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)
© K&M Technolog Technology y Group Group - 2008
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
© K&M Technolog Technology y Group Group - 2008
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 ?
© K&M Technolog Technology y Group Group - 2008
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 ? •
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 cle • I n re reali ality, ty, hole hole cle cleaning aning sys syste tem mhas sh shut ut dow down n whe when low low--RP
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 so • 1st cavings reported at this point
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 ≈ 30 shakers blind with lot’s of cuttings… and cavings. Packs off also inside casing
5. Trip Back In •
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 Practic 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
Tripping & Backreaming Practic • Part 1 – What is happening downhole
– How does the cuttings cuttings bed & BHA interact when trip • 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 ?
What happens downhole when POOH
Most people visualize that tripping looks something like
And that “tight “tight hole” hole” looks looks like like this this …
What really happens downhole when POOH ?
What happens downhole when tripping in a deviate 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 c
–
BHA design is critical critical to “flow around” around” ability
–
Has significant implications implications for how to manage tight tight hol ho
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
What really happens downhole when POOH ?
The dirt must be able to flow through the bit & B
• 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 funn
When driller sees tight hole … what is happening downhole
If this component blocks the flow of dirt, then tight hole looks like this …
What is tight hole ? Note that this this volume of dirt is small
• Only require requiress kilograms kilograms (not (not tons) t
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
Backreaming Practices What is backreaming?
Sta Standa ndar d tri trip – no rotation or circulation, harmless cuttings cuttings bed by-pa
Backreaming – rotate and circulate circulate while POOH, cuttings cuttings bed fully re
from the bottom of the hole. Cuttings drop out to form a dune above the
Backreaming Practices
Backreaming Practices Pumping Out is Even Worse! Pumping Out – dirt still piles piles up behind the BHA due to high velocity velocity the bit, stabilizers, and drill collars, but the conveyor belt is off!
Video Clip
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
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 problems… – Sudden large ECD pressure shock below pack-off
• Same principle principle will destroy destroy pipel pipelines, ines, power power stations stations,, etc etc ...Wh ...Wh expect it to be less severe in a wellbore? • These These are often often too large large for PWD to measur measuree
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 on what’s left are dampening thru the bit, BHA & drillstrin e l a c s g p p 3
Backreaming Basics
• Inter Interpr pret etati ation on of “we “well llbo bore re stab stabil ility ity”” probl problem emss ch entirely if the wellbore has been “Hamm ammered”
– Often, the presence presence of cavings after after packoffs is perceiv perceiv 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 ca 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 awa tripping practices are modified (due to avoidance of packoffs)
Tripping & Backreaming Practic 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 you you hav hav But exp expe erienced nced E R peopl ople “know know” ” that no-m no-matte atterr w proce procedur dure es say say,, that’s that’ s th the onl only way they they can get out 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
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
BHA components are critical to ability to trip
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 prio –
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
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 RE (OR INC I NCREAS REASE E ) RI RIS SK I N YOUR YOUR PRO PROJ E CT
BHA design for tripping What needs to be done to bit & BHA ? – Junk-slot-area & junk-slot-tortuosity junk-slot-tortuosit y are key 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
Sleeve vs. Integral Blade
How an I nte
l Bl de Sta Stabi billi
How a Sleeve Stabilizer
Component Trip-ability Examp
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 trippin trippin o Identical Identical fluids, fluids, practices, practices, drillpipe, drillpipe, BHA…
…However, the bits have changes “a bit”…
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 cir points required due to 50-60 k overpull in several locati 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 tigh trips tr ips out out.. “P eak” overpu overpullll of <15k. Average FF = 0.16-0.18
Bit Design for Tripping – Straighten up highly tortuous components component s • Eg. TightTight-spi spiral ral long-g long-gag agee bits bits
Bit Design for Tripping Prioritize Bit Junkslot Area – Steel body bits bits have much larger larger JSA than Matrix – Better impact impact resistance with Steel too
BHA Design for Tripping
– A very effective option to enable normal normal tripping wit “tight” “tight” componen components ts is to to enlarge enlarge the hole hole • Using Using Ream Ream-Wh -While ile-Dr -Drill illing ing (RWD (RWD)) underunder-rea reamer merss • Very Very popu popula larr in in the the Nort North h Sea Sea
Under-Reamer Considerations •
K&M K&M rec recom omme mend nd this this as a sho short rt-t -ter erm m “ba “band nd-a -aid id”, ”, unti unti root cause is fixed, due to side effects of using RWD –
The danger of this this technique is the the “false sense of security” gained from a trouble-free trip out prior to running casing…
Video C
Hole Cleanup Practices
Th T he hole must be cle lea aned up pr io iorr to tr ip ipp p • To be suc succe cess ssfu ful, l, the the fol follo lowi wing ng is is nece necess ssar ar
– Conveyor belt must be turned on (> 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
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 slid
•Hence, hole cleaning system is shut-down, convincing the team 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
RPM RPM vs Time lo g - Clean up on 18 July
Time-log showing RPM at end of during clean-up cycle
• Drilling Drilling RPM = 138, 138, clean-up clean-up RPM on
160
• Shakers Shakers cleaned cleaned up soon ... ... hole was in
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 th
• Or did the hole hole cleaning cleaning system just just sh 100 M P R 80 e p i P
60
40
20
p u n a e l c t r a t S . g n i l l i r D
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 wastefu wastefu
Hole Cleanup Practices Effective Circu Circu lation Volum e vs. Angle 20,000' (6000m) tangent length, shallow KOP 7
6
5 e m u l o V 4 n o i t a l u c r 3 i C . n i M
This gives some feel for how much circulation is necessary for different angles • Note – only convey convey or or belt belt circulatio circulation n counts counts !
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
1
Notice how “gut feel” and betray you, once angle angle
Hole Cleanup Practices – You are looking for at at least 2 waves of cuttings
• Salt Saltat atio ion n flow low side side eff ffeect • If you’ve you’ve been drilling drilling start start-stop -stop style, style, then then expec expectt more more wa 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
Norma Normal circulation
wave is often often At >80o, 2nd waveis rd after 3 bottoms up
•
It’ It’s ea easy to to ge get su suckered-in to to s clean-up when 1st wave finishes a
•
Shak Shaker erss wil willl red redu uce to a bac backg kgro ro (fines will never clean up)
•
I f ther ther e ar e stil till cutting uttings s stil till the shaker haker s, the the hole hole is NOT ye
– Pay now, or pay later (with inter
Hole Cleanup Practices Cleaning-up for a trip – This This proc rocess does lea leave cuttin ing gs in the ho
– The hole doesn’t have to be completely clea – The goal is to have trouble free trips.
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)
• Part 3 – Tripping Ou Out Pr Procedures – Following the road-map road-map • How to iden identi tify fy “abn “abnor orma mal” l” fr from om “nor “norma mal” l” • How How to to iden identi tify fy “a ledg ledge” e” fr from om “cut “cutti ting ngs” s”
– How to respond to tight tight hole • Do’s & Don’ts
– Pipe Stretch discussion discussion
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 (“roadm m • 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)
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 abnorm rm 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 commo 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,, t logic is OK
•
Butt rem Bu 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,
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
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” for for +/+/- 10 stan stands ds
• Usua Usuall lly y over over 4 – 5 stan stands ds
•And overpull is 45k -lbs
Tripping Out Procedure … co hole is encounte ncounterred • I f tight hol – Either via roadmap roadmap or not …
spot or incre ncreasing drag, ag, always assum • F or tight sp problem is cuttings
– Run in the hole 2 to 5 stands stands to get BHA away from t 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 do anything else –
If it took > 5 stands to pack pack the BHA, it will probably take th to un-pack it !!
– Remember that that cuttings can move move down hole with with BH avalanche regime <65°±)!
Tripping Out Procedure Tight Spot Procedure (…continued) •
Circulate & rotate at > 120 rpm for 30 minutes – –
•
Goal is to verify cuttings cuttings dune, so as as not to waste time time if othe
Conve onveyor bel belt mus ustt be on, if cutting cuttings s are are to be moved oved
POH carefully without rotation or circulation watchin tight spot to recur – –
If the tight spot has moved up hole, hole, then obstruction obstruction was cutt Continue cleaning cleaning the hole up, per per standard clean-up clean-up procedu
Tripping Out Procedure Tight Spot Procedure …continued
• If the tight spot has NOT moved up hole, then genuine ti 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 • Risk of stuc stuck k pipe • Pressure damage to wellbore below pack-off • Don’t want to lose returns –
Hole cleaning get’s really messy if we can’t circulate !
Pipe Stretch Implications - Vertical: Pick-up we weight = Rotating wt wt = Slack-of - 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 th 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 loa - 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 some
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 trip - What happens happens to to the bit when rotation rotation is imita imitated ted with the strin 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 buckl present)! - Can also also cause cause lost-r lost-retu eturns rns due to surg surgee effec effectt
• 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
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 cutting – 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 requ flotation
• For product production ion liner liner cement cement jobs, jobs, or running running screens screens
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 … 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 –
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 ….
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 connectio
–
When racking back back stands during the clean-up process.
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 we
–
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 befo tripping
How fast is safe to back-ream?
You must be pumping-out / backreaming slower th … remember the dune moves moves much slower slower for h
Pack-offs occur when the BHA is pumping backreaming faster than than the dune is mo
This is a good application for the •
Plac Placed ed in the the HWD HWDP P to to move move the the dune dune (if conveyor belt is on)
B E A C H
Backreaming Procedure • Cle Clean hol holee up up fir first st
• Never commence back-reaming while in overpull or tigh - 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 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 b - 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 pinch-points
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 - 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
Effective Circu Circu lation Volu me vs. Angle 20,000' (6000m) tangent length, shallow KOP 7
6
5 e m u l o V 4 n o i t a l u c r 3 i C . n i M
2
1
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 Safe speed slows significantly beyond 70o
Remembe Rememberr Saltation Saltation Flow, Flow, and it’s side side effects effects This has important implications for a drilling ope Side effect of back-reaming in a wellbore that has been cleaned-up But saltat saltatiion flow requi uirres that that the hole mus ustt rere-fill to ful ulll 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 d •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 com reaming from here …
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 flowrat flowrat 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 before final pick pick up to rack stand (without rotation– rotation– repeat cycle cycle i
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
10
15 Time (min)
20
25
30
Backreaming Procedure
• Always clean up hole immediately after finish of backre
-- 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 backr starts, it can’t be stopped (in reality, all we need to do in order to
to tripping on elevators is erode the due away from the top of th
• 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
Backreaming Consideratio
• Under Under-r -rea eame mers rs add add an addi additio tional nal leve levell of comp complex lex risk to backreaming
– Most RWD devices cannot cannot be locked closed, closed, causing vibration vibration an controlled hole enlargement / undercutting while backreaming (sin pilot BHA is unstabilized) unstabilized)
– One Exception is Halliburton’s Halliburton’s XRReamer XRReamer (drop-ball locking locking acti And A nd erGauge: erGau ge:
Smith:
Halliburton:
And A nd err er r eamer
Rinoreamer
XRReamer
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
© K&M Technolog Technology y Group Group - 2008
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 ?
© K&M Technolog Technology y Group Group - 2008
