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sing Nitohamed Fia

opyright 2012, Societ

his paper was prepare

his paper was selecteviewed by the Societ

fficers, or members.produce in print is res

bstractn the oil indu

perate withou

ke cementing,

f the jointed

lexibility. Untervention. T

een invented

his paper intr

oncept behin

umping a verbular fluids.

gainst the we

ansverse wav

f the tubing h

ach well ma

echnologies c

or use that is e

ntroductionoiled tubing i

ervices. Coileaster well int

tiffness make

eviated wells,

inusoidal wav

here are man

t the end of thoth the tubin

trings. This st

or other jobs.

inimum adde

rictional drag

his paper wil

alculations be

69

rogen fozudeen, SP

of Petroleum Engine

d for presentation at t

d for presentation byy of Petroleum Enginelectronic reproductiotricted to an abstract

stry, there is

a rig, cutting

stimulation,

string, the ne

ortunately, do extend its re

nd been used.

oduces buoya

this techniq

light fluid intThe higher d

ll floor. Mor

e pattern, simi

lp it to wriggl

need a differ

n be used to r

asily impleme

s a fast growi

d tubing usesrvention. Ho

s the tubing

the tubing f

e pattern.

tools availab

e tubing, pulliand the well

ing can be sp

Buoyancy red

d cost. It uses

against the we

l discuss a ca

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r Extend, Cairn India

ers

he SPE Annual Techn

n SPE program comers and are subject to, distribution, or storaf not more than 300 w

always a need

costs and time

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cy reduction,

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over, the lo

ar to that of a

e its way into

ent technique

each the plan

ntable at mini

g means for

smaller diameever, this a

ore suscepti

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le to achieve

g the tubingbore. If the jo

ecifically desi

uction is anot

a lower densit

l floor, thus in

se where buo

d ReacLimited

ical Conference and E

ittee following reviewcorrection by the autge of any part of thisords; illustrations may

to go deeper

by a great ext

ng, productio

satility also i

size, there aof tools and

e tools and te

one other tec

the net wei

hile interventinnular fluid c

density fluid

free flowing g

he well. In thi

for extended

ed measured

al added cost

ell services b

er tubing whivantage com

le to bucklin

ional forces

xtended reach

eeper into theb was at the

ned for each

er tool which

y fluid in the

creasing the r

ancy reductio

in Coile

xhibition held in San

of information containhor(s). The material dpaper without the wnot be copied. The a

and cheaper.

ent. To this da

, perforation

creases. Coil

re higher chaechniques lik

hniques can o

nique to exte

ht of the tub

on to create areates a buoy

also increas

arden hose. B

s case, simulat

each. As per

epth. Buoyan

.

ecause of its f

h allows it tos at the cost

g. Especially

hile being dr

. Tractor tech

hole. Frictionarlier stages

ell. Of cours

can be imple

ubing to redu

ach of the tub

n was used t

d Tubin

ntonio, Texas, USA,

ed in an abstract suboes not necessarily rritten consent of thebstract must contain c

Coiled tubin

y, coiled tubi

tc. As this tec

d tubing is

nces of tubinfriction redu

nly be used o

d the reach o

ing by creatin

arge differencancy effect o

s the rigidity

oth the lower

ions showed a

the requireme

cy reduction i

ast rig up and

be spooled arof stiffness.

with its incr

agged against

ology and rol

reducers decrf planning, t

e, this means

mented even

ce the buoyan

ing before it b

achieve exte

Operati

-10 October 2012.

mitted by the author(s)flect any position of tociety of Petroleum

onspicuous acknowled

s greatest ad

g has been us

hnology gains

ighly used in

getting lockcers, tapering

a case by cas

f coiled tubing

g a buoyancy

e in the densit the tubing a

of the tubin

eight and the

n extended re

nt of the case

s one other tec

its ability to b

ound a reel foDuring well i

asing usage i

the wellbore

lers achieve t

ease the effecte simplest te

hat the tubing

at the final sta

weight of the

uckles.

nded reach a

ns

). Contents of the paphe Society of PetroleuEngineers is prohibitegment of SPE copyrig

vantage is bei

d for many w

fame and tak

horizontal w

ed up in thetubing, tractor

e basis.

in horizontal

effect. This

ies of the annd thus reduc

and makes i

transversal w

ch of 23%.

, a combinati

hnology that i

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r easy transpotervention, t

n horizontal

and starts bu

is by giving a

of friction byhnique is to

may or may

ges of the pla

tubing. This

d the principl

r have not beenm Engineers, itsd. Permission toht.

ng able to

ell services

s the place

ells for its

process ofs etc. have

wells. The

s done by

lar and thes the drag

t follow a

ve motion

n of these

s available

th specific

rtation ande reduced

and highly

kling in a

dded force

lubricatingse tapered

ot be used

nning with

educes the

es and the

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ressures in thressure of the

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oefficient. In

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are highly im

well. If the pfluid inside t

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signing a well

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equation, twre difference

ate is inversel

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umping a lo

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er density fl

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a larger differ

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ave a more u

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only used tu

thus making

inside the tuwellbore pre

de the tubing,

note of. Fig.

to the velocit

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andard Condit

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tubing despit

iform pressur

ular fluid is f

it more resist

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the tubing wil

depicts a sk

of fluid flo

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re between th

the length a

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PE 159269

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ant to high

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l burst out.

tch (not to

. Eq. 1 is

(1)

(2)

e inlet and

nd friction

ngth of the

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bing. As thee inner wall

e entire tubin

aking this int

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f the tubing.

ives a gentle

q. 3states th

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hown in Fig.

he overall deebble sinks t

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bing acting

rictional drag

t this point, i

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ssuming the

bings densit

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to buckling.

ity on Flow Rrestrained gar

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Since one end

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from the wellb

f the water (8.

educe signific

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r Fluid in Andense fluid iannulus will i

case where t

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asing the denof the tubing i

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of the hose i

ection perpend

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n can be usedith the overall

y into the well

binghorizontal w

s not to scale

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ss due to grav

surface. It re

ore. This is w

33ppg) was re

antly allowing

the well befor

nulusthe tubing, thcrease the bu

e tubing cont

an the fluid i

ity of the fluin the fluid. Ta

igher pressurthe tubing w

tubing filled

a low flow ra

pattern. This

restrained, t

icular to the

significantly i

to our advantweight of the

.

ll in an open-nd shows tubi

Fig. 2: Sk

put together itubings densi

ity acting do

ches a point

en the tubing

placed with a

less weight t

e the frictional

e net buoyantyancy acting

ains nitrogen,

the annulus

d in the annul

ble 1shows d

drop across tll in an outwa

ith less dens

e of water. It

appens becau

e other end s

ovement of th

ncrease the fl

age. Using nittubing acting

ole section thng in a well w

tch of tubing i

s much higherty makes it si

nwards on th

where the pu

locks up.

less dense flu

act downwa

drag stops it.

weight of then the tubing.

the average

(oil is 7.1ppg

s increases thensities of co

Water

e length of thrd direction. T

fluid, will gi

can be observ

se the flowing

tarts moving

e tubing.

w rate. Taki

rogen insteadownward and

at is filled witith a high dog

well

than that of tnk to the bott

e wellbore inc

hing weight

d like nitroge

ds and thus r

ubing is redu

density of the

or water is 8

e buoyant formonly used fl

Oil

e tubing. Thishus, it makes t

ve you a stro

ed that once t

fluid exerts p

rantically in a

g the garden

of water, signwith this tran

oil. A sketcheg.

e oil in the wom of the oil

reases becaus

rom the surfa

n (0.0097ppg)

ducing the fri

ed. Similarly,

tubing woul

.33ppg), the t

ce on the tubiuids in the we

l

retained presshe tubing wall

g and stiff tu

e flow rate is

essure on the

transverse p

ose example

ficantly longsverse motion,

depicting this

ell. Thus, juston the well b

there is mor

ce cannot cou

, the weight o

ctional drag.

increasing the

be 17.5ppg.

bing would

g and hencell.

3

ure acts ons rigid and

ing that is

increased,

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ttern. This

(3)

in the well

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scenario is

like how aore. While

weight of

nteract the

f the entire

s a result,

density of

Since, the

ever float.

educes the

8/10/2019 SPE-159269-MS

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4

a

f

aa

s

imulation Ro achieve the

nnulus. To es

luids in the tu

his theory wa

as chosen for

irstly, a base

nnulus was filnd the tubing

ensity of theensity of the t

ifferent itera

imulations ca

esultsdeepest reac

imate how m

ing and annul

s tested using

the test becau

simulation wa

led with crudefaces a lot of

ubing complebing will dec

ions of this

be seen in Fi

into the well,

ch extended

us.

coiled tubing s

se of its compl

s run in conv

oil. The simufrictional dra

te with its fluiease significa

imulation we

. 4.

able 1: Densit

Fluid

Water

Oil

Brine

CO2

Nitrogen

it would be

each can be a

imulation soft

ex well path.

Fig. 3: W

ntional well i

lation showedagainst the

d is much higtly

e run with di

of common oi

Densit

8.

7.

10

0.0

0.0

est to have th

chieved with t

ware. The wel

ell used for tes

tervention co

a lockup at 8,ellbore. The

her. If the de

fferent fluids

lfield fluids

(ppg)

3

.1

.3

165

97

e lightest flui

his, a number

l survey used

ting

nditions i.e. t

164ft. At thatensity of the

sity of the flu

in the tubing

in the tubin

of simulation

for testing is s

e tubing was

depth, the wellfluid in the w

id in the tubi

and annulus.

and densest

s were run wi

own in Fig. 3

filled with wa

is completelyellbore is 7.1p

g is reduced,

The results

PE 159269

luid in the

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. This well

ter and the

horizontalpg and the

the overall

from these

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SPE 159269 5

Fig. 4: Variation of lockup depth with friction coefficient

Fig. 4 is a graph of the friction coefficient of the well plotted against depth of lockup. The friction coefficient of the well is a

factor that signifies the roughness of the well. A new well will have a lower friction coefficient whereas an older well will

have a much higher friction coefficient. This graph shows how the lockup depth would vary depending on the condition of

the wellbore. Also, the graph clearly shows that both decreasing the density of the fluid in the tubular and increasing the

density of the fluid in the annulus can achieve extended reach. Using a low density fluid in the tubing and high density fluidlike brine in the annulus, the tubing shows a lock up depth of 10,545ft in the well in this case study. This is a 23%

improvement over the initial 8,164ft. Table 2 shows the improvement in extended reach seen from the simulations in this

specific case.

Table 2: Lockup depth in diff erent scenarios

Base caseNitrogen in

OilNitrogen in

WaterNitrogenin Brine

Lockup Depth 8,164 8,998 9,647 10,545

Percentage of Extended Reach 0 9 15 23

Variation with tubing sizeIt is common knowledge that larger tubing sizes have more stiffness and are capable of reaching deeper before lockup. It is

also common knowledge that a higher wall thickness makes the tubing achieve extended reach as well. However, in

buoyancy reduction operation, the opposite happens. If the tubing contains a fluid of lower density, it was seen that a lowerwall thickness can achieve increased extended reach. Simulations were run to test this theory and the irregularities can be

clearly seen in Fig. 5. In the specific cases shown below, decreasing the wall thickness achieved an average of 500ft extended

reach.

6,000

7,000

8,000

9,000

10,000

11,000

12,000

13,000

14,000

0.21 0.25 0.29 0.33 0.37 0.41 0.45

LockupDepth

(ft)

FrictionCoefficient

WaterinOil

NitrogeninOil

NitrogeninWater

NitrogeninBrine

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mitless.

cknowledghis research

eferencesfghoul, A.C.

n Introductioigio, D. et al.

ao, L. A Brieontecinos, C.

IRARCO

ortman, L. Hi

imloaz, C. So

ameer, K.P.ek, M.R. 195

0

2000

4000

6000

8000

10000

12000

Depth(ft)

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