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Perforar es el proceso de hacer pozos en la corteza terrestre.Muchos métodos pueden ser utilizados para la perforación de pozos.Métodos de perforación se pueden clasificar de acuerdo con distintosprincipios. Cualquier método de perforación involucra desintegración formación,máquina (que se puede utilizar para la perforación, se desintegran y excavarroca) por cuatro mecanismos básicos: -A. Por tensiones inducidas mecánicamente.B. Por tensiones inducidas térmicamente.C. Por la fusión y la vaporización.D. Por las reacciones químicas.E. Por explosión, erosión, electrohidráulica, y la perforación de ultrasonidos.De todos los principios mencionados sólo sondeos mecánicos ampliamenteutilizado para la perforación de pozos de petróleo y gas. Métodos de perforación basados en otromecanismo de desintegración formación se pusieron a prueba en laboratorios yen el campo pero no se utiliza en la industria.Los métodos industriales de perforación mecánica pueden subdividirsede acuerdo con el carácter o las herramientas de diseño de rock movimiento.Métodos de perforación A. con movimiento de vaivén de la herramienta.B. Métodos de perforación con movimientos de rotación de la herramienta.________________________________________
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Drilling Engineering
1 Dri
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Introduction
Methods of drilling wells
Dilling is the process of making wellbores in the earth crust.
Many methods can be used for drilling wells.
Drilling methods can be classified in accordance with various
principles. Any methods of drilling involves formation disintegration,
machine (which can be used for drilling, disintegrate and excavate
rock ) by four basic mechanism :-
AA.. By mechanically induced stresses.
BB.. By thermally induced stresses.
CC.. By fusion and vaporization.
DD.. By chemical reactions.
EE.. By explosion, erosion, electrohydraulic, and ultrasonic drilling.
From all the principles mentioned only mechanical drillings widely
used for drilling oil and gas wells. Drilling methods based on other
mechanism of formation disintegration were tested in laboratories and
in the field but not used in the industry.
Industrial methods of mechanical drilling can be further subdivided
according to the character or rock design tools motion.
AA.. Drilling methods with reciprocating motion of the tool.
BB.. Drilling methods with rotary motions of the tool.
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Mechanical methods of drilling with rotary motion of the working
tool are the most widely used methods in the oil and gas industry.
These methods can be classified in accordance with the position of a
mover that drives the tool :-
AA.. Drilling methods with the mover on the earth surface (rotary table
or top drive system).
BB.. Drilling methods with the mover situated near the bottom of the
hole (sliding mode).
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Casing and Tubing Design
1- Casing:
Casing is the major structural component of a well. Casing is
needed to maintain borehole stability& prevent contamination&
isolate water from producing formation
In addition, control well pressures during drilling, production, and
work over operations. Casing provides locations for the installation of
blowout preventers (BOP’s), wellhead equipment production packers.
CASING TYPE:
1 - Conductor.
2 – Surface casing
3 – Intermediate casing
4 – Production casing
5 - Liner.
1) Conductor casing:
is set below the drive pipe or marine
conductor that is run to
protect loose, near surface formations
and enable circulation of drilling fluid,
it Prevents Washing-Out around the
base of the rig. The conductor isolates unconsolidated formations and
water sands and protects against shallow gas. Normal depth for
Conductor pipe is from 30 to 250 feet. It is often driven with a pile driver
until it will not go any further.
Drilling Engineering
4 Dri
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
2) Surface casing:
The surface casing is the first string of any sequence to be
run into a well, after a hole has been drilled. It ranges from (7 5/8)" to
20" commonly (13 3/8)". Attached to the surface Casing, after it has
been cemented, is the following pieces of equipment:
1 - Casing head from which part of the suspended weight of subsequent
strings are hang.
2 – Blowout preventors: This will control any formation gas or fluid
pressures, which might be encountered. The casing must be strong
enough to support this weight and to contain any possible pressures. For
this reason, it is always cemented to surface.
The surface casing is also designed to seal off fresh water aquifers and
prevent them from being contaminated by hydrocarbons or salt water,
which may be encountered in deeper drilling.
3) Intermediate casing:
Isolates unstable hole sections, lost circulation zones, low pressure
zones, and production zones.
It called protective casing The size ranges from (6 5/8)" to 20 "and
Commonly (9 5/8)".
Problems that Might Necessitate Intermediate Casing are:
1 - Weak formations, which break down and cause loss of circulation
of the drilling fluid.
2 - Abnormally high pressure zones (usually geo-pressured gas) So
that drilling cannot then continue with a lighter mud.
3 –“Heaving Shales" that swell when in contact with water or drilling
sand fall into the hole
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
4)A Liner:
Is a casing string that does not extend back to the wellhead, extending
from the bottom of a well to a point 100 feet-or more the lower end of
the intermediate string. Liners are used to reduce cost, improve
hydraulic performance during deep drilling, and allow the use of larger
tubing above the liner top.
Number of casing string and setting
depth
4) Plot Hydrostatic, formation, and fracture pressure gradient against depth. 5) Plot another curve equal fracture pressure -0.5 ppg for safety. 6) from plotting we can find the number and setting depth of the casing
string.
ft / psi 1 stress overburden verticalis
388.0 ratiopoisson is
where,
psi ,P P1
P
:pressure fracture theDetermine 3)
psi ,200PP
:pressureformation theDetermine 2)
ft depth, ish
ppg density, mud is
wher,
psih * * 052.0P
:pressure chydrostati theDetermine 1)
v
fffr
hf
m
mh
v
Drilling Engineering
6 Dri
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Depth,m Depth,ft Formation
pressure,psi
Formation
gradient,(psi/ft)
Trip
margin
gradient
,(psi/ft)
934 3064 1180 0.385 0.411
1390 4560 1914 0.42 0.446
1432 4698 1998 0.425 0.451
1710 5610 3931 0.701 0.727
2199 7215 5113 0.709 0.735
2486 8156 5806 0.712 0.738
2660 8727 3202 0.367 0.393
Depth,m Fracture
pressure,psi
Fracture
pressure
Gradient,psi
kick
margin
gradient
,(psi/ft)
mud
(ppg)
934 2375 0.775 0.7489 8.6632
1390 3591 0.788 0.7615 8.9131
1432 3710 0.79 0.7636 8.9964
1710 4995 0.89 0.8644 14.161
2199 6445 0.893 0.8673 14.161
2486 7295 0.894 0.8684 14.161
2660 6704 0.768 0.7422 7.497
Drilling Engineering
7 Dri
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Casing Depth, ft
Casing Length, ft From To
7 " linar 7956 8727 771
9 5/8" csg 0 8157 8157
13 3/8" csg 0 4698 4698
20" Conductor 0 115 115
Drilling Engineering
8 Dri
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Casing string design:
Steps of design
The process of casing string design is divided into three stages
For collapse resistance:
Minimum collapse resistance for the bottom section is
Where,
fc = collapse safety factor ~ 1.125
= mud wt., ppg
H = total depth, ft
The length of the bottom section is determined as follows;
Pc2 = 0.052 (H – L1) fc, psi
Where :
Pc2 = collapse resistance of selected second section.
L1 = length of the bottom section, ft
From tables select suitable grade with stand collapse
pressure
psi , f H 0.052 P cminc
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
for tensile strength ( upper part ):
Wt. Of every section is determined from table
Wi = Wi x Li, lbs
The top end is checked for tensile strength
- Stronger casing should be used for the next upper sec. and its length
is determined as follows
ni
i cf
ncP
iLH
cf
cPLH
cf
cPH
1 052.0
)1(nL
generally,
ft ,052.0
312L
ft ,052.0
21L
(1.8). efor tensilfactor design ,f
lbs. table,from sec. topofstrength tensile,
,
t
1
in
tn
ii
in
P
where
f
LW
P
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Checking for internal ( bursting ) pressure:
The weakest section is checked of internal pressure as follows
At first calculate Maximum formation pressure (Pf ) and then find
the minimum allowable internal pressure (Pi ) = Pf * 1.1
From tables, and by using the value of Pcmin , and minimum internal
pressure, thesuitable casing grade wt. required is selected.
Design of 7 " liner:
1- Pc min = 0.052 * 1.125 * 0.9*8.33* 8727 = 3827 psi .
2- Maximum formation pressure expected Pf = 3403.4 psi.
So, minimum internal pressure Pi must be > 1.1 * 3403.4
Pi > 4118 psi
From Rabia page 210,
To From
771 8727 7956.17 7 "
CasingCasing Length, M Depth ,ft
kt
n
itik
i
n
kLiitik
Wf
LiWfP
L
where
WLWfPk
1k
ik
1
L
Pstrength tensileofK sec. theoflength ,
,
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Checks:
1- For tensile strength:
2- For internal bursting pressure:
Design of 9 5/8 “ casing:
1) Pcmin = 0.052*1.7*8.33*1.125*8157= 6757 psi .
2) From tables selection of suitable grade &nominal weight .
3) Determine length of each grade,or nominal weight ,by
L1=H-PC2/(FC*MUD GR.*0.052)
4) Maximum formation pressure expected Pf =6007 psi.
So, minimum internal pressure Pi must be > 1.1 * 6007
Pi > 6607psi
From Rabia page 203
Use Grade MW-C-95 # 47lb, MW-C-95 # 44lb, MW-C-95 # 40lb,
have collapse resistance and we calculate their length
case Tensile.S.F Tensile.Strength WT ,lb N.WT ,lb/ft Length ,ft GRADE
SAFE 36 566000 15700 23 727 L-80
case PI/Pf PI N.WT GRADE
SAFE 2.33 7930 23 L-80
Collapse
s.f .
safe 1.18 6006.6 7100 6760 -8157 1397 47 MW-C-95 9.625
safe 1.125 4977.8 5600 5106 -6760 1654 44 MW-C-95 9.625
safe 1.125 3760 4230 0 - 5106 5106 40 MW-C-95 9.625
Casingcase formation Pressure collapse resistance Casing Depth ft Casing Length ft N.W GRADE
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Checks:
1- For tensile strength:
Case T.S.F T.strength CUM.WT Wt. N.Wt Length Grade
safe 22.17 1289000 58*103
58137 47 1397 MW-C-95
safe 9.734 1193000 122.6*103
64423 44 1654 MW-C-95
safe 3.6 1088000 303*103
180828 40 5106 MW-C-95
2-For internal bursting pressure:
Case Pi/Pf Pi N.WT Grade
safe 1.357 8150 47 MW-C-95
safe 1.509 7510 44 MW-C-95
safe 1.184 6820 40 MW-C-95
Design of 13 3/8 “ casing:
Pcmin =0.0.052*1.08*8.33*4699 *1.125=2473 psi .
2- Maximum formation pressure expected Pf =2199 psi.
So, minimum internal pressure Pi must be > 1.1 * 2199
Pi > 2418.9 psi
From Rabia page 198
Use Grade C-75 # 72lb , C-75 # 68lb C-75 # 61lb have collapse
resistance
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Collapse Pc Pf Casing depth Length N.W Grade
s.f. psi psi ft ft lb
2.29 2590 2199 4218 - 4699 481 72 C-75
2.39 2220 1974 3154 - 4218 1064 68 C-75
2.86 1660 1476 0 -3154 3154 61 C-75
Checks:
1- For tensile strength:
Case S.F. T.strength Cum.Wt. Wt Length N.W Grade
safe 50.84 1558000 30648 30648 481 72 C-75
safe 15.39 1458000 94708 64060 1064 68 C-75
safe 4.95 1312000 265044 170336 3154 61 C-75
2-For internal bursting pressure:
Case pi/pf pi Pf N.W Length Grade
safe 2.29 5040 2198.25 72 481 C-75
safe 2.39 4710 1973.33 68 1064 C-75
safe 2.86 4220 1475.55 61 3154 C-75
Design of conductor pipe:
Choose low grade for conductor design because the collapse
resistance is very low at surface.
Select grade J-55 or H-40, and is set at the refusal point from
115 ft conductor 20 "
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Cement
Function of cement:
1) Restriction of fluid movement between permeable zones within
the well.
2) Provide mechanical support for the casing string.
3) Protection of casing against corrosion by sulphate rich
formation waters.
4) Support for the well-bore walls to prevent collapse of
formations.
Classes and types of cement:
The API has classified nine types of cement, depending on depth,
and conditions of hole to be cemented these are as follows;
1 - Class A:
Intended for use from surface to 6000 ft. depth when special
properties are not required. Available only in ordinary type.
2- Class B:
Intended for use from surface to 6000 ft. depth when conditions
require moderate to high sulphate resistance. Available in both
moderately and highly sulphate resistance type.
3- Class C:
Intended for use from surface to 6000 ft. depth when conditions
require high early strength. Available in moderately and highly sulfate
resistance type.
Drilling Engineering
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
4 - Class D:
Intended for use from 6000 ft. to 10,000 ft. depth, under
conditions of moderately high temperatures and pressures.
5- Class E:
Intended in use from 10,000 ft. to 14,000 ft. depth under
conditions of high temperatures and pressures. Available in both
moderately and highly sulfate resistance types.
6 - Class F:
Intended for Use from 10,000 ft. to 16,000 depth, under
conditions of moderately high temperatures and pressure. Available
in both moderately and high sulfate resistance types.
7 - Class G:
Intended for use as basic cement from surface to 8,000 ft. depth
, as manufactured, or can be used with accelerators and retarders to
cover a wide range of well depths and temperature.
8 - Class H:
Intended for use as basic cement from surface to 8,000 ft; depth as
manufactured, and can be used with accelerators and retarders to
cover a wide range of well depths and temperatures.
9 - Class J:
Intended for use as manufactured, from 12,000 ft. to 16,000 ft.
depth under conditions of extremely high temperature and pressure,
or can be used with accelerators and retarders to cover a wide range
of well depths and temperatures.
Drilling Engineering
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Production casing cementing program:
1 - Slurry volume calculations:-
- Annular cross-sectional area between casing string and bore-
hole
where D = bore-hole diameter , inch
O.D = casing out side' diameter, inch
- Slurry volume = A * H * excess "safety' factor"
- Excess volume of slurry = 25%
2 - No. of sacks of cement:
-Yield of slurry means the, No. of cu. ft of slurry that is produced by
using one sack of dry cement.
Methods of Cementing :
1)Single Stage Cementing
Is normally to cement conductor and surface pipes. A single
batch of cement. is prepared and pumped down the casing. it should
be noted that all The internal parts of the casing tools including
the float shoe, wipe plugs, etc are easily drillable.
2in ,2.2
4 A
cDOD
sack)ft / (cu.slurry of yield
ft) (cu. umeslurry vol
Drilling Engineering
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2)Multi stage Cementing
It is employed in cementing long casing string in order to reduce
the total pumping pressure, reduce the total hydrostatic Pressure on
weak formations& using retardard . There preventing Their fracture,
allow of selective cementing of formations and ensure effective
Cementing around the shoe of the previous casing string.
In multistage cementing a stage cementer is installed at a
selected position in the casing string, the position of the stage
cementer is indictated by the total length of the cement column and
the strength of formations.
Cement calculations for well SIDRI 13
Casings setting depths:
Casing
Measure Depth, ft Casing Length, ft
To From
20" Conductor 115 0 115
13 3/8 " 4698 0 4698
9 5/8 " 8156 0 8156
7 " linar 8727 7956 771
As shown from this table all setting depths in the range of (8000 ft)
So; we can select cement class (G).
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Cement (class “ G”) description
component Weight Lb sp.gr Volume ,gal
Cement 94 3.14 3.6
2% bentonite 1.88 2.65 0.086
mix water for cement 41.36 1 4.97
Mix water for bentonite 9.4 1 1.13
Slurry weight =94+1.88+41.36+9.4 =146.6 lb
Slurry volume = 3.598+.0853+4.971+1.1298 = 9.78gal
Slurry density =146.64/9.7841 = 15 ppg
Slurry yield =9.7841*5.615/42 = 1.308 ft3/sack
For 13 3/8 “ casing string:
Determine no. of cement stage
At casing shoe string
P slurry = 0.052*slurry density*setting depth
= 3665.87 psi
P f = 0.052*sp.Gr of brine water*setting depth=0.052*1.08*8.33*4698
=2197 psi
Drilling Engineering
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P frac = (2/3)*(4698-2197)+2197
=3864.35 psi
Note that: Pfrac > Pslurry > Pf
So ,one stage will be used
Volume of slurry :
v1(cement annulus volume between13 3/8 “ and 22 “ )
=3.14/(144*4)*(162-13 3/8 2) *115
=164.3 ft3
v2( cement annulus volume betweeen csg.v& open hole)
=3.14/(4*144)*1.25*( 4698.2-115)
=2409 ft3
v3 (cement volume in casing below floating collar)
=3.14/(144*4)( 12.47516)^2*40=40 ft3
Total slurry volume = 2608 ft3
No. of cement sacks =slurry vol. /slurry yield
= 2299 sacks
Mixing water =water for cement +water for Bentonite
= 334 bbl
total water = 354 bbl
Volume of Bentonite =.0853*2299 =196 gal
Drilling Engineering
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Assume mixing rate = 2.5 bbl/min.
Mixing time =water volume / mixing rate
=133.6 min.
Average inside diameter for 13 3/8 =12.47516 in
Displacement volume =V(inside casing)-V(shoe)
=3.14/(4*144)*( 12.47516)^2(4698-42))
= 3950 ft3
Assume displacing rate = 8 ft3/min
Displacement time = 494 min.
Put drop of plug time =10 min.
Safety Time =30 min
Total time =mixing time +displacement time +drop of plug time +
Safety Time
Total time =133.6 + 494+30+10 =668 min.
For 9 5/8 “ casing string:
At casing shoe :
P slurry = 0.052*15*4698
= 6364 psi
P formation = 0.052*1.7*8.33*8157
=3814 psi
Drilling Engineering
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P fructure =(2/3)*(8157-3814)+ 3814
=6709 psi
Volume of slurry
v1(cement annulus volume between13 3/8 “ and 9 5/8 “ )
= 1613 ft3
V2 (annulus cement volume at open hole ) = 1354 ft3
V3(cment volume below floating collar) = 35.4 ft3
Total cment volume = 3002 ft3
No. of cement sacks = 2298 sucks
Volume of mixing water = water for cement +water for Bentonite
= 334 bbl
Total water volume =334+20
Total water volume = 354 bbl
Volume of Bentonite = 196 gal.
Mixing time = 133.6 min.
Setting of plug time = 10 min.
Displacement volume = 3401.7 ft3
Displacing time = 425.2 min.
Safety time = 30 min
Total time = 599 min.
For 7 “ liner:
At casing shoe string
Drilling Engineering
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P slurry = 0.052*slurry density*setting depth = 6810 psi
P f = 0.052*sp.Gr of brine water*setting depth=0.052*1.08*8.33*8727
= 4081 psi
P frac= (2/3)*(8727-7956)+ 4081
=7178 psi
Note that: Pfrac > Pslurry > Pf
So ,one stage will be used
Volume of slurry :
v1(cement annulus volume between7 “ and 9 5/8 “ )
=3.14/(144*4)*( 8.79242-7 2)*200=30.9 ft3
v2( cement annulus volume betweeen casing and
open hole )
=3.14/(4*144)*1.25*(12.5^2-7^2)( 8727-8157)
=90.5 ft3
v3 (cement volume in casing below floating collar
=3.14/(144*4)( 6.366)^2*40 = 18.6 ft3
Total slurry volume = 140 ft3
No. of cement sacks =slurry vol. /slurry yield
= 108 sucks
Mixing water =water for cement +water for Bentonite
= 16 bbl
total water = 16+20 = 36 bbl
Drilling Engineering
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Volume of Bentonite=.0853*2299 =196 gal
Assume mixing rate = 2.5 bbl/min.
Mixing time =water volume / mixing rate
= 6.4 min.
Displacement volume =V(inside casing)-V(shoe)
= 945 ft3
Assume displacing rate = 8 ft3/min
Displacement time = 118 min.
Put drop of plug time = 10 min.
Safety Time = 30 min
Total time =mixing time +displacement time +drop of plug time +
Safety Time
Total time =6.4 + 118 +30+10 = 165 min.
Drilling Engineering
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Drill String Design
The design of drill string involves the design of drill collar and
drill pipe.
Drill collar design
By using drilling data handbook and according to the size of
the borehole, (outside diameter, inside diameter and nominal
weight of the drill string )can be selected.
The Calculations are as follows:
Where,
B.f : is the buoyancy factor = (1- γm / γs)
γm , γs : is the density of drilling fluid and steal
respectively.
WB : is the weight on bit, lbs.
Wc : is the nominal weight of drill colar, lb/ft
Lc : is the length of d/c, ft
Drill pipe design:
The diameter of the drill pipe is selected according to the
borehole size from the handbook
ft ,c W* B.f
BW *
3
4cL
ft) (31joint oflength
L joints) of (no.N c
c
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B.SC. PROJECT 2009 – ABU RUDEIS – SIDRI FIELD
Lp = L - Lc
Where,
Lp : is the length of drill pipe, ft
L : is the depth , ft
From Oil Well drilling Engineering out side and in side diameter of
the drill pipe can be selected.
Selection Of Drill Pipe Grade
Where,
Ymin : min. yield strength, psi
Wp : Weight of d/p, lb/ft
Wc : Weight of d/c, lb/ft
ft : Safety factor ( 1.5)
D : out side diameter of d/p,inch.
d : inside diameter of d/p , inch.
From table of Petrolum Enginnnering H.B., select the drill pipe
grade where,
ft) (93 stand oflength
L stands) of (no.N
p
p
psi ,
22785.0
tf * .pW minY
dD
fBcLcWpL
5.1min.Y
selectedY
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Check for collapse:
Where,
Pcmin : Hydrostatic pressure, psi
γm : d/f density, ppg
H : total length of d/s, ft
From Petrolum Engineering H.B., determine the collapse
pressure of the selected grade ;
Then repeated the previous procedure for every bit size run
in the hole.
Drill String Design
For firist bit run:
Bouncy
B=1-(1.04*62.4/489.5)=0.8674
Drill collar
From Rabiaa page (34 )
OD = 14" ; ID = 3" ; WC = 361 lb/ft
psi , H m 0.052 mincP
safe isdesign 5.1
.mincf If
cP
selectedcP
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Length of D/C (LC CAL.)
LC=4/3*(22046/(361*0.8674)) = 93.84 ft
No. of joints
N=93.84/31
= 3.03
LC=4*31= 124 ft
Drill pipe
From Rabiaa page (26 ,27 )
OD = 5" ; ID = 4.276" ; WC = 19.5 lb/ft
Length of drill pipe
LD/P =3064 -124 = 2940 ft
No. of drill pipe joits
N=2940./93=31.6 = 31
D/p actual length
L d/p =31*93 = 2883 ft
Check on tensile
Min. yield force applied on drill pipe
Y min= ((19.5*2883) + (361*124)) *0.8675
= 87604 lb
From Rabiaa page (26) class 2
Y =311540 lb
F=311540 /87604 = 3.56 >1.5 safe
Check on collapse
Pc=.052*8.33*1.04*3064 = 1381 psi
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From Rabiaa page (27 ) class 2
Pc select =4760 psi
Fc=4760/1381 =3.5 >1.5 safe
By the same method the other bit run will be as following
From Rabiaa page (34 ) table 2.9
Drill Collar Design
W.O.B W.O.B
(ton) Bit run Depth ft Depth m
size of
hole, in (lb)
22046.2 10 1 0 - 3064 0 - 934 16
39683.2 18 2 3064 - 4560 934 -1390 16
26455.5 12 3 4560 - 4698 1390 - 1432 16
30864.7 14 4 4698 - 5610 1432 -1710 12.25
26455.5 12 5 5610 - 7214.5 1710 - 2199 12.25
26455.5 12 6 7214.5 - 8156 2199 - 2486 12.25
22046.2 10 7 8156 - 8727 2486 - 2660 8.5
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Drill collar specification
N.W.,LB/FT I.D.,in O.D.,in size of hole, in
361 3 12 16
246 2.8125 10 12.25
114 2.5 7 8.5
From Rabia page(26,27) oil well drilling engineering
Drill Collar Design Continued
N D/C
D/C length Calc. ft
size of
hole, in Act. ft
N D/C
calc..
Bit
run Depth , ft
124 4 3.03 93.86 1 0 - 3064 16
186 6 5.47 169.7 2 3064 - 4560 16
124 4 3.65 113.3 3 4560 - 4698 16
217 7 6.89 213.53 4 4698 - 5610 12.25
186 6 5.9 183.03 5 5610 - 214.5 12.25
186 6 5.9 183.03 6 7214.5 -8156 12.25
310 10 9.39 291.24 7 8156 - 8727 8.5
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Drill Pipe Design
D/P Length NO.D/P N .D/P D/P Length Bit run Depth , ft Hole
Act. ft Stands. stands CaL. CaL. ft size in
2883 31 31.61 2940 1 0 - 3064 16
4371 47 47.03 4374 2 3064 - 4560 16
4557 49 49.18 4574 3 4560 - 4698 16
5301 57 57.99 5393 4 4698 - 5610 12.25
6975 75 75.58 7028.5 5 5610 - 214.5 12.25
7905 85 85.7 7970 6 7214.5 -8156 12.25
8370 90 90.51 8417 7 8156 - 8727 8.5
Bit
run
Grade
Ymin ,lb Ygrade ,lb Ygrade/Ymin PCmin ,psi PCgrade ,psi PCmin/ PCgrade
class (2)
1 E 87603.9 311540 3.56 1380.29 4760 3.449
2 E 131610 311540 2.37 2113.47 4760 2.252
3 E 115241 311540 2.7 2197.78 4760 2.166
4 E 148139 414690 2.8 4131.05 9420 2.28
5 E 175738 414690 2.36 5312.56 9420 1.773
6 E 194390 414690 2.13 6005.85 9420 1.568
7 S135 175791 560760 3.19 3402.17 5970 1.755
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Drill pipe specification
N.W.,LB/FT Grade I.D.,in O.D.,in size of hole, in
19.5 E 4.276 5 16
25.6 E 4 5 12.25
19.5 S135 4.276 5 8.5
Directional drilling
The most common applications of directional drilling are illustrated in and
discussed briefly below:
Multiple wells from artificial structures.
Today's most common application of directional techniques is an offshore
drilling where an optimum number of wells can be drilled from a single
platform. This operation greatly simplifies production techniques and
gathering systems, a governing factor in the economic feasibility of the
offshore industry.
Fault drilling
Another application is in fault control where the wellbore deflected across
or parallel to the fault for better production. This eliminates the hazard of
drilling a vertical well through a steeply inclined fault plane, which could slip
and shear the casing.
Inaccessible locations
The same basic techniques are applied when an inaccessible location in a
producing zone dictales remote rig location, as in production located under
riverbeds, mountains, cities, etc.
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Sidetracking and straightening
This is used as a remedial operation, either to sidetrack an obstruction by
decimating the wellbore around and away from the obstruction, or to bring
the wellbore back to vertical by straightening out cooked holes.
Salt dome drilling
Directional drilling programs are also used to overcome the problems of salt
dome drilling, to reach the producing formations, which often lie
underneath the overhanging cap of the dome.
Relief wells
Directional drilling, was first applied to this type of well so that mud and
water could be pumped in to kill a wild and cratered well.
Basic hole patterns:
A carefully conceived directional drilling program on geological information,
knowledge of mud and casing program, target etc., is used to select a hole
Pattern suitable for the operation.
Type I
Is planned so that the initial deflection is obtained at a shallow depth
pproximately 1000 ft), and the angle is maintained as a "locked in," straight
approach to the target. This pattern is mainly used for moderate drilling in
areas where the producing formation is located in a single zone location and
where no intermediate casing is required. It is also used to drill deeper wells
requiring a larger internal displacement.
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Type II
Called the "S" curve pattern, is also deflected neat the surface. The drift is
maintained, as with type I, until most of the desired lateral displacement is
obtained. The hole angle is then reduced and/or returned to vertical in order
to reach the target.
Type III
Is planned such that the initial deflection is started well below the surface
and the hole angle is maintained to buttonhole target. This pattern is suited
to special situations, such as fault or salt dome drilling, or to any situation
requiring redrilling or repositioning of the bottom part of the hole.
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Deflection tools
are
- Down hole hydraulic motors (with a "bent sub").
- Jet bits.
- Whip stocks.
Deflection tools
are
- Down hole hydraulic motors (with a "bent sub").
- Jet bits.
- Whip stocks.
Design Of Directional Trajectory
The given data is:
Well head co-ordinates: X= 828750 m = 2718996 ft E
Y= 683900 m = 2243766 ft N
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Target co-ordinates: X=828660 m = 2718700 ft E
Y=684160 m = 2244619 ft N
Well Type :Type III
Kick Of Point(K.O.P) : 4698 ft
Build Up Rate(B.U.R) :2o/100 ft
Vertical Depth @ Target: 8120 ft
Displacement @ Target : 903 ft
The Design:
1-Radius Of Curvature:
R1=(180/3.14) * (1/q )
=(180/3.14) * (100/2 o )
=2865 ft
2-Angles
Tan ℓ = BA/AO
=(r1-X3)/(D3-D1)
ℓ =29.84 º
Sin Ω =r1/OB
Ω =46.55 º
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3-Maximum inclination:
= Ω - ℓ
= 16.71º
4-Length of A.R.C:
DC = /q
=16.71 º /(2 º /100)
=835.5 ft
5-Length of trajectory path at constant inclination angle:
CB = r1/(tan Ω)
= 2865/tan(46.55 ))
= 2714 ft
5-Total Measured depth at end of build
Dm = D1 + DC
= 4698 + 835.5
= 5533.5 ft
6-Horizontal depature at end of build:
X2 = r1 (1- CoS ) = 2865 (1- CoS16.71º) = 1932.25 ft 7-T.V.D at end of build:
T.V.D = D1 + (R* SIN = 4698 + (2865 * SIN 16.71º) = 5521.8 ft
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5-Total Measured depth at target:
T.M.D= Dm = D1 + DC + CB
= 4698+ 835.5+ 2714 = 8247.5 ft
Design of a horizontal trajectory
Note:
Well will be inclind dowd word as reservoir is under-saturated.
In accordance with the horizontal well drilling, there are three
sections namely:
1) Vertical section:
It is drilled from seabed (mud line) until kick-off point (KOP).
Point M . D Ft
T.V . D ft
KOP 4698 4698
End of build 5533.5 5521.8
Target 8247.5 8120
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2) Turning or curved or angle build section:
It is drilled from kick-off point (KOP) to the end-of-curve
(EOC). This section includes the first build arc, the straight
tangent, and the second build arc.
3)Tanget section:
It is drilled from the end of second build arc (EOC) to the end
of proposed distance to be drilled horizontally in the pay zone, in
accordance with the type of horizontal well to be drilled.
Design of horizontal well trajectory for S/D 13
By using Dr. Farahat's research
Assume Surface location co-ordinates:
X = 828750 m =2718996 ft E
Y =683836 m =2243556 ft N
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Target co-ordinates :
X =828660 m =2718700 ft E
Y =684160 m =2244619 ft N
Assume B.U.R = 8.5 o /100
Assume Tanget angle “I2” = 45 o
Assume Tanget angle “I3” = 90 o
assume length of straight tangent =150 ft
Vertical Depth @ Target : 8120 ft
Horizontal Displacement @ Target = 781 ft
The three sections may be designed as follows:
1) The build radius of the build arc:
R = 5730/Β
R = 5730/8.5
= 674 ft
2) The height of the first build arc:
D1 = R (Sin I2 - Sin I1)
D1 = 674*(Sin 45 - Sin 0)
= 477 ft
3) The height of the straight tangent:
D2 = L2 Cos I2
D2=150*Cos 45
=106 ft
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4)The height of the second build arc
D3 = R (Sin I3 - Sin I2)
D3 = 674(Sin 90- Sin 45)
= 198 ft
5) The length of the first section of horizontal well KOP:
KOP = TVD –( D1 + D2+D3 )
KOP = 8120 – ( 477+ 106 + 198 )
= 7340 ft
6) The displacement of the first build arc:
H1 = R (Cos I1 - Cos I2)
H1 = 674 (Cos 0 - Cos 45)
= 198 ft
7) The displacement of the straight tangent:
H2 = L2 Sin I2
H2 = 150*sin45
= 106 ft
8 )The displacement of the second build arc
H3 = R (Cos I2 - Cos I3)
H3 = 674(Cos 45 - Cos 90)
= 477 ft
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9) The length of the first build arc:
L1 = 100 (I2 - I1) / B
L1 = 100 (45 - 0) / 8.5
= 530 ft
10)The length of the second build arc
L3 = 100 (I3 – I2) / B
=100 (90 – 45) / 8.5
= 530 ft
11)the measured depth at end of the first build arc
MD1= KOP+L1
= 7340 +530
= 7870 ft
12)The measured depth at end of straight tangent
MD2 = MD1+L2
= 7870+150
= 8020 ft
13) The measured depth at the end of the second build arc:
MD3 = MD2 + L3
= 8020+530
= 8558 ft
14) The length of horizontal section or third section
H = 3000*674/800
= 2528 ft
15) The total measured depth of horizontal well
= MD3 + H
= 8558 + 2528
= 11086 ft
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Intelligent Well Completion
The Intelligent Well Completion of tomorrow will have significantly enhanced capabilities such as the following namely:
1. Sensors and flow control devices in the laterals branches 2. Downhole separation of water from oil. Also, the ability to reinject the water
downhole 3. Detection of water encroachment 4. Detection and / or prevention / removal of sand , scale , or corrosion 5. Three- phase flow measurement 6. Infinitely variable choke 7. Fiber optics developments for various uses including communication as well as
distributed measurement of temperature and pressure 8. Higher temperature capability 9. Downhole power source
10. Downhole seismic sources and / or receivers to provide in-well vertical seismic profiles (VSP) or cross-well tomography
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Drilling Problems During Drilling SID-13 and
Remedy
1. Mud losses:
Are expected while drilling 16`` hole, through the unconsolidated
sand of Post Miocene and Zeit formation.
Conventional plugging materials or suitable LCM can successfully
control this kind of losses. It is recommended for this matter to
extend circulation time and spot high viscous pill to keep the hole
clean and avoid overcharging to the formation.
Some mud losses are expected in 8 ½ `` phase while drilling in
Belayim sand, in this case non damaging plugging material are
recommended in addition to the conventional fin plugging materials.
2. Over pressure:
Is expected while drilling 12 ¼ `` hole in bottom Zeit and top
South Gharib formation. especially if high-pressure water flow
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encountered reaching value 1.8 to 1.9 kg/lit., it is recommended that
to control well with mud weight 1.82 to 1.92 kg/lit.
3. Differential sticking:
Might be encountered while drilling depleted sand zones
through 8 ½ `` of Belayim fm., this type of problem can be avoided by
keeping string always in motion and reducing as low as possible the
number of drill collar in the BHA. In addition, it is suggested to reduce
filter cake thickness and cake permeability to minimize this problem.
Mechanical sticking is expected while drilling the salt zone of South
Gharib, this type of problem can be avoided by keeping the mud salinity
little bit under saturation and also keeping string always in motion, in
case of stuck against salt zones, fresh mud batches have to be pumped
coupled with jamming action to solve this kind of problem.
Drilling problems associated with direction
well drilling and remedy
There are five main problems during drilling horizontal wells and
drain holes, namely :
1. Delivering weight to the bit.
2. Reducing torque and drag forces.
3. Hole cleaning.
4. Protection of water sensitive shale.
5. Directional control.
1- Delivering weight to the bit:-
Applying sufficient bit weight for optimum drilling rate that is
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often a problem , especially at higher angles and while drilling a
horizontal section. Conventional bit weight for efficient drilling is a
bout 2000-5000 lbf. Per inch of bit diameter. Motor assemblies drill
efficiency with less bit weight then rotary assemblies, they
compensate for bit weight with higher rotational speed of turbines
and motors.
Remedy:
Bit weight may be increased by reducing drag and torque by
using the split assembly, including the bit, motor, directional control
tools, and the non-magnetic collars, which left at the bottom of the
drill string.
And by using slick assembly (drill collars be in vertical section)
2- Reducing torque and drag forces:-
Drag is a force restricting the movement of the drill tools in
directions parallel to the well path . Torque is the force resisting
rotational movement. Drag and torque are measurements of this
frictional resistance to the movement of the drill tools .
Excess drag and torque cause directional drilling problems ,
especially in the turning and horizontal sections of horizontal well
often very severe in this well.
The drill string can be failed from tension due to excess
drag or twist off duo to excess torque.
Remedy:
Reduction of torqe & drage that by :
-Reduction of weight of BHA.
-Reducing build up rate
-Oil base or water base mud with good lubricating qualities .
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3- Hole cleaning or cutting removal:-
A particular problem that arises in the drilling horizontal wells is
the difficulty of removing rock cuttings from the horizontal section of
the well .
The source of the problem is that cuttings tend to settle in the bottom
of the hole and increase the friction in the hole , produce poor cement
Remedy:
A great improvement in removing cuttings has been an achieved by
using top drive drilling rigs . in these rigs, the drill string is rotated by a
large , geared electric or hydraulic drive motor rather than by the
conventional rotary table and Kelly.
With this arrangement , it is possible to rotate the drill string and to
circulate mud as removed from the hole . this tends to keep the drill
cutting in suspension and to provide a cleaner hole , the removal of
cuttings reduces friction between the drill pipe and the hole and reduces
the tendency for sticking .
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4- Protection of water sensitive shale:-
Shale layer frequently tend to collapse in contact with fresh water.
Remedy:
Water -base mud can be inhibited to reduce the attack on water-
sensitive shale by addition of NaCl or CaCl2 .
Or,by using of oil-base mud.
5- Directional control:-
Overcoming the force of gravity is a fundamental problem in
directional and horizontal drilling. The bottom hole assembly (BHA) is a
heavy weight hanging on the bottom of the drill string .
Remedy:
A adjustable assemblies “the steerable versions” are more flexible
for use in various situations , the steerable BHA consists of bit, down hole
motor with build in dog-leg tendency , measurement-while drilling
(MWD) .
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Average penetration rate “ R ”
Each formation is drilled by using one bit or more.
The average penetration rate can be calculated from the
following equation:
R = ∑RI *HI / Ht
Where :
RI is the penetration rate in the I-th formation.
HI is the meters drilled in the I-th formation.
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Lithology Depth OF
Formation
Depth
In
Depth
Out
Avg.
Depth
ROP Avg.Penetration
Rate
Post
Miocene
1315 35 934 899 15.91 13.41
934 1315 381 7.54
Zeit 1492 1315 1390 75 7.54 5.62
1390 1432 42 3.23
1432 1492 60 4.88
South
Gharib
1580 1492 1580 88 4.88 4.88
Belayim 1692 1580 1692 112 4.88 4.88
Kareem 1788 1692 1710 18 4.88 7.33
1710 1788 78 7.89
Rudies 2457 1788 2199 411 7.89 8.06
2199 2457 258 8.32
Nukhul
2620 2457 2486 29 8.32 3.99
2486 2620 134 3.05
Abu
Zenima
2640 2620 2640 20 3.05 3.05
Depth vs. rotating time
For every depth interval, the bit rotating time is determined,
Then :
j
iicj tT
1
Where,
Tcj : cumulative rotating time at depth, hrs
Ti : Rotating time in i-th interval, hrs
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Then,
Depth vs. cumulative rotating time is calculated as in the
following tables
Bit no. Interval (m) Depth Out,ft Rotating Time,hr Cum.Rotating Time
1 35 - 934 3064.27 56.5 56.6
1RR 934 -1390 4560.31 60.5 117.1
2RR 1390 -1432 4698.11 13 130.1
3 1432 -1710 5610.17 57 187.1
3RR 1710 - 2199 7214.48 62 249.1
3RR 2199 - 2486 8156.07 34.5 283.6
4 2486 - 2660 8726.93 57 340.6
The Trip time per trip vs. depth
Where,
Tt : Tripe time , hrs
Ts : Time for pull one stand, 4 min.
Ls : Length of stand, 93 ft.
D : Drilled footage by one
Trip time vs. depth
Depth Trip time per trip hr Rotating Time,hr
,ft
0 0 0
3064 3.11 56.5
4560 4.63 60.5
4698 4.77 13
60* 2
D
sL
sTtT
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5610 5.7 57
7214 7.33 62
8156 8.29 34.5
8727 8.87 57
Depth , ft
Total trip time, hr
0 0
3064 56.5
59.6
4560 120.1
124.7
4698 181.7
187.4
5610 249.4
256.8
7214 249.4
256.8
8156 291.3
299.6
8727 356.6
365.4
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 2 4 6 8 10
De
pth
(ft
)
trip time per trip (hr)
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ROTARY DRILLING RIGS
MARINE
Bottom support
barge jackup platform
Self contend tender
FLOATING
semisubmersable
Drill ship
LAND
CONVENTIONAL
MOBILE
JACKNIFE Portable mast
Drilling Rigs
The complexity of the drilling operation determines the level of
0.0
1000.0
2000.0
3000.0
4000.0
5000.0
6000.0
7000.0
8000.0
9000.0
10000.0
0.0 50.0 100.0 150.0 200.0 250.0 300.0 350.0 400.0
De
pth
, f
t
total trip time , hr
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under with only a few exceptions are similar and common to each.
Rigs are generally divided into two categories
1- Onshore. 2- Offshore.
Onshore (land) rigs are all similar, but offshore rigs are of five
basic types - each of which is designed to suit specific offshore
environment.
(A) LAND RIGS:
Before rig equipment is brought in, the land must be cleared
and graded, and access roads must be prepared.
Conventional platforms build in place and left over ahole after
hole completedThe most common arrangement for a land drilling
rig is the cantilever mast (sometimes called a jack-knife derrick)
(2) OFFSHORE RIGS:
1. Barge:
The barge is a shallow draft, flat-bottom vessel equipped as
an offshore drilling unit, used primarily in swampy areas. This rig
can be found operating in the swamps of river deltas , Waste
Africa or in the coastal areas of shallow lakes such as Lake
Marcaibo, Venezuela. It can be towed to the location and then
blasted to rest on the bottom.
sophistication of the various rig components. However, even with
the considerable variety of rig types, the basic components
described
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2. Jack-up:
This mobile drilling rig is designed to operate in shallow water,
generally less than 350 ft deep. Jack-up rigs, are very stable
drilling platforms because they rest on the seabed and are not
subjected to the heaving hull which may be ship-shaped,
triangular, rectangular, or irregularly shaped,When the rig is
located at a drilling location the legs(3, 4,or 5 legs) are lowered
by electric or hydraulic jacks until they rest on the seabed and the
deck is level, some 50 feet or more above the waves.
The chief disadvantages of the jack-up are its vulnerability
when being jacked up or relocated, but as a class, they are
cheaper than other mobile rigs.
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3. Fixed platforms:
There are two basic types of fixed platforms :
3. A) Piled Steel platforms:
These are conventional drilling and production platforms, and
hundreds of them are installed offshore in many parts of the
worlds. The standard configuration consists of a steal jacket
pinned to the seabed by long steel piles, surmounted by a steel
jack deck with supports equipment and accommodation buildings
or modules, one or more drilling rigs, and a helicopter deck. Piled
steel platforms have the advantage of being very stable under the
worst sea conditions, but they are virtually immobile. In shallow
waters the plied platforms is probably preferred over the jacket in
separate sections usually begins onshore.
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3. B) Gravity Structures:
This is a family of deep-water structures usually built of
reinforced concrete, but may be of steel or a combination of steel
and concrete. These structures rely on gravity to keep them stable
of the seabed. Unlike piled steel platforms, they are relatively
mobile and need no piling to hold them in place. Gravity structures
tolerate a wide range of seabed conditions. While they can be
used for development drilling and production, they also have the
advantage of being able to store oil in their structural cells. A
typical gravity structure consists of a cellular concrete or steel base
for storage or ballast, a number of vertical columns, which support
a steel deck and give access to the risers, and deck
accommodation in the form of detachable modules.
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4. Semi- Submersible rigs
These are floating drilling rigs consisting of hulls or caissons,
which carry a number of vertical stabilizing columns, support a
deck with derrick, and associated drilling equipment. Semi-
submersible drilling rigs differ principally in their displacement, hull
configuration, and the number of stabilizing columns. Most modem
type have a rectangular deck, a few are cruciform shaped, others
pentagon shaped, while some of the smaller rigs have a triangular
deck.
The semi-submersible is very stable because its center of gravity
is low in water. It can operate in deeper water than a jack-up rig.
Operational depth is limited principally by the mooring equipment
and by riser; handling problems so most semi submersibles have a
limit of abut 200 meters. However, some units have a capability of
drilling in 500 meters of water with the aid of "dynamic positioning".
This is a method of maintaining the position of a vessel with
respect to a point on the seabed by activating on-board propulsion
units in response to signals received from a position error detector.
5. Drill Ships:
These are ships or "floaters" specially constructed or converted for
deep-water drilling. Drill ships offer greater mobility than either
jack-up or semi-submersible rigs, but are not as stable when
drilling, their main advantages is an ability to drill in almost any
depth of water. Many are anchor-moored, but modem ships are
fitted with dynamic positioning equipment, which enables them to
keep on-station above the borehole. Having greater storage
capacity than other types of rigs of comparable displacement, drill
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ships are often is to drill deeper wells, operate independent of
service, and supply ships.
Drilling rig and its elements
Drilling rig is a set of mechanisms and prime movers designed for
drilling wells,
A conventional rig consists of:
a) Hoisting system, b) Rotary system,
c) Prime movers & transmissions (power system)
d) Slush pumps, e) Drilling fluid circulating system,
f) monitoring system, g) control system.
h) special marine equipment.
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A) Hoisting system consists of:
1- The derrick or the mast.
2- The draw-works.
3- The crown-block.
4- The traveling block.
5- The wire rope.
6- The hook.
The Derrick
Is a tapered tower made of steel which serves to suspend the drill
string or casing strings or place drill pipe stands during housing
operations (round trips)
The draw-works
Is the main item of any drilling rig. It serves as the power control center of the
rig. The power plant of the rig supplies motive power to the hoisting drum,
permitting reeling and unreeling of the drilling line from the hoisting
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drum,When the drilling line is wound on the hoisting, drum the travelling
block moves upward lifting the drill string. When the drilling line is unwound
from the hoisting, drum the travelling block moves downward lowering the
drill string in the borehole.
Crown block
Is mounted on the top of the derrick. it is the stationary block of the block
and tackle system.
The traveling block
Is the moving block of the system and suspended from the loops of the
wire rope which passes over all the sheaves of the two blocks one after
another
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The rotary hook
is suspended beneath the traveling block from its bail. The function of the
hook is to suspend the swivel, an elevator, while drilling, or making round
trips.
One of the ends of the wire rope is attached to the drilling rig substructure.
This end is called the dead line. The other end of the wire rope is fixed to the
hoisting drum of the draw-works. This end is called the working line or the
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drilling line.
b) Rotary system
Is intended for transmitting the rotary to the drill string to which lower
end a drilling bit is attached.
Two mechanisms constitute the rotary system of a drilling rig:
1- The rotary table or the top drive system ( TDS).
2- The swivel.
3- Kelly.
4- Drill pipe and Drill collars.
5- Bits.
The Rotary Table
Is situated in the center of the derrick floor, its function is to rotate the
drill string in the process of drilling and serve as a support for the drill
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string while round tripe are being made.
Top drive
Power swivel or power-sub installed just below aconventional
swivel can be used to replace the Kelly ,Kelly bushing & rotary
table Drilling rotation is achieved through ahydrulic motor
incorporate in the power swivel or power sub.
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The Swivel
Is probably the most ingenious element of the drilling rig. While drilling
is in progress, the swivel is suspended from the hook and suspends the
whole weight of the drill string. It permits free rotation of the drill string
and serves as the passageway for the drilling fluid from the hose lo the
drill string, which is rotated.
The Kelly
Is the first section of pipe below the swivel . the outside section of
the kelly is squared or hexagonal.
Drill pipe
Is the major portion of drill string ,it is spciefied by its outer
diameter ,weight per foot,steel grade& range length.
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Drill collar
Is the lower section of drill string . it is aheavy thick wall steel
tubular.
Bit
Is used to disintegrate the rock ,Types is(PDC bit& rock bit)
c) Slush (or Mud) pump
Usually a drilling rig is provided with two slush pumps. Their function is
to circulate drilling fluid in the process of drilling.
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d) Prime movers and transmissions:
Are necessary to provide motive power for all the mechanics of the rig,
the hoisting system, the rotary system and the mud pumps
e) Drilling fluid circulating system:
Consists of mud pits and tanks, an auxiliary pump and mechanisms for
mixing, chemical treatment and solids controls of the drilling fluid (a
mud hopper, a shaker, a hydro cyclone etc.)
f) Well control system:
Is used to prevent the uncontrolled flow of formation fluids from the wellbore .when the bit penetrate apermeable formation which is pressurized formation.
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Type of BOP's 1-Annular preventer Stop the flow from the well using aring of asynthetic rubber that contract in the fluid passage in annulus.
2-Ram preventer. Have two packing element on opposite sides that close by moving toward to each other (pipe ram,blind ram & shear ram)
g) Well monitoring system:
use devices to display :
- Penetration Rate, - pump rate,
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- Depth, - pump pressure,
- Hook load, - mud salinity,
- rotary torque, - mud density,
- gas content, - pit level
- mud temperature, - rotary speed.
Select the suitable rig type and its components
Selection of the wellhead (BOP)
The safest procedure for designing preventer pressure ratings
is to ensure that the preventer can withstand the worst pressure
condition possible. This condition occure when all drilling fluids
have been evacuated from the annulus and only low density from
fluids such as gas remain, so
a- Maximum formation pressure = 0.052*8.33*1.7*8156
= 6006 psi.
b- Determine minimum hydrostatic pressure assume only
assume gas density = 1 ppg
assume that well will be contain gas to its half section
Phmin = 0.052 * 1 * 8156 = 424 psi.
Working pressure = resultant pressure
= (Pfmax. – Phmin)
= 5582 psi
Using the API designations at 10000 psi working
pressure.
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Selection of BOP:
From data hand book page 408
1- Use Cameron ram type " U : BOP, Operating Data:
From the drilling handbook 411 page:
1-Hydril annular B.O.P.
Type GK
Size , inch 13 5/8
Working pressure , psi 10,000
Vertical bore , inch 13 5/8
Overall height flanged , inch 72 1/2
Diameter , inch 68
Volume at chamber , gal 34.53
2-Ram B.O.P. (cameron type “U”)
Nominal size , inch 13 5/8
Working pressure , psi 10,000
Vertical bore , inch 13 5/8
Overall height “Double-flanged” , inch 66 5/8
Overall length , inch Opened 173 1/2
Closed 130 1/8
Overall width , inch 29 1/4
Fluid volume to operate ram,gal To open 5.45
To close 5.8
Closing ratio 7 : 1
Top Drive Selection
Find the maximum d/s weight in mud:
d/s max. = Weight bit max. + Weight d/p max. + Weight d/c max
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Where,
Wb, Bit weight (assume: 86 lbs)
Fc , factor to compensate fraction (1.5)
d/s = (86 +194390) * 1.5 = 291714 lb
= 132 ton
From composite catalog specification of top drive are:-
specification of top drive
Type
Maximum torque
(lb/ft)
Maximum speed
(rpm)
Nominal rated load
(ton)
Maximum circulation pressure
(psi)
Approximate weight
(lb)
TD 120 P
277000
200
350
5000
10400
Hook selection
For total hook load during casing,
Determine the maximum casing capacity,
Effective weight = weight in air *bouncy factor
For 13 3/8 Wc1 = 299367*0.8675 = 259700 1b
For 9 5/8 Wc2 = 342675*.0.7834
=122 ton “The maximum”
For 7 Wc3 = 16721*0.8853
= 14804 lb
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For safety
Maximum load =1.35*122
=165 ton
So ,Hook specification
H-175
Rated load 175 tons & Weight 3170 lbs =1.4 ton
Hoisting system Design :
1-traveling block
Max. weight on T/B =Max .casing weight + weight of Hook
= 165 +1.4 =166.4 ton
From from Rotary Drilling Handbook page 140,
API working load strength 200 tons
No. of sheaves 5
Approximate weight 8210 lbs
Line size 1.125-1.25
inch
Total HL = Max .casing weight + weight of Hook +Weight of T/B
=165+1.4+3.72
= 170.12 ton
2- Hoisting cable:
Total HL = Max .casing weight + weight of Hook +Weight of T/B
=165+1.4+3.72
= 170.12 ton
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D.L =((H/L)*KN)/(E*N)
= 170.12*( 0.9615)10 / (10*0.81)
=14.2 ton
1- Consider the maximum tension in the line in tons, which
expected for the drilling operation
TF.L = H. L. / (N * E)
= 170.12 / (10*0.81) = 21 ton
2- Multiply this tension by ( 2 ) as safety factor to obtain the safe
ultimate strength of the required cable
= 42 ton
From Drilling equipment farahat book page 49 , select the
cable which has the closest ultimate strength and has the suitable
diameter for hoisting sheaves.
Select 6 * 19 classification wire rope, bright (un coated) or Drawn-
Galvanized wire independent wire rope core
Hoisting cable specification
Nominal strength
Approximate
mass, lb / ft
Nominal
diameter, in Improved plow
steel
Extra
improved
plow steel
159000 lb 138800 lb 2.89 1.25 in
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3- Crown block
Total c/ b load = Total HL + F.L.tension + D.L. tension
=170.12 +21+14.2 = 205.3 ton
From Drilling Data Handbook page 140, select the following
specification,
crown block specification
API working load strength 240 tons
No. of sheaves 6
Sheave diameter 54 inch
Approximate weight 2.1 tons
Diameter of sand line sheaves 42 inch
Drilling line 1.125- 1.25
in
4-Draw work design:
For D/W H.P input
= Brake H.P./EB
= Wm * Vmin / (33000 * EB )
where,
EB = Average efficiency factor for block and tackle system =
0.841
Vmin = Minimum expected velocity of the hook, (150 ft / min)
Wm = The total hook load, lb
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D/W H.P = 150 * 375222.92 ( 33000 *0.841 )
= 2105 hp.
From Drilling Data Hanabook page102
Draw work specification
10000 Nominal depth rating
54 " Size break rims
35 " Drum length
26 " Drum dia.
1 1/8 " Size line
35000 lb Weight
Ton miles calculations :
Drilling line is maintained in good conditions by following a
schedual Slip-and Cut program ,slipping the d/line involves loosing
the dead line anchor and placing a few feet of new line in service
from the storage reel
5- Max.Ton mile during triping:
Ton- miles during round trip @ 8156 ft =
Where , Ls : drill pipe stand length
000.640.2
)*2/1(
000.560.10
*)(* CMDWpDLsDT
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Wp = W d/p * B.F. M = total WT. of ( Hook +T/B)=21780 lb C = L * (W d/c – W d/p) *B.F. = 186 * (246 –25.6 ) *.7833 = 32116.6 lb T = 244.68 Ton-miles Max. Ton mile during casing, Is for Inter. Csg @ 8157
T = 1/2 ton mile for round trip
T = 1/2*((D(Lc+D)*Wca)/1056000)+(D*M/2640000))
Where ,
Lc :is the casing joint length (42 ft)
Wca : Wc*B.F
T = 1/2*((8156 * (42 + 8156) * 42*.7834/10560000) +
(8156 * 21780 / 2640000))
= 137.8 Ton-miles
Calculation of derrick efficiency factor :.
D.E.F. =
legloadequavelant
TNloadBC
.max*4
*)2(./.
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A-For position no.1 D.E.F. = =(N + 2) / ( N + 2) = 100 % B- For position no.2 D.E.F. = (8 + 2) / (8 + 4) = 83.33 % C- Position no.3 D.E.F. = 83.33 % , note same as position 2 D-position no.4 D.E.F.
= 71.4 %
Selection of mud pump:
Based on the last phase 8 1/2 " hole
For fast drilling in soft formation, V=180 ft/min
)4(
)2(
N
N
)224
*(
*)2(
TTTN
TN
)24
*(
*)2(
TTTN
TN
)24
*(*4
*)2(
TTN
TN
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Q = Annular area * Velocity
= (open hole diameter ^2-drill pipe diameter^2)*velocity
= (3.14/4)*(8.5^2-5^2)/144*180(ft/min) * 7.48(gal/cu ft)
= 347 gpm
For pressure loss,
∆Pt=∆Ps+∆ Pd/p+∆ Pd/c+∆P*d/p+∆ p*d/c+∆ pb
Where
∆ Pt : total pressure loss, psi
ΔPs : total pressure loss in surface connection, psi
ΔPp : total pressure loss in d/p, psi
ΔPc : total pressure loss in d/c , psi
ΔPb : total pressure loss in bit, psi
ΔPc* : total pressure loss in annulus outside d/c, psi
ΔPp*: total pressure loss in outside d/p, psi
(A) ΔPs : total pressure loss in surface connection:
From GATLIN page 99 @ Q=347 gpm & 1st system .
ΔPs =93.75 psi
(B) ΔPp : total pressure loss in d/p:
Using the following calculations
1- Calculate the critical velocity,
d
PYdV
m
mppc
2122
.3.908.108.1
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where,
Vc : critical velocity = 5.8 ft / sec.
μp : plastic viscosity = 12 c.p
ρm : mud density = 7.488 ppg
d : inside diameter d/p(ID) =4.276 in
Y.P : yield point =20
2- Calculate the actual velocity,
245.2 d
qV
where,
V : actual velocity (average velocity) ft/sec.
q: flow rate gpm
d: inside diameter of d/p inch.
V = 7.75 ft/sec
While, V >Vc
Then, turbulent flow.
3- Calculation of pressure losses
p
m dV
2970Re where; 2970(constant)
Re = 61455.7
Then,from chart Gatlin Page ( 96 )
F=0.0068 where:F;(friction factor)
So,
d
VLfP m
p8.25
2
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ΔPp = 234.285 psi
(C) ΔPc : total pressure loss in d/c:
Using the following calculations
where,
d : inside diameter of d/c (2.5")
1- Calculate the critical velocity,
d
PYdV
m
mppc
2122
.3.908.108.1
VC = 6.12 ft/sec.
2- Calculate the actual velocity,
245.2 d
qV
V = 22.66 ft/sec.
While, V >Vc
Then, turbulent flow.
p
m dV
2970Re
Where,
Re = 105113.8
3 - Then,from chart Gatlin Page (96 )
F=0.006
d
VLfP m
c8.25
2
where,
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L : length of d/c ,ft
P = 111psi
(D) ΔPd/p : total pressure loss in annulus outside d/p:
(at open hole section )
,Using the following calculation
1- Calculate the critical velocity,
d
PYdV
m
mppc
2122
.3.908.108.1
where,
d : diameter = open hole diameter – O.D of drill pipe
d = 8.5-5
= 3.5 inch
VC = 5.9 ft/sec
2-2 Calculate the actual velocity,
245.2 d
qV
Where,
D2= 8.79242-52
V = 2.71 ft/sec
While, V < Vc
Then, laminar flow.
ΔPd/p = (L*Y.P/300*d)+(up*V *L/(1500*d2))
Where ,
D2 = (8.7924-5)^2
ΔPd/p = 155.68 psi
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(F) ΔPc* : total pressure loss in annulus outside dc:
Using the following calculations
Where ,
Open hole diameter =8.5"
1- Calculate the critical velocity,
d
PYdV
m
mppc
2122
.3.908.108.1
Where ,
D = 8.5-7=1.5"
Vc = 6.65 ft/sec
2 -Calculate the actual velocity,
245.2 d
qV
Where ,
D2= 8.52-52
V = 6.09 ft/sec
While V < Vc “laminar flow”
ΔPd/c = (L*Y.P/300*d)+(up*V *L/(1500*d2))
Where ,
D2 = (8.5-5)^2
ΔPd/p = 20.5 psi
F- ΔPb : total pressure loss in bit:
Assume a cone bit has 3 nozzles
1-calculate the nozzle diameter as
D=((Q/n)/(2.45*V))^.5
Where,
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Q : flow rate,347 gpm
N :no. of nozzles
V : jetting velocity throught nozzle (assume 250 ft/sec)
So,d=.4345 "
For standard d= 13/32 " (From Gatlin 105)
Deq = (n*d^2)^.5
Deq = 0.704 "
Assume Bit nozzle coeff.(c) = 0.95
ΔPb = 549psi
So,
∆Pt = 1073 psi
For mud pump horsepower:
Assume
Hydraulic eff. (ŋh) = 0.9
Mechanica eff. (ŋm) = 0.85
Engine ff. (ŋe) =.87
1-Hydraulic horsepower = (Qt*Δpt)/(1714* ŋh)
=241 hp
2-Brake horsepower = (Hydraulic horsepower/ ŋm)
= 283 hp
3-Prime mover eng. Hp = (Brake horsepower *1.4)/ ŋe
=456 hp
4.*2*7430
*2
equDc
mqbP
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Derrick Desgin
For its API specification:
Determine the maximum derrick capcity
= C/B load + C/B weight
=2.1+205.3
= 207.4 ton =457234 lb
Length of derrick =1.5*93=139.5 ft
From rotary drilling handbook page (12) the derrick specifications
Derrick specifications
Derrick size No. 19
Height 140 ,ft
Base size 30 ,ft
Water table opening 7.5 , ft
Casing capacity 450,000 lbs
API capacity ,lb 950000
Pipe setback 200000 lb
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Rig selection
Using jack nife land rig with medium duty depth 4000 ft – 10000 ft
Cost for the well S/D 13
The drilling cost can be calculated from the following equation
Cf = ( Cb +( Tb + Tt)) / ΔD )
Where,
Cf = Drilling cost, $/ft
Cb = Bit cost,$
Tb = Bit rotating time, hrs
Tt =Trip time, hrs
ΔD =Footage, ft
Cr = rig rent = 833 $/hr
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Hole Tt Tb Tb+Tt, Tp,hr Cb Cost, Cum Cost
hr hr hr ,$ ,$/ft ,$
16 0 0 0 0 0 0 0
16 3.11 56.5 59.6 3.11 5000 17.8 54674.8
16 4.63 60.5 65.1 4.63 5000 39.6 113949.6
16 4.77 13 17.8 4.77 5000 143.7 133757.9
12.2 5.7 57 62.7 5.7 6000 63.9 192007.6
12.25 7.33 62 69.3 7.33 6000 39.8 255782.4
12.25 8.29 34.5 42.8 8.29 6000 44.2 297440.6
8.5 8.87 57 65.9 8.87 5000 104.9 357332.1
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0
500
1000
1500
2000
2500
3000
0 100000 200000 300000 400000
De
pth
ft
Cum cost $
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0.0 50.0 100.0 150.0 200.0
De
pth
ft
Cost $/ft
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References:
1- Farahat, M.S., “ Horizontal well drilling technology “,
Suez Canal University, Faculty of Petroleum & Mining Eng.
2- Bourgoyne, A. T., “ Applied drilling engineering “,
Society of Petroleum engineers Rechardson, TX 1991.
3- Economides, M. J., “ Petroleum well construction “,
John wiley & Sons, 1998.
4- Gatlin C., “ Petroleum engineering “, Department of Petroleum
engineering, University of Texas, 1960.
5- Rabia, L., “ Oil well drilling engineering “,
John Wiley & Sons, 1998.
6- Rotary drilling data handbook.
7- N. J. Adams, “ Complete Well Planning Approach “.
Recommended