Drill Well Path Design

8/17/2019 Drill Well Path Design

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Well Path Design

The Well path design process is a tool which enables users to generate well trajectories based on reservoir properties, seismic attributes or any other data. Well trajectories can bemanually digitized in the 3D window. The design points can be displayed in a spreadsheet

and can be easily cut and pasted between Petrel and other windows software applications.eservoir targets defined by the user can be used as input to the Well Optimizer. Thisfeature will, given a set of reservoir targets and a cost model, find well trajectories and platform locations that minimize the total cost of the project. Wells designed in Petrel areautomatically placed under the Wells folder in the !nput pane in a sub"folder called#Proposed wells$.

The Well path design process allows the user to plan a new well trajectory through a 3Dmodel. Points along the trajectory can be digitized in 3D space, which gives the usercontrol of%

•

&tratigraphic targets

•Precision of fault penetration

•Property values at target

•Well performance at target

•Technical limitation of drilling operation with respect to well deviation 'doglegs(

) well designed in Petrel allows the user to obtain important information such as well

path coordinates, e*pected 'synthetic( log values, e*pected zone penetration log and faultintersections.


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Well Path Algorithm

Petrel uses the )dvanced Design Trajectory ')DT( algorithm, both for manual welldesign and in the generation of optimized well trajectories. This algorithm will attempt torestrict curvature to a specified dog leg severity 'D+&(. The resulting well paths aremade up of straight sections and curves. ow this wor-s is described in more detail

below.

!n Petrel //0 it used to be possible to ma-e well traces as standard spline curves. Thisoption is no longer available for ma-ing new well traces. owever, wells in an old project that were made using spline curves, can be still be used in a Petrel //1 project.

ADT algorithm and settings

The )dvanced Design Trajectory ')DT( algorithm that is used to draw well paths and hastwo user"defined settings%

Requested upper this is the dog leg severity 'D+&( number that is re2uested for thecurved sections of a new well trace. The number is defined in degrees per 3/ m or // ftdepending on the project units.

Maximum the ma*imum dog leg severity that can be used in the well path. !f this optionis deselected, the D+& must always be lower than the re2uested upper value.

How does the algorithm work?

The algorithm will attempt to design a well that passes through all the design points witha curvature which is smaller than the #re2uested upper$ dog leg severity 'D+&( set by theuser. This is done by using a series of straight sections and curves of the re2uested D+&.

The user can loc- the inclination and the azimuth of the tangent through a design point byselecting the design point and pressing the #4reeze56nfreeze design point tangent$ icon inthe function bar. To see which design points have been loc-ed, open the spreadsheet forthe new well by right clic-ing it and selecting #&preadsheet$. !f the tangent has beenloc-ed, the #se$ bo* in the #T)7897T$ column of the spreadsheet is chec-ed.


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The user can edit the tangent through a design point by moving the arrow which indicatesthe direction of the path through a point 'see illustration below(

!f the tangent is not used, the algorithm will use a straight line between point one andtwo, then #r$ curves between subse2uent points 'curve then straight section(. &ubse2uent points added to the start of the well path will also be connected by #r$ curves. !f there2uested D+& can not be achieved because of the positioning of the design points,'points are too close together and at a too severe angle(, then the user is prompted withthe dialog%


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!f you press

• #:es$ ; The point will be added to the spreadsheet, but either this point or the

succeeding one is not included in the well path since the D+& constraint was not met.owever, the point is stored in the spreadsheet. !f a neighboring point is later deleted, theobsolete point will be included in the well path if the D+& constraint can be met.

• #7o$ ; The ma*imum allowed D+& number is increased such that the path can be

constrained to the new D+& value.

• #


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The settings for a designed well also control how the well path is drawn between the firstand second designed points. and ?D at -ic-off point. The well isassumed to be vertical from the well head to the -ic-off point. The user has the optionwhether to generate the well from the well head or from the -ic-off point.

"ide tra'k % The user must specify the main well and it$s ?D at start of the side trac-.Entering a specifed kick o depth will ensure a straight well path down

to the specifed depth. ) -ic- off angle can be given interactively by editing thedirection of the initial point in the well path. The user has the option to include the mainwell when generating the well trace.


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-erti'al Plane Onl. " the editor widget can only be moved in the vertical plane.

Mo,e Along Tangent ; the editor widget will be aligned along the proposed well path.

"how/Hide D%" ; toggles between showing and hiding the dog leg severity colors.

"how/Hide Pipe ; toggles between showing and hiding well path pipe.

"how/Hide 0rror 1one ; toggles between showing and hiding the error cones.

+reeze/un2reeze design point tangent ; toggles between having the direction of the well path at a target point defined by the user or by the algorithm.

Digitizing wells

7ew wells can be digitized directly in 3D in Petrel. This can be done by clic-ing on anytype of data displayed in the active window. orizons surfaces or intersection planes are

particularly useful to use when digitizing new wells. !ntersection planes can be activatedthrough any of the folders in the !nput window of the Petrel 9*plorer '&ee 8eneral!ntersection( or by using the !ntersections option in the ?odel window.

?a-e sure none of the proposed wells are active, and press in the function bar to start anew well. &et the desired D+& settings from the &ettings tab in the Well Path Design process dialog. To add points to an e*isting well, select that well in the Petrel e*plorerand clic-. 7ew wells will, by default, appear under a sub folder to the wells folder called proposed wells.

Digitizing a new well

)s the user digitizes points for the new well, a trajectory is drawn between the points.Digitized points will continue to be visible as long as the Well Path Design process isactive.


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Pressing 1trl repeatedly will move the widget round @/ degrees.

To edit the angle of the well path at a design point, simply move the edit arrow to thechosen direction. To restore the angle bac- to the optimum, as calculated by thealgorithm, select the point and press.


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• A7oB% the target point is added to the well trajectory and the D+& constraints for the

well modified accordingly. This D+& value will be the minimum re2uired D+& to fitdesign points to the well, and its value will be updated in the Max field in the &ettings page for the well.

• A


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The spreadsheet format ma-es it easy to copy data to other applications 'e.g. ?& 9*cel(for editing, and paste it bac- into the spreadsheet.

To loc- the well path angle at one of the design points, chec- the #6se$ bo* in the#T)7897T$ column or select the design point and press in the function bar.

How to edit 'oordinates

. ight clic- a Proposed well in the Proposed Wells +older and select #&preadsheet$on the drop"down menu. The spreadsheet can also be accessed from the "howspreadsheet icon under the !nfo tab in the settings window.

. ?a-e the editing and clic- F= when finished.

3.


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6mplementing external 'oordinates

9*ternal coordinates 'G, :, ( can be imported as a new well, by importing a te*t filewith G, : and coordinates. Well Path Design G, :, , ')&

When importing e*ternal coordinates a new well will be created and stored under theProposed Wells 4older.

9*ternal coordinates can also be implemented on an e*isting designed well, by enteringcoordinate data from other applications 'e.g. ?& 9*cel( in the Point 9ditor.

How to import a 2ile with external 'oordinates

. Fpen the pull"down menu for the Proposed Wells 4older, by clic-ing on it with theright mouse button.

. &elect the option !mport 'on selection(, and the !mport 4ile dialog will pop up.

3. &elect an appropriate file type. &elect the file to import.

E. 9nter well name in the !mport Data dialog, and press F=.

0. The coordinate data will be stored as a new well in the Proposed Wells 4older.

7ote% Petrel creates the Proposed Wells 4older when a new well is being designed. Thefolder can also be created from the !nsert pull down menu in the ?enu bar.

How to import external 'oordinates 2rom M" 0x'el

Fpen the pull"down menu for a Proposed well by clic-ing on it with the right mouse button.

. &elect &preadsheet.

. Fpen the data file in ?& 9*cel and copy the data to import.

3. Paste the data into the &preadsheet in Petrel, by using


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Dog %eg "e,erit.

Dog leg severity 'D+&( is a measure of the degree of curvature in the designed well path.This is displayed along the length of the well by the use of a changing color representingthe degree of curvature at each point. )t a specific curvature, the color displayed willchange dramatically highlighting areas of the well path that will cause problems during

drilling.

The dog leg severity color template can be edited directly via the icon. )lso, the colorused to mar- a ma*imum dog leg severity can be set directly in the Max D%" bo*.

0rror 'one

9rror cone is a display of the uncertainty that may arise during the drilling of a new well.This is specified in terms of error in distance units per /// distance units drilled and is

drawn as a cone shaped structure.

9rror can be specified separately in the vertical and the horizontal directions, as aconstant value or as a log, and is always drawn perpendicular to the well path. !f a log isused to define the error cone, it should describe the error at the corresponding point onthe well path rather than the error propagation. The Drilled depth is always assumed to be correct, thus the error in a completely vertical well will only be in the horizontaldirection and the vertical error propagation will not affect the error cone.

6se the log calculator together with zone logs to create a log with different error propagation in different zones.

The radius of the error cone in a particular direction normal to a point on the well path isgiven by the formula%


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Where rh is the potential error in the horizontal direction and rv is the potential error inthe vertical direction. 4or e*ample, error propagation divided by /// 'propagation isspecified per /// units( multiplied by the distance traveled vertically or horizontally.

9rror cone display is set through the Wells settings or the settings for a wells sub"folder.&ee &tyle 'Wells( for information on other well display options.

Well Optimizer

8iven a set of reservoir targets the Well Optimizer will calculate well trajectories and platform locations that minimize the total cost of a drilling project. The user specifiestargets and a cost function as minimum input. The output is a set of optimized trajectories based on geometrical drilling constraints e*tending from the reservoir bac- to the surfacelocation. These trajectories are automatically sorted into special folders to distinguish theoptimized wells.

There are three main factors that control the optimization process%

• Optimizer settings& Targets are defined as data points for which the optimized well

paths must pass. They can be digitized well trajectories, or simple point sets. )combination of the two data types is also possible. When point sets are used as input, theoptimizer will wor- out the most optimal way to join the data points determined by theD+& constraints and the cost model used. When designed wells are used as input, theoptimizer selects the first design point in the well as the attachment point. !n both casesthe well trajectories are designed bac- to the optimal surface location. Targets can be

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loc-ed to plat2orms and target"platform sets can be constrained by closed (oundaries.)ny e*isting well in the project can be used as a platform.

• 1ost Model& The purpose of the optimizer is to generate wells at a minimum cost for

the given input data. The cost model is designed up front before the optimizer can bee*ecuted.


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•Tra5e'tor. 'onstraints& The output well trajectories are constrained by a user defined

D+&. Fnly well trajectories that conform to the D+& settings are generated. The welloptimizer utilizes the )TD algorithm and is therefore consistent with manually digitizedwell paths.

How the Optimizer algorithm works

The algorithm wor-s as follows%

• Fnce the ordering of targets is set, the well trajectories are computed using the )TD

algorithm

• The final cost is computed. ) ma*imum of 0 solutions may result.

7a'kground to DD6

The Drilling Difficulty !nde* 'DD!( provides a first pass evaluation of the relativedifficulty to be encountered in drilling a well. The principle behind DD! is that the ris-associated with drilling a comple* well is greater than drilling a simple well due variousfactors 'Temperature, Pressure, rig capabilities, etc(. ?oreover, the cost of drilling isli-ely to increase due to e*tended rig time or even abandonment for comple* wells. 4or adetailed e*planation of how DD! evolved the user is referred to the "P0 paper& IADC/SPE 59196 “The Directional Difficulty Index – A e! A""roach to Perfor#ance

$ench#ar%in&'( Ali)tair *+ ,a&( SPE( and -i%e *illia#). Schlu#er&er+

The DD! e2uation is a relationship between the ?D and THD of a well%


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WhereK

?D L ?easured Depth

THD L True Hertical Depth

)D L )long ole Displacement

Tortuosity L Total curvature imposed on a wellbore

Typical DD! values range from 0 'low ris- short wells( and 1 'highly comple* longwells(. The range M./ to M.E is considered a medium comple* well.

1ost Model

To ma-e a cost model, press the #9dit5


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ROP 1osts& This part of the dialog is used to specify the drilling5completion cost and toinput directional constraints.

Drilling/1ompletion 1osts& &pecify the cost 'J5unit( to drill a vertical section of thewell.

Max in'line 2or ,erti'al& &pecify the ma*imum accepted angle tolerance 'degrees( for asection to be categorized as vertical. Well segments with a greater incline are considerednon"vertical. Their cost is computed using the #Tangential$ divisor as multiplier.

Dire'tional Di,isor& &pecify the multiplier used to calculate the decrease in FP'increase in cost( for drilling curved segments. :ou can specify different multipliers forthe first three curved segments.

Tangent di,isor& &pecify the multiplier re2uired to calculate the decrease in FP'increase in cost( for drilling non"vertical linear segments.

The cost model is stored once the Appl. button is selected and can be accessed from the


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Targets ta(

Datum& !f a project is situated offshore, then the Mean sea le,el datum level should beselected. ) surface can be input to represent the platform elevation using the blue arrow.) constant datum reference is also available. When "ur2a'e is used as datum, well pathswill be posted bac- to the datum only if all targets lie within the surface boundary. !f any

target lies outside the surface area, ?&+ will be used as datum.

:ou can force well trajectories to a surface datum even if targets lie outside the surfacearea by employing a boundary.

6nput Targets& To add input targets, activate the subject in the !nput pane and then pressto insert the data. Targets can be point sets or e*isting proposed wells. )ny combination

of the two data types can be selected. Targets can be generated in Petrel using theMake/0dit Points tool in the Make/0dit Pol.gons process step.

Plat2orms& >y default the platforms column is empty. !f wells are to be added to e*istingwells in the project they can be input using the icon. !f platforms are added, the numberof available slots should be specified in the "lots field. !f new platforms are allowed, tic-the Allow new plat2orms bo*.

7oundaries& 9nter boundaries as closed polygons in this field. Platforms can onlyconnect to targets that lie within the boundary. The list is hierarchical, so the order inwhich the optimizer uses the boundaries is from the top down.

The 8i'k4o22 point is an optional setting. The value should be specified in project unitsand represents the ?D value at which the first curved well section from the platform is permitted. !f the well plan is to be based entirely on the FP cost model then theoptimizer can be e*ecuted by selecting the Run button. !f the Make Report icon isselected a spreadsheet will be written showing all the input parameters used in the runand the cost details.

DD6 0nhan'ed 1ost

!n Petrel, there is an option to optimize wells based on minimizing ris- by incorporatingthe DD! factor in to the calculation. When the DD! 9nhanced

Documents

Drill Well Path Design