201.5/1.08) = 130.0 sack of dry cement

Or for Class A + 4% Gel: (201.5/1.55) = 130.0 sack of dry cement

Note (1): Most of the older tables for hole and pipe capacity are based on an estimated yield of 1.1 cu ft per sack

of thumb to make sure that there is a sufficient cement on the location to do the job When drilling in a new or

"wildcat" area, a safe practice is to run a "Caliper Log," so that the average diameter of the hole can accurately bedetermined -particularly in the zone to be cemented

Glossary of Cementing/Casing Terms

A glossary of cementing terms commonly used is included for better understanding of the data presented in thissection This is in addition to the description of API classes in Section T1

ASTM Type Cement A portland cement, of which there are several types, meeting requirements of ASTM C

150, Standard Specifications for Portland Cement

Common Cement Either API Class A or ASTM Type I cements referred to as "common cement"

Construction Cement ASTM Type I, II or III and air-entrained modifications Although API Class A, B, and Cconform similarly to these cements, respectively, the air-entrained variations are not suitable for oil well cementing.Gel Cement A cement or cement slurry modified with addition of bentonite

High Early Cement API Class C or ASTM Type III cement

High Temperature Cement A cement designed to overcome strength retrogression

Hydraulic Cement Cement that hardens underwater

Modified Cement A cement whose properties are altered through the use of additives,

Neat Cement Cement or slurry containing no additives

Oil Well Cement Cement or any mixture of cement with other materials that is intended for use in oil, gas orwater wells (API definition)

Portland Cement A closely controlled combination of lime, silica, alumina, iron and small amounts of otheringredients, to which gypsum is added in the final grinding process to regulate setting time Named for an islandfamous for its gray limestone quarries

Pozzolan Cement A mixture containing cement and pozzolan, a volcanic ash type substance, with advantages incertain high temperature, deep wells, or as an expanded lightweight cement Some 2000 years ago Roman engi-neers mixed the first "pozzolana" or volcanic cement, which was the first hydraulic cement, hardening underwater.Retarded Cement Cement in which the thickening time is extended by adding a chemical retarder API Classes

D and F are retarded cements

Slow-Set Cement Cement in which the thickening time is extended by eliminating the rapid hydrating nents in its composition or by adding a chemical retarder API Classes D, E, and F are slow-set cements

compo-Weighted Cement Cement slurry containing additives to increase the normal density

Definitions Of Oil Well Cementing Additives

Accelerators Used for accelerating the early strength of oil well cementing slurries Small additions of thesematerials in cement reduce waiting on cement time, promote greater early strength and result in a saving of rigtime to the operator

Cement Dispersant Use of dispersants lower the apparent viscosity of the slurry This dispersing or thinningeffect means that a slurry will go into turbulence at a flow rate lower than would be required without such anadditive

Fluid Loss Additives Provide fluid control for deeper penetration and more efficient use of expensive acid Smallamounts of special additives may be combined with most fracturing fluids to help confine them within the fracture,thus increasing extension efficiency and enhancing proper placement of the propping agent

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IADC Drilling Manual - Eleventh Edition

Heavy-weight Additives Added to different type cements to increase density of slurries in deep wells where it isdesired to have the weight of the cement near that of drilling mud at the time of cementing for the control of highpressure oil and gas zones

Latex Added to cement to achieve low fluid loss values, lower viscosity in fresh and salt brine slurries, betterflow properties, and improved bonding

Light-weight (extenders) Used for the reduction of slurry densities and to increase fill-up of cement between thecasing and formation

Mud Decontaminant An additive to reduce the effects of contamination of cement slurries by the organicchemicals commonly found in drilling muds

Retarders Retarders make possible the formation of cementing compositions for any range of high temperaturewell conditions

Silica (Flour) Used as an additive to oil well cement making it possible to maintain low permeability and improvecement compressive strength under "hot hole" conditions

Special Additives Used to control gas migration problems in cement

Thixotropic Cement Thixotropic cements possess the ability to rapidly develop a high degree of gelatin, or staticgel strength, giving some unique advantages in special applications

Spacers & Washes

Fibers Synthetic fibrous materials are used for reducing shattering due to perforating, and improving total

resiliency

Spacers Aid in preventing combining of cement slurries with drilling muds, and in the minimizing of formationdamage

Special Cements Used to control gas migration problems in cement

Washes Used principally as reactive flush ahead of primary cementing to improve mud displacement, controlfluid loss, and alleviate lost circulation during cementing

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International Association of Drilling Contractors

Chapter U: SCR Systems

Chapter U Electric Drilling Rigs

Table of Contents - Chapter U

Electric Drilling Rigs

U-1 Silicon Controlled Rectifier Systems U-4

1 Introduction U-4

A DC/DC and SCR Systems U-4

B DC Drilling Motors U-4 U-2 SCR (AC/DC) Power Systems U-6

A Ac Electrical Power Generation U-6 A3 AC Switchgear U-7

B AC/DC Conversion U-8 U-3 DC/DC Power Systems U-13

A Introduction U-13

B Controls U-13

C Braking U-13

D System Protection U-14

E Driller's Console U-14 U-4 Maintenance U-15 General U-15 Maintenance Section Outline U-15 Daily Maintenance: U-22 Monthly Maintenance: U-22 Repair: U-22 U-5 Technical Index U-23

1 Maintenance Checklists: U-23

2 Reference Handbooks U-24

inter-It is not intended that the contents of this manual replace or take precedence over manufacturer's, operators orindividual drilling company recommendations, policies and/or procedures In those areas where local, state andfederal law is in conflict with the contents then it is deemed appropriate to adhere to suer laws IADC has endeav-ored to insure the accuracy and reliability of this data, however, we make no warranties or guarantees in connec-tion with these recommendations.

As technology continues to develop this manual will be updated It is important that the user continue to updatetheir knowledge through research and study

FIGURE U1-2: DC Series Motor Schematic

The shunt motor is the simplest to control since its speed is directly proportional to the DC volts supplied across itsarmature and its torque output is directly proportional to amperes Load does not appreciably effect the speed ofthe motor The speed of an uncontrolled series motor is greatly affected by its load With light loads, a series motorcould overspeed and damage itself and the equipment it is driving There are many methods in use today to protectthe motor and equipment from this overspeed condition

They include:

Electronic circuitry to make the series motor characteristic simulate that of a shunt motor (Load has no ciable effect on speed.)

appre-Speed regulation is provided via a motor mounted tachometer

A motor mounted overspeed device shuts off the motor if it exceeds a set speed

The motor is shut down any time the load (current) decreases below a given volume signifying a broken chain, belt,sprocket, etc

Series motors have excellent speed-torque characteristics for accelerating loads from a standing start to full speedwhich is perfect for efficient drawworks operation Series motors also have excellent load sharing characteristicsfor multiple motor loads

The following is a list of components found in all SCR cubicles:

B2a Circuit Breakers

The circuit breaker connects and disconnects the 3 phase AC power bus to the SCR rectifier section with theadded function of limiting fault current

B2b Fuses

Aiding in this protective function are current limiting power fuses

Some SCR systems have six fuses (one negative and one positive on the DC or load side of the bridge)

Some SCR systems have 3 current limiting power fuses (one per phase on the AC or line side of the bridge)

All power fuses have the task of limiting damage to the SCR's in a fault condition.

FIGURE U2-2: Power Circuit Diagram

B2c SCR Heat Sink Assemblies

Since SCR's control a great deal of the current and all real world electrical components have some resistance, heat

is generated This heat is removed by mounting the SCR in a heat sink assembly consisting of an aluminum

extrusion The heat is passed from the SCR to the heat sink and then to the air by forcing a large volume of airover the heat sinks (by a blower assembly) When the cabinet doors of most SCR cubicles are opened the heatsinks are usually the most obvious components in view

B2d Electronic Controls

The DC control electronics have five (5) basic functions:

1 Receive a throttle signal

2 Convert this signal to a synchronized gate firing signal to turn the SCR's on at the proper time

3 Measure the result (DC power output) and make any error corrections

4 Measure the DC current being produced and compare it to the current limit setting and inhibit the current fromexceeding that setting

5 Accept power limit signal from AC generator control section

B2e Throttle Signal

The throttle signal comes from the driller's console and represents a desired speed for a drilling load (mud pumpstrokes per minute or rotary table rpm) By determining when an SCR turns on in an electrical cycle the output DCvoltage can be varied from 0 to 750 volts DC See Figure U2-3

U-12 International Association of Drilling Contractors

IADC Drilling Manual - Eleventh Edition

B3d 600 to 480 Volt Distribution Transformer

Electric rig power is produced at 3 phase, 60 hertz, 600 volts AC to allow efficient usage of the drilling motors at

750 volts DC However, most AC motors of the size required on a drilling rig are built to use 3 phase, 60 hertz, 480volt AC A transformer is used to convert 600 volts to 480 volts AC

B3e Motor Control Center (MCC)

This 480 volts AC is used to power a motor control center which is a self contained collection of AC motorstarters, all connected internally to a common AC bus A typical MCC will contain approximately 30 starters and

10 to 12 circuit breakers only

The output of each starter is wired to a given AC motor on the rig The starters purpose is to safely start and stopthe AC electric motors on a bridge The starters all contain: a disconnecting device (electrically operated switch);and an overload relay to protect the motor against a continuous overload

B3f Lighting Panel

Most lighting circuits run on 120 volts AC or 208 volts AC and, therefore, most rigs have another transformerwhich is connected to a lighting circuit breaker panel (just as a house has) which is connected to the lights on a rig

8 Inspect printed circuit boards, modules, and other electrical components for damage or overheating.

Monthly Maintenance Procedure:

1 Clean each SCR bay monthly to remove dust and dirt by using the suction side of a vacuum cleaner Neverblow the equipment with forced air to clean it

CAUTION: Be sure all power is off before this procedure is followed

2 Thoroughly tighten all bolts and hardware in the equipment and replace any hardware that is missing

CAUTION: Be sure all power is off before this procedure is followed

3 Calibrate all meters from a reference source

4 Check operation of all controls, including assignments, reversing, dynamic braking, operation of mud pumps, andother functions

a Replace fuses

b Replace SCR bridges, cells, or assemblies

c Replace printed circuit cards

d Replace control modules, such as AC Module, DC Module, Voltage Regulator, Governor, Reverse Power, orsimilar assemblies

e Repair wiring terminations

f Replace damaged DC contactor tips

g Replace defective relays

h Repair mechanical damage

i Adjust instrument "zero" with screwdriver

j Replace any overheated component and determine cause of problem

B AC GENERATOR CONTROLS

Daily Maintenance Procedure:

1 Inspect exterior surfaces of panels for dirt, grease, oil or physical damage

2 Inspect interior for dust, dirt, oil, grease, metal, water, or corrosion (CAUTION: Do not touch live electricalparts.)

3 Inspect meters for proper operations, including KW, KVAR, POWER FACTOR, AMMETER, VOLTMETER,FREQUENCY METER, and SYNCHROSCOPE Cheek for proper load balance between paralleled genera-tors using these instruments

International Association of Drilling Contractors

Chapter U: SCR Systems

5 Check all modules and equipment for overheating or electrical damage through visual inspection

6 Are generator controls and governors operating properly? Cheek for instability of voltage or frequency

7 Check the status of all control switches, circuit breakers, and controls

Monthly Maintenance Procedure:

1 Clean each generator control bay monthly with a vacuum to remove dirt, dust, and oil particles

CAUTION: Be sure all power is off before this procedure is followed

2 Thoroughly tighten all bolts and hardware in the equipment and replace any hardware that is missing

CAUTION: Be sure all power is off before this procedure is followed

3 Calibrate all meters from a reference source

4 Check operation of all controls, including voltage regulator, governor paralleling, synchronizing, load sharing, andcircuit breakers

Repair:

1 All repairs should be performed by competent, trained electricians or technicians who are familiar with tor control equipment All power should be removed from the equipment before any repairs are made to avoidcostly accidents

genera-2 Those items that can be easily repaired or replaced are included in the following list and are considered modules

or significant components Repair of printed circuit cards, or other electronic components, should not be attemptedexcept in emergencies

a Replace circuit breaker

b Replace AC Module, DC Module, Voltage Regulator, Electronic Governor, Reverse power Relay, Overvoltage/Underfrequency Module or other control modules

c Replace defective meters or instruments

d Replace defective voltage or speed control adjusts

e Repair wiring terminations

f Replace defective lamps

g Repair mechanical damage

h Adjust instrument "zero" with screwdriver

i Replace any overheated component and determine cause of problem

C MOTOR CONTROL CENTER AND SWITCHGEAR

Daily Maintenance Procedure:

1 Inspect exterior surfaces of MCC sections and controls

2 Inspect interior of each section for overheating and proper operation of components Inspect for dust and otherforeign matter

3 Check for loose hardware

4 Check all circuit breakers and disconnect switches

Monthly Maintenance Procedure:

1 Clean each MCC cubicle and switchgear bay with a vacuum to remove dust and other debris; do not blow thedust loose with a vacuum

CAUTION: Be sure all power is off before this procedure is followed

2 Thoroughly tighten all bolts on components and equipment Replace any missing hardware

CAUTION: Be sure all power is off before this procedure is followed

3 Calibrate all meters and instruments from a reference source

4 Inspect each overload relay and motor protective device

c Pushbuttons, lamps, controls, switches

d Wiring terminations, connectors, plugs

D DRILLER'S CONSOLE AND FOOT THROTTLE

Daily Maintenance Procedure:

1 Inspect exterior of console for damage to the enclosure or instrument window

2 Inspect exterior of console for damage to connectors, throttles, meters, switches, pushbuttons, or other nents

compo-3 Inspect exterior of foot throttle for damage to pedal or connector

4 Inspect air pressure equipment to console and throttle to assure positive pressure or flow

5 Inspect interior of console for dust, dirt, or foreign material

6 Inspect interior of console for overheated components or loose connections

CAUTION: Be sure all power is off before touching any electrical terminal or component

7 Check instruments and lamps for operation

8 Operate the throttles and other controls for proper operation

9 Operate the foot throttle for proper operation

Monthly Maintenance Procedure:

1 Clean the console and foot throttle monthly with a vacuum to remove dust, dirt and other debris

CAUTION: Be sure all power is off before following this procedure

2 Tighten all loose hardware and replace any missing hardware

International Association of Drilling Contractors

Chapter U: SCR Systems

4 Inspect all wiring terminations and reconnect as required

5 Operate all control functions, including throttles, switches, assignments, and meters to assure proper operationfrom the driller's console

6 Operate the foot throttle in conjunction with the driller's console

Repair:

1 All repairs should be performed by competent electricians or technicians who are familiar with the operation ofthis equipment Power should be removed from all equipment that is being repaired or replaced

2 The following items can be repaired or replaced in the driller's console or foot throttle:

a Throttle potentiometers or variable transformers

b Meters or instruments

c Pushbuttons, switches, or other controls

d Connectors, wiring terminations, plugs

e Adjust instrument "zero" with screwdriver

f Mechanical components

E CABLE AND WIRING

Daily Maintenance Procedure

1 Inspect all cable and wiring for mechanical damage

2 Inspect all terminations to lugs, connectors, or compression devices

3 Remove any grease, oil, or chemicals from the wiring insulation

4 Protect any cables that are not covered in traffic areas

5 Replace any tie wraps or supports that become defective

6 Inspect junction boxes that are frequently used

7 Inspect for signs of arcing at points of connection or where cuts or fraying are detected

Monthly Maintenance Procedure:

1 CAUTION: Power must be turned off Tighten all lugs and connections to cables

2 Replace any cut or damaged cable or wiring

3 Rerun cable that is subject to heavy traffic

4 Check all connectors and plugs

Repair:

1 All repairs or replacements should be performed by competent electricians with power turned off

2 Repair or replace the following:

a Defective cable

b Defective or damaged plugs, connectors, or lugs

c Overheated connections or cable.

F ELECTRIC BRAKE

Daily Maintenance:

1 Inspect cooling water supply to assure that proper volume of water is being supplied to the brake

2 Inspect the exhaust ports of the brake to assure that free flow of the cooling water is assured with gravity flow

3 Determine that brake is not overheating during operation

4 Check coupling between brake and drawworks

5 Check mounting bolts to brake frame for tightness

6 Inspect cable to junction box of brake

3 With power applied to the brake control, turn the control to full on and determine that the full DC voltage isreceived by the brake Operate the throttle over the full range and determine that the controller output voltage issmooth and continuous over the full range of operation

4 Any controller in a east aluminum box should be opened and the cooling/insulating oil replaced with clean oil.Remove any foreign liquid or matter in the box before replacing the oil

5 Other controllers in a NEMA box should be kept clean and free from dust and debris

Repair:

1 The brake should only be repaired by competent mechanics and electricians who are trained for this purpose.Only external hardware should be repaired or replaced on the brake under normal conditions

2 Replace any electrical cable that becomes damaged or oil-soaked

3 Replace the throttle if damaged and assure that the wiring is replaced correctly

4 The brake control should be replaced in its entirety and not repaired at the rig site except in emergencies

5 The transformer should be replaced in its entirety if damaged or faulty

G DC MOTORS AND GENERATORS

Daily Maintenance:

1 Inspect the motor for excessive vibration

2 Inspect the motor couplings, sprockets, hubs, mounting, and other mechanical connections

3 View the motor commutator and brushes for proper commutation and minimum connections

4 Confirm that the cooling blower motor is operating properly

International Association of Drilling Contractors

Chapter U: SCR Systems

6 Confirm that the motor is not overheating during operation

7 Inspect the field supplies and yield voltage on shunt motors

8 Check bearings for excessive temperature after continuous running

9 Blow out dust and debris with clean, dry air

10 Lubricate bearings with proper grease, if not sealed bearings

11 Check tightness of mounting bolts

Monthly Maintenance:

1 Disassemble, clean, inspect and repair as necessary Repack bearings as required

2 Inspect brushes for proper tension on commutator and position

3 Inspect commutator for proper surface conditioning

4 Check cooling blower for proper operation

5 Check mounting of hub or coupling

Repair:

1 Replace brushes and brush springs as required

2 Clean commutator according to motor manual

3 Resurface commutator if evidence of uneven wear or pitting is observed

4 Replace blower if found defective

5 Remove motor/generator from service if bearings or windings are found defective and replace motor/generator

on rig

H AC GENERATORS AND MOTORS

Daily Maintenance Procedure:

1 Inspect for excessive vibration when running

2 Assure that proper mating between Diesel Engine and AC generator is maintained

3 Inspect motor couplings and mounting connections

4 Inspect wiring to motor and generator

5 Blow out dust and debris on motor and generator

Monthly Maintenance Procedure:

1 Check motor currents for overloads

2 Check generator currents for overloads or unbalanced loads

3 Inspect motors for overheating

4 Operate each motor and generator for proper performance

5 Tighten all mounting and coupling hardware

6 Inspect all wiring and connectors

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International Association of Drilling Contractors

Chapter V: General Information

Chapter V

General Information