Section 05 - Tripping & Backreaming Practices

Tripping & Backreaming Practices  Th  T his is the most im imp por tant subj ect of this school  – The practices used used by most groups are completely inappropriate inappropriate  – The serious problems problems experienced are are self-inflicted, self-inflicted, and unnecessary

This section will cover: ¾ What is required for safe tripping ¾ ¾

¾

Practices BHA requirements

Backreaming ¾ ¾ ¾

Is it good or bad ? Why do you see what you do ? How to do it safely (and when to do it)

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Tripping & Backreaming Practices • Back Back-r -rea eami ming ng or or pum pumpi ping ng ou outt sho shoul uld d be be avo avoid ided ed whenever possible in high-angle wells  – The ability to trip out without pumping or backreaming backreaming is a critical objective  –  Choosing any practice or equipment that forces you to

backream to trip out makes a mockery of risk-management • Because Because back-r back-reami eaming ng and/or and/or pumping pumping out out are the single-mo single-most st dangerous operation in any ER well  – Maximum risk of stuck pipe, and of destabilizing destabilizing the wellbore  – It is also time consuming, consuming, and destructive on BHA BHA equipment

 – Engineers : • It’s It’s not not just just a matte matterr of circu circulat lating ing more more … it’s it’s a desig design n issue issue too

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Classic train-wreck story • K& K&M M see see / rev revie iew w a lot lot of hi high gh-a -ang ngle le tr trai ain n wre wreck ckss  – Most have almost almost identical identical chain-of-events chain-of-events  – 2 common themes themes : • Those that had bad bad hole hole cleaning cleaning while drilling drilling (but (but they they thoug thought ht it was good). These also tend to have poor tripping practices. practices.  – More common with motor motor BHAs  – Note – Can have good hole hole cleaning with motors motors !!

• Those Those that that had good good hole hole clea cleanin ning g while while drilli drilling, ng, but still still have have poor  poor  tripping practices.  – This has become the most most common of the two, ever since RSS became  popular 

 – Does the following following sound familiar ?

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Say operator is drilling high or medium angle hole

1.

No problems drilling to TD •

Good hol holee cle clean anin ing g wh while ile dri drill llin ing g, an and no no cav cavin ing gs re report ported ed

•

How do they know it wa was go good hole cleaning ?

© K&M Technolog Technology y Group Group - 2008

•

No tight hole at connections

•

Good cuttings flow

2. At TD, TD, hole hole is clean cleaned ed up • Multi Multipl plee bot botto toms ms up circ circul ulat ated ed at TD • Shak Shaker erss cle clean an up quit quitee soo soon n … teamthinks thinks hole hole must be cle clean • I n re reali ality, ty, hole hole cle cleaning aning s sys yste tem mhas sh shut ut dow down n whe when low low--RPM RP M

used for clean-up cycle

3. Trip Trip comme commenc nces es • Soon pulls ti tight. • Atte Attemp mptt to back back-r -rea eam m thr thru u tig tight ht spot spot • Hole Hole pack packss off off (init (initiati iating ng circul circulati ation on or or soon soon after) after) • 1st cavings reported at this point

© K&M Technolog Technology y Group Group - 2008

4.

Back-reaming continues … •

Packing off all the way to the shoe •

•

Rela Relati tiv vely ely litt little le cutt cuttin ings gs while ile backack-re ream amin ing, g, until ntil ≈ 30o, then shakers blind with lot’s of cuttings… and cavings. Packs off also inside casing

5. Trip Back In •

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For so some re reason, th the tr trip back-in is is wh whistl istlee-clea lean… despite the nightmarish trip out…

Tripping & Backreaming Practices What we will cover in this section: • Part 1 – What is happening downhole • Part 2 – How to to ena enab ble tr trip ipp ping on el eleva vattors • Part 3 – Tripping procedures • Part 4 – Backreaming pr procedures

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Tripping & Backreaming Practices • Part 1 – What is happening downhole  – How does the cuttings cuttings bed & BHA interact when tripping tripping ? • Trou Troubl blee-fr free ee tri tripp ppin ing, g, vs vs tigh tightt hole hole • Normal Normal trippi tripping ng vs. vs. BackBack-rea reami ming ng vs. vs. Pumpin Pumping g Out

 – Separating myth myth from reality  – Why do we see what what we see ?

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What happens downhole when POOH ? Most people visualize that tripping looks something like this …

And that “tight “tight hole” hole” looks looks like like this this …

If this is correct, then normal reactions are valid © K&M Technolog Technology y Group Group - 2008

What really happens downhole when POOH ? What happens downhole when tripping in a deviated well ? holle is NOT 100% clean  – Firstly, assume that the ho  –

Even with a thorough clean-up clean-up

 –

Even with Rotary Steering Steering Tools !

 – The BHA does NOT pull cuttings up up the hole  –

Cuttings flow arou round nd the BHA, until they become too compressed

 –

BHA design is critical critical to “flow around” around” ability

 –

Has significant implications implications for how to manage tight tight hole

© K&M Technolog Technology y Group Group - 2008

What happens downhole when POOH ?

• When pulling pulling out, out, the the BHA BHA pulls pulls up throu through gh the the dirt dirt … • For a trouble-f trouble-free ree trip, the dirt must flow around around the BHA as the BHA moves through the bed

 Video Clip © K&M Technolog Technology y Group Group - 2008

What really happens downhole when POOH ? The dirt must be able to flow through the bit & BHA • Just like mud, we have a serious problem when the dirt can’t get past the BHA • Consider Consider ketchup ketchup / sauce sauce poured poured through through a kitchen kitchen funnel

© K&M Technolog Technology y Group Group - 2008

When driller sees tight hole … what is happening downhole ?

If this component blocks the flow of dirt, then tight hole looks like this …

 Video Clip

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But if this component blocks the flow of 

What is tight hole ?  Note that this this volume of dirt is small … • Only require requiress kilograms kilograms (not (not tons) to be stuck) stuck)

Unfortunately, Unfortunately, this is the most common situation • Because Because of typical typical bit bit & BHA BHA designs designs •If you pull too far, you can’t go back down •Turning pumps on is worst-possible response to tight hole © K&M Technolog Technology y Group Group - 2008

Backreaming Practices What is backreaming? Sta Standa ndar d tri trip – no rotation or circulation, harmless cuttings cuttings bed by-passed

Backreaming – rotate and circulate circulate while POOH, cuttings cuttings bed fully removed removed from the bottom of the hole. Cuttings drop out to form a dune above the BHA

 Video Clip © K&M Technolog Technology y Group Group - 2008

Backreaming Practices

© K&M Technolog Technology y Group Group - 2008

Backreaming Practices Pumping Out is Even Worse! Pumping Out – dirt still piles piles up behind the BHA due to high velocity velocity around the bit, stabilizers, and drill collars, but the conveyor belt is off!

 Video Clip

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Backreaming Basics • What What are the the downsi downsides/ des/ris risks ks associ associate ated d with with Backreaming?  – Stuck pipe  – BHA equipment equipment failures due to vibration vibration  – Key seating  – Lost returns (if packoffs packoffs exceed fracture fracture gradient)  – Self-inflicted wellbore stability problems

© K&M Technolog Technology y Group Group - 2008

Backreaming Basics • Backre Backreami aming ng itself itself doesn doesn’t ’t damage damage the the wellbo wellbore… re…  – Rather, it is the Hydraulic Hammer effect that causes all the  problems…  – Sudden large ECD pressure shock below pack-off  • Same principle principle will destroy destroy pipel pipelines, ines, power power stations stations,, etc etc ...Why ...Why expect it to be less severe in a wellbore? • These These are often often too large large for PWD to measur measuree

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Hydraulic Hammer  • What What PWD PWD sees sees when when hydrau hydraulic lic hamm hammer er occur occurss … • Press Pressure ure spik spikes es are are often often “off “off the the scal scale” e” • Remember, Remember, when you see see a packpack-off off at surface, surface, you you only see what’s left are dampening thru the bit, BHA & drillstring   e    l   a   c   s   g   p   p    3

 Normal drilling ECD … © K&M Technolog Technology y Group Group - 2008

How bad was this ECD spike ?

Backreaming Basics • Inter Interpr pret etati ation on of “we “well llbo bore re stab stabil ility ity”” probl problem emss chang changes es entirely if the wellbore has been “Hamm ammered”  – Often, the presence presence of cavings after after packoffs is perceived perceived as the very cause of the packoffs • K&M conte contend nd that that it it is more likely likely the the packoff packoff created created the the cavings cavings due to the hammer effect • Eviden Evidence ce of this this is “wel “wellbo lbore re stabili stability” ty” proble problems ms ofte often n go away away when when tripping practices are modified (due to avoidance of packoffs)

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Tripping & Backreaming Practices nabl ble e tr triipp ppiing on el elevato torr s • Par t 2 – How to ena Many ope operator ators say say “don’t on’t backback-rream unl unless y you ou hav have e to …” …” But exp expe erienced nced E R peopl ople “know know” ” that no-m no-matte atterr what the the proce procedur dure es say say,, that’s that’ s th the onl only way they they can get out of the hole  Th  T he abilit ility y to tr ip r egula larr ly on ele lev vator s is possib ible le  – But simply circulating circulating more isn’t the the answer 

© K&M Technolog Technology y Group Group - 2008

How clean must the hole be for tripping ? −

It depends on the bit & BHA ... • Junk slot area area affec affects ts how thick a safe safe cuttings cuttings bed can can be. be.

© K&M Technolog Technology y Group Group - 2008

BHA components are critical to ability to trip

© K&M Technolog Technology y Group Group - 2008

BHA components are critical to ability to trip •

Unle Unless ss the the BHA BHA comp compon onen ents ts are are addr addres esse sed d as a high high prio priori rity ty ….  –

Conventional tripping tripping may be impossible despite despite best practices practices

 – 

I t only only take takes s one one compone ponent to make a BH BHA unun-tri trippabl ppable e •

No matter how much circulation is done

 –   Th  This is makes a mockery of every ris risk k management precautio ion n we make, if 

this isn’t addressed as the highest priority  THI S I S THE SI SI NG NGL L E BI BI GGE ST THI NG YO YOU U CA CAN N DO TO RED REDUC UCE E (OR INC I NCREAS REASE E ) RI RIS SK I N YOUR YOUR PRO PROJ E CT

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BHA design for tripping What needs to be done to bit & BHA ?  – Junk-slot-area & junk-slot-tortuosity junk-slot-tortuosit y are key BHA design priorities • Remove Remove slee sleeve ve stabi stabiliz lizers ers on on big-OD big-OD coll collars ars  – 6¾” tools for 8½” hole, 5” tools for 6 ½” hole  – Especially on RSS, motors motors and MWD-LWD tools  – Shoot for a minimum minimum of 30% open area

• Or dow downs nsiz izee to sma small ller er col colla lars rs  – Eg. 6 ¼” tools instead of 6 ¾” ¾” for 8 ½” hole (or drill 8 ¾”) ¾”)

• Replace Replace sleev sleevee stabiliz stabilizers ers with with integr integral al blade blade stabil stabilizer izerss © K&M Technolog Technology y Group Group - 2008

Sleeve vs. Integral Blade

How an I nte nteg gr al Blade Sta Stabi billize zerr sees the hole © K&M Technolog Technology y Group Group - 2008

How a Sleeve Stabilizer sees the hole

Component Trip-ability Example Consider this New Zealand ER Well… • 9 1/2” tangent tangent to ±6100m ±6100m (20,000 (20,000’) ’) MD • Excell Excellent ent HC param paramete eters rs o 700 gpm / 150 150 rpm rpm o 3xBU cleanup cleanup cycles, cycles, shakers clean clean after 2xBU

• Previous Previous wells have have never had had problems problems tripping tripping o Identical Identical fluids, fluids, practices, practices, drillpipe, drillpipe, BHA…

© K&M Technolog Technology y Group Group - 2008

…However, the bits have changes “a bit”…

Bit #1 5 Blade, 2y Group © K&M Technolog Techn ology Group - 2008 14.5in

Bit #2 9 Blade 12.5 in 2

Bit #3 8 Blade, 20.9in 2

Trip #1 (5 (5 Blade, Bl ade, 14.5in 14.5in2 JSA) No problems, very similar to behavior on first well (similar bit) Minor 20-30k “peak” “peak”over over pull pull in places (fairly slick slick on average) Average Aver age F F =0.1 0.16 6 – 0.18

Trip #2 (9 (9 Blade, Bl ade, 12.5in 12.5in2 JSA) Long and troublesome trip with several intermediate circulation points required due to 50-60 k overpull in several locations Average FF = 0.19-0.20

Trip #3 (8 (8 Blade, Bl ade, 20.9in 20.9in2 JSA) Very smooth trip with the fewest number of tight spots of all the trips tr ips out out.. “P eak” overpu overpullll of 120 rpm)  – Sufficient circulation is required • Mult Multip iple le BU BU requ requir ired ed at at > 120 120 rpm rpm • Look Lookin ing g for for at leas leastt 2 wave wavess

Remember saltat altatiion flow flow side-effects • Rem

© K&M Technolog Technology y Group Group - 2008

Cleaning up for a trip • The The Con Conve veyo yorr bel beltt req requi uire ress > 120 120 rpm rpm • Comm Common on dire direct ctio iona nall-dr dril illi ling ng prac practi tice ce …. •RPM is often slowed whenever off-bottom (see next slide) •Hence, hole cleaning system is shut-down, convincing the team that the hole is clean • Cuttings don’t know if the bit is on or off bottom !! • Conveyor Conveyor belt belt must must be on when bit bit is off-bott off-bottom om too. too.

This is one of the most common mistakes … and one one of the most most illo illogica gicall ones ones too !! © K&M Technolog Technology y Group Group - 2008

RPM RPM vs Time lo g - Clean up on 18 July

Time-log showing RPM at end of drilling, and then during clean-up cycle • Drilling Drilling RPM = 138, 138, clean-up clean-up RPM only only 80 – 90

160

• Shakers Shakers cleaned cleaned up soon ... ... hole was interpre interpreted ted as clean

140

R P M drops from f rom 138rpm to 80+rpm. This was their their expected expected Cleanup is therefore largely nonexistant, and tripping starts in dirty! rotary-steerable hole

•

120

result since since they were using a

• Or did the hole hole cleaning cleaning system just just shut down ? 100    M    P    R 80   e   p    i    P

  p   u   n   a   e    l   c    t   r   a    t    S  .   g   n    i    l    l    i   r    D    d   n    E

60

40

20

0 0:00:00

2:24:00

4:48:00

© K&M Technolog Technology y Group Group - 2008

7:12:00

9:36:00

RPM 14:2rpm Time 12 :00:00 4:00

16:48:00

19:12:00

End Drilling / Start Clean-up

21:36:00

0:00:00

Hole Cleanup Practices How much clean-up is necessary ? Cleaning up takes time  – Bottoms up is irrelevant for high angle wells • Expe Expect ct 2 – 4+ x BU BU for for clea cleanu nup p tim timee  – This is very sensitive sensitive to angle above above 70 o (see nex nextt page) page)  – Patience is critical

• AND AND only only “con “conve veyo yorr bel beltt ON” ON” time time coun counts ts  – Circulation time time at < 120 120 rpm is irrelevant irrelevant and wasteful wasteful

© K&M Technolog Technology y Group Group - 2008

Hole Cleanup Practices Effective Circu Circu lation Volum e vs. Angle 20,000' (6000m) tangent length, shallow KOP 7

This gives some feel for how much circulation is necessary for different angles

6

• Note – only convey convey or or belt belt circulatio circulation n counts counts !

5   e   m   u    l   o    V 4   n   o    i    t   a    l   u   c   r 3    i    C  .   n    i    M

This is a minimu minimum m volume volume requirement requirement … the “talking” “talking” at the shakers shakers takes priori priority ty in decision-making.

2

 Notice how “gut feel” and “experience  betray you, once angle angle gets > 70o

1

0 0

10

20

30

40

50  Ang le

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60

70

80

90

Hole Cleanup Practices  – You are looking for at at least 2 waves of cuttings • Salt Saltat atio ion n flow low side side effe ffect • If you’ve you’ve been drilling drilling start start-stop -stop style, style, then then expec expectt more more waves waves A 2nd wave of cuttings flow is very common, if  circulati cir culation on conti continue nues s (with (with the con conve veyo yorr bel belt on) Similar to gr gr avel packi packing ng,, in in re r ever ver se • Sim

 s  g    i  t     n  t    u  c  e  m  l    u  o V   

 s  g    i t n     t    u  c  e  m  l  u    o  V  

wave is often often At >80o, 2nd waveis rd after 3 bottoms up

Norma Normal circulation

•

It’ It’s ea easy to to ge get su suckered-in to to st stop st clean-up when 1 wave finishes at ≈ 1 x BU

•

Shak Shaker erss wil willl red redu uce to a bac backg kgro rou und lev level (fines will never clean up)

•

I f ther ther e ar e stil till cutting uttings s stil till on the shaker haker s, the the hole hole is NOT yet yet cle clean …  – Pay now, or pay later (with interest) !

1

2 bottoms up  Time  Times bottoms

© K&M Technolog Technology y Group Group - 2008

3

4

Hole Cleanup Practices Cleaning-up for a trip  –  This  This proc rocess does lea leave cuttin ing gs in the hole  – The hole doesn’t have to be completely clean.  – The goal is to have trouble free trips.

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Tripping practices When hole has cleaned up …  – Trip out on elevators

(i.e. no pumping or backreaming)  – Back-reaming is only to be used as a last-resort option (more later)

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• Part 3 – Tripping Ou Out Pr Procedures  – Following the road-map road-map • How to iden identi tify fy “abn “abnor orma mal” l” from from “nor “norma mal” l” • How How to to iden identi tify fy “a ledg ledge” e” from from “cut “cutti ting ngs” s”

 – How to respond to tight tight hole • Do’s & Don’ts

 – Pipe Stretch discussion discussion

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Tripping Out Procedure 1. Pull out of hole without rotation or circulation • Trip Trip spee speed d is is impo import rtan antt … cont contro rols ls spee speed d of of dir dirtt flo flow w through the stabilizers & bit • Tigh Tighte terr BHAs BHAs requ requir iree slow slower er spee speeds ds

2. Monit Monitor or P/U P/U wei weight ght whil whilee tripp trippin ing g out of of hole hole • Compar Comparee realreal-tim timee to theo theoret retica icall drag drag trends trends (“road (“roadmap maps” s”)) • Must Must have have a roa roadd-ma map p to to kno know w wha whatt “no “norm rmal al”” is (see following plots)

© K&M Technolog Technology y Group Group - 2008

Using Road-Maps 1. If you you are are to to make make wise wise decis decision ionss abou aboutt when when “som “someth ething ing is abno abnorma rmal”, l”, you need to know what normal looks like … Experienced hands assume that they know this

… “ I don’ don’tt need a com compute puterr to tel tell me when I’ I’ve got got tigh tightt hol hole”

2. Peop People le als also o assu assume me tha thatt they they are are loo looki king ng for for a sud sudde den n chan change ge

Both of these are vertical hole logic, and are perhaps the most common reason wells get into trouble while tripping •

If we ha had d a gen genui uine nely ly cl clea ean n hol hole, e, an and d “le “ledg dges es”” we were re th thee pro probl blem em,, the then n thi thiss logic is OK 

•

But rem But remem embe berr we we are are lo look okin ing g for for di dirt rt bui build ld-u -up p bet betwe ween en st stab abil iliz izer ers, s, wh whic ich h happens gradually

© K&M Technolog Technology y Group Group - 2008

 Video Clip

45k 

15k 

Here is a trip tr ip out, plotted against depth • Is this this OK OK ?

But this is about to get stuck … • Can’t you see the train-wreck coming at you ?

This is the next stand pulled ? • What What is the the overover-pul pulll ? • Looks Looks like like 15 k ?

Classic indication of cuttings  building up is diverging diverging PU loads • Betwee Between n “norma “normal” l” and actu actual al load loadss

In reality, reality, hole hole is “talking” “talking” to you you for for +/+/- 10 stan stands ds

• Usua Usuall lly y over over 4 – 5 stan stands ds

•And overpull is 45k -lbs

© K&M Technolog Technology y Group Group - 2008

Tripping Out Procedure … conti ntinue nued hole is encounte ncounterred • I f tight hol  – Either via roadmap roadmap or not …

spot or incre ncreasing drag, ag, always assume ume the • F or tight sp problem is cuttings

 – Run in the hole 2 to 5 stands stands to get BHA away from tight spot •

If obst obstru ruct ctio ion n is is dir dirt, t, you you must must un-p un-pac ack k the the BHA BHA bef befor oree doin doing g anything else  –

If it took > 5 stands to pack pack the BHA, it will probably take that many to un-pack it !!

 – Remember that that cuttings can move move down hole with with BHA (in avalanche regime 120 rpm for 30 minutes  –  – 

•

Goal is to verify cuttings cuttings dune, so as as not to waste time time if otherwise

Conve onveyor bel belt mus ustt be on, if cutting cuttings s are are to be moved oved

POH carefully without rotation or circulation watching for the tight spot to recur   –  –

If the tight spot has moved up hole, hole, then obstruction obstruction was cuttings Continue cleaning cleaning the hole up, per per standard clean-up clean-up procedures

© K&M Technolog Technology y Group Group - 2008

Tripping Out Procedure Tight Spot Procedure …continued • If the tight spot has NOT moved up hole, then genuine tight hole is likely (key seat, ledge, swelling formation, etc.)  – Circulating or or backreaming may be used with caution caution  – Must avoid pack-off pack-off while circulating circulating or backreaming backreaming out of the hole • Risk of stuc stuck k pipe • Pressure damage to wellbore below pack-off  • Don’t want to lose returns  – 

© K&M Technolog Technology y Group Group - 2008

Hole cleaning get’s really messy if we can’t circulate !

Pipe Stretch Implications - Vertical: Pick-up we weight = Rotating wt wt = Slack-off wt wt - High High angl angle: e: We Weig ight htss are are very very diff differ eren entt ….s ….so o wha whatt ? Consider what’s actually happening downhole when the weight indicator changes when you kick the rotary on … - BHA imme immedia diatel tely y sucks sucks up the the hole, hole, with with miss missing ing forc forcee load load - typ typical ical stre stretc tch h is 1’ per per 1000’ 00’ MD (ie, (ie, 12’ at 12000’ 000’ MD)

- If you rotate rotate with with any any tensio tension n rem remain aining ing … - I think think I’m stuc stuck, k, will will just just make make sure sure about about that that befor beforee I call some somebo body dy !

© K&M Technolog Technology y Group Group - 2008

Pipe Stretch Implications The same thing happens while tripping in … - How many many time timess have have you you trie tried d to roll roll off off a “ledge “ledge”” while while trip trippin ping g in? in? - What happens happens to to the bit when rotation rotation is imita imitated ted with the string string in compression? - The The bit bit leap leapss forwa forward rd,, uncon uncontr trol olla labl bly y - This is is a reall really y good good way way to destroy destroy a drillstrin drillstring g (if buckling buckling is  present)! - Can also also cause cause lost-r lost-retu eturns rns due to surg surgee effec effectt

© K&M Technolog Technology y Group Group - 2008

• Part 4 – Back-reaming Ou Out Pr Procedures  – When is back-reaming back-reaming OK ?  – How to back-ream safely safely • Do’s & Don’ts

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Backreaming Basics • Som Sometim etimes es bac backr krea eami ming ng is is nece necess ssar ary y…  – Tight hole on trips

after verifying that the obstruction is NOT cuttings  – after  – Swabbing (can’t (can’t trip conventionally) conventionally)  – When removal removal of ALL cuttings is necessary necessary • To clean clean up hole hole for for extreme extreme casing casing runs in ER wells wells • Typica Typicall “trig “trigger ger”” is if casi casing ng run is so challe challengi nging ng as to requ require ire flotation

• For product production ion liner liner cement cement jobs, jobs, or running running screens screens

© K&M Technolog Technology y Group Group - 2008

Back-reaming Introduction When back-reaming, back-reaming, have you ever noticed ?.... •

Once Once you you star startt bac backk-re ream amin ing g in in a dire direct ctio iona nall wel well, l, you you can can’t ’t stop stop …unt …until il you you get get to to +/+/- 30o  – 

•

Actuall Actually, nor norm mal tri trippi pping can be resu sum med, wi with change changes to to nor norm mal practi practice ces s

You You don don’t ’t see see cut cutti ting ngss whi while le back backre ream amin ing, g, unti untill you you get get to to abo about ut 30 o  –

Then you get get lot’s of cuttings suddenly suddenly

•

Backack-rream eaming ing was was easie sier on on low loweer ang angle le wel wells ….

•

The The fas faste terr you you go, the the mor more pro probl blem emss you you have have ….

•

Have Have you you eve everr not notic iced ed seve severe re cavi caving ngss aft after er back back-r -rea eami ming ng,, des despi pite te neve never  r  seeing them before hand ? © K&M Technolog Technology y Group Group - 2008

Is back-reaming OK ? •

•

Firs Firstl tly y, le let’s t’s de define fine what hat ba back-re k-ream amin ing g is is …  –

Tripping, while rotating rotating & pumping

 –

A means of fighting fighting tight hole

Back-reaming is not …  –

Working the pipe up (with rotation) rotation) during normal connections

 –

When racking back back stands during the clean-up process.

© K&M Technolog Technology y Group Group - 2008

Back-reaming (continued) • What is is K& K&M’s opi opinion on ba back-r k-reaming ?  –

Dangerous, with high risk risk of stuck pipe, packing packing off, and inducing wellbore failure (more later) •

Only Only oper operat atio ion n that that has has hig higher ris risk is pum pumpin ping out !

 –

Tough on MWD & BHAs (vibration), (vibration), and causes casing wear  wear 

 –

Can be done safely … •

But needs to be done slowly to be safe

•

Practices must vary according to angle

•

Back Back-r -rea eami ming ng is not not fast faster er than than clea cleani ning ng up thor thorou ough ghly ly befo before re tripping

© K&M Technolog Technology y Group Group - 2008

How fast is safe to back-ream? You must be pumping-out / backreaming slower than the dune … remember the dune moves moves much slower slower for higher higher angles Pack-offs occur when the BHA is pumping-out or   backreaming faster than than the dune is moving moving This is a good application for the bladed DP •

Plac Placed ed in the the HWD HWDP P to to move move the the dune dune fast faster  er  (if conveyor belt is on)

B E   A C  H 

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Backreaming Procedure • Cle Clean hol holee up up fir first st • Never commence back-reaming while in overpull or tight hole - BHA is lite literal rally ly embedd embedded ed in cuttin cuttings gs - Consid Consider er pipe pipe stretc stretch: h: what what direct direction ion does does the the BHA move move if pipe pipe is in tension and we start to rotate? - Always Always drop down away away from from the the tight tight spot before before beginnin beginning g to backr backream eam - Appl Applie iess als also o to to tri tripp ppin ing g in in - …. actu actuall ally, y, this this may be wors worse, e, sinc sincee cutti cutting ngss must must now now clea clearr the the bit & BHA BHA  pinch-points

© K&M Technolog Technology y Group Group - 2008

Backreaming Procedure • Think Think of of backre backreami aming ng as as drilli drilling ng backw backward ardss • Be pati patien entt - Back Backre ream amin ing g mus mustt be be don donee slowly - 10 min/s min/stan tand d sounds sounds slow, slow, but but is equi equival valent ent to to ROP of of 600 ft/hr  ft/hr  - Accept Acceptabl ablee speed speed is very very sens sensiti itive ve to angl anglee when when above above 70 o - Dune Dune will will move move slowly slowly,, espec especial ially ly if if using using low RPM - Pack-off will occur if pickup speed is too fast

• Very Very few few opt optio ions ns if if lose lose retu return rnss

© K&M Technolog Technology y Group Group - 2008

Effective Circu Circu lation Volu me vs. Angle 20,000' (6000m) tangent length, shallow KOP 7

Back-reamin Back-reaming g “safe speed” speed” is driven driven by same “salta “saltatio tion n flow” flow” mechan mechanism ism that that drives drives how how much much circulation is necessary to clean the hole for a trip

6

5   e   m   u    l   o    V 4   n   o    i    t   a    l   u   c   r 3    i    C  .   n    i    M

Safe speed slows significantly beyond 70o

2

1

0 0

10

20

30

40

50  Ang le

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60

70

80

90

Remembe Rememberr Saltation Saltation Flow, Flow, and it’s side side effects effects This has important implications for a drilling operation … Side effect of back-reaming in a wellbore that has been cleaned-up But saltat saltatiion flow requir uires that that the hole mus ustt rere-fill to full ull drilling height, before you see cuttings at surface … This sucker-punches drilling operations all the time … • You have back-ream back-reamed ed for for 12 hours hours at slow slow ROP, ROP, and and haven’ haven’tt seen any dirt dirt … •How do you interpr interpret et this … the hole must must be clean •So back-reaming back-reaming get’s get’s faster … and then the hole packs packs off  Imagine we have cleaned the hole up, and commence backreaming from here …

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Backreaming Procedure • Torque Torque is is prima primary ry tool tool to moni monitor tor pull pulling ing spee speed d • If rig systems systems allow, allow, conside considerr pumping pumping at drillin drilling g flowrate flowrate & rotate at 120+ rpm (for larger hole sizes) - This This will will help help dispe disperse rse cutt cutting ingss dune dune above above BHA BHA - Howeve However, r, hard hard on top driv drivee & may may cause cause casi casing ng wear  wear  - Alternat Alternative ive is is low RPM RPM while while up-ream up-reaming, ing, then high high RPM RPM down-ream down-reaming, ing,  before final pick pick up to rack stand (without rotation– rotation– repeat cycle cycle if tight)

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Backreaming Procedure 40

4000

Packoff Tendencies (ie, BHA is colliding with cutting dune) 3500

35    )   s    b    l     t    f    k    (

  e   u   q   r   o    T

30

3000

   )    i   s   p 2500    (    P    P    S

25 20

 Torque SPP

15 10

2000 1500 1000

0

5

© K&M Technolog Technology y Group Group - 2008

10

15 Time (min)

20

25

30

Backreaming Procedure • Always clean up hole immediately after finish of backreaming

-- nev never jus ustt pul ulll out of the hol hole  – Applies for cased hole hole as well as open hole  – This explains the industries “typical” “typical” experience that that once backreaming backreaming starts, it can’t be stopped (in reality, all we need to do in order to return

to tripping on elevators is erode the due away from the top of the BHA)

• Take Take spec special ial care care comin coming g into into a cas casing ing shoe shoe  – Large OD rathole/washout rathole/washout accumulates accumulates cuttings  – Consider extra circulation circulation with with rotation before before proceeding

© K&M Technolog Technology y Group Group - 2008

Backreaming Considerations • Under Under-r -rea eame mers rs add add an addi additio tional nal leve levell of comp complex lexit ity y/ risk to backreaming  – Most RWD devices cannot cannot be locked closed, closed, causing vibration vibration and uncontrolled hole enlargement / undercutting while backreaming (since the  pilot BHA is unstabilized) unstabilized)  – One Exception is Halliburton’s Halliburton’s XRReamer XRReamer (drop-ball locking locking action)  And  A nd erGauge: erGau ge:

Smith:

Halliburton:

 And  A nd err er r eamer 

Rinoreamer 

XRReamer   Video Clip

© K&M Technolog Technology y Group Group - 2008

Unde Underr rrea eame merr Cons Consid ider erat atio ions ns • • •

Backr ackreeame amed 8 1/2 1/2”x9 ”x9 7/8 7/8” with with RWD RWD in stri string ng Memo Memory ry resi resist stiv ivit ity y sho shows ws rugo rugous us and and was washe hed d out out hole hole afte afterr bac backr krea eami ming ng Mult Multip iple le pac packo koff ffss and and subs subseq eque uent nt ins insta tabi bili lity ty ens ensue ued d on tri trip p in

Intended Gauge Hole Diameter 

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A Final Word On Backreaming • Back Backre ream amin ing g at high high angl anglee in lar larger ger hole hole size sizess shoul should d be thought of as “drilling backwards”  T he cuttin ing gs dune is for for ced up-hole by the flow flow r estr ict iction ion -  Th ar ound und the BH A

• Backrea Backreamin ming g at 1-2 1-2 minute minutes/st s/stand and may may not not be enoug enough h time for the dune to “get out of the way”

 The e time fo forr patie ien nce is when backreamin ing g to ru run n • Th casing

© K&M Technolog Technology y Group Group - 2008

So, let’s talk about how this impacts what “good oilfield oilfield practice” practice” means for for different different wells: wells: •Consider our response to a major equipment failure … • Lose 1 of 2 pumps pumps (24hr (24hr repair)… repair)… • Swivel Swivel packing packing leak (1hr (1hr repair)… repair)… • Top Drive Drive pinion pinion gear breaks breaks (3 day repair)… repair)… • Washout Washout in the drillp drillpipe ipe • 1000’ 1000’ (300m) (300m) from from surf surface ace… … • 1000’ 1000’ (300m) (300m) above above the the BHA… BHA…

What about a high angle well ? What about a Medium angle well ?

What should we do on a vertical well ?

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