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PE-201

DRILLING

ENGINEERING

ASSIGNMENT

Roll No. 008

Roll No.034

Roll No.036

Roll No.041

Roll No. 043

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PART I

 STRATIGRAPHIC COLUMN

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PART 2

ROCKS WHICH CAN CAUSE SLOW

PENETRATION RATE: -

1) Chert/Sii!i"e# Sh$e :It is very hard rock having the hardness factor of 7 on Mohs

scale which causes slow penetration rate.2) G$%%r& : They are intrusive igneous rock due to which they possess

extreme hardness and its hardness factor on Mohs scale is

also 7 can cause slow penetration rate problems.

ROCKS WHICH CAN CAUSE PIPE STICKING

PRO'LEMS: -

1)C$(2)Sh$e $# *r$!t+re# Sh$e ,)Lie.t&e/D&&ite

.

ROCKS WHICH CAN CAUSE LOSS O* MUD

CIRCULATION: -

1)S$#.t&e:-#+e t& it. hih ere$%iit( $# hih

&r&.it( r&ert(2)*r$!t+re# Sh$e:-&r$ti& +# !$ eetr$te

thr&+h the r$!t+re. ,)Lie.t&e/D&&ite:-the( h$e $t+r$( &!!+rri

r$!t+re. $# hih ere$%iit( 

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PART ,

3UESTION NO41

HPHT WELLS:We !$ i#eti( hih teer$t+re $# hih re..+re 5e.

%( it. iit$ti& i6e

The re..+re 7 108000 .i

  The teer$t+re 7 ,009* &r 109C

A# ie teer$t+re .$ti.(i the $%&e !&#iti&

;teer$t+re

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Here the pore pressure !."# $g% h#&''m

(.(. )in ppg* )!."#+'.#&&*,'.'-

(.(. )in ppg* !-.& ppg )which exceeds the re/uired

!-.&ppg*(.(. )in psi,ft* !-.&+'.'-(.( )in psi,ft* '." psi,ft

I*  The total pressure is:( )in bars* 0 +g +h( )in bars* !."+'.'1"!+#&''( )in bars* 772.!2 bars or 77.2!2 M(a )which exceeds

the re/uired 2".1- M(a*()in psi* 0ppg+ T34m + '.'- +&."!( )in psi* !!&1 psi )which exceeds !'''' psi*

SPECIAL CASES IN HPHT WELLS

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 The drilling of H(HT wells pose special challenges compared to

standard wells:

  I!re$.e# .&i#. .e.itiit( th$t i. re$te# t& hih

teer$t+re.

• $mall margins between pore and fracture pressures will

prevail in sections of the well

• Hih ri.6 & CO2 !&t$i$ti& r& the &r$ti&

%ei #rie# $#/&r r& the #er$#$ti& & &r$i!

+# $##itie.

• HPHT 5e. $re e>+$( h$r# & e!h$i!$ t&&. $#

#ei!e. +.e# i #&5 h&e r+!ti& te.ti4

• HPHT eir&et h$. $5$(. $ !h$ee &r ther$

e+tr& &r&.it( & e$.+reet4

• It he i i#eti"!$ti& & .h$e %e#. $# .$ie 5$ter

.$t+r$ti& ?&e.4

• I HPHT 5e. .eer$ !h$e. $re $!e# i 5e

!&tr& #+e t& #i@eret re$.&. .+!h $. $. .&+%iit(

$# $.hi i &i %$.e# +#4

• 4rilling of inclined and hori5ontal wells will make the

conse/uences of barite sag serious.•  The fre/uency of well control incidents is higher than one per

H(HT well% and an increasing number of these take place

during completion.

3UESTION NO42

 BACKUP RIGS

$uch rigs are generally designed for water depths of up to&-' ft water depth.

$ince the water depth here is - meters hence 6ack up rigs

are used

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3UESTION NO4, 

In conventional rotary drilling operations% the setting depths

are determined principally by the mud weight and the fracture

gradient8 which is sometimes called a well plan. /uivalent mud

weight )M8* is pressure divided by true vertical. M8 e/uals

actual mud weight when the 9uid column is uniform and static.

(ore and fracture gradient lines must be drawn on a welldepth

vs. M8 chart. These are the solid lines

$afety margins are introduced% and broken lines are drawn%

which establish the design ranges. The o;set from the predicted

pore pressure and fracture gradient nominally accounts for kick

tolerance and the increased e/uivalent circulating density )

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from the facture gradient dashed line )point @* down to pore

pressure dashed line )point >*. $o the Arst casing should be set

from surface to !-''m T34.

Bext% draw the hori5ontal line from (oint > to (oint < locatedin the fracture dashed line curve. Then draw the vertical line from

(oint < to intersect the formation pressure dashed line curve at

(oint 4. This is the section casing string which should be set from

&-' mT34

@pplying the same concept to the next string% draw the

hori5ontal line from (oint 4 to intersect the fracture gradient with

safety factor chart at (oint and draw the vertical line from (oint

to the depth at (oint C. The casing string should be set from#-'m T34.

@pplying the same concept to the next string% draw the

hori5ontal line from (oint C to intersect the fracture gradient with

safety factor chart at (oint = and draw the vertical line from (oint

= to the target depth at (oint H. The last casing string should be

set from #7''mT34.

 Thus% the shoe of the conductor casing is to be set at --m%as is generally re/uired.

 The shoe of the second casing% surface casing is to be at

!-'m

 The shoe of the third one% the intermediate casing% is to be

at"-' m. This will protect from the fractured shale at 7''m.

 The shoe of the fourth one is to be at #&'' m

 The shoe of the liner should be at #7''m

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Hole section Casing sizeSetting depth from

RKBMud weight

36”30” 55m ?

26” 18 5/8” 1500m ?

Run BOP (Blow out preventer on riser)

17 ” 13 3/8” 3250m ?

12 !” " 5/8” #250m ?

8 ” 7” liner #700m ?

3UESTION NO4

 The mud weight at di;erent intervals will be

Hole section Casing sizeSetting depth from

RKBMud weight

36” 30” 55m 1$25

26” 18 5/8” 1500m 1$6

Run BOP (Blow out preventer on riser)

17 ” 13 3/8” 3250m 1$6

12 !” " 5/8” #250m 1$"

8 ” 7” liner #700m 2$1"

 

3UESTION NO4

 The following problems can occur:

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14 Sh$&5 G$.

24 Sh$e I.t$%iit(

Mechanical Instability . 

 This may cause: 'ritte/S&+hi Sh$e4 These

shales slough into the hole after breaking into pieces.

Chemical Instability.

 This causes $welling Sh$e4 The indications of swelling are:

• tor/ue increases during drilling

• re/uirement for repeated reaming of sections

• diDculty in sliding the >H@ when orienting

• excessive drag when (EEH

• drag in connections

• Increase in M>T of water based muds.

,4  LOST CIRCULATIONCormations susceptible to lost circulation have the following

characteristics:

• Fnder pressured or depleted

•

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 Preeti&

• maintaining proper mud weight%

•

minimi5ing annularfriction pressure losses duringdrilling and tripping in%

• ade/uate hole cleaning%

• avoiding restrictions in the annular space%

• setting casing to protect upper weaker formations

within a transition 5one%

4 L$re '&+#er. *$i it& the H&e

Indications of boulders are:

• erratic tor/ue

• erratic drag on connections

•  Tendency to stick when pulling out of hole.

4 *r$!t+re# $# $+te# &r$ti&:$ymptoms of fractured and faulted formation include:

• Increased tor/ue% drag and rate of penetrationG

• @ small amount of lost circulation.

 The problem can be prevented by:

• educing drill string vibrationG

• $uDcient hole cleaning to reduce hole pack o; 

4 Pie Sti!6i:Here pipe sticking can occur because of:  REACTIE *ORMATIONS

  *RACTURED *ORMATIONS

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3UESTION NO4

14 Pie Sti!6i:

DI**ERENTIAL STICKING

 It is a problem that occurs when drilling a well with a greater well

bore pressure than formation pressure% as is usually the case. The

drill pipe is pressed against the wellbore wall so that part of its

circumference will see only reservoir pressure% while the rest will

continue to be pushed by wellbore pressure. @s a result% the pipe

becomes stuck to the wall% and can re/uire millions of pounds of

force to remove% which may prove impossible.

https://en.wikipedia.org/wiki/Oil_wellhttps://en.wikipedia.org/wiki/Drill_pipehttps://en.wikipedia.org/wiki/Oil_wellhttps://en.wikipedia.org/wiki/Drill_pipe

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*ACTORS CAUSING THE DI**ERENTIAL

STICKING

Pere$%e &r$ti& as sand stone% lime% carbonate% etc.

Oer%$$!e  typically mud weight in the well is more thanformation pressure. More overbalance in the wellbore% more

chance of getting di;erential sticking.

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*iter !$6e  (oor and thick Alter cake increases chances ofsticking the drill string.

Pie &eet  if the drill string is station for a period of

time% the Alter cake will tend to develop around permeable 5onesand the drill string. Therefore% potential of getting di;erentially

stuck is increased.

METHODS O* PREENTION

4i;erentialpressure pipe sticking can be prevented or its

occurrence mitigated if some or all of the following precautions

are taken:

• Maintaining lowest continuous 9uid lossG

• Jeeping circulating mud free of drilled solidsG

• Jeeping a very low di;erential pressure with allowance for

swab and surgeG

•

Fsing a mud system that yields smooth mud cake )lowfriction coeDcient*G

• Maintaining drill string rotation at all timesG

• Fsing grooved or spiral drill collarsG

• Minimi5ing length of drill collars and >ottom Hole @ssembly

)>H@*.

MECHANICAL PIPE STICKING

 The mechanical pipe sticking is due to inade/uate removal ofdrilled cuttings from the annulusG borehole instabilities% such ashole caving% sloughing% or collapseG plastic shale or salt sectionss/uee5ing )creeping*G and key seating.

http://petrowiki.org/Stuck_pipehttp://petrowiki.org/Stuck_pipe

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CAUSES O* STICKING

Mechanical causes for stuck pipe include:

• Jeyseating

• (acko; from poor holecleaning

• $hale swelling

• 8ellbore collapse

• (lastic9owing formation )i.e.% salt*

• >ridging

http://petrowiki.org/Mechanical_pipe_sticking#Key_seatinghttp://petrowiki.org/Hole_cleaninghttp://petrowiki.org/Mechanical_pipe_sticking#Key_seatinghttp://petrowiki.org/Hole_cleaning

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METHODS O* PREENTION

Creeing mechanically stuck pipe can be undertaken in a number

of ways% depending on what caused the sticking.

• if cuttings accumulation or hole sloughing is the suspected cause%

then rotating and reciprocating the drillstring and increasing 9ow

rate without exceeding the maximum allowed e/uivalent

circulating density )

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H$r# $# $%r$.ie &r$ti&. 

L =ranites% basalts% /uart5ite and

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  'it %$i ;%it $!6e# 5ith &r$ti&)

PDC 'ITS

 ADVANTAGES

L(4< cutters are self sharpening

  L(4< cutters deteriorate /uickly at temperatures above

7''

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L Handles changes from soft to hard rock

L ess vibrations

 L Increased E( potential

L it

• !-''&-': (4< >it

• &-'#&'': Hybrid >it

• #&''#7-': Hybrid >it

3UESTION NO4

 Ad!anta"es

• Eften more compatible with the reservoir

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• ess risk for fracturing the well at the last casing shoe in

case of a kick )H(HT*

• educe problem with swelling clay% thinner mud Alter cake

which means reduced risk for getting stuck

• More ubrication

Disad!anta"es

LH$% environment% more expensive

L

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begin to 9ow from the formation into the wellbore and the kick

occurs.

Ir&er h&e "-+ & tri.

 @s the drill pipe is pulled out of the hole% the mud level falls

because the pipe steel no longer displaces the mud% therefore

hole must be periodically Alled up with mud to avoid reducing the

hydrostatic pressure and preventing kick problem.

S5$%%i

(ulling the drill string from the borehole creates swab

pressures. $wab pressures are negative% and reduce the e;ectivehydrostatic pressure throughout the hole and below the bit.3ariables controlling swab pressures are:

(ipe pulling speed

Mud properties

Hole conAguration

 The e;ect of PballedQ e/uipment

G$. C+t +#

=ascontaminated mud will occasionally cause a kick%although this is rare. >ut in this occasion there is gas at shallowdepths. @s the gas is circulated to the surface% it expands andmay reduce the overall hydrostatic pressure suDcient enough toallow a kick to occur.

L&.t !ir!+$ti&

Eccasionally% kicks are caused by lost circulation. @decreased hydrostatic pressure occurs from a shorter mudcolumn. 8hen a kick occurs from lost circulation% the problemmay become severe.

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