Well Planning

Well Planning

Sperry Drilling Services2006

Directional Well TypesNew wells

Existing wells DeepeningSidetracking

Basic Data Application Type Well Profile Reservoir Conditions Completion Needs Target Constraints Hole and Casing Sizes Casing Points Mud Data Surveying Requirements

Steps in Designing a Well ProfileSelection of KOP depthSelection of well profileSelection of BURSelection of tangents section (length and angle)for horizontal displacementTVD uncertainty adjustmentdirectional performance uncertaintycompletion requirementsSelection of 2nd BUR (if any)Considering the length of lateral holereservoir constraintstorque and drag limitationshydraulic requirements and limitations (ECD, SPP)

Selection of Kick-off Depth

Consider at planned kick-off depth :

Formation properties (possible washouts)Inclination and direction (use of gyro or single shot, MWD)Directional assembly performance (bit selection, BUR)

If cased hole sidetrack, the options are (casing survey, CBL, CCL are needed) :

Section milling Whipstock + window milling

Open hole sidetrack / kick-off :

Distance from casing shoe is important (rathole, magn. interference)Cement plug might be necessaryOpen hole whipstock is optional

Well Profile Selection (1) Considerations :

Avoiding nearby wells Depth of kick-off Shape of trajectory Curvature, build-, drop-, turn rates Length and inclination of tangent section(s) Length and inclination of horizontal section Target intersection details

Well Profile Selection (2)Selection is based on Vertical depth between intended KOP and targetHorizontal displacement to target entry pointCompletion designFormation evaluation programHole size in reservoir

Profile must provide tangent section(s) forCasing shoe tracksExternal casing packer(s)Completion equipment (packer, beam pump, ESP)Adjustments if directional drilling difficulties arise

Minimum Build Up RateMinimum BUR is defined by a circular arc from the KOP to the target entry point

Minimum 15 inclination in the tangent section for stable direction

Maximum Build RateLimited byCasing / liner running should be possibleCasing /liner bending stress must remain within pipe strength limitsMechanical loads imposed on drillstring elements (torque, drag, fatigue) or casing (wear, tensile strength eduction due to bending stress in doglegs)Rig power limitsMax curvature for surveying and logging toolsFormation evaluation requirementsCompletion requirementsRisk of casing wear or keyseat in open hole

high contact forcesfriction forceshape of an arcshape of a chain curvetensionKeyseat Development

Hole Inclination Ranges near vertical 0 - 10

low 10 - 30

intermediate 30 - 60

high 60 <

Critical Hole Angle for Hole Cleaning Critical range for hole cleaning can not be avoided, but it must be as short as possible

Avoid planning a tangent section within the critical angle range4565090

Critical Issues Horizontal WellsLength of horizontal reservoir engineering requirements well placement problems ECD limits the length - limitations due to drillstring strength - hole cleaning difficultiesProfile of the lateral hole straight, curved or wavyCasing or liner to be run buckling and lockup might be a problemCementing requirements use of ECPsHole size selection different bit sizes for the build and the lateralDrilling torque and overpull margin available

ECD Limited Length of a Horizontal Hole

Target Definition

What is a Target ?A defined area - or volume - to be penetrated by the wellbore at a fixed location within the Earths crustSize (tolerance)Shape (circle, rectangle, polygon)Inclination at penetrationDirection at penetrationWhat matters :

Target Shape (1) Point coordinates must be given inclination and direction into target

Circle coordinates of center radius or diameter inclination and direction into targetRN

Rectangle coordinates of preferred aim point extent coordinates of one point orientation

Polygon coordinates of preferred aim point coordinates of cornersTarget Shape (2)NTabTTTh

Geological vs. Drillers Targetgeological target

Horizontal Well Target (1)target corridortarget windowdirection of horizontalrectangletrapezoidtop view

Horizontal Well TargetHorizontal Well Target (2)

Target Approach (1)TVDdisplacementinclination... and correct direction, too targetlanding pointbuild

Payzone Intersection Options Borehole across payzone

deviated : reservoir is thickhighly laminatedpermeability ratio is high (kv / kh)

horizontal : reservoir is thin there is a gas cap, or underlying aquifier thick reservoir with low permeability ratio (kv / kh)

Length of lateral depends on

Naturally Fractured ReservoirsFracture orientationsmust be knownDrill the lateral normal to known fracture directionand intersect multiple fracturesNdirection of the lateral

Example

Payzone Penetration Length

Well 8X4 - Pad 2x0

K-field

Version 4.0

SST

SHALE

SHALE

25m

2330.3m TVD-SS

642.8m

2397.00

2422.00

K8x4PPL.doc

SSDS-AC00

Formation : (1-2)

TVD-ORT

m

270.6m

Elevation to RT = 66.7m

2355.3m TVD-SS

Inclination =: 84.7(

Example

Payzone Penetration Length

Well 3-0 / Pad 4-1

S Field

Version 2.0

SST

SHALE

SHALE

n/a

1620.70m TVD-SS

586.4m

1681.80m

TVD-ORT

1741.10m

TVD-ORT = (Absolute Depth) + (Original Altitude)

Altitude = Rotary Table Elevation from Baltic MSL

Original Altitude for 3-0 = 61.10m

Original Rotary Table Height = n/a m

S3-0PPL.doc

SSDS-AC00

Formation : AV11-2

Inclination = 50 (

Example70 mD.m18.2 mD.m12.6 mD.m

Payzone Penetration Lengths

Well 4-8 /Pad 1-3

S Field

Version 4.2

Inclination = 70(

SST

SST

SST

SHALE

SHALE

SHALE

2.0m

4.9m

2.6m

4.0m

1.8m

13.7m

2146.6m TVD-SS

2161.9m TVD-SS

40m

TVD-ORT = (Absolute Depth) + (Original Altitude)

Altitude = Rotary Table Elevation from Baltic MSL

Original Altitude for 4-8 = 58.8m (rig NUBR-2)

35mD

7mD

Original Rotary Table Height = 6.8m

S4-8PPL.doc

SSDS-AC00

Formation : BV10

2175.6m TVD-SS

7mD

Example

Payzone Penetration Lengths

Well 2-8 / Pad 1-1

S Field

Version 2.0

SST

1728.00

1702.00

1640.90m TVD-SS

xxxx.xx m TVD-SS

TVD-ORT

m

TVD-ORT = (Absolute Depth) + (Original Altitude)

Altitude = Rotary Table Elevation from Baltic MSL

Original Altitude for 2-8 = 61.1m (rig XXX)

Original Rotary Table Height = ??? m m

S2-8PPL.doc

SSDS-AC00

1666.90m TVD-SS

TVD-NRT

???

xx m

Inclination = 53.4(

Formation : AV1(1-2)

Inclination = 40(

Example

Payzone Penetration Lengths

Well 3-9 / Pad 4-1

S Field

Version 1.0

SST

SHALE

SHALE

6.5m

1636.1m TVD-SS

441.33m

1697.10m

1703.60m

TVD-ORT

100m

TVD-ORT = (Absolute Depth) + (Original Altitude)

Altitude = Rotary Table Elevation from Baltic MSL

Original Altitude for 3-9 = 61.00m

Original Rotary Table Height = n/a

S3-9PPL.doc

SSDS-AC00

24.82m

416.51m

1700.35m

Formation : AV11-2

Inclination = 90 (

Pilot Hole for Optimizing Wellbore Placement

Well Profiles

Well ProfileThe trajectory - or well path - from the surface location through the target(s)

Conventional (2D) or compounded (3D) trajectories

Basic design data :

kick-off depth vertical depth of target horizontal displacement to target from surface location

HalliburtonWell Profile TerminologyVertical SectionTangentDrop Section EOHEOBKOPBuild SectionRKBTVDRKB = Rotary Kelly BushingKOP = Kick-off PointEOB = End of BuildEOH = End of HoldTVD = True Vertical Depth TD = Well DepthTD

Deviated Well Profiles ClassesLong radiusMedium radiusIntermediate radius Short radius

Whenever is possible, 2D profiles are preferred

Curvatures and Radii

Long radius 2-6/100ft 90-200m 3000-1000 ft

Medium radius 6-35/100ft 290-50m 1000-160 ft

Intermediate 35-65/100ft 50-25m 160 90 ft

Short radius 65-115/100ft 25-15m 90 50 ft

Basic Well ProfilesJ - shapeB & H : build and holdS - typeUndercut

JSB & HUC

KOPTVDvertical sectionContinuous Build Profilevertical section directiondeg/100 ftR2-D profileX

RTVDKOPdaJ-Shape Profile Design

Most simpleKick-off point depends on target displacementBuild rate : minimum possibleFeatures :J-Shape Profile Constant & Continuous Build

Catenary Profile Details

KOPTVDvertical section Continuously increasing build rateThe Catenary Profilevertical section directionforce defines profileinclination is not 0 !

Catenary Profile EquationUS Patent 4,440,241 24.Aug.,1981UK Patent GB 2 044824 5.March,1980

by Dailey Petroleum Services SPE 13478

KOPTVDTDBuildCatenaryRComparison of Catenary and Circular Arc ProfilesCircular arc

Build & Hold ProfileFeatures :

SimpleKOP determines inclinationLarge horizontal displacements from shallow kick-off depths

Build-Hold-Build-Hold Profile

Build-Hold-Drop-Hold Profile

S-WellFeatures :

Near vertical target penetration possibleMultiple target intersection possibleDirectional control is difficult Torque and drag could be highHorizontal displacement is limited

Walk CompensationLeft LeadRight Hand WalkWithout Left LeadRotary drilling assemblies with tricone bits have a tendency to walk to the rightPDC bits tend to walk to left

3-D Well Proposal

Nudging of Wells for Better Shallow Depth SeparationThe Nudge

KOPTVDBuild sectionTDHold (tangent, sail) sectionBuild & Hold Profile with NudgeNudgeREOB

3D Profiles 3-D Visualization

3-D Visualization

3-D Visualization

ERD Well3D Profile

3D Profile

3D Profile

Computer Programs for Well PlanningIdeas (Unix based) Sysdril Ltd.Compass (Windows) Landmark Graphics Corp.DrillQuest (Windows) Sperry-Sun Drilling Services

Now What ?

Well, You made it this far

***No other comments*No other comments*Formation at kick-off depth must be consolidated, otherwise washouts could potentially degrade directional performance of the drilling tool selected for the kick-off.

If the borehole has 5-8 degrees minimum inclination, high-side reference could be used for the initial orientation.

In vertical well open hole, magnetic toolface orientation is the method to be used. No need for gyro survey.

In casing sidetrack, gyro has to be utilized when the well is vertical at the kick-off depth.

Marking pipe when tripping in could only be used in shallow wells.

Necessary distance from casing shoe : practice prevail, no written rules for this.***Hole direction at inclinations less than 12-15 degrees is hard to maintain (low friction between pipe and hole).*Keep in mind one of the requirements : a casing string has to be run and cemented.

*The borehole and the drillstring take different shapes. As recent planning prqactice, the borehole is an arc, the drillstring is a catenary. The result is interference, causing normal forces on the high-side. In less than competent formations, the drillpipes and tool joints cut into the high-side of the borehole creating a keyhole shaped enlargement. When the drillpipe or drill collars are pulled into this section(s), differential sticking develops quite easily. Give the reason.*This classification is arbitrary. *While we know that the hole inclination range of 45-65 degrees is the most problematic to clean from cuttings, we just could not avoid to go through it.*Self explanatory requirements.*This is more-less a theoretical limit, rather to be called to a warning, indicating that at certain length (depth) the density, rheology of the mud must be changed in order to avoid fracturing and consequent loss of circulation.**Who is defining the targets, and gives the specs ?*Note, that (temporary) point targets for the well planning process only (impossible to drill to and hit a point in the 3D space with certainty ).

Circular targets are more common. Note, it has to be clarified with the customer, that the size of the target the specify is a radius or a diameter.**If the well is landed within the drillers target (including the perimeter of it), the well bottom is certainly within the geological target.*Horizontal wells targets could be specified in various ways.*Depending on the formation or permeability changes within the formation, the target could be pinching out.*Directional drillers worries : target TVDdisplacement to targetdirection at target penetrationinclination at target penetration*When the target is thin, easier and more practical to lan d on the top of the target, and descend into it.***Practical well plan where the client wanted us to drill through the payzone a deviated section.*Similar wellplan, with long rathole below the payzone (for logging purposes).*Layered reservoir, where the deviated final hole section opened up all 3 layers. Again, the rathole is for additional (definitive?) wireline logging.*Requirement was to drill into the payzone as long hole as possible. Arriving with a tangent section to the top of the reservoir, hole angle was further built until TD.*Textbook-like well plan, actually drilled as planned in 5 days.*Pilot holes are utilized for finding the correct depth of the horizontal section.*****This classification is arbitrary, the sole purpose is to group wells, statistics, etc.**Recent well planning procedures using circular arcs for the profiles.*Simplest possible profile is a continuous arc from kick-off to target.*The profile not necessarily ends at 90 degrees, it could be at any angle.*Formula and calculations are simple, but you need a scientific calculator for that.*Summary of features based on previously discussed issues.*The full catenary is split : at the deepest point where the cut is made the remaining hal catenary is supported by horizontal forces (Th) which represents the friction in a lateral (horizontal) section.*The catenary profile presents a deviation from the circular arc shapes. Remember, the drillstring (actually any heavy flexible body hanging freely) takes the shape of a chaine curve, hence this profile.

Why is it better than a circular arc ?*Edward O. Anders :

Method and Apparatus for Drilling a Well Bore*What are the difficulties with the catenary profile ?Why this profile is not used on wide scale ?What are the legal problems ?*Back to the recent practice, the most frequntly used 2D profile is this. The purpose of the tangent section (test question).*Summarizing the features*Most typical horizontal wells profile is this. The included tangent section might be sacrifized, if necessary.*S-profiles are useful combination of the previous features. Increased displacement, close to vertical target penetration (even vertical is possible).*Summary of features. Note, that the drop-off section could be drilled with simple rotary assemblies, not requiring mud motors or turbines.*Walk compensation could be part of the drilling plan, incorporated into theWell profile design. The purpose is to reduce directional drilling work (corrections), utilizing the natural tendency of the BHA for turning or walking.*An example well plan (wall plot) for directional driller.***Alaska Natl Wildlife Refuge is East of these pads. Limitation to amount of land the public can occupy due to the tundra environment.Spine road runs E/W with pads located N/S of road. Approx. 2-3 mile spacing between pads. Arco operates to the East and BP to the West. From one 96 acre production facility they can drain 498,000 acres.2 pads (eastern side of North Slope) in Alaska in Prudhoe Bay.ANWRBPArco*3D view of designer well showing multiple targets and zones*Note that this picture indicate the possibilities of the visoalization, and not an actual well (pure graphic art).*Actual well drilled with rotary steerable system (GEOPILOT).*GEOPILOT case.*Actual wellpath of the drilled designer wells Gullfaks B29 and B29BT2. An azimuth change was planned at the bottom of of the B29 BT2 well, but could not be achieved due to PDM steering difficulties at this great depth.

The last six targets could not be reached because the wellpath could not be turned in the horizointal plane at such a great displacement. A rotary steerable system would, in this case, have been particularly useful, but it was not available.

Gullfaks West Field, 1994

Source : Z. Djerfi J. Haugen E. Andreassen H. Tjotta :Statoil Applies Rotary Steerable Technology For 3-D Reservoir DrillingPE International, February 1999, pp.29-34

*Ideas was expensive (rented only)DrillQuest is phased outCompass is the recent software (for well planners, and directional drillers field use !)*This is a perfectly correct run.*