section 4 well construction

8/10/2019 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

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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

section 4 well construction

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