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Chemical

Methods

for

Shutting

Off Water Oil and Gas

Wells

By H. T.

KENNEDY*

(New York Meeting, February, 1936)

THE fact

that

intrusion of water into oil wells can be prevented

by

treating the

sand

adjacent to the well seems to have been only recently

recognized. Swan

l

mentions the process of solidifying

naphthalene

in

strata. R. Van

A

Mills

2

recommends

the

use of materials such as

sodium silicate

and

sodium carbonate, which

react

with oil-field

water to

form solid plugging agents.

When a well is drilled in a new field the oil

sands

are found essentially

devoid of

water

(Fig. 1). Unless a completely impermeable

break

exists

FIG.

1

W A TER CONDITION:> WHEN

FIELD

IS DRILLED.

over wide areas

in

the field, no water is found above

the

lower limit of the

oil zone and no oil is found below the upper limit of the water zone.

After considerable oil has bepn takC'n from the well, however,

it

is

almost

universal experience

that

water intrusion occurs. This intrusion

may

be

of two kinds. The water may follow a path parallel to the bedding

planes of the producing formation through loose

streaks in

the pay sand,

as shown in Fig.

2,

or the water level of the field

may

rise and enter the

well by coning (Fig.

3).

Water entering from the side is

called

edge

water, and

that

coming in from the hottom is called

bottom water.

Effectiveness of any method for shutting off water depends not

ollly

Oil

thl'

effpe(.ivp

t J ( ~ a t m ( , l I t

or

t.he Hand adju('PIlt.

to the

well

but

011

Manllscript

('e('ei\'pd

at

tl,c office of the In:>titlltc

March

19, 193fi.

* Gulf Research Dc\'elopment Corporation, Pittshurgh, Pa.

I

U.S. Patent 1379657 (1921).

2

U.S.

Patent

1421706 (1922).

177

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178 CHEMICAL METHODS FOR

SHUTTING OFF

WATER

IN

OIL AND GAS

WELLS

the geologic conditions of

the

sand.

t

is possible, of course,

that

oil

and water, or gas and water, may enter the well through the same sand,

although probably this is

not

a frequent occurrence. f this occurs,

it

is

obviously impossible to shut off water without at the same time shutting

off

the

flow of 11

or

gas,

and

no

method

of sand treating can be effective.

FIG 2 . -CONDITION

AFTER EDGE WATER

IS

ENCOUNTERED.

Edge water can be completely

shut

off without in

any

way interfering

with the flow of oil or gas. As a matter of fact,

the

flow of these fluids

may

be substantially increased

by water

shutoff, provided

that

essentially

impermeable layers exist between

the

water-bearing

strata

and the

strata

bearing gas

or

oil,

or

that

the

vertical permeability

of the sand is low

compared to

the

horizontal permeability of

the

loose streaks.

The efficiency of

any

process for shutting off bottom water depends

largely on

the

uniformity of

the

sand horizontally and vertically.

The

I

I

WELL

WATER

OIL

= ---------- i ------------- ·=-----

I

I

77777777777777777777777 /777777 /

/ ,

FIG

3 . -CONING

OF

BOTTOM WATER.

m i t unfavorable condition would be a perfect ly homogpneouti sand with

out

hale breaki or o t l l ~ r barrierti. No sand of thiti

nature

has ever been

found,

but

the couditioll may he approaehed ill

salldi

ill whieh the i hale

breaki

occur over very small areas, i that water may rise vertically

between the breaks

not

far from

the

well. Even in these unfavorable

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H. T.

KENNEDY

179

c o n d i t i o m ~

however considerablr- reduction in water

or

increase in

amount of oil without wat.er can be acnompliKhed. On theoretical

grounds Muskat and Wyckoff have calculated that a disk 5 ft. in radius

at

the bottom of a well will increase

the

permissible oil production

without water by about 40 per cent.

f

productive streaks of sand are

separated

by impermeable breaks bottom water may be entirely elimi

nated by simply plugging with cement or lead wool

but

these

bottom

plugs can

bfnlsed

only at the bottom of a well and often pay sands exist

below this level from which oil could be obtained

by

the

use of chemical

water shutoff and deeper drilling.

Chemical water shutoff as described

in

this paper involves the forma

tion of a precipitate in

the

pores of

the

water-bearing

strata by

the use of

chemicals that may be

precipitated in

water-bearing strata without at the

same time affecti.ng oil or gas-bearing strata. The effectiveness of a water

shutoff

treatment

depends upon the amount of precipitate that can be

formed

in

the porr-s and

upon

the

nature

especially the hardness of the

precipitate. f precipitating solutions are injected into both oil and

water

strata it is evident that precipitation must be avoided

in

the former

and in selective shutoff only one solution must be required since in

a

method

using two solutions injection and

precipitation into

both strata

cannot be avoided. In this case therefore we are limited to

the

use of

chemicals that will

precipitate

in contact with natural oil-field waters.

The

bulk

of the dissolved

constituents

in

most

water consists of

sodium chloride which cannot be precipitated by any ordinary reaction

because salts conta ining sodium are all soluble in water and because

there

is no commercial material that can be added to precipitate an insoluble

chloride. The precipitab le compounds of oil-field brines are thus limited

to calcium

and

magnesium salts which occur only in small amounts

seldom more than 1 or 2 per cent by weight. However several mater ials

are known which form voluminous precipitates

on contact

with

water

itself and in which the volume of the precipitate is limited only by the

amount of water available to

react;

among

them antimony

trichloride

which in contact with water forms a voluminous precipitate of antimony

oxychlorides.

This material may be

injected

either in

a concentrated

water solution

or

dissolved

in

oil.

Silicon tetrachloride also reacts with water to form a voluminous

precipitate of silicic acid which in addition forms

an

effective cementing

material to consolidate and strengthen the sand

in

the walls of the well.

There

are several other materials that may be advantageously used

such as superfatted soaps finely divided cements made up in nonaqueous

suspensions

and

colloidal solutions which on dilution

or contact

with

salt

water are precipitated and form precipitates many times larger than may

be obtained by any reaction involving chemicals dissolved

in

oil

field water.

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180 CHEMICAL

METHODS FOR SHUTTING OFF WATER IN OIL

AND

GAS WELLS

T h ) s ~ ~ llOt.

ill

d i l f ~ d , (·ont.ad, wit.h

t.lw

wat.er ('ondit,jolls ill\'olvpr

ill

oil production will no doubt. be surprised

to learn that

more

water than

oil

is produced

by

the oil wells in

the

United States. As a matter of fact, for

the

1,000,000,000

bb1.

of oil,

we

annually produce

about

2,200,000,000

bb1.

of water.

The

lifting cost

at

10¢

per

barrel amounts

to

$220,000,000, a

large

part

of which is avoidable. Table 1 shows the water-oil ratios for

wells in different fields. This does

not

include

water

produced in gas

TABLE

l. Water oil

Ratios

in

il Wells

Water

to

Oil Ratios

Locality

umping

Flowing

Total

Gulf Coast ' 4.1

0.13

0.9

Texas (exclusive of Gulf Coast) 3.2

2.4

2.7

Louisiana and Arkansas 14.3 14.3

Mid-Continent

(Kansas, Oklahoma, N. Mexico).

2.4

0.1

2.1

Grand average

2.2

wells,

the

lifting for which,

per

barrel, is much higher, since pumps

must

be installed for the sole purpose of lifting water.

The

elimination of the

lifting expense is

not the

only

advantage to

be gained

by shutting it

off.

When a nearly perfect shutoff can be obtained emulsion troubles and

consequent expense of

treating

emulsions can be eliminated. Oil

production

and

oil recovery per acre may be substantially increased

by the

utilization of

the

driving force of water, which in

many

cases is the

primary

source of energy

in

forcing oil from sand. In competitive fields

many

wells are found in which the daily production is limited by

the

capacity

of

the

pump,

and the water that

is produced decreases

the

oil

production

by an

equal amount . Also,

many

wells are abandoned

because

the

lifting cost of water

and

oil cannot be paid for by the oil

production. Often wells produce 95

to 99 per cent

water,

and the

expense of handling

the

water

rather

than

the

shortage of oil production

leads

to their

abandonment.

Perhaps one of

the

most

important

applications of chemical

water

shutoff is in

the

saving of casing expense, especially in cable-tool d r i l l i ~ g .

Many

casings are

set

for

the

sole purpose of preventing intrus ion of

water

into the hole while drilling

but

frequently this function can be performed

by an

inexpensive

treatment

of

the water sand by the

proper application

of

the

methods here deHcrihed, ami one

OJ' m O f ~

Rtrings of cal'ing may p.

Haved on each well.

The

method of injecting ('hemieall' into saud naturally variel' with

the

condition of

the

well and equipment available.

For

a well pumping

with fluid level substantially at

the

bottom, it is convenient to injeet

the

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H 1 . K E N N l ~ I H

J:O;

ehclllieal through thc eatlillg without ditlturbing thc pumpillg eq uipmcnt,

except

to

pack off

the

polished rod. t is desirable to remove all water

from

the

hole

by

continuing

to pump with standing

valve

set

practically

on

bottom

while 10 or 15 bbl. of oil are injected

into the

casing. This

procedure allows the water

to

be removed without coming in contact

with

the

chemical charge.

f the

chemical is soluble

in

oil, such as

FIG 4. EQUIPMENT FOR INJECTION OF CHEMICAL

FIG 5 . W E L L H E A D

CONNECTIONS

FOR

CHEMICAL

INJECTION

antimony trichloride or silicon tetrachloride, it is

best to

employ

the

oil

solution direct ly following the oil, the amount to be used being determined

by

the

thickness of

sand to

be shut off

and the depth to

which it is desired

to penetrate. Experiments have shown that 1000 lb. of either of these

chemicals is ample for 20

to

30

ft.

of average sand, although it is evident

that very loose sands require more than

tight

sands; also, that a chemical

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182 CHEMICAL METHODS FOR SHUTTING OFF WATER IN OIL AND GAS WELLS

like silicon tetrachloride, which forms a hard, voluminous precipitate,

can

be used

more sparingly

with good results

than materials that are

less

effective for the purpose. After the chemical is pumped into the casing

it

is general procedure to apply an oil load, to make sure that the chemical is

forced from thl wrll into the sane\. Fig. 4

how

the equipmrnt used

in

FIG i . -O O U BLE-P A CK ER .\IETHOlJ OF INJECTING C H E ~ I l C A L

mixing the chemical and pumping it into the well, and Fig. 5 show the

well-head connections on a well

in

the Seminole area to which

this

process

was applied.

Although silicon tetrachloride and other ehl micals of thiR elass do

not

react in

the

absence of water,

and

therefore would do no

harm

to an

oil

sand,

it

is sometimes convenient, in

order

to avoid waRtl of ehl mical, to

FIG

7 . INJECTION OF

CHEMICAL

THROUGH PERFORATED CASING.

employ the double-packer

method

of treating sand (Fig. 6). This

is done

by

setting an

anchor packer

near the top of

the sand

to be treated,

and a hook-wall packer just below on tubing closed

at

the bottom and

perforated

between

the

packers.

Water present

in

the tubing may

be

displaced by oil

ahead

of the ehemieal chargp in order to avoid precipitates

of

the

chemical ill

the

well.

Thi nwthod ha

diHtinet advantages of

economy of material, especially where the oil and i more permeable

than the

water sand

or

where

the

pressure of the

latter

is high.

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H.

T.

KENNEDY

183

9

1

8 - l O . - EQ U I P M EN T AND CONNECTIONS FOR CHEMICAL INJECTION ON A WELL IN

CRESCENT

FIELD OKLAHOMA.

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184 CHEMICAL METHODS FOR

SHUTTING OFF

WATER

IN

OIL AND GAS

WELLS

Fig. 7

HhowH the

applieatiol1 of water Rhutoff method to t salld

behind a Htring of

eaHing,

where the eaHing Hllat may be

imperfed

and thUH

cause leakage into

the

well, or where

entry

of

water

from one

sand into

another

behind

the

casing is undesirable. Perforation of

the

casing can

be conveniently accomplished by either a knife or a gun perforater.

When

the

fluid in

the

well cannot be

pumped

down

to

bottom the

injection of chemicals without mixing with water is somewhat more

difficult, but can still be applied. Oil is pumped down

the

casing and

up

through tubing

until

returns

of clear oil are obtained,

the

velocity of flow

being great enough

to

carry the

water up

the tubing.

The

direction of

flow

is then reversed, the chemical being pumped down through the

tubing

until

it

reaches bottom.

The

casinghead is closed

and

sufficient

pressure is applied through the tubing

to

accomplish

the

injection.

Figs. 8, 9

and

10 show

the

equipment

and

connections used for

the

purpose on a well in

the

Crescent field, Oklahoma.

Regarding

the

effectiveness of water shutoff treatments it is evident

that

sand conditions have

an

important

bearing.

f water

enters a well

through cracks

and

crevices, only materials that set

up

to

very

firm

cements can be effective, but if water enters

the

porous sand, as usually

occurs, a perfect shutoff of

water

can be accomplished. One well making

25

bbl. of

water per day

before

treatment

was allowed

to stand

for five

days after

treatment

without

·making a measurable

quantity

of water.

In other

wells shutoffs

better than

99.5 per cent effective have been

accomplished. A gas well in Pennsylvania was making 1000 gal. of

water

per

day

before

treatment. The

second

month after

treatment

this

well

averaged

2 -2

gal. per day, which indicates

that water

shutoff

by this

method is

both

effective

and

permanent.

ACKNOWLEDGMENTS

t is a pleasure

to

acknowledge

my

indebtedness to Dr.

Paul

D. Foote,

Vice President

and

Director of

the

Gulf Research Development Corpo

ration, for encouragement

in

this work

and

permission to publish this

paper;

to

Dr. B. B. Wescott;

to

Dr. W. P.

Rand;

to

the Petroleum

Engineering

Departments

of

the Houston and Tulsa Production

Divi

sions of

the

Gulf Oil Corporation of Pennsylvania;

and

to Mr. D. E. Cona

way, of

the United Natural

Gas Co., for assistance in development

Qf

field technique in treating oil and gas wells.

DISCUSSION

T. V. Moore pre.,iding

B. B.

Cox

New York, N.Y.-If it is necessary

to

shut off a flow of gas and water

hcfore oil is encountered

in

a horing, would

it be

necessary to use oil as

the solvent

of

silicon

tetrachloride

or antimony trichloride to get the charge into the bore?

Producing Department Socony-Vacullm Oil Co.

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DISCUSSION

185

H. T. KENNEDY.-The

antimony

trichloride has a peculiar

property

of being

perfectly soluble

with

small

amounts

of

water

and, as diluted, becomes

totally

insoluble

to

form the oxychlorides. So that

with antimony

trichloride either

water

or oil

can

be

used.

B. B.

Cox . I

gathered from your

paper

that

antimony

trichloride did not form

a

hard

precipitate that would

support

a friable sand. Therefore, as I

understand

it,

it

would seem necessary, in

shutting

off a heaving water-bearing sand,

to

inject

a charge of oil in which silicon tetrachloride is dissolved.

H. T. KENNEDY.-The silicon tetrachloride

cannot be

used

with

water.

t

does

not

have

this property

of being a clear solution

with

only small

amounts

of water.

t

has

to be

used

with

oil.

It can

be used

with

oil better than

with antimony tri-

chloride because it

is

soluble in oil proportions.

MEMBER.-What does

antimony

trichloride cost?

H. T. KENNEDY.-Five

hundred

pounds cost 80, which is small, compared

with

the other

cost. Silicon tetrachl oride costs from 10

to

15¢

per

pound, depending

on

the quantity purchased. The cost of manufacturing

this material is

small and the

price undoubtedly will be lower when

greater

quantities

are

used.

MEMBER.-I understood you

to

say you needed

to

use the

material

you could

remove in case you

made

a mistake. How do you remove it?

H. T. KENNEDY.-I neglected to mention that with silicon tetrachloride

you

simply treat it

with

a caustic soda solution, provided, of course,

you can get

it in the

sand.

f

you

cannot get

it

in the sand or

if

it

goes in

very

slowly,

that

may be

a long

job. Antimony trichloride forms

the

oxychlorides that

may be

removed by

hydro-

chloric acid.

MEMBER.-When

the

well is

treated with

silicon tetrachloride

and it

reacts

with

water, it must generat e hydrochloric acid. Would that not

react

in the casing

seats

and

cause trouble?

H. T. KENNEDy.-Ordinarily it does not cause

much

trouble. As you

probably

know, a

great many

wells

have

been treated

with much

larger and

much

more con

centrated

shots of hydrochloric acid

without an

inhibitor. Of course, acid is not

formed

until

the water is reached.

That

is one of the reasons we like to take the

water

out of the well in addition to plugging the well, but

there

is always some acid.

f it is not

absolutely 100

per

cent

shut

off at first,

there

is some of

the

acid that

comes back. But

there

is

very

little trouble from

it

because

the amount

of acid

involved

is

really rather small. We

get

some pitting of valves,

but

at

most

it means

the

replacement of

the

valve.

MEMBER.-Does the silicon tetrachloride precipitate in an oil

sand i there

is

no water?

H. T. KENNEDy.-No, only by action of the water.

The

reaction is

SiCI. + 3H

2

0

=

H

2

Si 0

3

+ 4HCI

t

is only ill

contact

with

water

that silicon tetr aehloride changes form.

T.

V. MOORE

* HOllston, Tex. Mr. Kennedy, do you

think there

is

any water

in these oil sands?

* Humble

Oil Refining Co.

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186 CHEMICAL METHODS FOR SHUTTING OFF WATER IN OIL

AND

GAS WELLS

H. T. KENNEDy.-Do

you mean

coming through with the oil?

T. V. MooRE.-No, I mean intimately associated with the oil in

the

so-called

oil

sands

themselves.

H. T. KENNEDy.-Probably there is a small amount. Howcver one of the

advantages of silicon tetrachloride is that a hard

precipitate

is

not

formed with

small amounts of water. There must be an excess of water. I belicve it figures

out

that

about 7 or 8 per cent of water will not cause precipitation.

T. V.

l\IooRE.-I

believe

that

with

the amount

of work

that has been

done on this

problem

we can look forward in a short time

to

being able to plug off all our wells

exactly where and how we want to

plug

them by simply pumping the

proper mixture

of chemicals down into

the

well. However this process certainly must be used with

care. We tried

it

once on one of

our

wells in Southwest Texas and we cut the water

production of the well from 70 bbl. to 7 bbl. The

only trouble

was that we

cut

the

oil

production

from 30 bbl. to about

two

barrels.

H. H. POWER Tulsa, Okla.- I

can

go you the opposite on tbat, Mr. Moore.

One of

the

wells

that

was

treated

in

Oklahoma did not

cut water

production, but

increased the oil production.

T. V. MooRE.-I

said this method. I did

not mean

Mr.

Kennedy's method,

because

it

was a different method,

but it

had the same end in view simply pumping

down

the right

sort of

mixture into the

well and bringing

the

water well back into a

nice pipe line oil well.

H.

T.

KENNEDy.-Perhaps

I should

mention

that

we

changed

the

watcr-oil

ratio on one well we treated, before we had the

advances

we

have

now

from

2.2

to

0.7.

As a matter of fact we increased the oil production substantially, probably bccause

of

the

mechanism I showed.

f

the water comes

into

a well without pushing oil ahead

of it

it

is essentially like a piston without any piston rings. t just blows

by.

f

we start

it

off and increase pressures back where we want the

pressure

to push the

oil in we would expect to increase oil production.

E. A. STEPHENSON t Rolla

Mo.-Probably

you are familiar with some of the

work done

at

Conroe; originally I think, by Mr. Buck. Cement is pumped into the

water sand below

the

oil

sand,

while a high pressure is maintained on the casing.

The cement penetrates and seals the water sands at a pressure approximately half

that required to penetrate

the

oil sands.

This

method has

been

used

very

success

fully. It would be difficult

to

remove the cement by

any known

means if part of the

oil sand were accidentally plugged and the

production reduced;

modern

perforating

devices will solve this problem.

MEMBER.-What constitutes the charge?

H. T. KENNEDy.-We have

used

various amounts. t

depends largely

upon

tl 1C

depth of sand we need

to

treat

and

upon the permeability of

that sand.

Loose sands

naturally require more than

tight

sands. Sometimes we

have treated

sands that

required only

about half

a drum of silicon tetrachloride.

t

was impossible to

inject

more chemical because it had completely sealed the formation. At other

times

we

have used a drum. Sometimes we have used a charge of 1000 lb. of antimony tri

chloride and sometimes 500 pounds.

Chief

Production

Engineer

Gypsy

Oil Co.

t Professor of Petroleum Engineering Missouri School of Mines and Metallurgy.