10-Under Balance Drilling.ppt

INSTITUT ALGRIN DU PTR!L

School of Boumerdes UFR: Drilling and Production

Under Balance Drilling

!utlines 

Introduction

 "h#

Under$alanced drilling

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Under $alance t#%es

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UBD Design consideration

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UBD &ui%ment

 Ad'antages

( disad'antages of UBD

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Poor candidates of UBD

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Good candidates of UBD

Introduction 

Under$alanced drilling is an acti'it# em%lo#ing a%%ro%riate e&ui%ment and controls )here the %ressure e*erted in the )ell$ore is intentionall# less than the %ore %ressure in an# %art of the e*%osed formations )ith the intention of $ringing the formation fluid to surface+ !'er$alanced Drilling ,!BD-

Under$alanced Drilling ,UBD-

P ,f- . P ,$h%- / P ,h#d- 0 P ,af%-

P ,f- 1 P ,$h%- / P ,h#d- 0 P ,af%-

 "h# Under$alanced drilling 

Reser'oir Benefits

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Pre'ent formation damage

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arl# %roduction

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Reduced stimulation

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nhanced reco'er# 

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Drilling Performance

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2igh R!P

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Fractured3Loss formation

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Reduced 4D for e*tended reach )ells

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Differential stic5ing %rone formation

Under $alance t#%es 2#drostatic head ma# $e induced or ma# $e naturall# less than the formation %ressure Natural

under6$alance

6  A%%lications for normal to a$o'e normal %ressured reser'oirs utili7ing fluid s#stems in a controlled flo) drilling techni&ue+ Induced

under6$alance

6 De%leted Reser'oirs: adding natural gas8 nitrogen or air to li&uid %hase of drilling fluid

UBD Design consideration 

B2P re&uirement 6 2#draulics 9 ho) much under $alance

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Drilling fluid o%tion 6 Gaseous 3 4om%ressi$le fluids ,air8 mist or foam drilling6 Single %hase fluid ,clear li&uid8 "B;8 !B;6 Gas lift s#stems ,Natural gas8 N< 8 4!< and !