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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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