Section 4 Well Construction
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Transcript of Section 4 Well Construction
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Oilfield Services Energy & Logistics Engineering Production EnhancementEnergy Logistics
WELL CONSTRUCTION
Well Constructionis a part of WellPlanning
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What is Well Construction?
Well construction a specic part of well planning It is an
engineering !esign process that starts with a clearun!erstan!ing of the o"#ecti$es to "e achie$e! %s a&ini&u&' the following !ata are re(uire! to co&&ence the!esign an! planning process
Well !epth
Location ) lan!' o*shore +water !epth,-eolog. ) litholog.' structural features' ha/ar!s'
sta"ilit.0or&ation Pressure prole0racture -ra!ient prole1ownhole target+s, ) $ertical or !irectional well
T.pe of well ) e2ploration' !elineation' appraisal'!e$elop&ent
E$aluation re(uire&ents ) sa&pling' coring' logging'testing
T.pe of 3ui! an! anticipate! 3ow rates
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Well Construction
Any given well requires several strings of
casing, starting with the largest diameter pipeon top. Subsequent strings of casing are
progressively smaller in diameter as they must
pass through the inside of the previous casing.
The diameter of the deepest casing is
generally dictated by the size of the
production tubing required for anticipated
flow rates.
The primary purpose of each casing string is to
isolate one geological regime from the other
and enable further drilling with full control ofanticipated downhole pressure conditions of
the net interval.An understanding of
downhole pressure variations is essential for
selecting the setting depth of each casing.
Conductor
Surface
!ntermediate
"roduction
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The Core Concepts for Well Construction and #rilling
"ressure
$ydrostatic "ressure
"ressure %radient
Conversion of &nits'uoyancy
"ore "ressure
(racture %radient
)ud Weight Window
Casing Seat Selection
Wellbore Schematic
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Pressure is the force e2erte! per unit areaUnits of &easure&ent4psi' "ar' 5gf6c&7' 5Pa
8 at& +stan!ar!, 9 8:;7 5Pa8 "ar 9 8== 5Pa 9 =
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* cu. ft. + .-* &.S. gallons, and * sq. ft. + *-- sq. in.
To convert gradient from psi/ft to pounds per gallon, divide
by the factor 0.-*/*--1, or 2.234
To convert gradient from pounds per gallon to psi per foot,
multiply by 2.234
5ercise6
Convert *4.2 ppg to psi/ft 7777777
Convert *.2 psi/ft to ppg 7777777
Conversion of Oilfield Pressure Units
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* cu. ft. + .-* &.S. gallons, and * sq. ft. + *-- sq. in.
To convert gradient from psi/ft to pounds per gallon, divide
by the factor 0.-*/*--1, or 2.234
To convert gradient from pounds per gallon to psi per foot,
multiply by 2.234
5ercise6
Convert *4.2 ppg to psi/ft 7777777
Convert *.2 psi/ft to ppg 7777777
Conversion of 9ilfield "ressure &nits
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Well :A; Well :';
T# *2,222;
T
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"ressure gradient of compressible fluids is comple as itdepends on several factors, such as specific gravity of the
gas, bottomhole and surface pressures, temperature,
compressibility factor, and height of column. The
following relationships could be used for approimation
where precision is not critical6
2.* psi/ft for a gas column down to *2,222;, and 2.*3
psi/ft if deeper
What is "ressure %radient of a %as Column8
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What is 'uoyancy8
'uoyancy is the loss of weight when a body is immersed in liquid.
!t depends on the density and volume displaced.
!n drilling applications it is important to >now the buoyant
weight of steel drill pipe, casing and downhole tools when they
are lowered in the wellbore. This done by first calculating the
'uoyance (actor for the given mud density, and then multiplying
the weight in air with the 'uoyancy (actor.
'uoyancy (actor + *= 0)ud density in ppg/?3.31
where, ?3.3 is the density of steel in ppg
5ercise6A drilling assembly weighs @-2,222 lbs in air. $ow much will it
weigh when lowered in a well full of *@.2 ppg drilling fluid8
Answer 777777777
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"ore "ressure is the pressure of the fluids withinthe pores of the formation
Bormal "ressure is equivalent to the pressure
of a column of water with a pressure gradient
ranging from 2.-@@ psi/ft 0.@ ppg1 for fresh water
to 2.34 psi/ft 0*2 ppg1 for salt water. Typical valueis 2.-?3 psi/ft 0. ppg1
Abnormal 0overpressure1 is any pressure above
normal
Subnormal is any pressure below normal
What is "ore "ressure8
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Under-compaction:5ntrapment of pressure due to rapiddeposition of overlying seal not allowing water to escape
Uplifting:(ormations compacted at great depth can be
uplifted to a shallower depth due to tectonic forces.
Centroid:#eeper fluid pressure in communication with
shallower part of a dipping formation
Artesian: 9utcrop at a higher elevation
Diagenesis:Temperature and pressure causing alterations in
the composition of formations over time
What is the 9rigin of Abnormal "ressures8
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(racture gradient is the mud weight required to fracture, orcause the formation to separate and ta>e fluid. !t is the static
mud weight, or equivalent dynamic mud weight, at which lost
circulation occurs
Dost circulation is a maEor cause of well control problems
At a given depth (racture %radient depends on6
Dithostatic or overburden gradient
"ore pressure
Fatio of vertical and horizontal stresses in the matri
What is (racture %radient8
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#uring the planning
stage, the two profilesare developed from
offset well data analysis,
basin models, and
seismic data
#uring drilling, real time
data is derived fromactual mud weight
requirements, downhole
logging tools, drilling
responses, and Dea> 9ff
Tests. AdEustments in the
program may berequired for observed
differences between
prediction and actual
)ud Wt 5quivalent 0ppg1
#epth
0feet1
"" FG
(ore (ressure 1racture &radient (ro$les
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/epth
!feet"
Mud Wt Equivalent (ppg)
Trip 2argin&enerally 0.3 0.*
ppg oer (ore(ressure
5n eep 6ells may
switch to 7*0 +00psi oer (ore(ressure
%afety 2argin
8ic9 Tolerance
&enerally 0.3 0.*ppg under 1&
)ud Weight
Window
The )ud Weight vs #epth %uidelines
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#epth
0feet1
"" G (%, )ud Wt 5quivalent 0ppg1
'ottom &p
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FH' 2 ft
)SD *32 ft
)ud Dine ?22 ft
Typical Well Schematic
@2I Conductor
42I Surface Casing
*@=@/I !ntermediate Casing
=3/I "roduction Casing
I "roduction Diner
"ay Jone
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%rades of Casing K according to strength G properties
API General Service
Grade
H-40
J55
K55
L-80
C-95
T-95
N-80
C-95
P-110
Q-125
in !ield S"ren#"$ - %&i
40000
55000
55000
80000
95000
95000
80000
95000
110000
125000
API Hi#$ S"ren#"$
API S'(r Service