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Chapter  Four Extended Reach Drilling & Multilateral Wells Prepared By:                         Dr.  Yousif   Bagadi Ass. Prof. in Sudan University  Of science & Technology College Of Petroleum Engineering  Petroleum Department

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As reserves become even smaller and difficult to access, this becomes an ever-more important enabling technique to exploit hydrocarbons which otherwise would be uneconomic to produce.  Our on site improvements reduce drilling and completion costs, improve production rates and minimize environmental impact. ERD wells are an efficient, elegant and environmentally  favourable  solution to producing hydrocarbons . The standard definition can be unsatisfactory as wells with true vertical depths may fall outside the definition despite carrying ERD challenges.  The objective is to set a definition to allow changes in risk to be considered.

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The world experience in extended-reach well (ERW) construction in England, Argentina,   China, Norway, Denmark and other countries has confirmed their ecological and economic efficiency.  At the  Wytch  Farm oil field (England), British Petroleum and Schlumberger have drilled a well of 10658m measured depth (MD) with 10114 m departure from vertical. Hundreds of wells have been constructed with departure from vertical in excess of 5000 m. Works are carried out concerned with feasibility study of construction of wells with departure from vertical up to 20000 m.

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The term ERW suggests the well with the departure /true vertical depth (TVD) ratio ≥   1. It is difficult or almost impossible to apply conventional techniques to complete ERW in reservoirs composed of incompetent and loose sands occurring directly beneath loose rocks prone to borehole collapse and key-seating. To stabilize the borehole walls, it is necessary to use expensive drilling  muds , run more casing strings or to give up the idea of tapping the reservoir at the location which is considered optimal from the point of view of the field development or exploration.

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“A form of directional drilling” The standard definition uses the ratio between surface and bottom hole locations : step out (horizontal departure) greater than twice vertical depth.  High angle is an inclination greater than 30 degrees. Extended reach drilling is carried out on long, high angle wells, when the position of the surface location and targets do not allow a short throw, low angle to be drilled.

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The principle of ERD is simple, however designing a well that minimizes the risk of a major NPT event is not – the industry is littered with avoidable drilling problems where it was thought that just another 10 degree inclination or an extra 500m of tangent section would not be a problem! In addition to integrated team efforts, the application of new technology provides economic incentive for continued exploration and production.  Drilling technology now allows wells to be drilled laterally thousands of feet away from drilling platforms.  This technology required not only downhole motor and steering assemblies, and a new generation of drilling  muds  to reduce friction on the drill string, but development of geologic techniques to keep the bore-hole within the objective pathway.

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CHALLENGES Hole cleaning and hydraulics ECD management Wellbore stability Torque and drag Stuck pipe avoidance Equipment selection

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To increase the reliability of ERW construction and to reduce the labor input and material expenses,   the novel drilling method has been introduced (Fig. 1). The vertical section 1 is drilled within   the interval  I of incompetent rocks prone to key-seating and borehole collapse. The inclination angle is   built which should not exceed the critical value for the given geological conditions that otherwise might   lead to infringement of .  the borehole stability.

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Introduction to Extended Reach
and Multilateral Wells
Describe ERD and ML levels
• Application
Economic benefits
examples

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Technical difficulties
Lost circulation and other well
control problems
•Torque, drag, and buckling
Casing wear
Cementing

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New drilling technologies that
can enhance ML/ERD
Dual Gradient Drilling
• Expandable tubulars
• High lubricity muds
• Hole cleaning

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Introduction to Extended Reach and Multilateral Wells

Wytch  Farm O&GJ, Jan. 19, 1998, P.24 SPE 28293 (1994)

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David Knott
Senior Editor
BP Exploration Operating Co. Ltd.
completed a well in U.K. Wytch Farm
oil field with a horizontal reach of 10.1
km, setting a world record.
The M-11 well was drilled from an
onshore drill site into a reservoir that
extends offshore and was brought into
production on Jan. 12 at a rate of 20,000
b/d of oil.

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Oeutag Drilling is the drilling contractor for extended-reach wells in BP's VVytch Farm oil field. The rig on drill site
M, used to drill the record-breaking M-11 well, is the largest in Europe, with a hp draw works, three hp mud pumps,
and a top drive. photo courtesy Of BP.

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WYTCH FARM EXTENDED-REACH WELL DESIGN*
Goathorn Poole
peninsula Hartor
8 1.5m
Coastline
Poole
Bay
4.5m
Sea level
Tertiary
Chalk
Mercia mudstone
600
•Generic design.
Source: BP Exploration Operafing Co. Ltd.
Meters

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Stepout (Horiz. Depart.) = 33,181 ft
Exceeded previous record by 6,729 ft
Measured Depth = 34,967 ft
True Vertical Depth (at TD) = 5,266 ft
Time to drill and case = 173 days
Mll is the 14th ERD well at Wytch Farm
REF: Anadrill Press Release 1-23-98

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• One third of reserves are offshore under Poole
Bay
• ERD project began in place of an artificial
island in 1991
• Saved 150 million in development costs
• Development time saved - 3 years
Scheduled with reach of 6.2 km
• Prod. before ERD project = 68,000 BOPD
• Prod. with 3 ERD wells = 90,000 BOPD

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11
605
617
Ia
595
60.
% 595
505
VII
61
582
VI 660
Va 627

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“Multilateral”  or   “Multi-lateral”? Are both of  these   multilaterals?

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trunk (main   wellbore) lateral splay lateral branch junction

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Cased Junction:  A junction that connects the trunk to  the lateral, using tubulars, either hydraulically or  physically. Are typically required for easier re-entry,  for pressure isolation, or because formation in  junction area is   unstable. Uncased Junction:  A junction where no tubulars  connect the trunk to the   lateral. Cased   Junction

Whipstock:  A device with a hardened,  angled face set in the junction and used to  force a mill to cut or to deflect tools  through the trunk   casing. Uncased Junction

Multilateral Junction  Some   Definitions

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*DLS  also reduces  burst  pressure   rating

7” csg, 4.5”   liner 9.625” csg, 7”   liner

7”  csg, 3.5”   DP 9.625”  csg,  5”   DP

DLS Window 7” csg, 4.5”   liner 7.5 18.8   ft 9.625” csg, 7”   liner 5.1 27.5   ft 7”  csg, 3.5”   DP 5.1 9.625”  csg,  5”   DP 3.3

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Economic   benefit New technology (everyone else is doing   it)

HAS CeMÉ TO
CCM
Irs
kJéÉD tJN& /
DILBERT 0 United

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Add   reserves Reduce   reserves  recovery   time Optimize  productivity Reduce   operating  costs Exploit   deep   rese A rvoirs Increase   reservoir  access

Reduce   facilities  cost Conserve   slots Reduce impact   on  environment Reduce   lateral   displacement Reduce   damage Reduce  some   stability   problems

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Tier 1:  Complexity   Ranking DESCRIPTION	ILLUSTRATION

Open/ Unsupported Junction:   Barefoot  mother-bore & lateral or  slotted   liner hung-off in either   bore

Mother-bore Cased &   Cemented, 2	 Lateral Open:  Lateral either barefoot  or   with slotted liner hung-off in open   hole

Mother-bore Cased &   Cemented, Lateral Cased  but Not Cemented:  Lateral liner  'anchored'  to mother  bore with a liner 'hanger'  but  not   cemented

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Downhole or Surface Splitter:  Large  main  wellbore  with 2  (smaller)  lateral bores  of  equal  size

Pressure Integrity at the Junction  :  (Cement is   NOT acceptable)  Achieved with  the   Casing.

Mother-bore &  Lateral  Cased &  Cemented:  Both bores cemented  at the    junction

Pressure  Integrity  at  the  Junction:   (Cement is  NOT  acceptable)  Achieved  with  the   Completion

Tier 1:  Complexity Ranking   (cont) LEVEL	DESCRIPTION	ILLUSTRATION

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PA  - Producer with  Artificial  Lift PN  - Producer  with Natural   Lift

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Same   categorization   as   the  Tier 1  'Complexity  Ranking   '

Each junction will  have its own   level  indicator which  may or may not  be the   same.

Accessibility   (alpha) N R 	No  Selective   Re-entry

REM 	 Remote Monitoring RMC 	 Remote Monitoring  &   Control

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Most   common Easy to   drill Cheap Easy   reentry

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Multilateral/multilbranch well  Petrozuata, Venezuela

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Stable formation  at  junction Loss of  laterals  and   reentry Drilling  sequence Well  control

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Stable borehole for drilling,   completion, and   production May have to be cased for   production Characteristics of good   junction Impermeable (if   possible) Stable Possible   alternative Junction in producing   zone

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The  “retrievable”  whipstock   ? Not  always   retrievable Milling  whipstock  usually cannot  be  milled   out if   stuck

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Remove milling whipstock as soon  as window is   milled Limit cuttings   size Mill   selection Penetration   rate Remove all   debris Viscous mud system   best Viscous pills not as   effective Have contingency   plans Flow through or around   whipstock Perforate hollow   whipstock Special diameters and fishing   tools

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Diverter   devices Bent   subs Hydraulic flex   subs Depth   testing Directional/inclination   surveys Self contained sensor  tools, battery   operated,  pulse   telemetry

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Exit Direction from  Laterals for   Reentry

Top and  bottom  of hole  exits are   the  most  difficult for   reentry

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Stable formation at   junction Minimum curvature at   junction Remove all milling   debris Dedicated whipstocks (milling,   drilling,   completion) No coupling in   window Centralize for good cement   job Good cement slurry (latex,   foam) Keep it simple and have contingency   plans!

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Run programs uploaded in  webside Multilateral well.xls

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Run the programs in the folder Well Productivity.xls

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Attempt to reduce the cost per barrel
of oil produced.
Same or increased reservoir
exposure with fewer wellbores
Substantial increase in drainage
area.
Increased production per platform

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More reserves
Production from natural fracture
systems
Efficient Reservoir drainage
Exploiting reservoirs with vertical
permeability barriers

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Improving thin oil zone reservoirs
production performance
L Increase ROI
Reduce well cost
Reduce time
Reduce capital cost

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Modeling of multilaterals
Problems during production phase
Increased cost compared to one
conventional well
Higher risk
Technology still in development
stage

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Complex well geometries boost Orinoco heavy oil producing rates Oil & Gas Journal, Feb. 28, 2000 ~ 9 deg API Oil. ~ 1.2  ×   10 12     bbls  in place, 250  10 9  recoverable.

Single horizontal lateral
Gull-wing well
Stacked multilateral
Fishbone well
Gull-wing, fishbone well
Stacked fishbone well

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Single horizontal lateral
133/8-in. casing in
16-in. holes. 500-600 ft
500-600 ft
Completion string
ESP or PCP pump
95/8-in. casing in
121/4-in. hole, 2,000-2,500 ft
81/2 -in. hole
7-in. slotted liner in
81/2-in.
hole, ft TD

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