water shuoff techniques in air or gas drilling

8/10/2019 Water shuoff techniques in air or gas drilling

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Water shutoff Techniques in Air or Gas Drilling t

C H R L E S

K

SUFALL

ABSTRACT

Water-shutoff

techniques

have reached a point where

they ar e generally accepted f or field us age ~f economlc

galn can be reallzed The success, both econonl~cal

and t ha t of shu ttl ng off permeable zones, 1s a tr lbute to

the plannlng of a job and the fine work done by the

research and servlce organlzatlons. Several types of

shutoff nlaterlal are now readily available through the

servlce companies as a re th e tools and techniques needed

to complete a water-shutoff job.

INTRODUCTION

Alr and g as drllling is economically 11mlted In use to

areas where format~onwaters do not present too great

a problem. Aerated mud and the use of surfactants to

mist drlll have helped where competent fonnatlons are

penetrated

1

However, almost all economlc failures In

alr or gas drllling are caused by for mat ~onwaters.

A fa st , lnexpenslve method of shu ttl ng off wa ter has

been a major objective for many research or ga n~ za t~ on s.

This report is Intended a s a revlew of the mat erials

and niechanlcs now

111

use for the purpose of shuttl ng

off format~onwaters.

HISTORY

The f irs t t ~ m e water-bear~ng ormation was pene-

trated with ai r or gas a s a drllling flu~d , he idea of

water shutoff arose. The old standby, cement, was first

used in the early attempts to plug the water zone. A

few jobs were successful; however, the cost Involved In

waltin g time made thls approach unacceptable

Gels and

emulsions

that had been used In selective

complet~onwork were tried with no degree of success.

Another approach was to form a sheath in a n enlarged

well bore where low-pressure zones were encountered.

Thls

technique

used hlgh-velocity air to erode the hole

through the water-bearing section. A length of

plastic

plpe w ~ t h up-type packers spaced to cover the interval

to be treated would be filled with an epoxy resin and

spotted op pos ~te he zone see Flg.

1

The resin was

then displaced Into the enlarged hole and chemically

tlmed to set

according

to the temperature. Therefore,

no appreciable w a ~ t l n g ~ n ~ eas required The resln

Techn~cal Dr ~l l~ ngervrce, Inc M~dla nd,Texas

;Presented at the sprlng meetlng of the Rocky Mountaln D ~ s t r ~ c t

D ~ v ~ s ~ o nf Product~on.Casper. y o Ap r~l

960

References are a t the end of th e paper

expanded while setting to as much as five tllnes ~ t sng-

lnal volume. After the resin had set up, the drlll pipe

was rotated to break a neck on the plastlc plpe. A blt

was then run to drill a hole through the plastlc plpe and

resln, thus leavlng an impermeable sheath to exclude

the water.

T h ~ sechn~qu e howed some success, but was hm ~t ed

to low-pressure format ~ons.As research capaclty was

hmited,

attention

was dlrected to ot her shutoff methods.

Research a t thls polnt was dlrected toward a lnaterlal

tha t could be squeezed Into the fo nn at ~o n t relatively

low pressures.

Thls material would need a very low

v~scosityu n t ~ l t was squeezed i nto place. Thus placed

Into the formation ~t would set up elther on contact

w ~ t h he water or through the chem~c al lmer.

s B r e o k off Ne ck

by

R o l o t ~ n g P

Plost~cP ~ p e

Fig

1

Resin Displaced into the Eroded Well Bore

with a Culculated Hydrostatic Head of Water

and Allowed to Set


2/4

After the inater ia l has se t up w ~ t h ~ nhe water zone

tt will be subjected to co ns~de rabl e ~ffe rent ial ressures

once t he hole

IS

unloaded and relleved of its hydrostat~c

head. Therefore, a prime character~st~cor the set-up

nlater~alwould be e~ t h er reat strength or deep pene-

t r a t ~ o nnto the permeable zone.

Also, the material must not be affected by contaml-

nants The method of mixture and ~nject~onhould be

ea s~ ly ccompllshed on locatlo~lw ~ t h hm~ter l mount

of special equ~pment.The se t t ~ng e r~odmust be easily

regulated to prevent pres ett ~ng r t o a vo ~d ostly wait-

lng t ime. F~nal ly , he ~n at er ~a lould need to be safe

enough to be handled on locat~onw ~ t h ormal safety

precaut~ons.

Two products were ~nt rodu ced o the field wh ~c h on-

t a ~ n e dmost of the foregoing

characteristics.

One was

a wa ter gel th at i s pumped in a 11qu1d form The gel

sets with the use of a chenlical t ~ n ~ e rnd w ~ t hempera-

ture. Dilution w ~ t h ater tends to accelerate ~ t setting

t ~ m e he other product

IS

a pl as t~ c h~ ch s also sensl-

tlve to water. Both

of these products have had wide

u sa ge w ~ t home remarka ble successes

A d~f fer ent pproach was the use of a liqutd and gas.

The.liqu~dwas fi rst ~ntroduced n t ohe permeable zone

and was followed by the g as \vl ~~cl ieactecl to form an

insoluble precipitate. Thus, with the perlneab~ll ty ealed

off, water shutoff had been acconlpl~shed

The use of g as alone as a shutoff n le d~ u~ nas devel-

oped after the successful acco~npl~shmentf the l ~ q u ~ d

and gas. The gas In t h ~ s ase 1s s~licotl etrafluor~de

which reacts with wate r In the form at ~o n o form a gel

and thereby seals off the permeabil~ ty T h ~ s airly

recent technique has seen w~ d e sage w ~ t h coils~der-

able degree of s~ c c e s s . ~ , ~

The most recent approach to water shutoff is a l~quld

which combines w ~ t h ater to form a gel

T h ~ s a t er ~ al

has just been released to the field and ~ t sharacter~stics

are not ava~lable.However.

~t

s known that the ~nitial

field trials of the liqu~d ave been highly successful

ECONOMICS

The pr~maryconsideration for in~tiattnga water-

shutoff procedure s economics R I ~~ m e s generally

the lar gest cost factor Therefore, by the use of advanced

planning much trine can be saved If geological data

~ n d ~ c a t epotentla1 a qu ~f er s to be penetrated and the

a v a ~ l a b ~ l ~ t yf m at er~ als nd tools needed fo r a water

shutoff ar e known In advance, the clownt~tne ol the rtg

may be cut to 24 hours or less

depending

upon well

depth.

The cost of water-shutoff in at er ~a lwould depend upon

the zone ~tse lf. n other words, the zone detern i~ne s he

amount of shutoff m at er ~a l eeded

Other costs would include a pump truck, a n~trogen

truc k, a plughead an d pump-down plug, diesel or alcohol

a s a s w e e p ~n g ~ a t e r ~ a l , packer, and a h~gh-pressure

compressor. I t should be noted, however, th at on mos t

jobs only a portion of this equipment would be neces-

sary. Generally, th e total cost, ~nc ludl ng lg time, would

rang e from 2,000 to 6,000 de pe nd ~n g pon depth and

formation character~st~cs.

Several cons~derationscan eliminate lost time. The

id en t~ ty f t he wa ter zone can be cl~fficult.The top can

usually be p~ck ed y nottng the depth penetrated when

the well stops du st ~n gThe lower portion of t he perme-

able zone can be picked by the use of geological info r-

ma t~ on nd the change In dri ll ~ng ates In some cases

a s ~n al l one may n ot be noticed while drilling a t fas t

rates and will show up after a trip or when the drilling

rate decreases So n~ et ~m eslog may be needed to define

the permeable zone.

Some hole should be made below the water zone to

act as a reservoir for wet cuttings and sloughing mate-

r ~ a lo accumulate. The hole should be cleaned as much

as poss~ble r io r to pu l l~ng he b ~ t

h ~ s ay be best

accompllshed by a dd ~n g foaming agent to wate r and

~nje ctln g nto the alr stream The hole clea ~nn g lso

allows the formation to ~~r odu cet sluid which a t t~ m e s

may draw down the zone's pressure, and thus allow the

shutoff nlaterial to enter the zone at a lower pressure

The packer se at should be p~c ked n a co~ilpetent one

as near a s poss~ble o the permeable s ect~ on

The job should be planned so as to use a mlnlmum

amount of fl u~dLo ad ~n g he hole can charge up a zone

above the packer that would bleed back into the well

bore dur ~ng ry~ng-up pe ra t~ons T h ~ s ould result in

l o s t t ~ men d r y ~ n g p the hole, and could also glve a

false evaluat~onof the shutoff Several shutoffs have

been aceompl~sheduslng only d~esel s a sweep ~ng lu~d

and air, gas, or nitrogen as the flush No other flu ~dwas

used. An inflatable-type fortnat~onpacker 1s used to

w~ths tand he h ~ g h ~ f fe ren t~a lressures

All poss~ble recautions should be taken to allow the

squeeze mat er~ al o enter the for mat~ ons t as low a

v ~ s c o s ~ t ys poss~ble A swee p~ngmaterial should be

used ahead of all wate r-se ns~t ive hem~ cals

Straddle packers may be con s~dered n some cases

Each job w ~ l l epend upon tools, mat er ~a ls , nd hole

cond ~tio ns o be designed fo r speed and effic~entopera-

t ~ o n

CASE HISTORIES

The follow~ngcase htstones a re representatwe of

some of th e d~ ff er en t roblenls encountered These jobs

all used the s111con tetr aflu onde ga s However, the tech-

nique used In a water-shutoff op er at ~o n s In general the

same for other water-shutoff agents.

Well A-Peeos County. Texas

In t h ~ s ell ( see

ig

2) , 9.56-111. cast ng was se t a t

6.088 f t Gas drt ll ~ngwas used unt~la fishing job

occurred and was unsuccessful A wlnclow wa s cut In

the ca s~ ng t ap prox ~mat ely ,600 f t and the old hole

was s~detracked nd dr ~lled o about 5,900 f t w ~ t h ud

The hole was the n unloaded and ga s-d r~l led o 5,970 ft

where approximately 5 bbl of water per hour were

encountered. The hole was then blown and ~mst-dr~lled

to 6,466 f t in an att empt to dr y up the zone As the

wate r ~n fl us ersisted, a water-shutoff was planned

The well was cleaned with a f oa ln ~n g gent and wa ter

p rior to pul llng the b ~ t

traddle packers of the inflat-

able type were then placed a t 5,950 f t and 6,088 f t to

include any possible water zone. Then 6 gal of diesel


3/4

Fig. 2 - A Straddle-packer Squeeze Job

After squeeze, gas drilling continued to below

12 000 ft without a water problem.)

were pumped into the drill pipe to be used as a sweep-

ing agent and to inflate the packers, after which 252

Ib of silicon tetrafluoride were injected as a shutoff

material. This amount was less than 2 lb per f t of hole

exposed; however, the water zone was only a few feet

thick.

Natura l ga s was used to bring th e pressure up to 725

psi maximum line pressure. A pump-down was released

and followed with a 4-bbl diesel blanket which, in turn,

was followed by water. When the drill pipe contained

18

bbl of water, the bottom-hole pressure approached

1,500 psi. A s th e annulus wa s unloaded t he packers were

set with this differential pressure.

Wa te r mjection continued until the bottom-hole pres-

sure of 3,540 psi was reached and maintained. During

this period the formation apparently took the diesel a t

3 180

psi bottom-hole pressure and

a

slight pressure

dro p occurred when th e silicon tetrafl uoride wa s injected.

The pressure then increased rather rapidly, indicating

the plugging action taking place in the permeable zone.

After the zone was apparently shut off, the drill-pipe

pressure was released, unloading almost all the water,

and the packers were unseated and pulled. A bit was

run back in and the hole was cleaned with a foaming

agent. Some silicon tetrafluoride was noticed, indicating

the zone had plugged before all the gas had been

displaced.

The hole was dry-drilled with ga s for over two weeks

without any fur th er indication of water.

In this particular area the formation that was gas-

drilled is principally a shale that is water-sensitive.

Therefore, mis t drilling with chemicals presently avail-

able is almos t impossible. More tha n 50 day s were saved

by the continued use of gas drilling.

This job used the bottom-hole pressure to determine

when the plugging action was complete. The pressure

gradient of 0.74

psi per f t of depth will generally frac-

ture formations with fluid. However, gas has been

found to fractur e a t considerably lower pressures. Fo r

this particular well a gradient of 0.6 psi per f t of depth

was used; and when the formation supported the 3,540

psi bottom-hole pressure the job was complete.

Well B-Logan County, Ark ans as

This well had 10 -in. casing set a t 733 ft. A 9 -in.

hole was drilled out with air, and water was hit about

1,520 ft. Another 29 f t were drilled, using a foa ming

agent and water injected a t a constant rat e into the a ir

line. Then when all geological data indicated that the

permeable zones had been penetrated, a water shutoff

with silicon tetrafluoride was planned to stop t he 4 bbl

of water influx.

The hole was cleaned with a foaming agent and an

inflatable packer wa s run t o 1,503 f t and set with wate r

pressure. The packer was then opened

t

circulating

position and the hole was unloaded.

The packer was opened below and 155 gal of diesel

were injected, followed by

320

lb of silicon tetrafluoride.

Nitrogen w as used t o complete the squeeze with a maxi-

mum bottom-hole pressure of 975 psi. Upon unloading

the hole after the packer w as pulled a small amount of

water was still being produced by the permeable zone

and, therefore, the use of mist drilling was necessary.

The job wa s classed a s a pa rtial wate r shutoff. However,

logs run on the completion of the well indicated a zone

of pe rmeabi lity a t 1,549 f t which could have accounted

for the small influx of water.

Well C--Haskell County, Oklahoma

This well was making about 2 bbl of water an hour

from two zones in the Hartsharn sand. The 9-in. hole

was drilled with gas as a circulating medium and pene-

tration rates were fast enough

t

generate sufficient

dust to keep the hole dehydrated. However, slow drill-

ing below 3,500 f t allowed the moisture to form mud

rings that eventually formed a severe annular restric-


4/4

tlon. Logs Indicated that the permeable zones were

between 960 f t and 1,050 f t and between 1,160 f t and

1,250 ft.

Slhcon tetrafluoride mas used to shut off both zones.

Inflatable-type straddle packers were set a t 1,145 f t and

1,273 f t to trea t th e lower zone. Afte r th e packers were

111 pos~tlon, 40 gal of dlesel and 400 lb of slllcon tetra-

fluoride were used. Natural gas was used to set the

packers, and was also used a s a flush A bottom-hole

pressure of 630 psi wa s used to sh ut off t he lower zone.

The packers were then released and pulled up to treat

the upper zone.

Natural ga s was used to set the packers a t 953 ft and

1,081 ft Then 340 gal of dlesel and 200 lb of slllcon

tetrafluorlde were injected, followed by natural gas for

a flushlng agent. The inaxlnluin bottom-hole pressure

used for the upper zone was 525 psl.

Subsequent logs indicated t ha t a considerable zone of

permeability

exlsted a t a d epth of 3,500 ft . Thls zone

had not been anticipated and was, therefore, not con-

sldered for wa ter shutoff This zone a t 3,500 f t was prob-

ably producing most of the water.

Well E--Andrews County. Tex as

.

The format1011 frac ture d d uri ng th e squeeze of thi s

job and st111 a high percentage of wat er shutoff w as

attained

The 8%-in. hole was air-drllled f rom t he casing point

a t 4,100 f t to 4,364 f t, where damp cutti ngs were noted.

At 4,912 f t th e voluine 0 water enterlng the hole

approached 60 bbl per hour. At this point the hole was

cleaned and an inflatable packer was iun and set at

4,514 f t, th en 300 gal of dlesel wei e used a s a sweeplng

age nt The silicon tetrafluorlde was diluted with nitro-

gen In consideration of the long sect~onof hole to be

squeezed. A nltrogen buffer followed the silicon tetra-

fluorlde and the buffer was, in turn, followed by air

pressure Nitrogen was again used to the maximum

pres sure limlts of the equipme nt and th e pump-down

plug was released. Water was used to complete the

treatment

At slightly over 2,500 psi bottom-hole pressure, a

pressure drop of 500 psi was noted. This pressure drop

probably Indicates the breaking down of the formation.

Aft er t h ~ she maxiinurn bottom-hole pressure attained

wlth further displacement was 2,135 psl

The packers were pulled and the hole unloaded The

water production was now measured a t 6 bbl per hour

T h ~ s as a pleasant surpnse,

considering

a fractured

formation.

Well D-Alberta Canada

Large-diameter holes can present an unusual problem

of gre at forces with small dlfferentlal pressures. In t his

well, 13%-in casi ng was set a t 3,720 ft. A 12%-ln. hole

was drilled out to 3,808 f t with a small influx of wa ter

apparently entering the hole a t or near the casing shoe

Thls meant that the ~a c k e r eat would have to be lnslde

the caslng. As an inflatable packer was the only type

rea d~l y vailable,

lt

was seated In the float collar to

att aln a s much frictlon a s posslble The hole had been

cleaned

Nitrogen was used as a sweeping fluid and as a buffer

behind the silicon tetrafluorlde Air pre ssur e was used

as a squeezing medium Annulus pressure was inain-

tained to keep the dlfferentlal pressure a cross the packer

froin becoming too great. Water and air pressure were

used for this.

A bottom-hole pressure of 2,315 psi was attained and

the shutoff was colnpleted without any d~fficulty.

I t IS interesting to note that a force of a quarter of

a m~lllon ounds was acting beneath the packer.

These case his tone s ar e Intended t o illustr ate some of

the different problems and hole conditions that arise

They are not meant a s any stand ard, for each job should

be planned according to the hole conditions and tools

and materials

avallable

CONCLUSIONS

Water-shutoff techniques have advanced froin ,a tn al -

and-error method to an accepted procedure for alr and

ga s drilllng Varlous research organizations and service

companies hav e contributed greatly to modern nlaterlals

and techniques and are now strlving towards a inore

efficient method of water shutoff. Although water-shut-

off methods ar e st111 in the p rinl ary stag es, several

iinportant factors can now be concluded.

The less fractured or open the perineabillty, the bet-

te r th e chance fo r complete wate r shutoff. Therefore, a

stronger type of shutoff material 1s still needed.

Squeeze pressures must be maintained a s low a s pos-

sible to avold fracturing the water-bearing forn~atioli

Inltlal results of wat er shutoff ~nd lca te hat better

shutoffs are attained from

materials

that gel or set after

enterlng the permeable sectlon.

Flnally, and most important, the economics of shut-

tlng off water zones can be held to a surprising mini-

inuin by plannlng ahead This involves a st udy of t he

characteristics of t he fo rm at ~o n o be penetrated, a

knowledge of the tools and

materials

avallable, and

being ready to cope with the s~tuationwhen t arises.

The major cost of a water-shutoff treatment

IS

directly

related to the t i ine consumed, and planning is the

remedy.

REFERENCES

IRandall, B V; Lunlmus,

J

L; and Vincent, R

Combatting Wet Formation While Drllling wlth Alr or

Gas, D?-il l~n{/ ont,rnctor, Oct. (1958).

ZHower, Wayne F , McLaughlln, Charles, Ramos, Joe;

and Land, John: Water Can Be Controlled In Alr or Gas

Drllling, IVorltl 0~1 ~ n parts) Par t

I;

Feb. (1959),

P ar t 11, March (1959).

sGoodwin, Robert J and Teplitz, A. J : A Water-

shutoff Method for Sand-type Porosity in Air Drilling,

T,rcrlls Ant I ns t. i l f ~ ) ~ z n ge t. E T L Q ~ S .Petroleltm Devel-

op)~lemt

ind

T e c h n o lo q y ) .

2 1 6 , G3 Oct (1958).

4Sufal1, C. I . and McGhee, Ed: Water-shutoff Treat-

ments for Air and Gas Drlllii~g,011 Gus

J.

57 [5 1 Dec.

7 (1959)

sBecker, Frederick L and Goodwln, Robert

J:

Private

colnnlunlcation.

Wrabb, H. H. Pnvate communication.

water shuoff techniques in air or gas drilling

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