Note: Descriptions are shown in the official language in which they were submitted.
24
~cidizing and fracturing procedures using aqueous
acid solutions are commonly carried out ir subterranean
well formations to accomplish a number of purposes, one
o~ which is to facilitate the increase in the recovery
of hydrocarbons therefrom. II1 acidizing procedures, aqueous
acid solutions are introduced into well formations under
pressure so that the acid solutions flow into the pore
spaces of the formations and react with materials con-
tained therein whereby the pore spaces are enlarged and
the permeability o~ the formations increased. In fracture
acidizing procedures, one or more fractures are produced
in the formations and the acid solutions are introduced
into the fract~res to etch flow channels therein and/or
to enlarge the pore spaces in the fracture aces and in
the formations.
Increasing the viscosity of an aqueous acid solution,
hereinafter re~erred to as "gelling," by the inclusion of
certain swellable materials or gelling agents therein has -
been accomplished heretofore. In acidizing and/or frac-
ture acidizing subterranean formations, gelled aqueous
acid solutions are useful in preventing the acid from be-
coming prematurely spent and inactive. In addition, gelling
of the acid solutions enables the development of wider
fractures so that live acid can be forced further into the
formation ~rom the well bore. Furthermore, increasing the
' -2-
~ 72i~
.
viscosities of the acid solutions also permits better
fluid loss control.
Gelled aqueous acid solutions have utility in indus-
trial applications other than in the treatment of subterran-
ean well formations such as in the cleaning of industrial
eq~ipment.
Gelling agents such as hydratable gums and cellulose
¦ derivatives have been utilized to increase the viscosity
i of aqueous acid solutions. However, the gels produced
~ 10 using such gelling agents generally haYe limited stability
¦ at high temperatures in the presence of acid. Other gell-
ing agents which increase the viscosity of aqueous acid
¦ solutions have been developed and used, but they are often
difficult to disperse and usually require considerable
mixing or agitation to develop full viscosity. Still other
` prior art gelling agents can form an undesirable precipitate
during the dissolution of formation materials such as lime-
stone or dolomite, which precipitate can remain in the
formation to thereby damage it by decreasing the perme-
ability thereof.
` 3y the present invention, a gelling agent for increas-
ing the viscosity of aqueous acid solutions, the resulting
gelled aqueous acid solutions and methods of using such
¦ gelled aqueous acid solutions are provided. The gelling
agent of the present invention can be easily dispersed into
~ 2 ~
an aqueous acid solution and only a small quantity of it
is required to rapidly increase the viscosity of the acid
solution with a minimum of mixing and agitation. The
resulting gelled aqueous acid solutions of the present
invention have excellent stability over a broad tempera-
ture range; they are relatively non-damaging to subter-
ranean formations treated therewith; and, upon becoming
spent in subterranean formations, and, without the
inclusion of chemical breakers or special additives
therein, they break to low viscosity liquids having
excellent fines suspension properties.
The gelling agent of this invention is comprised of
a water soluble organic solvent selected from the group
consisting of alkanols having in the range of from about
1 to 5 carbon atoms per molecule, ketones having in the
range of about 3 to 6 carbon atoms per molecule, poly-
hydroxy compounds having in the range of about 2 to 6
carbon atoms per molecule, ethers having in the range of
about 2 to 6 carbon atoms per molecule, compounds con-
20 taining both ether and alcohol functions having in the j
range of about 4 to 8 carbon atoms per molecule, esters
having in the range of about 2 to 6 carbon atoms per
molecule, lactones having in the range of about 3 to 5
carbon atoms per molecule and mixtures of two or more of
the foregoing compounds, and a mixture of ethoxylated
fatty amines dissolved in said water soluble organic
solvent having the general formula:
(CH2CH20) xH
R - N
(CH2CH20)yH (1)
wherein:
--4--
2~
- R is selected from saturated and unsaturated aliphatic
groups having in the range of from about 8 to about 22
carbon atoms, and mixtures thereof, and x and y each have
a value in the range of from about O to about 10. The
preferred ethoxylated fatty amines and mixtures thereof
useful herein are those wherein the average sum of the
values of x and y in the amines used is in the range of
from about 1.8 to about 2.2.
-4a-
A
.6~
Mixtures of ethoxylated tertiary fatty amines derived
fxom fats and oils such as coconut oil, soy bean oil, and
tallow are particularly su~table for use in accordance with
the present invention.
A ~referred mixture of ethoxylated fatty amines for
¦ use in this invention is a mixture of amines of the general¦ formula:
~C~2CH20 ) XH
}~
,~ 10 \~CH2cH~O)yH (2)
I wherein:
R is selected from the group consisting of saturated
and unsaturated aliphatic groups having in the range of from
¦ about 14 to about 18 carbon atoms and mixtures of such
¦ 15 groups; and
wherein the average sum of the values of x and y in the
I mixture of ethoxylated amines is equal to 2.
! In the most preferred embodiment, x and y each have
¦ a value of 1 ~one).
I 20 Examples of such amines are those derived from fatty
¦ acids of the type hexadecyl, tallow, soya and oleyl, either
I saturated or unsaturated and either as pure components or
¦ mixtures.
! A variety of organic solvents can be utilized in mak-
ing the gelling agents so long as such solvents are capable
_5_
of dissolving the ethoxylat:ed fatty amines and are also
water soluble. Examples of such water soluble organic
solvents include alkanols having in the range of about 1
to 5 carbon atoms per molecule, such as methanol, ethanol,
isopropanol and t-butanol; ketones having in the range of
about 3 to 6 carbon atoms per molecule, such as acàtone
. and methylethyl ketone; polyhydroxy compounds having in
- the range of about 2 to 6 carbon atoms per molecule, such
as ethylene glycol and glycerine; ethers having in the range
of about 2 to 6 carbon atoms per molecule, such as dioxane
and tetrahydrofuran; compounds containing both ether and
alcohol functions having in the range of about 4 to 8 car-
bon atoms per molecule, such as diethylene glycol and tri-
ethylene glycol; organic acids having in the range of about
1 to 10 carbon atoms per molecule, such as ~ormic acid,
malonic acid, acetic acid, gluconic acid, levulinic acid
and propionic acid; esters having in the range of about 2
to 6 carbon atoms per molecule, such as methyl formate,
dimethyl oxylate and dimethyl malonate; and lactones having
in the range of about 3 to 5 carbon atoms per molecule, such
~ as beta-propyl lactone and gamma-butyl lactone. Due to the
desirably low freezing point and/or high flash point (tag
~closed cup) of the resulting gelling agent the organic acids
are prefexred with acetic acid being the most preferred. -
The water soluble organic solvent useful herein is
~rrl~
preferably in liquid phase at the temperature at which it
is mixed with the ethoxylated fatty amine. Furthermore,
mixtures of the organic solvents can be used. An example
is a mix~ure of methanol ancl gluconic acid.
Tha gelling agents useful herein can be prepared by
mixing the water soluble organic solvènts with the ethoxy-
lated fatty amines for a period of time sufficient to com-
pletely dissolve the amines in the solvents. The quantity
of ethoxylated amines dissolved in the organic solvent
range i~ an amount of from about 10 to about 80, preferably
from about 50 to about 60 percent amine by weight of the
gelling agent.
~ As mentioned above, the organic solvents can be used
¦ singly, or in mixtures of solvents of the same chemical
lS class (acids with acids, ketones with ketones and the like)
or in mixtures of solvents of different chemical classes
I (acids with alcohols, ethers with ketones and the like). A
! preferred organic solvent is a mixture of chemicals of dif-
ferent chemical classes wherein at least one of the classes
¦ 2~ is an organic acid.
The ethoxylated fatty amines useful herein are very
difficult to dissolve directly in aqueous inorganic acid
solutions. However, the gelling agent of this invention,
comprising a solution of the amines dissolved in a water
soluble organic solvent, such as acetic acid, readily dis-
solves in an aqueous inorganic acid solution and substan-
tially immediately increases the viscosity of the acid
solution.
The gelling agents of the present invention cause an
~6,'Z~
. ' ' ..
increase in the viscosity oi aqueous inorganic acid solu-
tions having acid concentrations in the range from about
1 to about 25 percent active acid by weight of the solu-
tions. `~owever, acid solutions having acid concentrations
of greater than about 25 percent can be mixed with the
gelling agents of this invention and such acid solutions,
upon being reacted, will begin to exhibit a noticeable
! increase in viscosity when the acid concentration, due to
the reaction, is diminished to a value of about 25 percent.
Such increase in~viscosity continues with continued decrease
in acid concentration until the acid concentration reaches
a value in the range of from about 10 percent to about 15
percent. To this exten~ then, this invention features a
delayed gelling characteristic.
~ 15 The gelling agents of this invention will cause the
i viscosity of aqueous inorganic acid solutions having acid
¦ concentrations in the range of frbm about l to about 10
I - percent, and more particularly in the range of from about
¦ 1 to about 5 percent, to rapidly increase providing that the
I 2~ presence of dissolved salts in the acid solution is very low
i and preferably absent. In this connection, the presence of
dissolved salts in the gelled acids of this invention cause
the gels to break when the acid concentration is less than
about 10 percent and particularly when the acid concentration
is less than about 5 percent. This breaking feature, as will
. -8-
}
be further explained below, can be of particular value when
the acid gels of this invention are used to acid treat sub-
terranean formations.
The gelling agents are particularly useful in increas-
ing the viscosity of aqueous; inorganic acid solutions such
as hydrochloric acid solutions, sulfu~ic acid solutions,
phosphoric acid solutions, hydrofluoric acid solutions and
¦ solutions containing mixtures of such acids.
! In p~eparing a gelled aqueous acid solution of this
invention, the acid or mixture o acids utilized can be,
and is preferably, diluted with water to obtain an aqueous
! inorganic acid solution of desired acid concentration. A
I gelling agent of the present invention~ i.e., an ethoxylated
¦ fatty amine or mixture of such amines of the type described
¦ lS above dissolved in a water soluble organic solvent, is pre-
/ ferably combined with the aqueous acid solution in an amount
in the range of from about 0.1 to about 10, and more prefer-
ably in the range of from about 2 to 6, percent gelling
agent by weight of the aqueous acid solution. The acid solu-
tion and gelling agent are agitated or mixed for a short
period of time whereupon the viscosity of the aqueous acid
solution is increased. More specifically, some increase in
viscosity is obtained when as little as 0.1 percent gelling
agent is combined with the aqueous acid solution, and
greater amounts of the gelling agent bring about increased
_9_
.1 , . ' .
~ 2
viscosity. When the gelling agent is combined with the
aqueous acid solution in an ~nount of about 10 percent
by weight of the solution, viscosities of about 150 centi-
I poises càn be obtained.
¦ 5 Greater viscosity increase can be obtained through use
of gelling agent amounts in excess of io percent. Thus,
lO percent is not a limit on the capability of the gelling
agent to increase the viscosity of acid, but is viewed as
a working guide in view of current process economics and
the practical capabilities of currently known liquid hand-
ling and pumping e~uipment.
A gelled aqueous acid solution of this invention is
comprised of water, a water soluble inorganic acid or,mix-
ture o such acids, and a gelling agent comprised of a
solution of a water soluble organic solvent and an ethoxy-
lated fatty amine having the general formula:
~(CR2C~I20) XH
~ CX2CH2O)yH t3)
wherein: 9
- R is selected from saturated and unsaturated aliphatic
groups having in the range of from about 8 to about 22 car-
bon atoms, and mixtures thereof, and x and y each have a
- value in the range of from about 0 to about lO.
2S A pre:Eerred gelled aqueous acid solution'of this inven-
tion is comprised of an inorganic aqueous acid solution
--10--
comprising water and a water soluble inorgani~ acid or
mixture of such acids, and a gelling agent comprised of
a solution of a water solub].e organic solvent and a mix-
ture of ethoxylated fatty amines having the general
formula~
; : ~(CH2CH20) XH
R N ~
2CH2)y~ (4)
wherein: .
R is selected from saturated and unsaturated aliphatic
I groups having in the range of from about 14 to about 18 car-
¦ bon atoms and mixtures of such groups; and x and y each have
j a value in the range of from 0 to about 10 with the average
¦ .sum of the values of x and y in the mixture being in the
¦ 15 range of from about 1.8 to about 2.2.
I The most preferred gelled aqueous acid solution of
this invention is comprised of an aqueous acid solution
comprising water and an inorganic water soluble acid or a
mixture of such acids, and a gelling agent present in the
aqueous acid solution in an amount in the range of from
about 1 to about 10 percent gelling agent by weight of
the acid solution. The gelling agent is comprised of a
solution of a water soluble organic solvent, ana a mixture
of ethoxylated fatty amines present in the gelling agent
in an amount of from about 10 to about 80 percent amines
..
by weight of the gelling agent. The ethoxylated fatty
ami~es have the general formula:
, , . f CH2CH20) xH
; R - N~
5. ~ CH2CH20)yH (5)
wherein: .
R is selected from the group consisting of saturated
¦ and unsaturated aliphatic groups having in the range of
from about 16 to about 18 carbon atoms and mixtures of such
I 10 groups; and
¦ the average sum of the values o x and y in said mix-
¦ ture of ethoxylated amines is equal to 2.
In the most preferred embodiment, x and y in formula
~5) each have a value of one (1).
The gelled aqueous acid solutions of this invention
are stable over a wide temperature range and therefore will
not chemically degrade with time, even at a temperature as
high as 250F. It must be understood, however, that the
gelled acids of this invention, like other liguids, do
experience viscosity change with temperature change. Thus,
for example, with increasing temperature, the viscosity OL
these gels declines, but is regained upon decrease of tem-
perature. Thus, gels made according to this invention have
long storage life.
While~ the gelled aqueous acid solutions of this inven-
tion have a variety of uses, they are particularly suitable
, ' for carrying out acid treatments in subterranean welli formations for increasing the production of hydrocarbon
¦ fluids therefrom. When the gelled aqueous aaid solutions
I are introduced into subterranean well formation, the acid
1 5 spends by reacting wlth materials in the formation, e.g.,
limestone and/or dolomite, whereby salts (e.g., chlorides
I when HCl is used) are formed. The formation of salts in
j the spe,nt acid solution causes the viscosity of the solu-
tion to decrease. That is, as the acid'spends and salts
form, the viscosity of the spent acid solution begins to
decrease when acid concentration is in the range of about
10 to 15 percent. Thus, chemicals known in the art as
, "breakers" are not required when the gelled acid solutions
I of this in~ention are used to acid treat subterranean well
j 15 formations. The spent acid solutions, after breakingj have
viscosities in the range of from about 5 to about 15 centi-
, poises and have excellent particle suspension properties
I which facilitates the efficient clean-up of a treated forma-
tion.
In using the gelled aqueous acid solutions for carrying
j , out acidizing treatments in a subterranean well formation,
¦ an aqueous acid solution of desired acid strength is first
- prepared. For example, in carrying out acidizing or acid
fracturing treatments in limestone or dolomite formations,
aqueous hydrochloric acid solutions in concentrations in
.
-13-
~. .
the range of from about 3~ to about 28~ by weight are
often utilized. After the particular aqueous acid solu-
tion to be used has been prepared and diluted to the
desired strength, the gelling agent of the present inven-
tion is combined therewith, preferably in an amount in
the range of from a~out 0.1 to about 10 percent by weight
of the acid solution whereby the viscosity of the solution
is increased. Other conventional well formation treating
additives, such as corrosion inhibitors, non-emulsifying
agents, fluid loss additives, etc., can also be combined
with the solution. The resultant gelled aqueous acid
solution is introduced into the formation to carry out
an acidizing or acid fracturing treatment therein. After
the aqueous acid solution has become spent by reaction
with materials in the formation and thereby broken to a
low viscosi y fluid, it is produced from the formation and
the formation is cleaned up using conventional clean-up
procedures followed by placing the formation on production.
Nhen a gelled aqueous hydrochloric acid solution of
this invention having an initial acid concentration of below
about 22 percent by weight of solution spends on limestone
or dolomite to thus form calcium chloride and magnesium
chloride and cools, some water and the gelling agent can
separate out of the solution as a thick viscous phase.
Separation does not occur when the initial hydrochloric
.
; -14-
1~ ',, 2~
acid concentration is above about 22 percent by weight. In
order to prevent separation in spent solutions when acid
concentrations below about 2~ percent by weight are utilized,
calcium chloride can be addel~ to the aqueous hydrochloric
acid solution prior to gelling in an amount such that after
reaction, the spent solution contains a calcium chloride
concentration equivalent to a spent 22 percent by weight
! hydrochloric acid solu-tion. The amount of calcium chloride
required generally falls within the range of from about 1
percent to about 10 percent by weight of the spent solution.
' That is, when a gelled aqueous hydrochloric acid solution
I having an acid concentration of above about 22 percent by
weight of the solution is utilized in the treatment of sub-
terranean well formations containing calcium, no calcium
chloride is added to the live solution. When a gelled
aqueous hydrochloric acid solution at a co,ncentration of
20 percent by weight of solution is utilized, about 308
~ pounds of calcium chloride per 1000 gallons of aqueous
I acid solution are added thereto which prevents separation
1 20' at low temperatures (150F and below). When a gelled
¦ aqueous hydrochloric acid solution having a concen-trations of 15 percent by weight is utilized, about 1040 pounds of
J calcium ch:Loride per 1000 gallons of acid solution are com-
bined therewith to prevent such separation.
The following examples are given in order to further
-15-
. illustrate the gelling agent and gelled aqueous acid solu-
tions of the present invention.
' Example 1
Gelling agents of the present invention are prepared
using various mixtures o~ ethoxylated fatty amines dissolved
¦ ~ in glacial acetic acid. The gelling agents are added to
¦ aqueous acid solutions containing 15 percent by weight hydro-
I chloric-acid, and the viscosities of the resultant gels
! determined. The viscosities of the gels are apparent visco-
i 10 sities measured on a Model 35 FANN viscometer, no. 1 spring,
¦ standard bob and sleeve, at room temperature (72 - 76F) and
¦ at 300 rpm. The results of these tests are given in Table I
! below.
-16-
i
.
~ n.`6 ~
TABLE I - VISCOSITIES OF GELLED AQUEOUS
HYDROCHLORIC ACID SOLUTIONS USING VARIOUS GELLLN~ AGENTS
Ethoxylated Average Concentration concentratlon Vlscoslty
Fatty Amine Moles of of Amines Con- of Gelling of Gelled
Fatty Acid Ethylene tained in Gel- Agent in Aqueous
Origin Oxide ling Agent, ~ Hydrochloric HCl
Per Mole by Weight of Acid Solution,
of Amine Acatic Acid- Solution, cp
;:-; Amine % by Weight
Solution
... _ . . .. _ .. _ . . . _ ... _
Coconut
(Mixture of
. Chains Hav-
ing 8, 10,
1~ 12, 14, 16
:; and 18 Car-
bon Atoms) -2 33.3 9 3
Coconut
(Mixture of .
Chains Hav-
' ing 8, 10,
s 12, 14, 16
and 18 Car-
. bon Atoms) 5 33.3 9 3
~ 25 Soya (Mix-
~ ture of
Chains Hav-
ing 14, 16
and 18 Car-
bon Atoms) 2 33.. 3 9 77
Soya (Mix-
ture of
Chains Hav-
ing 14, 16
and 18
Carbon
Atoms) 5 33.3 9 3
Tallow
(Mixture
of Chains
Having
14, 16
and 18
. Carbon
Atoms) 2 33.3 9 55
Oleyl (18
Carbon
Atoms) 2 33.3 9 82
Palmityl
(16 Car-
bon Atoms) 2 50 6 52
-17-
i
~ ,r"'~
From Table I it can be seen that gelling agents con-
taining etho~ylated fatty amines derived from coconut,
soya, tallow, oleic, and palmitic fatty acids increase the
viscosity of aqueous hydrochloric acid solutions.
S The results provided in Table I also màke it clear
that ethoxylated fatty amines having an average of 2 moles
of ethylene oxide per mole of amine and containing hydrocar-
bon chain lengths of 14 to 18 carbon atoms significantly
increase the viscosity of aqueous hydrochloric acid solutions.
¦ 10 ` Example 2
A gelling agent is prepared by dissolving 3 grams of
l ethoxylated soya amines having an average of 2 moles of
! ethylene oxide per mole of amine in 6 mls. (about 7 grams)
¦ of glacial acetic acid. The approximate composition of a
, 15 commercial mixture of fatty acids from which the soya amine
is derived is as follows:
Acid % By Weight
myristic (C14) 0 to 1%
palmitic (C16) 6 to 10%
steariC (C18) 2 to 4%
oleic (C18) 21 to 29~
linoleiC (C18) 50 to 59%
linoleniC (C18) 4 to 8%
The gelling agent is combined with 125 mls. (about 134
grams) of an aqueous hydrochloric acid solution containing
- -18-
1~
15 percent by weight hydrochloric acid. After mixing, the
aqueous hydrochloric acid solution has an apparent visco-
-- sity of 95 centipoises measured on a Model 35 FANN visco-
meter, no. 1 spring, standatd bob and sleeve at room
temperature (72 - 76F) and 300 rpm.
. '
Example 3
Gelling agents are prepared by dissolving 5 grams of
ethoxylated tallow amines having an average ethylene oxide
content of 2 moles per mole of amine with various organic
solvents. The gelling agents are then each added in amounts
of 10 mls. to 200 mls. of an aqueous acid solution prepared
by combining 126.8 mls. of tap water with 73.2 mls. of a
hydrochloric acid solution containing 37~5 percent by
¦ weight hydrochloric acid to thus produce 200 mls. of 15
- 15 percent HCl solution which weighed 215 grams. The solu-
tion also contains 25 grams of calcium chloride and 0.4
ml. of a hydrochloric acid corrosion inhibitor. After mix-
ing the gelling agents with the acid solutions, the apparent
.
3 viscosities of the resulting gelled aqueous hydrochloric acid
3 20 solutions are determined using a Model 35 FANN viscometer,
no. 1 spr~ng, standard bob and sleeve at 80F and 300 rpm.
The results of these tests are shown in Table II below~
' .
' .
-19-
TABLE II - VISCOSITIES OF GELLED AQUEOUS HYDROCHLORIC ACID
SOLUTIO~S USING GELLING AGENTS CONTAINING VARIOUS ORGA~IC ACIDS
Quantity of Organic Quantity Degree of Viscosity
I Ethoxylated Solvent of Difficulty of Gelled
Tallow Organic in Dissolv- Aqueous
Amines, ml 501vent, ing Amines Hydrochloric
(grams-)~ ml in Solvent Acid
(grams) Used solutions
.
5 t 5 ) Propionic 5 (5.0) Easily 51
~10 acid ` dissolved
5 ( 5 ) Acetic 5 (5.2) Very easily 70
acid dissolved
5 ( 5 ) Formic 5 (5.9) Difficult 88
Acid - 88%
5 ( 5 ) Acetone 5 (3.9) Easily 67
dissolved
5 ( 5 ) Ethylene 5 (5.5) Easily 75
Glycol dissolved
Example 4
Gelling agents are prepared by dissolving ethoxylated
tallow amines having an average of 2 moles of ethylene
oxide per mole of amine in various organic acids in amounts
of 50 percent by weight of amine-acid solution. Each of the
gelling agents are combined with aqueous hydrochloric acid
solutions in amounts of 5 percent gelling agent by weight of
the acid solutions, and the viscosities of the resulting
gelled aqueous acid solutions are determined at various tem-
peratures. Each of the aqueous acid solutions contain 15
percent hydrochloric acid by weight, 12.5 grams of calcium
chloride per 100 cc of acid solution, and 0.2 percent by
weight o a hydrochloric acid corrosion inhibitor.
.
-20-
I TABLE III - VISCOSITIES OF GELLED HYDROCHLORIC ACID SOLUTIONS
. . AT VARIOUS TEMPERATUES USING GELLING AGENTS
-~ . CONTAINING VARIOUS ORGANIC ACIDS
¦ Organic Viscosities of Gelled Aqueous HC1 Solutions, cp1 5 Acid
- - _ .
9~F.100F 110F 120F 130F 140F 150F 160F 170F 180F
Formic 70 66 61 55 48.5 40 30 ~3.5 19 16
I Acetic 67 61 ~4 46 35 29 23 19 14.5 10.5
! Prop- 41.5 30 21.5 16 1310.5 8 6 4.5 3.5
l 10 ionic
.' .
- As illustrated in Tables II and III above, gelling agents
! wherein formic acid is used as the amine solvent achieve the
highest apparent viscosity in hydrochloric acid solutions. How-
ever, because the dissolution of ethoxylated fatty amines in
formic acid is difficult, acetic acid is praferred for use in
aFcordance with this invention.
¦ Example 5
! A gelling agent is prepared by dissolving ethoxylated
! tallow amines having an average ethylene oxide content of 2
! 20 moles per mole of amine in acetic acid in an amount of 50
percent by weight of the amine-acid solution. Various amounts
of the gelling agent are combined with aqueous hydrochloric
¦ acid solutions containing 15 percent by weight hydrochloric
' acid and 0.4 percent ~y weight hydrochloric acid corrosion
1 25 inhibitor. The apparent ~iscosities o the resulting gelled
I aqueous hydrochloric acid solutions are determined at var-
1 ious temperatures using a Model 35 FANN viscometer, no. 1
.i .
; -21-
-
spring, standard bob ard sleeve at 300 rpm. The resultsof these tests are given in Table IV below.
TABLE IV - VISCOSITIES OF GELLED AQUEOUS HYDROCHLORIC ACID
. SOLU~IONS AT VARTOUS TEMPERATUES USING VARIOUS
. 5 ; QUANTITIES OF GELLING AGENT
~ .
Percent Viscosities of Gelled Aqueous HCl Solutions, cp
~elling
Agent By
Weight of
Acid Solu- 90F 100F 110F120~F 130F 140F 150F 160F
tion
198.5 4 32.5 --~
3 37.5 35 31.5 27 21 15.5 6 2.5
4 48.5 45 `. 40 31.5 24 18 14 10
68.5 65 5û 38 31 24 19 14
i From Table IV it can be seen that by increasing the
¦ amount of gelling agent combined with an aqueous soiution,
I the viscosity of the resultant gelled solution is increased.
¦ . Example 6
! 20 A gelling agent is prepared by dissolving ethoxylated
tallow amines having an ethylene oxide content of 2 moles
! per mole of amine in glacial acetic acid in an amount of
¦ 50 percent by weight of the resulting solution. A portion
¦ of the gelling agent is combined with an aqueous hydrochloric
l 25 acid solution in an amount of 5 percent by weight of the
acid solution. The acid solution contains 15 percent by
weight of hydrochloric acid, 12. 5 grams of calcium chloride
, ,-
I -22-
per 100 cc of the solution and 0.2 percent by weight of a
hydrochloric acid corrosion inhibitor. The resulting gelled
aqueous hydrochloric acid solution is spent to 10.3 percent
by weigh~ live hydrochloric acid by reacting the solution
. . ,
with limestone. Viscosities of the spent solution are
determined at various temperatures using a-Model 35 FANN
viscometer, no. 1 spring, standard bob and sleeve at 300
rpm. The results of these tests are given in Table V.
TABLE V - VISCOSITIES OF GELLED 15% BY WEIGHT
AQUEOUS HYDROCHLORIC ACID SOLUTION AT VARIOUS TEMPERATURES
AFTER BEING SPENT TO 10.3~ BY WEIGHT LI~E ACID
.. .. . ... _ . ..
Temperature, F Vlscosity, cp
84 ` 70
100 7
110 5
120 3-5
130 2
From Table V it can be seen that when a gelled 15
percent by weight hydrochloric acid solution is spent to
a live acid concentration of 10.3 percent by weight, the
acid solution is broken to a viscosity of less than about
10 cp at a temperature of 100F.
-23-
---
~ 2fl~
Example 7
¦ A gelling agent is prepared as described in Example 6and is combined with an aqueous hydrochloric acid solution
in an amount of 5 percent by weight of acid solution. The
hydroch ~ric acid solution contains 28 percent by weight
hydrochloric acid and 0.5 percent by weight acid corrosion
inhibitor. The resulting gelled aqueous hydrochloric acid
solution is spent by reaction with limestone to various live
~ - acid concentrations, and the viscosities of such partially
3 10 spent solutions are determined at various temperatures using
a Model 35 FANN viscometer, no. l spring, standard bob and
sleeve at 300 rpm. The results of these tests are shown
in Table VI below.
. TABLE VI - VISCOSITIES OF GELLED 28% BY WEIGHT AQUEOUS~YDROCHLORIC ACID SOLUTIONS AT VARIOUS TE~E~AT~RES
; AFTER BEING SPENT TO VARIOUS LIVE ACID CONCENTRATIONS
_ _ _ _ _ . r ~ . . . . . ~ .. _ _
I Spent
Solution Viscosities of Spent Acid Solutions, cp
Live Acid
20 - Concentra-
~ tion, %
¦ - By Weight 90F 100F110F 120F 130F 140F150F 160F
19.9 19.5 20 20 19 18 16.515 13
j 1~5.9 70 66.5 60 51 40 30 5 3
10.3 45 8.5 6 5 4 3 2 1.5
~.2 6
7 From Table VI it can be seen ~hat when a gelled aqueous
3 hydrochloric acid solution of this invention containing 28
I ~
-24-
i
~ 2~
. . , `
percent by weight hydrochloria acid is spent to a live
acid concentration below about 16 percent by weight, such
spent solution is broken to a viscosity below about 5 cp
- at 150F.
Example 8
A gelling agent of the present invention is prepared
by dissolving ethoxylated tallow amines having an ethylene
¦ oxide content of 2 moles per mole of amine in glacial
! acetic acid in an amount of 50 percent by weight of the solu-
¦ 10 tion. Portions of the gelling agent are added to aqueous
hydrochloric acid solutions, and the resulting gelled hydro-
chloric acid solutions are spent by reaction with limes~one.
, The apparent viscosities of the spent solutions are measured
I on a Model 35 FANN viscometer, no. 1 spring, standard bob
and sleeve at 300 rpm. the particle or fines suspending
properties of the spent acid solutions are determined by
placing 2 grams of fines in 100 ml portions of the spent
solutions, mixing the solutions and then allowing the ~ines
to settle in the solutions for 6 hou,s. The fines remaining
suspended in the solutions after the 6-hour periods are
`¦ determined by collecting the fines by centriugation, wash-
ing, drying and weighing. The results of ~hese tests are
given in Table VII below.
-25-
1. .
~ .
~
T~BLE VII - FINE SIJSPENSION ABILITY OF
SPENT GELLED AQUEOUS ACID SOLUTIONS
. . -- . . ..
Gelled Aqueous Acid Solul:ion Solution
' Live
5. Acid Acid Suspended
. -~aicium Corro- Concen- Viscosity Fines in
, Chloride, sion tration .Of Spent Spent Acid
Grams/ Inhi- Gelling After Acid Solution
HCl, 100 cc bitor, Agent Spending, After After 6
l-Q by Acid ~ By % By % HC1 By Solution, Hours, mg/
Weight Solution Weight Weight Weight cp 100 cc
15 12.5 0.2 5 1.5 10 t74F)206
20 3~7 0.2 5 1.2 5 (80F)279
~ 28 0 0.2 5 1.4 7.5 (64F) 330
! 1S Deionized water only 5
.
~ From Table VI it can be seen that the spent gelled
i aqueous acid solutions of this invention have excellent
. fines suspension capability.
, ..
~ .
I ~ -26-
;
