Well Path Design The Well path design process is a tool which wh ich enables users to generate well trajectories based on reservoir properties, seismic attributes attributes or any other data. Well trajectories can be manually 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 . This feature 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 are automatically placed under unde r the Wells folder in the !nput pane in a sub"folder called #Proposed wells$. The Well path design process allows the user to plan p lan a new well trajectory through a 3D model. Points along the trajectory can be digitized in 3D space, which gives the user control of% &tratigraphic targets
•
Precision of fault penetration
•
Property values at target
•
Well performance at target
•
Technical limitation of drilling operation with respect to well deviation 'doglegs(
•
) well designed in Petrel allows the user to obtain o btain important information such as well path coordinates, e*pected 'synthetic( log values, e*pected zone penetration log and fault intersections.
Well Path Algorithm Petrel uses the )dvanced Design Trajectory ')DT( algorithm, both for manual well design and in the generation of optimized well trajectories. This algorithm will attempt to restrict curvature to a specified dog leg severity 'D+&(. The resulting well paths are made up of straight sections and curves. ow this wor-s is described in more detail below. !n Petrel //0 it used to be possible to ma-e well traces as standard spline curves. This option is no longer available for ma-ing new well traces. owever, wells in an old project that were made using spline curves, can be still be used in a Petrel //1 project.
ADT algorithm and settings The )dvanced Design Trajectory ')DT( algorithm that is used to draw well paths and has two user"defined settings% Requested upper this is the dog leg severity 'D+&( number that is re2uested for the curved sections of a new well trace. The number is defined in degrees per 3/ m or // ft depending on the project units. Maximum the ma*imum dog leg severity that can be used in the well path. !f this option is deselected, the D+& must always be lower than the re2uested upper value.
How does the algorithm work? The algorithm will attempt to design a well that passes through all the design points with a curvature which is smaller than the #re2uested upper$ dog leg severity 'D+&( set by the user. 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 by selecting the design point and pressing the #4reeze56nfreeze design point tangent$ icon in the function bar. To see which design points have been loc-ed, open the spreadsheet for the new well by right clic-ing it and selecting #&preadsheet$. !f the tangent has been loc-ed, the #se$ bo* in the #T)7897T$ column of the spreadsheet is chec-ed.
The user can edit the tangent through a design point by moving the arrow which indicates the 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 and two, 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 the re2uested 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 with the dialog%
!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, the obsolete 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. •
•
#
!f tangent is used! then the well path will be adjusted accordingly. !f the re2uested D+& cannot be achieved, then the algorithm will incrementally increase the re2uested D+& for that section until a well path can be drawn. !f the re2uested D+& reaches the Maximum D+& and the well path can still not be drawn, then the algorithm will fail. This will be shown during the edit in the info bar at the bottom left and the user will see a warning message. When tangent is used, the algorithm must wor- iteratively to find a solution. !f a solution cannot be found at the re2uested D+&, then the same calculations will be performed at each step, up to the ma*imum, until a solution is found. !n these cases, it may ta-e several seconds to arrive at a solution after each edit.
Well Path Design "ettings The settings controlling how a designed well is drawn are found on the &ettings tab for the individual designed wells. Double clic- the well$s icon in the Petrel 9*plorer to access this tab. ) number of interactive controls for designing and editing wells are found on the well design toolbar. The draw style for wells is set on the settings dialog for the well folder, see &tyle 'Wells(.
"ettings #Designed Well$ This tab is available for wells designed in Petrel and controls how the well trace is computed between the design points.
The settings for a designed well also control how the well path is drawn between the first and second designed points. and ?D at -ic-off point. The well is assumed to be vertical from the well head to the -ic-off point. The user has the option whether 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 specified kick off depth will ensure a straight well path down to the specified depth. ) -ic- off angle can be given interactively by editing the direction of the initial point in the well path. The user has the option to include the main well when generating the well trace.
Well path design tool(ar i'ons The following icons appear on the Well path design toolbar% Add )ew Points * adds new points to the active well +ree Mo,ement ; the editor widget will be aligned vertically in space.
-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 any type 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 activated through 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 a new 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*plorer and 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 is active.
Dragging the cylinder section of the widget will move it along the direction the cylinder points. Dragging the rounded section of the widget will move the point in a plane perpendicular to the cylinder.
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 the chosen direction. To restore the angle bac- to the optimum, as calculated by the algorithm, select the point and press.
!t is 2uite common to e*ceed the D+& constraints while digitizing design points in 3D. ) common problem for new"comers to the Well Path Design Process is digitizing design points too close together. This can lead to unwanted sinusoidal patterns in the resulting trajectory. 7ormally this can be overcome by spacing the design points further apart. owever, in most situations crowded design points will e*ceed the D+& for the trajectory and the user is prompted to select an option from the following message.
#: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, the obsolete point will be included in the well path if the D+& constraint can be met. •
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 fit design points to the well, and its value will be updated in the Max field in the &ettings page for the well. •
•
A
emember that if the 34 "'ale setting in the active viewer is set to C then the well path will loo- e*aggerated in the direction.
How to make a new well tra5e'tor. ighlight the Well path design process, under the Well engineering folder in the Processes pane, by clic-ing on the icon. The function buttons for the Well path design process will appear in the 4unction bar. . Display an object in the 3D Display window. 9.g. an intersection plane or a horizon. . ?a-e sure no proposed wells are active 'bold(. )ctivate the Add new point icon in the 4unction bar and start digitizing the new well. 3. 9dit the well points as re2uired, either interactively or in the editor 'see 9diting coordinates(. E. ight clic- the well in the !nput pane and select &ettings to display the draw style for the active well, and to select how to connect the well to the surface. 7ote that if using an intersection plane, the position of the intersection plane can be changed while digitizing. 7ote that if the Drag parallel to 6nterse'tion button is selected, the points will be moved parallel to the intersection plane.
0diting 'oordinates The coordinates for a designed well can be displayed in the wells spreadsheet. Points can be added and coordinate data can be edited or removed.
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 "how spreadsheet icon under the !nfo tab in the settings window. . ?a-e the editing and clic- F= when finished. 3.
Fpen the pull"down menu for a Proposed well, by clic-ing on it with the right mouse button. . &elect the &preadsheet. . &elect the cells with data to e*port, and copy them by using
6mplementing external 'oordinates 9*ternal coordinates 'G, :, ( can be imported as a new well, by importing a te*t file with G, : and coordinates. Well Path Design G, :, , ')&
How to import a 2ile with external 'oordinates . Fpen the pull"down menu for the Proposed Wells 4older, by clic-ing on it with the right 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. The folder 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
Displa. options 2or well path design The user has a number of display options aimed specifically at well design, such as Dog %eg "e,erit. and 0rror 1ones . These as with other well display options are set on the settings panel for the Wells folder, see &tyle 'Wells(.
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 representing the degree of curvature at each point. )t a specific curvature, the color displayed will change 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 color used 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 a constant value or as a log, and is always drawn perpendicular to the well path. !f a log is used to define the error cone, it should describe the error at the corresponding point on the 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 horizontal direction 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 is given by the formula%
Where rh is the potential error in the horizontal direction and rv is the potential error in the vertical direction. 4or e*ample, error propagation divided by /// 'propagation is specified 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 specifies targets 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 surface location. These trajectories are automatically sorted into special folders to distinguish the optimized 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, the optimizer will wor- out the most optimal way to join the data points determined by the D+& constraints and the cost model used. When designed wells are used as input, the optimizer selects the first design point in the well as the attachment point. !n both cases the well trajectories are designed bac- to the optimal surface location. Targets can be •
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 be e*ecuted.
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 well optimizer utilizes the )TD algorithm and is therefore consistent with manually digitized well 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 relative difficulty to be encountered in drilling a well. The principle behind DD! is that the risassociated with drilling a comple* well is greater than drilling a simple well due various factors 'Temperature, Pressure, rig capabilities, etc(. ?oreover, the cost of drilling is li-ely to increase due to e*tended rig time or even abandonment for comple* wells. 4or a detailed 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 $ench#ar%in&'( Ali)tair *+ ,a&( SPE( and -i%e *illia#). Schlu#er&er+ The DD! e2uation is a relationship between the ?D and THD of a well%
WhereK ?D L ?easured Depth THD L True Hertical Depth )D L )long ole Displacement Tortuosity L Total curvature imposed on a wellbore Typical DD! values range from 0 'low ris- short wells( and 1 'highly comple* long wells(. The range M./ to M.E is considered a medium comple* well.
1ost Model To ma-e a cost model, press the #9dit5
ROP 1osts& This part of the dialog is used to specify the drilling5completion cost and to input directional constraints. Drilling/1ompletion 1osts& &pecify the cost 'J5unit( to drill a vertical section of the well. Max in'line 2or ,erti'al& &pecify the ma*imum accepted angle tolerance 'degrees( for a section to be categorized as vertical. Well segments with a greater incline are considered non"vertical. Their cost is computed using the #Tangential$ 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 for the 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
Well Optimizer ta( )fter generating a cost model the targets and constraints need to be specified in the Well Fptimizer tab. &elect first between% •
•
Fverwrite e*isting
Targets ta( Datum& !f a project is situated offshore, then the Mean sea le,el datum level should be selected. ) 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 paths will 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 surface area by employing a boundary. 6nput Targets& To add input targets, activate the subject in the !nput pane and then press to 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 the Make/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*isting wells in the project they can be input using the icon. !f platforms are added, the number of available slots should be specified in the "lots field. !f new platforms are allowed, ticthe Allow new plat2orms bo*. 7oundaries& 9nter boundaries as closed polygons in this field. Platforms can only connect to targets that lie within the boundary. The list is hierarchical, so the order in which 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 units and 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 the optimizer can be e*ecuted by selecting the Run button. !f the Make Report icon is selected a spreadsheet will be written showing all the input parameters used in the run and the cost details.
DD6 0nhan'ed 1ost !n Petrel, there is an option to optimize wells based on minimizing ris- by incorporating the DD! factor in to the calculation. When the DD! 9nhanced
