Note: Descriptions are shown in the official language in which they were submitted.
3 0~ ~)
In the drilling and completing of oil, gas and
water wells, cement slurries are commonly utilized for
carrying out cementlng procedures such as cementing casings
in the well bores, sealing subterranean zones penetrated by
the well bores, etc~ In most cases, the cement slurries are
pumped into the well bores and allowed to harden once in
place in the well bores or desired zones in formations.
A variety of additives have been developed and
utilized heretofore for improving the properties of cement
slurries and bringing about desired results including addi-
tives for reducing water loss from such slurries while or
after the slurries are placed. Excessive water loss from
cement slurries can prevent proper hydration of the cement,
and in cementing wells, excessive water loss while the
slurries are being flowed through well bores can result in
dehydration o~ the slurries to the point where bridging of
the cement and other solids takes place in the well bores
preventing completion of cement displacement, etc. While the
water loss reducing additives utilized heretofore are effec-
tive in cement slurries formed with fresh water or water con-
taining very low concentrations of salts therein, such addi-
tives are substantially ineffective in cement slurries con-
taining high concentrations of salts, and particularly, in
cement slurries which are saturated with salts. For example,
a number of cellulose derivatives have been utilized to con-
trol fluid loss from cement slurries containing little or no
salts. However, such heretofore used cellulose derivatives
are substantially ineffective in reducing water loss from
salt water cement slurries. In addition, other heretofore
used fresh water cement slurry water loss reducing additives,
such as polyacrylamides, polyethylene imines mixed with
naphthalene sulfonic acid and poly-2-acrylamide-3-propylsulfonic
- 1 - ~
~,
`i ~ 63~0
acid salts are not effective in reducing water loss from salt
water cement 9 lurries.
By the present invention, water loss reducing addi-
tives for salt water cement slurries are provided which are
effective in reducing water loss from the slurries over a
broad temperature range. In addition, methods of using the
additives and salt water cement slurries containing the addi-
tives are provlded. The term "salt water" is used herein to
mean sea water, brines and other aqueous solutions of salts
including ammonium, alkali metal and alkaline earth metal
halides, and nitrates having salt concentrations therein up
to saturation. Salts other than those mentioned above can be
tolerated in the cement slurries of this invention to some
extent even though they may react with or alter the performance
of the slurries, e.g., bicarbonates, phosphates and sulfates.
The term "salt water cement slurry" is used herein to mean a
cement slurry comprised of water, cement, one or more salts
and other components or additives to bring about desired
slurry properties or use results. The salt amounts or con-
centrations in the cement slurries set forth hereinafter areexpressed in percentages by weight of the water in the cement
slurries. The amounts of water loss reducing additives in
the cement slurries set forth hereinafter are expressed in
percentages by weight of dry cement in the slurries.
The water loss reducing additives for salt water
cement slurries of the present invention are comprised of
very low molecular weight carboxymethylhydroxyethylcellulose
polymers. More specifically, the particular car~oxymethyl-
hydroxyethylcellulose polymers which are useful in accordance
with this invention have a carboxymethyl degree of substitu-
tion (D.S.) in the range of from about 0.1 to about 0.7 and a
ratio of moles of ethylene oxide to anhydroglucose unit (M.S.)
-- 2 --
i ~30~)
in the range of from about 0.6 to about 2.8.
The carboxymethylhydroxyethylcellulose polymers
axe derived from the cellulose class represented as a series
of anhydroglucose units as follows:
t ~ o H~ O 1
C n
~ le portion of the above structural formula in
brackets constitutes two anhydroglucose units, each having
three reactive hydroxyl groups. n is an integer which gives
the desired polymer molecular length. When the polymer is
treated with sodium hydroxide and reacted with chloroacetic
acid and ethylene oxide under controlled conditions, carboxy-
methylhydroxyethylcellulose is produced shown as follows:
CEI OH H OH
H ~ \ ~
_ ~ ~H o ~ + _
L 2-CH2-H OEI2-o=~E2-C-O Na
.
The sodium salt of carboxymethylhydroxyethylcellulose
shown above has one of the side hydroxyl groups substituted by
carboxymethyl, and therefore, the carboxymethyl degree of sub-
stitution (D.S.) is 0.5 per anhydroglucose unit. As stated
.. above, the preferred carboxymethyl degree of substitution for
the carboxymethylhydroxyethylcellulose used in accordance
with this invention is in the range of from about 0.1 to about
0.7. At a carboxymethyl D.S. of less than about 0.1, the
carboxymethylhydroxyethylcellulose has limited solubility in
water and at a carboxymethyl D.S. above about 0.7, the carboxy-
methylhydroxyethylcellulose has too much anionic characteristic
and causes a precipitate to be formed when combined with a
3 -
o
a cement slurr~.
The above structural formula also shows that the
ratio of moles of ethylene oxide to anhydroglucose unit
(M.S.) is 1 mole for two units or 0.5~ The preferred ethylene
oxide M.S. for the carboxymethylhydroxyethylcellulose used in
accordance with this invention is in the range of from ahout
0.6 to about 2.8. Carhoxymethylhydroxyethylcellulose having
an ethylene oxide M.S. outside the range given above does not
give adequate water loss reducing properties to a salt water
cement slurry.
The molecular length of the carboxymethylhydroxyethyl-
cellulose polymers, i.e., the molecular weight of the polymers,
must be very low in order to impart a low viscosity to a salt
water cement slurry with which the polymers are combined.
More specifically, the carboxymethylhydroxyethylcellulose
polymers suitable for use in accordance with this invention
have a very low molecular weight whereby a 1% by weight aqueous
solution of the carboxymethylhydroxyethylcellulose at a tem-
perature of 78F has a viscosity in the range of from about 10
20 to about 225 centipoises measured on a FAN~ viscometer at 300
rpm using a ~o~ 1 spring, standard bob and standard sleeve.
At molecular weights higher than those falling within the
above given range, the viscosity of the salt water cement
slurry to which the carboxymethylhydroxyethylcellulose is
combined is too high whereby the resulting slurry cannot be
pumped or otherwise handled. The FAN~ viscometer referred to
herein is a FANN Model 35 viscometer manufactured by Fann
Instrument Co. of Houston, Texas.
While the carboxymethylhydroxyethylcellulose
polymers described above are effective in reducing water loss
from salt water cement slurries, when the concentration of
salts in the slurries is above about 18% by weight of water,
-- 4 --
~;;
~1. ' `.
3~ 0
the effectiveness of the polymers by themselves decreases.
However, when a hydroxycarboxy acid is combined with the
carboxymethylhydroxyethylcellulose polymers, the resulting
additive is highly effective in reducing water loss from salt
water cement slurries having high salt concentrations. More
specifically, for salt water cement slurries having salt con-
centrations therein in the range of from about 18% by weight
of water to saturation, an additive comprised of the carboxy~
methylhydroxyethylcellulose polymers described and a hydroxy-
carboxy acid present in the additive in an amount of about50% of the weight of carboxymethylhydroxyethylcellulose in the
additive is utilized. Particularly suitable hydroxycarboxy
acids which can be used are gluconic acid, tartaric acid,
lactic acid, citric acid, maleic acid and mixtures of such
acids. Of these, gluconic acid, tartaric acid and citric acid
are preferred with citric acid being the most preferred.
A preferred water loss reducing additive for salt
water cement slurries having salt concentrations below about
18% by weight of the slurries is comprised of carboxymethyl
hydroxyethylcellulose having a carboxymethyl D.~. in the range
of from about 0.1 to about 0.7, an ethylene oxide M.S. in the
range of from about 0.6 to about 2.8 and a molecular weight
such that a 1% by weight aqueous solution of the carboxymethyl-
hydroxyethylcellulose at a temperature of 78F has a viscosity
.in the range of from about 10 to about 225 centipoises measured
on a FA~N viscometer at 300 rpm using a ~o. 1 spring. The most
preferred additive of this type is comprised of carboxymethyl-
hydroxyethylcellulose having a carboxymethyl D.S. of about 0.~,
an ethylene oxide ~.S. of about 2.0 and a molecular weight
wherein the viscosity of a 1% by weight aqueous solution is in
the range of from about 10 to about 200.
-- 5 --
63~s~
~ preferred water loss reducing additive for salt
water cement slurries having salt concentrations thereln in
the range of from about 18% by weight of water to saturation
is comprised of carboxymethylhydroxyethylcellulose having a
carboxymethyl D.S. in the range of from about 0.1 to about
0.7, an ethylene oxide M.S. in the range of from about 0.6
to about 2.8, and a molecular weight such at a 1% by weight
aqueous solution of said carboxymethylhydroxyethylcellulose
at a temperature of 78F has a viscosity in the range of
from about 10 to about 225 centipoises measured on a FANN
viscometer at 300 rpm using a No. 1 spring, and a hydroxy-
carbo~y acid selected from the group consisting of gluconic
acid, tartaric acid~ lactic acid, citric acid, maleic acid
and mixtures of such acids present in the additive in a weight
amount of about 50% of the weight of carboxymethylhydroxy-
ethylcellulose in the additive.
The most preferred additive of this type is comprised
of carboxymethylhydroxyethylcellulose having a carboxymethyl
D.S. of about 0.4, an ethylene oxide M.S. of about 2.0 and a
molecular weight such that a 1% by weight aqueous solution
thereof at a temperature of 78F has a viscosity in the range
of from about 10 to about 200 centipoises measured on a FANN
viscometer at 300 rpm using a No. 1 spring, and citric acid
present in the additive in an amount of about 50% of the
weight of carboxymethylhydroxyethylcellulose in the additive.
A preferred salt water cement slurry having low
water loss when in contact with permeable earth formations
of this invention is comprised of salt water, cement and a
water loss reducing additive comprised of carboxymethylhydroxy-
ethylcellulose having a carboxymethyl D.S. in the range offrom about 0.1 to about 0~7, an ethylene oxide M.S. in the
~range of from about 0.6 to about 2.8 and a molecular weight
- 6 -
`~ :I B3~
such that a 1% by weight aqueous solution thereof at a
temperature of 78F has a viscosity in the range of from
about 10 to about 225 centipoises measured on a FANN visco-
meter at 300 rpm using a No. 1 spring.
Another preferred salt water cement slurry having
low water loss when in contact with permeable earth forma-
tions is comprised of salt water, cement, a water loss re-
ducing additive comprised of carboxymethylhydroxyethylcellulose
having a carboxymethyl D.S. in the range of from about 0.1 to
about 0.7, an ethylene oxide M.S. in the range of from about
0.6 to about 2.8 and a molecular weight such that a 1% by
weight aqueous solution thereof at a temperature of 78F has
a viscosity in the range of from about 10 to about 225 centi-
poises measured on a FA~N viscometer at 300 rpm using a No. 1
spring, present in the slurry in an amount in the range of
from about 0.2% to about 2~0% by weight of dry cement in the
slurry, and a hydroxycarboxy acid selected from the group
consisting of gluconic acid, tartaric acid, lactic acid,
citric acid, maleic acid and mixtures of such acids present
in said slurry in an amount in the range of from about 0.1%
to about 1.0% by weight of dry cement in the slurry.
The most preferred salt water cernent slurry having
low water loss is comprised of salt water, cement, and a water
loss reducing additive comprised of carboxymethylhydroxyethyl-
cellulose having a carboxymethyl D.S. of about 0.4, an ethylene
oxide M.S. of about 2.0 and a molecular weight such that a
1% by weight aqueous solution thereof at a temperature of 78F
has a viscosity of from about 10 to about 200 centipoises
measured on a FANN viscometer at 300 rpm using a No. 1 spring,
~` 30 the carboxymethylhydroxyethylcellulose being present in the
` slurry in an amount in the range of from about 0.25% to about
1.8% by weight of dry cement in the slurry, and citric acid
-- 7 --
.` ~
3 0 ~ 0
present in the slurry in an amount in the range of from
about 0.1% to about 0.9% by weight of dry cement in the
slurry.
In use of the water loss reducing additives of the
present invention for reducing water loss from a salt water
cement slurry used in cementing wells, the additive is com-
bined with the salt water cement slurry prior to the use
thereof. Preferably, the water loss reducing additive is
dry blended with other dry components and added to the mixing
water used to prepare the cement slurry. If the mixing water
does not already contain salts, the salt or salts used are
preferably also dry blended with other dry components and
the mixture then combined with the mixing water. Once the
slurry is thoroughly mixed, it is introduced into a well
bore and/or subterranean formations penetrated thereby and
allowed to set into a hard permeable mass. The water loss
reducing additives and cement slurries including such addi-
tives are effective in substantially reducing water loss at
temperatures over a broad temperature range, i.e. from about
100F to about 360~.
As is well understood by those skilled in the art~
the salt water cement slurries of this invention can include
a variety of other components and additives to bring about
desired results including solid fillers such as sand, set
time retarders, accelerators, etc.
In order to facilitate a clear understanding of
the additives, salt water cement slurries and methods of the
- present invention, the following examples are given.
Example 1
Cement slurries are prepared using fresh water
containing various concentrations of sodium chloride, cement
and water loss reducing additives of this invention comprised
; ~ - 8 -
~ 1~30~
of very low molecular weight carboxymethylhydroxyethylcellulose
polymers (D.S. of 0O~ M.S. of 2.0, and a molecular weight such
that a 1% by weight aqueous solution thereof at a temperature
of 78F has a viscosity of from about 10 to about 200 centi-
poises measured on a FA~N viscometer at 300 rpm using a No. 1
spring) and tartaric acid. The slurries and additives are
mixed in a Waring Blender for 35 seconds at high speed. The
surface mixing viscosities of the slurries are determined at
100F, 120F, 150F and 190F using a Halliburton consisto-
meter as described in U.S. Patent No. 2,122,765.
Fluid loss properties of the slurries are determinedin accordance with API standard methods (API RP-lOB) on a 326
mesh screen at 1000 psi at 100F, 120F, 150F and 190F.
The results of these tests are given in Table I
below.
,~,. _ g _
.~ I ~ 6~090
~o
r~ 0 ~ a~ D ~ ~ ~ 0 ~ 0
~ ~1 O O ~) 0 0 ~9 U') I` In Lr~ d' ~ d' d' Ll'~
H 1~ 1 V
a
a
:~
C~
Zi
.~, o
H :~ ~ U U~ d' 0 ~ 0 0 ~ (S) C5~ ~ ~ 0 C~
æ a ~ 1 U
H H ~> O m
o U~ ~ ^
C) o ~ ~
u~ ~a
~ ~;
H ~Ll Q) ~1 1:4
~; E~ Q, u~ o O O O O O O O O O O O O O O O O
P~ ~ E~ o o o o o (~
~ 3 E~ O
H
æ
~o ~ ~
o p~ >1 3
; ~ ~ _ ~) ~) .i~ .L~
~rt rl
~ P~ ~ ~ ~ o u o c~ ~ o ~ o ~ o o In o oo u~
E~ ~ S:: ~I h t~ ~1 ~1 ~ ~1 ~ ~1 ~ ~ ~1
r1
3 ~ ~ ~ ~1 a)
_~ ~ ~ 3
V7 S~
~ a
u~ ~E~ ~ ~ . '
~ rl
o ~ ~ ,~ a
H U~O ~ E~
IX O rl ~ q)
~7 ~ U C)
.
~ U ~,C . ~ . . . . . . . . . . . . . .
O ~ .~ O O O O O O O O O O O O O O O O
~ 1 a)
l ~ U~ 3
H
~ ,~
O O ~~1 1
~ o e
~Q
~ >1 ~ C~ 0 0 0 0 0 00 ~D ~
I ~ ~ ~r~ ~ d' d~ 1 Ln 0 0 0 0 0 0 0
r--l ~ r l >1 O O O O OO O O O O O O O O O O Q)
r~ . 3
~; c~ u~ 3
E~ ~
r~
1~ ~ C.) X
~ ~ U~ .~
U~
(D r-~ a
O ~) t~l N N N N NN N N N N N N N N t~l
C /~
r~ ~
,., ~) t O
r ~ C 3
X X
~' ...' oq u~
cl U~ Cq tq tQ tQU~ U~ r--l r-l ri r--¦ r--l r-J r-¦ U~
r~ ¦ r-¦r-¦ r--¦ r~ ¦r--¦ r--l
) C) ~ h r~
a 11) ~)
>-~ ) (U
u~
G~ r~ ~r~ ~r~ r~ r~ r~ rl r~
D
Q~ ~rl r~ -r~r~ r~ ~r~r~ ~1 ~/ ~ C
h h ~ h ~ O O O O O O O U~
-- 10 --
ii 3 ~30~()
From Table I it can be seen that the carboxymethyl-
hydroxyethylcellulose-tartaric acid additives produce good
surface mixing viscosities and fluld loss reduction in cement
slurries containing various quantities of salts.
Example 2
The procedure of Example 1 is repeated using water
loss reducing additives comprised of the low molecular weight
carboxymethylhydroxyethylcellulose polymers described and
various hydroxycarboxy acids.
The results of these tests are given in Table II
below.
'~``
~ -- 11 -
~ `3~30~JO
O ~ ~ O ~ r~ ~D 0 0 ~D ~ O ~ ~ ~D O C~ D t` O ~ O ~ ~ O O C
O ~ ~D a ~ ~ ~ ~ ~ ~ ~ ~ o ~ ~ Ln ~ ~ ~ ~, ~ o ~ ~ ~ ~r ~ ~ r~ ~ ~ r~
~ o ~; Ln ~ ~ ~ Ln ~ In
.. ~
~ o ~n
.,~ o o o Ln o o o o CO
~ ~ O ~ ~ Ln Ln ~ r~ ~ ~ ~ Ln ~ Ln ~ ~D ~ ~ o~ oD a: C
U~ ~ ~
~ oooooooooooo ooooooooo ooooooooOoo
E~ a) ~n O o o o o Ln Ln Ln Ln Ln Ln Ln Ln Ln IS) ~ ~ (
~ O C~
E~ O
h ~ ra ~a
:~ ~ ~ a.) a) aJ ~ ~ ~IJ a
~ C~ ~ h h ~/ ~1 h SJ h 51
u:~ ~ ~
U~ ~ ~1 0 ~ ~ ~ ~) .IJ .1_) .1_) ~) ~)
O ~ ,~ ~ ~: o o0 Ln ~ ri Ln ta c~ o~ o c0 c~ Ln ~a (a o o~ Ln
~ ~ ~d ~ ~ o O Lr ~1~1~ ~q ~ ~ u~ ~ ~1 o O Ln ~ ~ ~ ~ u~ ~ O o Ln ~1~1
.' '~
~ ~1
~ ~, ,~
~,~æ
~ rl ~
0~ ~ O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O
; ~ o ~n
V~
i ~ ~
UU ~ U
~ I I I I I I I ~ h I I I I II S~ I h ~ ~ U
1~ ord~ IIIIIII~\II IIIII~I IIIII1~1~1UO
:, V :~
'.`' ~ ~?
..' .- ~ ~
~' ~ ~o~
~ ~8 ~ ~ ~ ~r ~r ~ ~ ~ ~ Ln ~ ~ ~ ~ ~ ~D ~ ~ ~ r~ 0 0 r~ r~ o~ r~ 0 0 0
~ ~ ~ 000000000000 000000000 00000000000
H ~ ) 3
C~l ~
O 1-~ 0
~ o~ ~ X ~ C X ~ $ ~ X ~
. ~ ~ ~q ~q U) ~q U~ V~ ~q V~ ~q U~ ~q U) V~ V~ ~q ~q ~q U~ q V~ V~ V~ V~ q U~ V~ V~
H ~ ~ td U~ V~ q U~ tq ~q U~ ~q U~ ~q 11~ q ~q U~ ~q ~q 0~ ~q U~ ~q U~ ~q Lq ~q V~ ~q V~ V~
D ~ h h h ~ h ~ ~ ~ h ~ h )~
~ u a) u ~ a a~ a ~ c c a~ ~ a) u a) u ~ a~ a~ a~ a) a) ~ a) a) a
CCCCCCCCCCC~ ~:CC~CC~C C~C~C~.CCCCCC
o ~o ~ o ~ ~ ~ ~ o ~ ~ ~o o o ~ ~ o ~ ~ o ~ ~ ~o
-- 12 --
ID
n
o~
O U~ N N
H ~ O --1 ~1 ~1
a)
~ ~ O N ~ ~')
~i S-l
.' ~ ~ ~ ~ ~ ~
~ :~ '' ~
'; ~ ~
o,~ , ooo
~ u u ~ ~
` ~ ~ ~o ~' v ~
~ ~ ~ ~q ~q
~ ~
~o~ ~ 0
: ~ o
. ~ ~ ~ ~ ~ rl u ~
O ;~ r -t ~ O O OJ ~ ~ C C
C ~ ~ d ~ 0 11~ 'O a)
- H l ~d 0~ I ~ O
1--/ H ~1 ~rl ~ 0 1~ r~l ~) ~1
. . . H 0~ ~ cd U~ o~ 0 ~ ~)
, p ~d 3
G3 ~; r l r-~ ri ~ ~rl ~rl
h g ~ C.) U ~ a) 3 3
E-l ~ ~ . 1~ h S-l a 3
3 $
a~ a) a) ,'' ~ o~
c
O Q O
~, ~ ~ ~ r~ N ~`1
-- 13 --
6 ~
From Table II it can be seen that good fluid loss
reduction is obtained using the additives of this invention
at temperatures of from 100F to 360F. Further, it can be
seen that additives including hydroxycarboxy acids are more
effective in salt water cement slurries containing salt con-
centrations above about 18% by weight o~ water than those con-
taining CMHEC alone.
- 14 -
