Drill-Stem Testing 2

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Drill-Stem Testing (DST)

CONFERENCE PAPER ' ()*+)R !-#

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1 AUTHOR:

)1ad )deeb

+ni2ersit3 o 4urdistan 5 6awler

1 P+7LI8)9IO* 0 8I9)9IO*S

)ll inte;treerences underlined in bluearelin<ed to publications on

Research=ate, lettin 3ou access and read the> i>>ediatel3.)2ailablero>: )1ad

)deeb Retrie2ed on:

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http://www.researchgate.net/publication/271826746

http://www.researchgate.net/publication/271826746



#

Drill-Stem Testing (DST)

Prepared by: Azad Adeeb Noori

Supervised by: Dr. Kosra! "azra#san

Petroleum $eology

%niversity o# Kurdistan- &e!ler



Abstract

'ne o# te most important stages o# ompleting a !ell is disussed in tis report !i is

te Drill-Stem Testing (DST). Tis report disusses tree main aspets o# tis teniue* it

indiates te detailed #untion o# ea omponent o# te tool assembly. Ten it disusses te

reuired deisions to be made to per#orm a test. +ts main #ouses !ould be on te proedure o#

te test and igly empasizes on te best interpretation o# DST pressure arts.

Introduction

Drill-stem testing (DST) is one o# te most important ompletion teniues. +t is a type o#

temporary ompletion tat is used to evaluate te #ormation and inspet a reservoir,s properties.

Aording to (Ammann* /0)* te measurement o# te reservoir properties by te DST an be

delivered diretly or indiretly. Diret measurements means tat te data are reorded !en te

tool assembly !as do!n in te ole. Tose measurements inlude* te Stati 1eservoir Pressure*

#lo! rate measurement* reservoir depletion i# too2 plae during te test* and obtaining a reovery

sample o# te #ormation #luids. &o!ever* te indiret measurement or empirial measurements

are tose parameters tat yield #rom te use o# euations and it inludes* most importantly te

produtivity inde3 (P+)* e##etive permeability o# te #ormation to te #luid #lo!* #ormation

transmissibility* s2in #ator* drainage radius o# te investigation test* and detetion o# reservoir

anomalies (su as barriers* #luid ontats* permeability anges or layered zones). As ("la2*

4/) states tat speial ompletion euipment are reuired to per#orm te test* some o# tem are

ompulsory !ile oters are au3iliary depending on te !ell onditions and te test

reuirements. Te #ollo!ing setion disusses te tools tat ma2e up te DST tool assembly.



Equipment of the Drill-Stem Test tool

Te drill-stem tool as #our basi or ompulsory omponents tat sould e3ist in every tool

assembly made by any servie ompany. Tese #our omponents are: te pressure reorders* te

test valves* te ydrauli by-pass or eualizing valves and te pa2ers. A general diagram o# te

DST tool is so!n belo! in #igure ():

5igure (): +llustrates te omponents o# te Drill-Stem Test tool inluding bot sur#ae

euipment and do!n-ole tool.



. The Pressure recorders (the Brain of the DST tool assembl)!

Te DST tool is almost useless !itout te e3istene o# pressure reorders. Aording to

(Dolan* 46) te pressure reorders are built in a number o# pressure apaities as !ell as

lo2 speeds. Te pressure reorders used in te DST tool are usually sensitive #or lo! pressure gauges as mu as 7 psig and #or ig pressure gauges as mu as t!o tirds o#

te ma3imum pressure o# te !ell.

8. The Test "al"e!

Tis valve as a ma9or role in te drill-stem test. +t is plaed in te upper setion o# te

DST tool above te ydrauli by-pass valve. Aording to ("la2* 4/)* one o# its main

#untions is to provide a passage #or te #luids to #lo! into te drill pipe !en te pa2er is

set at te annulus. Seond* it prevents te drilling mud to enter te empty drill pipe !ile

running in te boreole. +t also assists in te prevention o# drilling mud entrane to te drill

pipe !ile pulling out te DST tool assembly and aids in te onservation o# te reovered

reservoir #luids to te sur#ae. 5igure (8) belo! so!s te test valve:

5igure (8): Test valve.



. The hdraulic b-pass "al"e!

Te ydrauli by-pass valve as a role in relieving te pressure in te boreole. +t

provides an additional spae #or te drilling mud to pass around te pa2er !ile running in

or pulling out o# te boreole. +t allo!s te drilling mud under ydrostatis pressure to #lo!do!n!ard troug te pa2er mandrel at te end period o# te test into te oles belo! te

pa2er. Tis ertain #untion provides te eualization o# pressures around te pa2er

ausing it to be retrieved easily to te sur#ae.

;. The Pac#ers!

Te pa2ers used in te DST tool are temporary* !i means tat tey an be retrieved

to te sur#ae unli2e oter types o# permanent pa2ers !i stay in te !ell. Aording to

(Petro!i2i* 80;) pa2ers are o# di##erent sapes and are made o# rubber-li2e materials tat

an be ompressed to e3pand against te boreole !all. Teir main #untions are to seal te

annulus spae and prevent te do!n-ole movement o# te drilling stem. Tis sealing

meanism prevents te vertial #lo! o# te #luids in tat setion o# te !ell. Pa2ers very

o#ten improve te prodution rate o# te !ell by direting te #ormation #luids to one !ay

passage rater tan going into te annulus spae. Aording to ("la2* 4/)* pa2ers are

usually set above te assigned per#oration zone to prevent te #ormation #luids #rom #lo!ing

troug te annulus spae to te sur#ae. Te pa2ers are set in te ole by rotation o# tedrill pipe ontrolled by te driller at te sur#ae. 5igure () belo! so!s some types o#

pa2ers:

5igure (): So!s di##erent types o# pa2ers.



+n addition to te basi omponent o# te DST tool tere are oter au3iliary omponents

tat most o# te modern DST assemblies are omposed o#* !i inlude te #ollo!ing:

. The Shut-in pressure "al"e!

Tis speialized valve is loated belo! te reverse irulating valve o# te DST tool

assembly. "redeoe#t (/4) states tat sut-in valves ave a role in te sut-in periods

!itin te test* meaning te initial sut-in and te #inal sut-in periods. 'ne o# its #untions

is to permit te test valve to be losed at te end o# te #lo! period !it redued prospet o#

unseating te pa2er or letting te pressure eualize around te pa2er troug te by-pass

valve. +t also elps in retaining te #ormation reovered liuids.

8. The Dis# "al"e!

Tis valve aids in te prevention o# te drilling mud entrane into te drilling pipe !ile

running in ole. +ts seond #untion is to allo! te pa2er to be set #irmly and te tester

valve to be opened* be#ore te tool is opened te dis2 valve rupture by te dropped go-devil

#rom te sur#ae. A sample o# te dis2 valve is so!n in te #igure (;) belo!:

5igure (;): Dis2 valve.

. The $e"erse %irculating "al"e!

Te importane o# tis valve is tat it allo!s te reovered #luid to be pumped out o# te

drill pipe by reverse irulation into sur#ae tan2s. +t also provides sa#e operation #or te test

by onditioning te mud in te annulus. A diagram o# te irulating valve is so!n belo!

in #igure (4):

https://www.researchgate.net/publication/227698876_The_DrillStem_Test_The_Petroleum_Industry's_DeepWell_Pumping_Testa?el=1_x_8&enrichId=rgreq-b38ca153-e177-4acc-8746-a61d6c97a92c&enrichSource=Y292ZXJQYWdlOzI3MTgyNjc0NjtBUzoxOTMxNTI1MzYzMjIwNTRAMTQyMzA2MjU2MTgwNA%3D%3D

https://www.researchgate.net/publication/227698876_The_DrillStem_Test_The_Petroleum_Industry's_DeepWell_Pumping_Testa?el=1_x_8&enrichId=rgreq-b38ca153-e177-4acc-8746-a61d6c97a92c&enrichSource=Y292ZXJQYWdlOzI3MTgyNjc0NjtBUzoxOTMxNTI1MzYzMjIwNTRAMTQyMzA2MjU2MTgwNA%3D%3D



5igure (4): 1everse <irulating =alve.

;. The &ar!

Te type o# 9ar used in te DST tool is a ydrauli 9ar tat is designed to provide

impat blo!s to set #ree te stu2 pa2er or DST tool !enever possible. A sample o# teydrauli 9ar is so!n belo! in #igure (/):

5igure (/): &ydrauli >ar

4. The Safet 'oint!

Tis tool is used to unsre! and retrieve te DST tool !en eiter te anor or te

pa2er is stu2 in ole. +t allo!s sa#e reovery o# pressure data to te sur#ae as !ell as #luid

samples. A sample o# te sa#ety valve is so!n in te #igure (6) belo!:



5igure (6): Sa#ety 9oint.

/. The Anchor shoe (Bullnose 'etting noles)!

Te anor soe is te ead o# te DST tool* plaed in te lo!er end o# te tool !i

enters te !ellbore #irst. +t is made o# ard material to absorb te damage aused by

restriting material in te !ell. Aording to (&yne* 808) anor soe ead ontains

nozzles or openings tat derease te buoyany o# te #luids in te !ell as !ell as brea2ing

te sur#ae tension o# te #luids. Anoter important #untion o# te anor soe is tat it

anors te DST tool in te bottom o# te !ell and olds it !eigt. Te bullnose #igure is

so!n belo!* in #igure (?):

5igure (?): Anor soe or "ullnose 9etting nozzles.

6. The Bottom ole %ho#e!

Te "ottom &ole <o2e is a sort sub tat an be loated belo! te pa2er and above te

per#orated pipe. +t aids in te restrition o# te #lo! do!n ole. +t olds some ba2pressure

under te pa2er and redues te ydrostati pressure on it.



?. Perforated pipe!

Aording to (1aymond* 800/) te per#orated pipe is loated above te anor soe

and its #untion is to soot per#orating bullets into te #ormation* as te go-devil is sent

#rom te sur#ae to start te per#oration. A diagram o# te per#oration proess is so!n

belo!:

Diagram (): So!s per#oration o# te #ormation.

. The Surface %ontrol ead (%hristmas Tree)!

Tis sur#ae assembly ontrols te #luid #lo! #rom te drill pipe to te sur#ae troug a

set o# valves and o2es. A diagram o# te <ristmas tree is so!n in te #igure () belo!:

5igure (): <ristmas tree.



#

Designing the DST plan

+n order to insure tat te desired in#ormation are delivered by te DST test detailed

onsiderations must be given to a number o# #ators. Ta2ing in onsideration te #ollo!ing

#ators inrease te probability o# suess o# te test:

. The amount of hole to test!

1aymond (800/) states tat it is needed to 2no! at !i dept or total dept (TD) te

test is going to be e3euted and !at type o# #ormation is inluded* !i o# ourse

most o# tese data ave been olleted !ile logging and oter geopysial teniues.

8. Pac#er sie selection and assigning the location of the pac#er seal!

Determining te suitable size o# te pa2er and its seal loation as a great e##et on te

suess o# te DST test. Aording to ("la2* 4/)* it sould be deided aurately

!i type o# pa2er is reuired tat totally mates te !ell onditions* !eter te

!ell is open-ole or ased ole* or !eter te #ormation #or inspetion is a sandstone or

limestone* et. Te loation o# te pa2er seals are assigned by te elp o# aliper logs

!i provide an appro3imate radius o# te boreole and te least learane bet!een te

!ell !all and te pa2er seal. As te pa2er size seletion depends on te type o#

#ormation* so te pa2er seal does.

. Selecting the suitable top and bottom hole cho#es!

Te seletion o# te top and bottom-ole o2es is made by onsidering te sa#ety point

#irst. Te rigt use o# te top and bottom o2es prevent o2e plugging or #luid #lo!

restrition. +n general* te bottom o2e is osen to be smaller in diameter tan tat o#

te top o2e to ontrol te amount o# #lo! to te sur#ae.

;. Estimation of the time required to perform the test!

Te pre-deision o# te lengt o# te test is a vital #ator in te proedure. $rant (4)

states tat troug tis step* te time reuired #or setting te pa2er* opening te test

valve* te initial #lo!* initial sut-in* #inal #lo! and #inal sut-in are all assigned teir

spei#i periods trougout te proess.



#

4. Selection of pressure gauges and manner of displacement in the tool!

As it as been mentioned be#ore te pressure gauges are onsidered as te brain o# te

DST tool* tere#ore as <ristie (n.d) states tat to per#orm te test at least t!o

subsur#ae pressure gauges are needed to run te tool in te !ell as one o# tem is

plaed inside te anor soe #or it to reord te pressures belo! te bottom ole o2e*

!ile te oter is plaed outside te anor soe to reord te pressures e3erted by te

#ormation #luids or te drilling mud. Te pressure reorders sould be osen orretly

so tat tey are able to reord pressure iger tan te ma3imum pressure o# te !ell #or

obtaining more aurate results.

/. Assigning the location of circulating "al"e* 'ars and safet 'oints!

Te irulation valve is usually plaed above te test valve* tis oie is made #or it

!ill permit te retention o# unontaminated #ormation liuid samples. Te 9ars are

usually plaed above and as near as possible to te pa2er to set it #ree. Te sa#ety 9oints

are plaed in a loation belo! te pressure reorders so tat te data !on,t be lost in

ase o# stu2 anor or pa2er.

6. %onsidering the use of +ater or gas cushion!

Te use o# !ater or gas usion sould be onsidered in order to prevent te abrupt #lasrelease o# pressure #rom tousands (psia) o# drilling mud pressure to atmosperi

pressure. Aording to (Timmerman* 68) undesired #las release auses damage to te

#ormation o# te !ell in te #orm o# aving o# te !ellbore !all. +t may also ause te

plugging o# te anor per#orations or even te bottom-ole o2e. @ater usions are

usually plaed in te drill pipe to redue te pressure di##erentials tat our aross te

!all o# te boreole and te pa2er as te tool is opened.



E,ecuting DST test and interpreting DST pressure chart

Te simplest !ay to desribe te proess o# Drill-Stem Testing is to present a typial DST

pressure art o# an open ole* see #igure (0) and desribe ea segment o# it. @en all te

#ators #or per#orming a DST are ta2en in onsideration as mentioned in te previous setion* te

plan #or te DST is ready to run. &o!ever* be#ore running te tool into te !ell* te tester inserts

te test art into te reorder and dra!s te baseline !i indiates (0 psig)* te blue line in

te #igure (0). Te !ell sould be onditioned and #illed !it drilling mud. Te driller pulls out

te !ole drilling string out to te sur#ae to replae te drilling bit !it te DST tool* ten e

enters te !ole string ba2 again into te !ell* stand by stand. Aording to "redeoe#t (/4)*

te DST test is per#ormed as #ollo!s:

igure (./)! DST pressure chart

• Te initial pase o# te test is observed in segment (A to ") as so!n in te art above.

As te tool runs do!n te ole te ydrauli by-pass valve is le#t open beause te

pa2er as limited learane bet!een te asing and te !ellbore. Te open by-pass

valve allo!s te drilling mud to go up te drilling pipe and up to te sur#ae* tis ation

is meant to lo!er te pressure surges reated as te tool runs do!n te ole. Te

pressure gauges start to reord an inrease in te pressure. Tis inrement is due to te

buildup in te ydrostati pressure o# te drilling mud olumn present inside te !ell. +t

an be observed tat te pressure urve is not smoot beause o# pressure surges !i

our even !en te by-pass valve is open. Te pressure surges are aused by te

addition o# onnetions



to te drilling string. Anoter reason #or tat is te e3istene o# tigt spots enountered

in te ole as te !ell !all is not straigt do!n!ards. Sometimes pressure surges our

due to addition o# !ater usion or repair sur#ae euipment. All o# tese noises are

reorded by te pressure gauges as tey run do!n te ole.

• A#ter te per#orated setion pipe as reaed te test interval or total dept (TD)* te

sur#ae euipment is onneted to te drill pipe during tis time te pressure stabilizes

at point ("). Te pressure surges end and te initial ydrostati pressure is reorded

relatively at te point !ere tere is #lat pressure values. Te driller ten slags o## te

bra2es reating a !eigt on te DST tool ausing te pa2er to e3pand. Te pa2er seals

o## te area bet!een te interval o# interest as !ell as te gage #rom te olumn o# mud

above te pa2er. 'ne te pa2er is set te driller rotates te drilling stem ausing te

tester valve to open momentarily #or #e! minutes (#rom " to <). Te initial #lo! ta2es

plae #rom (< to D) tis period lasts #rom 4 to 0 minutes. Te initial #lo! pressure

reorded at point (<) is nearly atmosperi unless a !ater usion is plaed in te drill

pipe. Tis ation allo!s te pressurized #ormation #luid and drilling mud to #lo! into te

tool and up to te sur#ae.

• Te test valve is ten losed and te initial sut-in period ta2es plae !it a duration o#

0-/0 minutes #rom points (D to ). Sur#ae indiation o# te #lo! are observed and te

pressure builds up reaing te Stati 1eservoir Pressure at point ().

• Te test tool is opened again #rom ( to 5) and te #inal #lo! period ours #rom (5 to

$). Te sape o# te buildup !ill depend on te properties o# te #ormation and te

#luids. Te duration o# tis period ta2es #rom tree ours to maybe days depending on

te o!ner reuirement.

• At te end o# te #inal #lo! period te test valve is again sut-in at point ($) and te

#inal buildup period ta2es plae #rom ($ to &). To remove te DST tool te driller #irst

opens te reverse irulating valve. +t is opened ydraulially by pumping te drilling

mud do!n te annulus* !it te valve open te drilling mud irulates do!n te annulus

and te up te drilling pipe to te sur#ae. Te drilling #luid 2ills te !ell by 2eeping te

#ormation #luids under ontrol. Ten te pa2er is released at point (&) eiter by rotating

te drilling string or by te use o# ydrauli 9ar. Te ydrostati pressure o# te mud

olumn is #elt



ba2 again by te pressure reorder at point (+)* ten te tool !ill retrieve #rom te ole

#rom points (+ to >).

%onclusion

Te integration bet!een tests results and data are ompulsory #or ompleting a !ell. $oing

blindly into ompletion o# a !ell !itout per#orming te drill-stem testing is a great loss. Tis

report as disussed te importane o# te DST. +t igligted te main omponents tat ma2es

up te DST tool ea !it teir o!n partiular #untion. +t also disussed te best design #or te

DST and o! it is e3euted. Te report ame up to onlude tat te ability o# a !ell to beompleted suess#ully is to orretly interpret te DST pressure art* !ere by te most

important parameter is obtained #rom it* te stati reservoir pressure* 2no!ing tis value and

oter parameters !ill aid in #urter development o# te !ell.

$eferences

) <. ". Ammann (/0). Case Histories of Analyses of Characteristics of Reservoir

Rock from Drill-Stem Tests. Soiety o# Petroleum ngineers. doi:0.8?B/-$8) .&. Timmerman C &.K. =an Poolen (68). Practical Use of Drill-Stem Tests. Te

>ournal o# <anadian Petroleum Tenology* ontreal* (pp. 8-;0).

) >.D. "redeoe#t* (/4). The Drill-Stem test: The Petroleum Industrys Dee!-"ell

Pum!in# Tests. Publised by te %.S. $eologial Survey.

;) >.P. Dolan C et.al (46). S!ecial A!!lication of Drill-Stem Test Pressure Data.

Petroleum Transations* A+* vol. 80* (pp. ?-8;).

4) . S. 1aymond C @.E. Ee##ler* (800/). $il and %as Production in &ontechnical

'an#ua#e( Penn @ell <orporation

/) N.>. &yne (808). &ontechnical %uide of Petroleum %eolo#y) *+!loration) Drillin# and

Production. Tird dition* Penn @ell <orporation.

6) 1. $rant C &. $ill (4). Ho" to Increase the Relia,ility of your $!en Hole Drill-

Stem Test Analyses( Te petroleum soiety o# <+.

?) 1.S. <ristie (n.d). Use of Recordin# Pressure %a#es in Drill-Stem Tests. Drilling

Pratie* (pp. ?-8).

) @. . "la2 (4/). A Revie" of Drill-Stem Testin# Techniues and Analysis. Soiety o#

Petroleum ngineers. doi:0.8?B4?-$

) ttp:BBpetro!i2i.orgBPa2ers

8) ttp:BBglossary.oil#ield.slb.om

http://petrowiki.org/Packers

http://glossary.oilfield.slb.com/

http://petrowiki.org/Packers

http://glossary.oilfield.slb.com/



0nline sources?@ %nited States Department o# Eabor:

ttps:BB!!!.osa.govBSET<BetoolsBoilandgasB!ellFompletionB!ellFompletion.tml

https://www.osha.gov/SLTC/etools/oilandgas/well_completion/well_completion.html

https://www.osha.gov/SLTC/etools/oilandgas/well_completion/well_completion.html

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Drill-Stem Testing 2