Chapter 11 - Fault Modeling

3D Geological Modeling

Chapter 11 – Fault Modeling

Fault Modeling Mode ling Generations of fault pillars, known as Key Pillars, are lines dening the slope and shape of the fault! "here are up to #e, #e, so call called ed $hap $hape e Points oints along along each each of these these line lines s to ad%ust the shape of the fault to perfectly &atch your input data! "he Key Pillars are generated 'ased on input data such as faul faultt su surf rfac aces es,, fault fault stic sticks ks,, faul faultt lines lines,, faul faultt poly polygo gons ns,, structural &aps, interpreted seis&ic lines, etc!

(n the pre#ious section, we did so&e editing on the input data to 'ring it to a for& suita'le to Petrel for 'uilding the 3D geological &odel! (n this section we will start 'uilding the &odel! "he 'uilding process &ay 'e deco&posed into the following steps)

• • • • • • • • • • • •

Dening a *ew Model! Creating Faults fro& Fault Polygons! +diting Key Pillars! uilding Key Pillars fro& Fault Polygons! Connecting Faults! Disconnecting Faults! Creating ranched and Crossing Faults! Creating Faults fro& $elected Fault $ticks! Creating Faults fro& -ll Fault $ticks! -uto&atic Generation of Faults! Faults! -uto&atic Connection of Faults! Faults! -nd -uto&atic -d%ust&ent of o f Key Pillars!

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Defning a New Model efo efore 'ui uillding a 3D geologi ogical &odel in Petr etrel, it is nece necess ssar ary y to den dene e a &ode &odel! l! Petr etrel lets lets you you work work with with se#eral di.erent &odels in one session! (t is i&portant to den dene e the the di di.e .errent ent &ode &odels ls 'y gi gi#i #ing ng the& the& appr approp opri riat ate e na&es!

Creating a new model 1! Dou'le Dou'le click click on the the Defne Model ite& under the Structural Modeling in the Processes Pane ! /! - Dene Model dialog dialog 'o0 'o0 pops up, gi#e gi#e the &odel a specic na&e Top Tarbert Model and click OK. "he &odel will 'e placed under the Models Mo dels pane, as shown in Fig! 11!1!

Fig.11.1 "he Dene &odel dialog 'o0

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Fig.11.! "he Top Tarbert new &odel

-s you did 'efore, create another tow &odels and call the&, Top Ness Model and Top "ti#e Model! -s shown in Fig!11!3!

Fig.11.$ "he Top Tarbert, Top Ness and Top "ti#e new &odels 3



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Creating Faults %rom Fault Pol&gons Fault polygons are line data representing the hangingwall and footwall for each hori2on! "he polygons could 'e separated into lines for each fault or lines for each hori2on! (n the latter case, the lines should 'e separated with ags to &ake sure that the sa&e line dose not denes two faults! (f there are no ags 'etween the line data, you should do so&e editing in the Make4+dit Polygons Polygons process in order to split the lines!

'ow to Create Faults %rom Fault Pol&gons 1! Go to to Structural Modeling ite& in the Processes Pane. /! -cti# -cti#ate ate the Fault Modeling process in the Processes Pane 'y clicking on it once and &aking it 'old! 3! Display Display one of the fault fault polygon polygon in the Top Tarbert Pol&gons folder in a 3D window e!g! Pol&gon ((, as shown in Fig! 11!5!

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Fig.11.) Fault Polygon displayed in a 3D window

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5! (n the function 'ar, click on the Set Select*Pic+ Mode icons as shown 'elow! Notice the color of fault polygon 6purple7 changed to 6white7 after you selected 'y it as shown in Fig!11!8 6to do this step press S,i%t7! 8! $elect the desired fault geo&etry fro& the Fault Model 9ption "ools tool'ar! (n this case, a linear geometr& is suita'le! :! Click on the Create Faults %rom Fault Pol&gons icon in the Function 'ar to generate Key Pillars along the selected polygons as shown in Fig!11!8! "he new fault has 'een added under the Faults folder in the Models Pane, and is called ;Fault 1
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Fig.11.- "he fault polygon after selected 'y the tool

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Fig. 11. Fault Polygons displayed in a 3D window after create faults fro& polygon

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=! >epeat the sa&e process for all fault polygons as shown in g!11!=!

Fig. 11.( Fault Polygons displayed in a 3D window along with Top Tarbert surface

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-nd also, repeat the sa&e process that you did it in Top !Ness and Top "ti#e! -s shown in Fig!11!?! and Fig!11!@

Fig. 11./ Fault Polygons displayed in a 3D window along with Top Ness surface

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Fig. 11.0 Fault Polygons displayed in a 3D window along with Top "ti#e surface

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T,e settings o% Pillar geometr& ma& be c,anged b& Ainear, #ertical, listric, $shaped, re#erse, #ertically truncated, 'ranched and connected faults can 'e created in Petrel! "he progra& allows you to create structurally and geo&etrically correct fault representations! - fault is dened 'y a set of Key Pillars! +ach Key pillar consists of a set of shape points! - Key Pillar can ha#e /, 3 or 8 shape points, and a fault can consist of Key Pillar with a #arying nu&'er of shape points! +ach shape point can 'e edited in 3D!

1! the faults are grouped into 5 &ain groups) a! ertical %aults consist of / shape points! "hey will always 'e #ertical! '! 2inear Faults consists of / shape points! "his is, in &ost cases, the type to use! c! 2istric %aults consists of 3 shape points! -ll three of the shape points can 'e edited separately in order to get a listric shape of the fault! d! Cur#ed %aults consists of 8 shape points, and can 'e used in order to dene a cur#ed or $shaped fault!

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c '

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/! 9pen the settings 'y dou'le clicking on the fault &odeling in the Process Pane! *ote the option to e0tend the Key Pillars a'o#e the gi#en &in point and 'elow the gi#en &a0 point of the input data! Bou can control how far Pillars are e0tended! For e0a&ple put it $33

Fig. 11.13 Fault &odeling with Gullfaks4Fault Model dialog 'o0

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"diting Ke& Pillars -fter you ha#e created a fault you &ay want to do so&e netuning on a specic Key Pillar or on the whole fault! Petrel has the option to edit single $hape Points or pillars as well as a selection of $hape Points or pillars! "o select &ore than one, press the $hift key as you &ake your selection! "he Fault Modeling and hence editing of Key Pillars is a #ery i&portant step in &aking an accurate and relia'le Petrel &odel! "he Key Pillars should descri'e the fault planes as dened 'y the input data! (t is possi'le to edit on a co&plete fault, a single Key Pillar or a shape point , B and E directions, which &akes the editing on faults #ery e0i'le! -uto&atically constructed Key Pillars are often &alfor&ed and often it is necessary to add new Pillars 'etween key pillars and to the end of a fault then &odify their shape! Bou ha#e to insert Key Pillars 'etween e0isting pillars when a faults shape contains &ore detail than the e0isting Pillar spacing can represent! se the tool for adds Pillars to end of fault and add pillar 'etween! +diting of shape points and4or entire Key Pillars will 'e reHuired to &ore closely t the input data! "his editing &ay reHuire adding &ore shape points to the pillar to achie#e the desired for&! -ll Key Pillars in a fault dont necessarily need the sa&e nu&'er of shape points! $ee Fig! 11!13!

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Fig.

11.11

(llustrate drawing to show hori2ons, fault planes and key pillars

To edit +e& pillars4 %ollow t,e steps 1! 9pen a new 3D Iindow! /! Display a few of the faults 6Key Pillars7 to 'e edited! 3! "oggle on the check'o0 ne0t to all of the faults in the Fault Model folder! 5! Click on the Toggle fll between pillars icon to &ake it easier when editing the plane 'etween Key Pillars is lled with color, as shown in Fig! 11!1/!

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Fig. 11.1! Fault Polygons displayed in a 3D window while Fault Model -ction 6Pillars7 "ools tool'ar is displayed

8! "he tool used for &o#ing points and lines in Petrel is the widget! :! Knowing that select a Key Pillar 'y clicking on one of the shape points, the widget will appear! (t consists of a plane and a cylinder! =! Click on the plane to turn it yellow and edit in a plane nor&al to the cylinder

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?! Click on the cylinder 6so it turns yellow7 to edit along the tangent of the cylinder! e sure that you are in the Select*Pic+ Mode 5P6 as shown 'elow!

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@! Press the left &ouse 'utton on the widget and &o#e the Key Pillar or the shape point! 1J! Make sure the Mo#e 7long 2ine Tangent Onl& tool is acti#e! "his tool li&its the &o#e&ent to the tangent of the Key Pillar and it is a #ery intuiti#e way of editing the Key Pillars!

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11! "o select only one shape point, &ake sure the Select S,ape Points icon is acti#e, as shown 'elow!

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1/! "o select an entire Key Pillar &ake the Select Pillars icon acti#e as shown 'elow! (f you click on the line 'etween Key Pillars, all shape points at that le#el will 'e selected, as shown 'elow!

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13! (f you click on the line 'etween Key Pillars while ha#ing the ;$elect Pillars< icon acti#e, all Key Pillars will 'e selected! "o select only a few Key Pillars4shape points, click on those that you want to select while pressing the shift key! 15! Check that the fault &odel has the correct orientation 'y displaying the top and 'ase hori2ons! (f not, edit the& as descri'ed a'o#e!

Comment Ihen nished editing, the Key Pillars should ha#e a s&ooth transition in E fro& Key Pillar to Key Pillar in a fault! "he Key Pillars in the faults should e0tend a'o#e the top of the top surface and 'elow the 'ase of the lowest surface!

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Fig. 11.1$ +diting Key Pillars 'efore  after

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8uilding Ke& Pillars %rom Fault Pol&gons "he sa&e steps of 9"diting Ke& Pillars9 are applied in this section! -nyhow do not forget to deselect the acti#e fault when creating a new one! 9therwise, the new fault will 'e attached to the pre#ious acti#e one, see Fig! 11!13!

Connecting Faults (f a fault is truncated 'y another fault in the hori2ontal direction, it &ust 'e connected to that other fault! "his &eans that a co&&on Key Pillar 'etween the two faults &ust 'e dened! Bou can 'oth use a Key Pillar that already e0ists and edit it into a position so that it ts 'oth fault planes, or you can add a new Key Pillar 'etween two e0isting Pillars and use that as the co&&on4connected Key Pillar! -ll faults intersecting each other in Petrel &odel &ust 'e properly connectedL "his is i&portant 'ecause the gridding process in Petrel will use the faults for guiding the gridding lines! "he faults which are unconnected are treated di.erently fro& the faults which are connected! Further&ore, faults which are close together 'ut unconnected are likely to lead to pro'le&s in Pillar Gridding and Make ori2ons! Petrel has an auto&atic fault connection option which will connect all the si&ple 'ranching and crossing faults in a single operation! se this option carefully and always NC the grid afterwards! -s connecting faults reHuire so&e editing of the fault position, you will nor&ally ha#e to edit the connection &anually afterwards! "runcated faults will not 'e handled 'y auto&atic connection!

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To connect two %aults4 %ollow t,e steps 1! Choose the two faults to 'e connected /! Eoo& in on the area where the two faults are to 'e connected $elect the two Key Pillars you want to connect using the Select*pic+ Mode icon and the S,i%t Key! 3! Click on the Connect Two Faults icon as shown 'elow!

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Fig. 11.1) "wo faults 'efore connection

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5! Dene how you want to connect the& when the Connect pillars dialog bo: pops up as shown in Figs! 11!18! and 11!1:!

Fig. 11.1- "he Connect pillars dialog 'o0

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Fig. 11.1 "wo faults connected to each other

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Disconnecting Faults "he undo 'utton does not work for connected Key Pillars! Bou will ha#e to disconnect the& instead!

To disconnect %aults4 %ollow t,e steps 1! $elect the two Key Pillars that should 'e disconnected! /! Click on the Disconnect Fault icon! $ee Fig! 11!1=!

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Fig. 11.1( "wo faults 'efore connection

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Fig. 11.1/ "wo faults 'efore and after disconnection

Creating 8ranc,ed and Crossing Faults 1. $elect the Key Pillar where you want the crossing or branc,ing fault as shown in Fig!11!1@! !. Click on either the New 8ranc,ed Fault icon! -s shown in Fig!11!/J! $. 9r click on the New Crossing Fault icon to generate a new fault, as shown in Fig! 11!/1!

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Fig. 11.10 - fault displayed in a 3D window

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Fig. 11.!3 - fault displayed in a 3D window after creating 8ranc,ed %ault

Fig. 11.!1 - fault displayed in a 3D window after creating Crossing %ault 29



Creating Faults %rom Selected Fault Stic+s Fault sticks can 'e used like fault polygons to create Key Pillars! Fault sticks are sets of line data that represent the fault plane! "he le with fault sticks can represent one fault are a set of faults and are generated in Petrel or another work station! "hese sticks represent the fault surface and are con#erted to Key Pillars! "his ðod is prefera'le if you ha#e fault interpretations that &ay contain a 'it of noise and you would like to ha#e the option to disregard so&e of it!

To create %aults %rom selected %ault stic+s4 %ollow t,e steps 1!

"urn o. all of the faults, fault polygons and any other data you &ay ha#e displayed in your 3D window! /! Fro& the ;nput pane display the fault sticks! $ee Fig! 11!//!

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Fig. 11.!! Fault $ticks displayed in a 3D window

3! $elect ertical, 2inear, 2istric or Cur#ed Pillars depending on the type of fault you are &odeling! +ither linear or listric %ault geo&etries will 'e ne 'ut e0a&ine the fault sticks 'efore you choose! 5! Click on the Select*Pic+ Mode 5P6 icon in the Function 'ar! 8! $elect so&e of the fault sticks on a fault 'y clicking on the fault stick and holding the S,i%t Key! $ee Fig! 11!/3!

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Fig. 11.!$ $electing fault sticks

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Click on the 7dd to or Create Fault %rom Selected Fault Stic+s icon in the Function 'ar to generate Key Pillars along the selected fault sticks! $ee Fig! 1J!/5! *otice that 'y choosing this ðod, a fault will only 'e generated that connects the sticks that you selected! "his could cause you to potentially lose so&e i&portant detail!

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Fig. 11.!) "he Key Pillars for fault sticks created as a &odel

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9nce you ha#e created the Key Pillars for a new fault, do the necessary editing and follow the procedure as descri'ed in the e0ercises a'o#e! ?! Connect the faults where necessary! $ee Figs! 11!/8! to 11!/=!

Fig. 11.!- "he two faults 'efore connection

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Fig. 11.! Connect pillars dialog 'o0

Fig. 11.!( "he two faults after connection

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Continue &odeling all the faults in the folder! -s shown in Fig! 11!/?!

Fig. 11.!/ -ll faults created as a &odel

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Creating Faults %rom 7ll Fault Stic+s (t possi'le to select the entire set of fault sticks representing one fault and &ake Petrel use e#ery nth fault stick as input! "his is a fast approach 'ut it reHuires that the fault stick are representati#e of the fault, i!e! do not contain lots of ;noise
To create %aults %rom all %ault stic+s4 %ollow t,e steps 1. Fro& the ;nput pane display the %ault stic+s in the
!. $elect ertical4 2inear4 2istric or Cur#ed Pillars depending on the type of fault you are &odeling! +ither linear or listric fault geo&etries will 'e ne 'ut e0a&ine the fault sticks 'efore you choose!

$. Click on the Select*Pic+ Mode 5P6 icon in the Function 'ar!

). $elect all of the fault sticks on a fault 'y clicking on the %ault stic+ and holding the S,i%t Key!

-. Click on the Create Fault %rom Fault Stic+s4 Sur%ace or ;nterpretation icon in the Function 'ar to generate Key Pillars along the selected fault! $ee Fig! 11!/@!

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Fig. 11.!0 Fault sticks displayed in a 3D window while the Fault Model -ction 6Pillars7 tool'ar is displayed

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. >epeat the sa&e process to the other faults! $ee Fig! 11!3J!

(. 9nce you ha#e created the Key Pillars for a new fault, do the necessary editing 'y following the steps as descri'ed in the e0ercises a'o#e!

/. Connect the faults where necessary and continue &odeling the faults in the folder!

Fig. 11.$3 "he Key Pillars for fault sticks created

7utomatic >eneration o% Faults $o far the faults ha#e 'een generated one 'y one! (n this e0ercise you will learn how to auto&atically create Key Pillars

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fro& sets of fault sticks in a folder in the Petrel +0plorer (nput ta'!

To create automatic generation o% %aults4 %ollow t,e steps 1! -cti#e the Fault Modeling fro& Process pane! /! Con#ert one set of fault sticks to Key Pillars) a! Find the fault sticks folder! 9pen the folder and right click on one of the fault sticks! $elect Con#ert to Faults in Fault Model? fro& the pulldown &enu! $ee Fig! 11!31!

Fig. 11.$1 "he fault sticks 'efore the con#ersion process displayed in a 3D window '! - dialog 'o0 will 'e pops up as shown in Fig! 11!3/!

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Fig. 11.$! Con#ert to Fault in the acti#e Fault Modeling dialog 'o0

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c! *ote the new fault in the 3D window and under the Fault Model folder in the &odel 6in the Models Pane7! $ee Fig! 11!33!

- new fault under the Fault Model Fig. 11.$$) folder after the con#ersion process displayed in a 3D window

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"his operation can 'e perfor&ed for all fault sticks in a folder) 1! "o a#oid dou'le sets of faults, delete the fault created a'o#e 'y selecting the whole fault in the 3D window or selecting it 6&aking it 'old7 in the &odels ta' of Petrel +0plorer and then pressing delete! /! >ight click on the folder called
Fig. 11.$) -ll faults sticks 'efore con#ersion displayed in a 3D window

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3! -ll new faults will 'e added under the Fault Model folder in the &odel 6in the Models Pane7! $ee Fig!11!38! 5! Continue doing the necessary editing of Key Pillars as descri'e a'o#e! 8! Connect faults where necessary!

Fig. 11.$- -ll faults sticks after con#ersion displayed in a 3D window

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To create automatic connection o% %aults4 %allow t,e steps 1! /!

Display all the faults you ha#e created in a 3D window! $ee Fig! 11!3:! Click on the Fault Modeling in the Processes pane !

Fig. 11.$ "wo fault sticks displayed 'efore auto connection while the Fault Modeling dialog 'o0 is displayed

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3! Go to the Operations ta' and click on the 7uto connect 'utton and use an ":tent distance of !-3m and do the auto&atic fault connection only for the #isi'le faults! $ee Fig! 11!3=! 5!

Check the connections and do &anual editing if necessary!

Fig. 11.$( Fault Modeling dialog 'o0 is displayed

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Fig. 11.$/ "wo fault sticks displayed after auto connection

7utomatic 7d@ustment o% Ke& Pillars (t is possi'le to ad%ust all the Key Pillars auto&atically 'y cuOng the& or e0tending the& relati#e to a surface or a constant #alue! $ince it is possi'le to edit all the Key Pillars &anually, and since &anual editing will always 'e necessary, the auto&atic ;tri&&ing< of Key Pillars functionality has 'een included as an optional e0ercise only! 47



(f the Key Pillars are tri&&ed 'y a surface then this surface should 'e s&ooth! (n the case of the - pro%ect, the ase Cretaceous surface is a good candidate to 'e used for tri&&ing since this is a nonfaulted surface! (n the e0ercise 'elow only the top $hape Points will 'e tri&&ed! (f the 'ase $hape Points should 'e tri&&ed as well, then a copy could 'e &ade of "op +tti#e surface, then this copied surface could 'e s&oothed to re&o#e &ost of the structure 6'ut keep the general dip7 and shifted downwards so that it is deeper than the entire "op +tti#e surface!

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To create automatic ad@ustment o% +e& pillars4 %ollow t,e steps 1! Display Top Tarbert surface with the generated Key Pillars together!

Fig. 11.$0 "he Top Tarbert Model displayed in a 3D window 'efore Key Pillar 9perations /! Dou'le click on the Fault Modeling process in the Process pane!

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3! Go to the Operations ta' fro& the dialog 'o0 that pops up and select the Top Tarbert surface in the ;nput pane 6click on the na&e to &ake it 'old7! 5! "oggle on the check'o0 ne0t to Top limit in the Operations ta' under Cut*":tend pillars and click on the 'lue arrow! 8! Click on the Cut*":tend 'utton! $ee Fig! 11!5J!

Fig. 11.)3 Fault Modeling dialog 'o0

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Fig.11.)1 "he "op "ar'ert and Fault Model displayed in a 3D window 'efore Key Pillar 9perations

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Chapter 11 - Fault Modeling

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