Note: Descriptions are shown in the official language in which they were submitted.
This invention relates -to new copolymers soluble in
water and aqueous acids which are stable in high concen-trations
of Bronsted-Lowery acids. More particularly, it relates to a
polymer which can be used as a friction reducer in the acid
stimulation of oil or gas wells. The copolymer comprises in
a statistical dis-tribution in the macromolecule at least 5% by
weight of entities containing a formylamino functionality (A)
and at least 10% by weight of entities con-taining an amino
carbonyl functionality (B).
-N-C~ -C ~~
R NH2
(A) (B)
A well stimula-tion -technique which can be used to
enhance the recovery of oil or na-tural gas from subterranean
carbonate Eormations is called fracture-acidizing. Carbonate
formations include dolomite, limestone or other reservoir rock
containing calcarious material. Normally, fracture-acidizing
involves the injection of an aqueous acid, which may or may not
contain a proppant, in-to a wellbore at such pressures as to
exceed the formation stresses thereby inducing new Eractures in
the ;Eormation. Fractures are natural or induced cracks or
?0 channels in the formation ma-trix. S-timula-tion by this techn:Lque
ls achieved by allowing the acid -to etch the fracture Eace or the
fluid can simultaneously e-tch the fracture face and -transport
proppant to the induced fracture. In each case, a more con-
ductive channel is provided by the nonalignment of -the fracture
faces which will allow the oil or gas to flow to -the wellbore
after the injecting pressure is relieved.
-2--
When injecting an aqueous acid solution into a
wellbore, a substantial amount of injection pressure is lost
due to friction which occurs between the fluid which is in
turbulent flow and the walls of the conduit. ~s the friction
pressure increases with the rate o~ injection, less treating
pressure is hydraulically transferred to the calcareous form-
ation. However, by adding a low concentration of polymer, the
turbulent flow of the fluid at even higher rates in the condui-t
becomes laminar and as a result, the friction pressure is
greatly reduced.
Friction reducers which are commonly used in fracture-
acidizing applications induce polysaccharides such as hydroxy-
ethylcellulose, xanthan gum or hydroxypropyl guar or synthetic
polymers based on polyacrylamide. The problem with poly-
saccharide friction reducers is their lack of durability in high
concentrations of acid. Normally, polysaccharides hydrolize or
degrade in the presence of strong acids which eliminate their
friction reducing characteristics. The synthetic polyacryl-
amides also possess un-Eavorable charac-teristics. In -the
presence of strong acids, polyacrylamides readily hyclrolyze to
insolubLe degrada-tion products. These precipitated
degradation products can act as potential sources of formation
damac3e restricting the flow oE oil or CJaS to the wellbore.
The present invention provides a polymer which can
act as an improved friction reducing agent for the fracture-
acid zing of subterranean calcarious formations. This improved
polymer is acid soluble and its degradation products are both
acid soluble and stable.
--3--
~ ,- ? ,~,
Particularly, the new copol.ymers of -this invention
comprise 5 to 50~ by weight of entities of the Cormula I
-CH2-C~I-
' O (I)
N-C~-
' - H
R
10 to 95% by weight of enti.ties of the formula II
-CH2-CH- (II)
CO-NH2
and 0 to ~5% by weight of entities of the formula III
R2
-CH2 C- (III)
wherein Rl stands for hydrogen or methyl or hydroxymethyl; R2
stands for hydrogen or methyl and X stands ror cyano; the
carboxyl group or its alkali or ammonium sal-ts, the alkoxy-
carbonyl group having 1 to 6, preferably L to 3 carbon atoms;
the hydroxyalkoxycarbonyl group having 1 to 3 carbon atoms; the
N-methylolamidocarbonyl group HOCH2NH-CO-; the methylol group
of which may optionally be etherified with alkano]s having 1
to 4 carbon atoms; an alkanoylamino group having 1 to 4 carbon
atoms which may optionally be N-substituted with methylol or
a:l.]cyl having 1 to 4 carbon atoms, pyrrolidonyl-(l), phenyl,
pyridinium; th~ sulfonic acid group; a sulEoalkylamidocarbonyl
group having ]. to 4 ca:rbon atoms; the phosphonic acid group,
it being possible for sulfonic and phosphonic acid groups to
occur as alkali or ammonium salts; a radical of the formula IV
o
-COOCH2CH2-O-P-R (IV)
R4
--4--
'~ ;`:,
wherein R3 and R4 are the same or di.fferent and represent alkyl
having 1 to 4, pre:Eerably 1 or 2 carbon atoms, a radical of the
formula V
--R
-coo-cpH2p-N ,, ~1 ( V )
wherein R3 and R4 have the meanings given above and p represents
a number .Erom 1 to 4, or a radical of the formula VI
R-
-CoNH-cpH2p-N = (VI)
R
wherein R5 and R6 are the same or di.fferent and represent alkyl
having 1 to 4, preferably 1 or 2 carbon atoms and p has the
meaning given above. Also included are the quaternized moieties
corresponding to formulas ~V) and (VI) quaternized ky dimethyl
sulfate or methyl chloride.
The copolymers of this invention are statistical.
That means that the distribution of the entities :[ to III in
the macromolecule is statistical.
It stands to reason tha-t the copolymers may conta.in
several di:E:Eerent en-titi.es of the formul.a (I) and (III), for
e~ample, sev~ral di.E:Eerent radicals X. As a rule, the radicals
X bein~ present in a single macromolecule have not more -than 3,
pre:Eerably not more than 2, different meanings. Copolymers of
this kind are prepared usiny several different comonomers
carrying an X radical, as a rule not more than 3, preferably
not more than 2. Generally, -the copolymers of this invention
have K-values (cf. Fikentscher, "Cellulosechemie" Vol. 13,
page 58 (1932)) of between about 25 and 250 which correspond
to molecular weights
--5--
:~
l 3~
of about 20,000 to 15 x 106. Polymers useful as friction reducers preferably
have a K-value between about 50 and 200 which correspond to molecular weights
of about 100,000 to 4 x 106.
Preferred copolymers according ~o this invention cons;sts of
5 to 30 by we~ght of entities of the formula I.
50 to 80% by weight of entities of the formula II, and
l to 60% by weight o:E entities of the formula III.
Further, copolymers are preferred in which K2 signifies hydrogen
or methyl or X signifies the carboxyl group; the sulfonic acid group; 3-sulfo-
2-methyl-propyl-(2)-amidocarbonyl oE the formula
C,H3
-C0NH-C-CH2 S03H
CH3
an alkanoylamino group having 1 to 4 carbon atoms which may optionally be
N-substituted wi.th nlethylol or alkyl having 1 to 4 carbon atoms; pyrrolidonyl-
tl) or a radical of the formulas V and VI given and defined above, where each
acid group can also occur as Na-, K- or NH4-salt.
Copolymers into which the units of formula. I have been :introduced
by tl~c usc of N-vinrlformamide and into which the units of fornlula III have
beell introduced by the use of N-vinyl-N-methylacetamideJ N-vinylpyrrolidone,
2-ncrylam:ido-2-methylpropane-sul:Eonic acid or mi~tures thereof in the co-
polymerization process are particularly valuab:le friction reducing agents
to be employed in a process of well stimulation by fracture acidizing.
-- 6 --
The copolymers of this invention are readily soluble in
water or aqueous acid solutions and hence can be easily handled.
In Eracture-acidizing applications, the polymer can be introduced
to the acid solution as an aqueous polymer solu-tion ranging from
0.5% to 6% by weight (polymer solutions in excess of 6~ are too
viscous to manipulate), hydrocarbon dispersions con-taining
emulsifiers and 20 to 50% polymer by weight or oil in wa-ter or
water in oil emulsions containing emulsifiers and 20 to 50%
polymer by weight. The preferred system is a water in oil
emulsion containing the highest possible percentage of polymer
to produce a stable emulsion, normally 20 to 75%. Suitable oils
useful in such water in oil emu]sions include normal or branched
paraffinic hydrocarbons having a boiling point of 150C -to
250C. Due to the polymer composition and propertiesl the
polymers are effective friction reducers in concentrations of
0.06 to 0.12% polymer and from ambient temperature to elevated
temperatures exceeding 80C Eor long periods of time exceeding
10 days. Although hydrolytic degradation of the ]inear polymer
occurs on the pendant groups of -the polymer, the products oE
the degradation remain acid solub:Le and will no-t precipitate
Erom solution. Preferred acids to be used with the copolymer
are those which are normally li~uid and are inorganic or are
strong lower organic acids. Examples of acids which are
compatible with the polymer include hydrofluoric, hydrochloric,
formic, acetic, monochloracetic, dichloracetic or trichloro-
acetic acid. The most common acid used in well stimulation is
hydrochloric acid and it is normally used in concentrations
between 3 and 28~ by weight depending on treating conditions
and reservoir characteristics.
--7--
The copolymers of the invention are manufactured by copolymerisa-
ing S to 50% by weight of an N-subs-tituted vinyl formamide of
the formula Ia
CH2=CH-N-C ~' (Ia)
10 to 95gO by weight of acrylamide and O to 85% by weiyht of an
ethylenically unsaturated monomer o:E the :Eormula IIIa
R2
CH2=C-~ (IIIa)
wherein Rl, R2 and X have the meaning given above. Preferably,
5 -to 30% by weight of the vi.nylformamide (Ia) 50 to 80go by
weight of acrylamide and 1 to 60Po by weight of the monomer of
the formula IIIa are copolymerised. A most preferred range is
10 to 20go N-vinylformamide, 50 to 70% acrylamide and 10 ~o 40gO
of monomers of formula IIIa.
If copolymers are desired which have several different
.radica].s X, several different comonomers of the :Eormula IIIa,
as a rule 3, preferably 2, are used in the copolymerisation.
The copolymerisation may be performed according -to any known
polymeri.sing process in a pH range from ~ to 12, pre:~e:rably
to 9.
~0 To adjust the pH value alkaline reacting salts of
al.kali metals, e.g. alkalicarbona-tes r alkalihydrogencarbonates,
a.l.ka].iborates, di- or trialkaliphosphates, al.kalihydroxides,
ammonia or organic amines of the formula NR3 are used wherein R
is hydrogen, alkyl having 1 to ~ carbon atoms or hydroxyethyl
whereby at least one of the radicals R7 is different from
hydrogen. Preferred bases for adjusting the pH value are the
alkali compounds mentioned above, especially sodium hydroxide,
potassium hydroxide, sodium carbonate and hydrogencarbonate,
potassium carbonate and hydrogencarbonate and sodium- and
`,( ~
6~
potassium borates. Another preferred base is NH3.
The polymerisation reaction can be initiated by
energetic, electromagnetic or corpuscular radiation or by all
substances which form radicals. Accordingly, possible
polymerisatlon initiators are organic per-compounds such as,
for example, benzoyl peroxide~ alkyl hydroperoxides, such as,
for example, butyl hydroperoxide, cumene hydroperoxide, p-
methane hydroperoxide, dialkyl peroxides, such as di-tert.-
butyl peroxide, or inorganic per-compounds such as, for example,
potassium, sodium or ammonium persulphate and hydrogen peroxide,
and azo compounds such as, for example, azobisisobu-tyronitrile,
2,2'-azobis-(2-amidino propane) hydrochloride or azobisiso-
butyramide. It is advantageous to employ -the organic or
inorganic per-compounds in combination with reducing agen-ts.
Examples of suitable reducing agents are sodium pyrosulphite,
sodium bisulphite or condensation products of formaldehyde
with sulphoxylates. The polymerisation reaction can be carried
out particularly advantageously using Mannich adducts of
sulphinic acids, aldehydes and amino compounds, such as are
described ln German Patent 1,301,566.
It is known furthermore to add, to the polymerisation
ba-tches, small amounts of modera-tors, which harmonise the
course oE the reaction by flattening the reaction ra-te/-time
diagram, improve the reproducibility of the reaction and hence
lead to uniform products with extremely little variation in
quality. Examples of suitable moderators of this type are
nitrilo-trispropionylamide or hydrohalides of monoalkylamines,
dialkylamines or trialkylamines, such as, Eor example,
dibutylamine hydrochloride. In manufacturing the copolymers
of the invention, such compounds can also be present wi-th
advantageO
_g_
Furthermore, so-called regulators can be aclded to the
polymerisation ba-tches, that is to say compounds which influence
the molecular weight of the polymers formed. Usable known
regulators are, for example, alcohols such as methanol, ethanol,
propanol, isopropanol, n-butanol, sec.-butanol and amyl alcohol,
alkylmercaptans such as dodecylmercaptan and tert.-dodecyl-
mercaptan, isooctyl thioglycolate, and some halogen compounds,
such as carbon tetrachloride, chlorform and methylene chloride.
As usual, the polymerisation is carried out in an
atmosphere of protective gas, preferably under nitrogen.
The reaction may be performed in solution, in emulsion
or under the conditions of precipitative polymerisation at a
temperature of from 20 to 120C, preferably from 40 to 100C.
If water is used as a solvent for -the reaction the polymerisa-
tion is run in solution and a viscous, aqueous solution of the
copolymerisates of the present invention is obtained. The
product can be isolated either by distilli.ng off the water
from the solution or by miY~ing the aqueous solution with organic
solvents miscible with water, whereby the copolymer precipitates
2n and can be separated :Erom the liquid phase, e.g. by filtration.
It is preferred, however, to use the aqueous solution
o:E the copolyme.r obtained directly, op-tionally a:E-ter having
adjusted to a certain desired concentration.
If copolymerising is performedin an organic solvent,
as for instance in a lower alkanol, preferably e.g. in tert.-
butanol, the reaction runs under the conditions of precipitative
polymerisation. In this case the copolymer formed precipitates
from the starting solution as a solid compound during the
course of the reaction. It can be easily isolated in the
usual manner, e.g. by filtration under sucti.on and drying the
filter residue. Of course, it is also possible, and sometimes
preferred, to distill off the organic solvent.
--10 ~
Monomers which provide units oE formula I in the
copolymer of -this invention are N-vinyl formamide, N-vinyl-N-
methyl formamide and ~-vinyl-N-hydroxyme-thyL Eormamide with the
first two mentioned monomers being preferred. Acrylamide is
the monomer used to provide units of formula II in the
copolymer. ~nits of formula III are introduced into -the
copolymer by copolymerizing said formamide and acrylamide
monomers with one or more and preferably two of the following
monomers of the formula:
/R2
CH2=C,- X
wherein R2 and X have the following meanings:
R2 ' H -CH3 -H -CH3 -H
X -CN -CN -COOH~ -COOE~ -COOCH3
R -CH3 -H -CH3 -H -CH3
X -COOCH3 -COOC2H5 -COOC2H5 -COOC4H9 -COOC4Elg
R2 H -H -CE13 -H -CH3
X -COOC~H~3 -Cc2H4H -COOC2H~OH COOC3 6 -COOC3~I60H
- 11--
6~
R2 H -CM3 -H -CH3
X -CONHCH20H -CONHCH20H -CONHCH20CH3 -CONHCH20CH3
R2 H -CH3 -H
X CONHCH20C2H5 CNHCH2C2H5 -CONHCH20C4H9
K2 -H -H --H
X -NHCOCH3 --NHCOC2H5 -NEICOC3H7
R -CH 3 -H -H -H -CH 3
X -N-CHO -N-COCH3 -N-COC2H5 -N-COC3H7 -N-CHO
CH 20H CH 2 OH CH 2 OH CH 2 OH CH 3
R -H -H -H -H -H
X -N-COCH3 -N-COC3H7 -N-CHO -N-COC2H5 -N-CEIO
CH3 CH3 C2H5 C2H5 C4H9
R2 -H -H -CH 3 -H -H
X -N -COCH 3 -N~ - SO 3 E1~3
O O
R -CH 3 -H -CH 3
X -S031-1 3 2 o3H2
.2 -H -H
X -CONH-CH2S03HCL) -CNHcH2cH2cH2s3H~)
--12--
i~$~
$~
R2 -H -H
2 4 3 ~CONHCH-CH2-S03H~
CH3
R -H -H
X -co-NH-cH2cH2cH2cH2-so3 -CO-NH-CH-CH2CH2-S03EI~
CH3
R2 H -CH3
CH
X -CO-NH-C-CH2-S03H(D -CONHC2H4S03H(~
CH3
R -CH3 -CH3
CH
X -CONH-C2H4S03H(~) -CO-NH-C-CE12S03H(~)
CH3
R~ -H -CH3
O O
ll ll
X -COO-CH2CH2-0-P-CE13 -Coo-c~l2cH2-o-p CH3
CI-13 CH3
R -EI -H
O O
X -coo-cH2cH2-o-p-c2H5 -Coo-cH2cH2_o_P-CH3
C2H5 C3H7
-13-
R2 H -H
O O
,. ,.
X -coo-cH2cH2-o-p-c4H9 -Coo-cH2cH2-o-p-c3H7
CH
3 C3 7
R2 H -CH3
~ CH3 ~ CH3
X -COO-CH2CH2-N -COO-CH2CH2-N
CH3 CH3
R2 H -CH3
X -COO-CH2CH2-N'~' 2 5 -COO-CH2CH2-N
C2H5 CH3
R2 -H -H
X -COO--CH2CH2-N -COO-CH2CH2-N
C4Hg \CH3
R2~ H -CH3
~ CH3 ~ CH3
-C-CH2CH2CH2--N -COO-CH2CH2CH2-N
CH3 CH3
R2 H -CH3
X -COO-CH-CH2-N / -COO-CH-CH2-N
CH3 C2H5 CH3 CH3
--1~--
R2 H -CH3
CH~ ~CH3
O C 2C 2 ~ -CONH-CH2CH2-N
CH~ CH~
R2 H -CH3
/ 2 5 / 2 5
X -CONH-CH2CH2-N -CONH-CH2CH2-N
2 5 C2H5
R -H -H
~ C3H / 4 9
X -CONH-CH2CH2-N -CONH-CH2CH2-N
CH3 C~H9
R -H -H
C~H9 ~ CH3
X -CONH-CH2CH2-N -CNH-CH2CH2CH2-N
CH3 CH3
R -CH3 -H
X -CONH-CH2CH2CH2-N -CONH-CH-CH2-N'~ 2 5
~ CH3 2 5
R -CH3 -H -H
X -CONH-CH-CH2-N ~ ~ -CONH-C-CH2-N
-15-
_ff
R -CH3 -CH3
X -N ~ -C-cH2cH2-N / -COO-CH2CH2-N /
Since N-vinyl amldes are not stable under acidic condi-tions,
reaction mixtures containing acidic substances must be
neutralized pri.or to the polymerization such as wi-th -the
above mentioned basic comonomers.
-15a-
36~
Pre~erred monomers used to provide units of formula III in the copolymer are:
N-Vinylformamide,
N-Vinyl-N-methyl-formamide,
N-Vinyl-acetamide,
N-Vinyl-N-methyl-acetamide,
N-Vinylpyrrolidone,
Acrylic acid, alkali or ammonium salts of acrylic acid,
C,H3
C~12=CH-CONH-C-CH~-S03H or alkali or ammoniwn salt thereof,
C~13
CH3 ~ CH3
CH2=CH-CONH-C-CH2-N , or
C~13 CH3
CH2=CH-COO-CH2CH2-N~
CH3
The above described copolymers are believed to be novel copolymers
except where X in formula III is the sulfonic acid group, the sulfoalkylamido-
carbonyl group and salts of such groups (cf. United States Patent 4,048,077).
The copolymers disclosed herein are also useful in the gelling oE
acid solutions useful for example in acid :Eracturing.
The present invention will now be further described, by way of
example only, with reference to the accompanying drawings, in which:
Figures l, 2 and 3 graphically ind:icate fluid low rates oF
two dif:Eerent solutions through three pipe systems respectively, against
pressure differential of pressures at opposed pipe ends in a system.
~ -16-
The following working examples demonstrate the mai~ufacture of the
copolymers of this invention~
The abbreviations used in the Examples and in the included tables
have the :Eollowing meanings:
AM acrylamide
VlMA: N-vinyl-N-methylacetamide
AMPS: 2-acrylamido-2-methylpropane sulfonic acid where the exponent
1 signifies the ammonium salt,
2 slgnifies the salt with dimethyl-~-hydroxyethylamine~
3 signifies the potassium salt and
~ signifies the sodium salt.
AS acrylic acid
MAS methacrylic acid
Mr~M N-methylol-acrylamide
VSSNa: sodium salt of vinylsulfonic acid
~MVA N-methylol-vinylacetamide
VIA: vinylacetamide
VIFA: vinylformamide
VIMFA vinyl-methyl-formamide
2~ MVIFA: N-methylol-vlnylformalllide
MVIA: N-metllylol-vinyl acetamide
VPA: vinylphosphonic acid
A a~ lol~iu~ )eroxidisulfate
B: a combination of ammoniumperoxidisulfate ~ dibutyl-ammonium hydro-
<~
-~ COOH
C: azo-isobutyronitrile.
Example l
Into a 2 l reaction vessel placed in a water ba-th and
fitted with a mechanical stirrer, reflux condensor 7 dropping
funnel and yas-inlet are placed 400 mls of deionized water and
17.7 mls of a 25~ by weight aqueous solution of ammonia. While
introducing a slow stream of nitrogen, 9.3 g of acrylamido-
methylpropane sulfonic acid are added and as soon as a clear
solution is obtained 60 g of acrylamide, 18.6 g oE N-vinyl-
pyrrolidone and 1~.7 g of N-vinylformamide are admixed. The pH
value of the solution is 6.5. The reaction mix-ture is heated to
50C and the polymerization is triggered by addition of 5 mls of
a 20% by weight aqueous solution oE ammonium peroxydisulfate~
After an induction period of about ~0 minutes the reaction
starts, the temperature rises to 65C and the reaction mixture
becomes viscous. The batch is then heated to 80C and kept at
this temperature for two hours. After recooling to room
temperature, a high:Ly viscous solution is obtained.
Example 2
Into a ' l reaction vessel placed in a water bath and
~() fi.tted with a mechanica:L stirrer, reflux-condenser, clropping
funnel and gas-inlet are placed 500 ml of tert~ butanol and
suspended therein 20 g of ~MPS while stlrring. Then 2.2 1 of
N~I3 gas are introduced and 65 g of acrylamide and 15 g of ~-
vinylEormamide are added. While introducing a stream of nitrogen
the reaction mixture is heated up to 50C and l.0 g of
azoisobutyronitrile is added. After an induction period of
some minutes the polymerisation starts. The reaction temperature
rises up to 81C and the polymer precipitates. The reaction
mixture is kept for another two hours at 80C during which time
it becomes a viscous suspension. The polymer may be isolated
by filtration under suction and drying under reduced pressure
-18-
t
at 50C. It is also possible to isolate the polymer by
distilling off the solvent under reduced pressure. The polymer
obtained represen-ts a white light powder easily soluble in
water. The K-value according to Fikentscher is 148.
According to the procedure described in the preceding
examples the copolymers o:E the following Tables 1 and 2 may be
prepared.
-18a-
~ -s Table I
`;~`
Concentration of monomers (% by ~eight)
Example AM AS AMPS VIFA VIMFA VIi~ VIA ~l MVIA l~iIFA further K reaction concen- pH cata- starting
No additives value medium tration value lyst tempera-
(% by ture C
weight)
3 65 20 15 155 water 18 5 A 50
4 65 20 15 129 " 18 8.4 A 50
193 " 18 4.8 A 50
6 65 20 15 149 " 18 8 A 50
7 65 20 15 169 " 18 4.8 A 50 .
8 65 20 15 124 " 18 8.3 A 50
9 65 20 15 154 " 18 4.9 A 50
122 " 18 8.0 A 50
11 90.6 9.4 130 " 21 10 B 20
12 81.1 18.9 111 " 21 9.8 B 20
13 81.1 9.4 9.4 140 " 21 7.8 B 20
14 65 20 15 208.5 " 18 8.3 A 40
188 " 18 4.9 A 40
16 65 20 15 199 " 18 8.2 A 40
bG I
.,1 0
~ ) O O O O n In o o
c~
V)
~n ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ¢ ~ c~ c~ ¢
;d ~
O ~
C;~ O C'J
~ ~ ~ c~ r~ GO r~ c,o r~ I-- o r~ n
O
,D bl)
c~ ,n n n oo c~ c~ c~ oo c~ ~ ~ o m
h O~o ~ ~ c~ ~ ~ ~ ~ ~ ~ ~ c~
o
,~ - h
a
~ .~_ -- -- -- -- _ _ _ _ _ _ _ _
~ 3
S~
n n
.
O ~ .n ~ c~ r~ o n ~
~ ~ n ~ o o C~l ~co c~ ~ r~
U~
rl ._
~, _
rl O
.9
i
¢
¢
¢
c
~3 ¢
~ ~ C~
rQ
o\o
~ n n
¢
o
¢
O L~ n In c~o ~ n rt n n
,
L~
~ O O a~
. . _ .
CQ O O O O O O O
~ I C`l C~l ~ ~
Z~ n o o n n n n n ~r~ o ~ n n
, . ..... .. . .. .... . .. ... ... . . .. ... . .. . . . .. . ...
a~
o ~ c~ a~ O ; ~ n `D r~ x cJ. o
z ~ ~ ~ ~ ~ ~ ~ ~ ~ c\l ~ c~
L
2 0 -
~ Table I
Concentration of monomers (% by ~:eioht~
Example A~i AS AMPS VIFA VIMFA VI~iA VIA ~`V~ iVIA ~VNIFA further K reaction concen- pH cata- starting
No additives value medium tration value lyst tempera-
(% by ture C
~eight)
31 71.7 9.4 18.9 136 water 21 8.0 B 35
32 71.7 9.4 18.9 143 " 21 8.3 B 35
33 55 15 20 188 " 18 8 A 40
34 61 14 25 174 " 18 8.2 A 40
56.8 13.2 30 171 " 18 8 A 40
36 65 15 20 144 " 10 8 A 40
37 61 14 25 139 " 10 8 A 40
38 56.8 13.2 30 131 " 10 8 A 40
39 56.8 13.2 30 139.5 " 10 8.1 A 40
71.7 9.4 18.9 borax188 " 21.6 8.4 B 35
41 71.7 9.4 18.9 " 149 " 21.6 7.9 B 35
42 65 20 15 151 " 10 7.3 A 40
43 65 20 15 143 " 10 7 A 40
44 80 20 borax 92 " 21.6 7.5 B 35
- ~ s
~able I
Concentration of monomers (% by weight~
Example A~ AS AMPS VIFA VIMFA ~VI.~l~ VIA ~M MVIA MVIFA further K reaction concen- pH cata- starting
. additives value medium tration value lyst tempera-
(% by ture C
weight
70.5 9.4 20.1 borax 131 water 21.6 7.5 B 35
46 60 20 15 5 186 " 17 4.8 A 40
47 60 20 15 5 172.7 " 17 4.8 A 40
48 60 20 15 5 210.9 " 17 4.8 A 40
49 60 20 15 5 198 " 17 4.8 A 40
164 " 17 4.7 A 40
51 51.8 i3~2 30 5 132.8 " 10 4.8 A 4Q
52 51.8 13.2 30 5 131.5 " 10 4.8 A 40
53 51.8 13.2 30 5 117.4 " 10 4.8 A 40
54 65 20 15 148tert. 20 9.1 C 50
butanol
178 " Z0 9.1 C 50
56 65 20 15 142 " 20 9.0 C 50
57 65 20 15 176 " 20 9.1 C 50
58 65 20 15 131.5 " 20 9.2 C 50
Table I
Concentration of mono3r.ers ~% by weight)
Example AM AS AMl'S VIFA VIMFA VIMA VIA MAM MVIA MVIFA further K reaction concen- pH cata- starting
Noadditives value mediurn tration value lyst teinpera-
(% by ture C
~eight)
59 65 20 15 157 tert . 20 8.8 C 50
butanol
65 20 15 141 " 20 8.9 C 50
61 60 20 15 5 144.5 " 17.5 9.0 C 50
62 60 20 15 5 179.5 " 17.5 9.6 C 50
N 63 60 20 15 5 177 17.5 9.3 C 50 ~ 3
64 60 20 15 5 181.5 " 17.5 8.9 C 50
60 20 15 5 146.2 " 1~ .5 8.6 C 50
66 60 20 15 5 182.7 " 17.5 8.9 C 50
Example 67
~ nto a 500 ml reaction vessel placed in a water bath
and fit-ted with a mechanical stirrer, reflux-condenser, dropping
funnel and gas-inlet is placed a solution of 0.23 g of sorbitan
monolaurate, 1.09 g of sorbitan monostearate, 0.14 g of sorbitan
mono-oleate and 3.61 g of polyoxyethylene sorbitan monostearate
in 56.4 g of Exxon's hydrocarbon Norpar* ]3, a paraffin
straight-chain hydrocarbon. The solutlon is degassed with
nitrogen and heated to 60C. Then a solution containing 33.6 g
of acrylamide, 5.4 g of AMPS, 6.6 g of N-methyl-~1-vinylacetamide,
G.6 g of N~vinylEormamide and 7.8 g of N-vinyl pyrrolidone is
added to 78.8 g of deionized wa-ter containing 2.6 ml of 10%
sodium hydroxide solution. The pH value was 7.4. Then 23 mg of
2l2'-Azobis-(2-Amidinopropane) hydrochloride is added to the
aqueous solution. This solution is added to the hydrocarbon
solution with moderate stirring forming a milky white emulsion.
As the temperature approaches 60C., the stirring is reduced to
approximately 60 revolutions per minute. After an induction
period of 10 minutes, the temperature begins to rise. At
approximately 80C., the emulsion becomes transparent and
stirring is increased. The peak temperature is 97C. After
cooling to 80C., the temperature is held for two hours yielding
a stable emulsion containing 30~ active polymer.
Example 6~3
67 g of Exsol* D, a deodorized kerosene boiling
between 190 to 240C., sold by Esso Chemie of Germany are
introduced into a l-liter polymerization flask and heated to a
-temperature of 60C., with weak stirring, 0.27 g of sorbitan
monolaurate, 1.3 g of sorbitan monostearate, 0.17 g of sorbitan
*Trade ~ark
-23-
monooleate and 4.3 g of polyoxyethylene sorbitan monostearate
being successively added and dissolved. Wi-th further weak
stirring a stream of nitrogen is passed into the solution and
the temperature is adjusted to 60C. 94 ml of water are given
into a separate vessel and 6.4 g of AMPS, 44.8 g of acrylamide,
9.2 g of vinyl pyrrolidone and 10.6 g of N-vinyl formamide are
added and dissolved while stirrlng. This solution is adjusted
to a pH value of 8 to 10 by the dropwise addition of 10%
strength aqueous solution of sodium hydroxide, 0.1 g of ammonium
persulfate being subsequently added. This monomeric solution is
then emulsified in the organic phase via a dropping funnel in the
reaction flask, with rapid stirring. The polymerization reaction
starts after approximately 30 minutes, which is recognizable by
a rise in the temperature. In the course of 15 minutes the
reaction temperature rises to 80-goc. The polymerizing reaction
having faded out, the solution is heated for another two hours at
80C. A stable emulsion having a polymeric content of 30% by
weight is obtained. The molecular weight of the polymer is
95,000.
Example 69
1.85 g of sorbitan monostearate are dissolved in a
technical isomeric hydrocarbon solvent Isopar* M having a boiling
range of from 200 to 240C. sold by Exxon Corporation. This
solution is introcluced into a 2~1iter reaction vessel fittecl
with a mechanical stirrer, thermometer and gas inlet for
nitrogen. A solution of monomers is produced by dissolving
*Trade Mark
-24-
~ ;~
25.0 g of acrylamide, 3.7 g of acrylic acid and 9.2 g of vinyl
formamide in 40 ml of deionized water and the pH value of the
mixture is adjusted to 8.5 by adding a 20% aqueous solution of
sodium hydroxide. Then the aqueous monomeric solution is
slowly added to the organic sorbitan monostearate solution while
vigorously stirring and the air in the reaction vessel is
replaced by nitrogen. 0.07 g of 2,2'-Azobis-iso-butyronitrile,
dissolved in acetone, are added to the emulsion of the monomers
and then the reaction vessel gently heated to 60C. while
stirring. The polymerizing reaction was finished with 2.5 hours
resulting in a stable emulsion of the copolymer.
Example 70
67 g of Isopar M are introduced into a l-liter
polymerisation flask and heated to a temperature of 60C., with
weak stirring, 0.27 g of sorbitan monolaurate, 1.3 g of sorbitan
monostearate, 0.17 g of sorbitan monooleate and 4.3 ~ of poly-
oxyethylene sorbitan monostearate being successively added and
dissolved. With further weak stirring a stream of nitrogen is
passed into the solution and the temperature is adjusted to 60C.
9~ ml of water are given into a separate vessel and 12.8 g VIMA,
39.8 g of acrylamide, 12.0 g of vinyl pyrrolidone and 6.4 g oE
N-vinyl formamide are added and dissolved while stirring. This
solution is ad~usted to a pH value of 8 to 10 by the dropwise
addition of 10~ strength aqueous solution of sodium hydroxide,
0.1 g oE ammonium persulfate being subsequently added. This
monomeric solution is then emulsified in the organic phase
via a dropping funnel in the reaction flask, with
-25-
\
rapid stirring. The polymeriza-tion reaction star-ts af-ter
approximately 30 minutes, which is recognizable by a rise in
the temperature. In the course of 15 minu-tes the reaction
temperature rises to 80-90C. The polymerizing xeaction having
faded ou-t, the solution is hea-ted for another two hours a-t 80C.
A stable emulsion having a polymeric content of 30 percent by
weight is obtained. The molecular weight of the polymer is
95,000. Alon~ the lines ~iven in Examples 58 to 70 -the produc-ts
of the following Table III can be produced which may be used as
valuable friction reducer for aqueous acids.
Table III
AM ASAMPS VF ~/rel. k-value
20 15 6.59 148
20 15 10.05 165.8
20 15 9.36 163
20 15 5 NMA 17.27 186
20 15 5 NMVA11.97 172.7
20 15 5 NMVF11.0 169.4
20 ]5 5 NMVF 7.0 151.2
20 15 5 NMVF9.47 164
5 NMA 35.0 210.9
5 NMVF24.43 198
51.8 13.2 30 5 NMA 4.66 132.8
51.8 13.2 30 5 NMVA4.53 131.5
51.8 13.2 30 5 NMVF3.41 117.4
51.8 13.2 30 5 NMA 12.16 173
51.8 13.2 30 5 NMVA 9.1 162.32
51.8 13.2 30 5 NMVF 9.3 163.16
5 NMA 31.~4 207.4
51.8 13.2 30 5 NMVF3O57 119.0
20 VIP29.3 204
All amounts given in Table III are par-ts by weight.
-26-
Example 71
To demonstrate the friction reducing properties of the
polymer described ln Example 1, an experiment was conducted
comparing an acidified polymer solution to a 7 1/2% hydrochloric
acld solution. The experimental data was obtained from a flow
loop. This device passes a Eluid through a series of pipes of
known length and diameter at selected rates while the exerted
pressure is measured at both ends of a given pipe. Knowing
the fluid rate and pressure diEEerential, the friction pressures
of various Eluids can be graphically shown. The initial
experiment was conducted using 55 gallons of 7 1/2~ hydrochloric
acid and 760 ml oE a common corrosion inhibitor at pump rates
of 10 to 15 gal./min. on a 0.364" I.D. pipe, 5 to 45 gal./min.
on 0.493" I.D. pipe, and 5 to 120 gal./min. for 1.049" I.D.
pipe. Then, 224 g of the polymer prepared in Example 1 was
added to the 7 1/2~ acid solution yielding a 0.1~ (by weight)
polymer solution. The experiment was repeated and -the data are
shown in Figures 1, 2 and 3 for 0.364", 0.493" and 1.049" I.D.
pipe, respectively.
Example 72
To demonstrate the acid solubility of the copolymer of
this invention, an experiment was conducted comparing -this
copolymer to currently marketed Eriction reducers. Into three
8 ounce jars was added 200 mls of 15~ hydrochloric acid. Into
jar 1 was added 2.0 g of the polymer prepared in Example 2 while
in jar 2 was added 2.90 g of an emulsified friction reducer,
LFR-l, and in jar 3, was added 3.2 g of a commonly used
emulsified friction reducer, LFR-2. LFR-l and LFR-2 are
-27-
'~
copolymers of acrylamide and acrylic acid with molecular weight
of 500,000 to 2,000,000. The polymer content of -the emulsions
LER-~l and LFR-2 are unknown, however, it is believed that
differences lie ln the amount of active polymers, types of
emulsiflers and ratios of comonomers. Each sample was heated
-to 60C. Eor 24 hours. In jar 1, the copolymer of -this
invention was completely soluble. In both jars 2 and 3, a
white insoluble plug had formed. The solids were filtered
under suction and washed with water followed by methanol. The
Eiltered solids were then dried at 40C. under reduced pressure
overnight. The final masses are shown in Table IV.
Table IV
Initial Weight of Percent
Sample Weight Insoluble Material Insoluble
Copolymer of this 2.0 g 0 0
lnventlon
LFR-l emulsion 2.90 g* 1.15 g 39.6
LFR-2 emulsion 3.20 g* 0.82 g 25.6
*It shou:ld be noted that the weight is based on the emulsion
no-t polymer.
Example 73
A gas well in West Texas is se:Lected to Eracture-
acidize. The producing interval is 3,620 to 3,680 Eee-t. At
this depth the bottom hole static temperature is 110F. while
the formation permeabili-ty averaged 0.15 millidarcy. The
tubing size is 2 3/8 inch, ~.7 lb. and the well productivity
prior to treatment is 6,000 ft.3/day. The fracture-acidizing
fluid is prepared by blending 1,000 gallons of 28% hydrochloric
acid with 9,5000 gallons of fresh water. In addition, 21
-2~3-
'\`~\
64~
gallons (0.2% by weight) of the emulsion prepared in Example 3
is added to the acidic solutlon. The fluid is injected into
the well at 10 barrels/min~ at a pressure of 4,500 psi. After
25 minutes, the pumping is terminated and -the well is shut in
to allow the acid to react. After 60 minutes the wellhead
pressure is relieved and the well is placed back into a flowing
status. The well productivity is tested and found to be
significantly improved.
-29-
