Hydrocarbon gels useful in formation fracturing

This invention relates to improved hydrocarbon gels finding use in the fracturing of formations which produce petroleum and other hydrocarbons. The gelling agents comprise combinations of ferric salts, selected orthophosphate esters, a low molecular weight amine such as triethonolamine or triethylamine, and a surfactant.

TECHNICAL FIELD 
This invention relates to improved hydrocarbon gels which find use in 
petroleum producing formation fracturing. In particular it relates to the 
use of a defined class of gelling agents for hydrocarbons which provide 
excellent results in such fracturing. 
The gelling agents are combinations of ferric salts; low molecular weight 
amines, and selected orthophosphate esters with or without optional 
surfactants. 
BACKGROUND OF THE INVENTION 
The development of the use of gelled hydrocarbons as fracturing fluids is 
reviewed by Weldon M. Harms in a chapter entitled "Application of 
Chemistry in Oil and Gas Well Fracturing", at pages 59-60of the book 
"Oil-Field Chemistry (ACS Symposium #396-1988)" published by the American 
Chemical Society in 1989. The basic technique of formation fracturing 
involves the injection of a fracturing fluid down the well bore, which is 
usually cemented in place and at least 0.3 mile long, and then through 
horizontal holes in the steel pipe, or casing, of the well, to obtain 
access to the subterranean formation. The fracturing fluid is under high 
pressure and must be able to survive the severe shear forces caused when 
flow is forced through the casing perforations of perhaps 1/4 to 1/2 inch 
in diameter, as well as the shear forces encountered at the leading edge 
of the fracture. Whatever chemical additives are used to influence 
viscosity, induce gel formation, stabilize against resident chemicals, pH 
or temperature conditions in the formation, inhibit scale formation or 
corrosion, or inhibit paraffin deposition, for example, must also be able 
to withstand the shear forces and other inhospitable conditions of use. 
Most commonly available liquids typically are viscosified before they are 
particularly effective in carrying the large quantities of proppants 
widely used in the fracturing process. 
When hydrocarbons are used in the fracturing process, they are commonly 
treated to increase their viscosity. As reviewed by Harms, an early 
viscosifying agent was napalm, an aluminum soap of fatty acids. Aluminum 
salts of orthophosphate esters were introduced in the late 1960's, 
followed by the suggestion of the use of Fe.sub.3 O.sub.4 for combination 
with the orthophosphate esters, in Monroe U.S. Pat. No. 3,505,374. While 
many other combinations of metals and other materials have been suggested 
as viscosifying agents, aluminum crosslinked orthophosphate esters are 
still, according to Harms, the most widely used. 
The aluminum compounds present problems, however, particularly where any 
significant amount of water is present. They generally will not 
satisfactorily perform the desired crosslinking function in the presence 
of more than about 1200 ppm of water, nor where the pH is outside a 
relatively narrow range. Moreover, an inadvertent excess of aluminum 
compound treatment is detrimental to the desired performance because the 
aluminum compound itself adversely affects the pH. The iron provided by 
ferric salts as in the present invention, on the contrary, permits 
operation in wider pH ranges. 
In describing a gel which can be used as a pig in a pipeline, Jaggard et al 
in U.S. Pat. No. 4,003,393 recite the possibility of iron as one of a 
number of metals to combine with a class of aliphatic substituted 
orthophosphoric esters. No other qualifiers are used to describe the iron, 
however. 
In U.S. Pat. No.4,153,649, Griffin proposes reacting a pentavalent 
phosphorous compound with a class of hydroxy ethers before employing the 
metal salt. Among the metal salts he uses is ferric nitrate, but he 
further requires a "separate source of base" to be used with the hydroxy 
ether modified phosphates, as spelled out in column 4, lines 55-58 and 
column 11, lines 37-68. 
Monroe, in U.S. Pat. No. 3,505,374, uses a gelling agent for hydrocarbons 
characterized as a ferroso-ferric salt of an alkyl oleyl diester of 
orthophosphoric mono acid. The iron compound is further described as 
magnetite, or Fe.sub.3 O.sub.4. He suggests this combination for 
fracturing subterranean oil-bearing formations, but says none of the 
"other oxidized forms of iron including ferrous and ferric oxides and 
hydroxides, chlorides, sulfates and nitrates" (col 3, lines 2-4) yielded a 
gel as obtained with the magnetite. 
Burnham, in U.S. Pat. No. 4,200,540, describes a large class of phosphates 
and phosphate esters which he mixes with aluminum salts, aluminates and 
aluminum metal. He chooses combinations of the materials as a function of 
various down-hole temperatures. No mention is made of iron salts; the 
reference is cited mainly for its comprehensive description of the 
phosphates deemed to be useful. See also Burnham's U.S. Pat. No. 
4,316,810. 
SUMMARY OF THE INVENTION 
We have found that ferric salts can be very advantageously used in the 
gelling of hydrocarbons, particularly for use in formation fracturing, 
rather than aluminum compounds, for combination with orthophosphate 
esters. 
The ferric salt has the advantage that it can be used in the presence of 
large amounts of water, such as up to 20%. One of the advantages of 
fracturing with hydrocarbon gels is that some formations may tend to 
imbibe large quantities of water, while others are water-sensitive and 
will swell inordinately if water is introduced; our invention permits one 
to use a hydrocarbon gel in areas where water may cause trouble not only 
with the formation itself, but with the fracturing agent or the gelling 
agent. Also, it is not adversely affected by commonly used alcohols, such 
as methanol and isopropanol. In addition, it can be used in broad ranges 
of pH, yet the linkages it forms can still be broken with gel breaking 
additives conventionally used for that purpose. In addition, ferric salts 
such as ferric sulfate crosslink rapidly and can be made to link even more 
rapidly with the use of surfactants and/or alkaline or caustic agents such 
as potassium hydroxide. This continuation-in-part application is directed 
specifically to combinations of the ferric salts, particularly ferric 
sulfate, with low molecular weight amines such as triethylamine and 
triethanolamine, referred to herein sometimes interchangeably as TEA. 
Other low molecular weight amines useful in our invention are within the 
generic description found elsewhere herein and include monoisopropanol, 
butyl amine, and hexyl amine. 
When dissolved in a hydrocarbon such as gasoline, diesel oil, crude oil, or 
kerosene, the ferric salt in combination with orthophosphate esters as 
defined below will cause the hydrocarbon to gel. The gel is generally 
stable to heat, and the degree of gelling can be controlled by the 
concentration of orthophosphate ester in the fluid.

DETAILED DESCRIPTION OF THE INVENTION 
The phosphate ester which we use is advantageously added first and mixed 
with the Diesel fuel or other hydrocarbon to be used as the fracturing 
agent, generally in amounts from about 0.3% to about 1.5% by weight, based 
on the total. Then the ferric salt is added in amounts to provide 
preferably about one mole of ferric iron for each mole of phosphate or 
phosphate ester. In this manner, the process materials can be prepared 
more or less continuously, as opposed to the batch approach sometimes used 
in the past. More broadly we may use any amount of ferric salt which is 
effective to make a gel with the phosphate ester. This will be 
accomplished at about 0.1 to about 1.5 mole of ferric iron for each mole 
of phosphate ester, preferably 0.8:1 to 1.2:1. 
A low molecular weight amine is also employed. The low molecular weight 
amine is preferably one of the formula N(CH.sub.2 CH.sub.2 R).sub.3 where 
R is H or OH, but may be any amine of the formula H.sub.3--n N(CH.sub.m 
H.sub.2m R).sub.n where m is an integer from 2-6, and n is an integer from 
1-3, the alkylene group represented by C.sub.m H.sub.2m may be linear or 
branched. Further examples of such compounds are diisopropylamine, 
triisobutylamine, and pentylamine. 
The low molecular weight amine is advantageously first mixed with the 
ferric salt in a molar ratio of ferric salt to amine of about 0.25:1 to 
about 6:1. This is accomplished by thorough blending. 
We have also found that surfactants have the effect of decreasing the time 
for crosslinking. Generally, in the absence of a surfactant, our 
combination of materials will crosslink in about two minutes at room 
temperature; when a surfactant is used also, this time is significantly 
reduced, and in the presence of our preferred class of surfactants, it is 
reduced to the neighborhood of twenty seconds, as determined by viscosity 
tests. About 0.1% to about 10% (based on the gelling agent) of surfactant 
is frequently advantageous also. 
The phosphate derivatives we use are described in the literature as 
orthophosphate esters. They are similar to those used by Burnham in U.S. 
Pat. Nos. 4,200,540 and 4,316,810, Griffin in U.S. Pat. Nos. 4,174,283 and 
4,153,649, and Harris et al in U.S. Pat. No. 4,622,155, having the 
structural formula 
##STR1## 
where R is a straight or branched chain alkyl, aryl, alkoxy, or alkaryl 
group having about 6 to about 18 carbon atoms and R' is hydrogen or an 
aryl, alkaryl, alkoxy, or alkyl group having up to about 18 carbon atoms. 
This structural formula will be referred to elsewhere herein as HPO.sub.4 
RR'. 
In the fracturing fluid, the iron from the ferric sulfate or other ferric 
salt forms linkages with the available oxygen, generally in more than one 
phosphate group, thus forming small chains which cause the hydrocarbon to 
gel. 
It has been demonstrated in the laboratory that our invention may be used 
to form hydrocarbon gels, and that the gels can be broken in a manner 
familiar to persons who work with hydrocarbon gels in the field such as by 
the addition of common alkaline materials. In the following examples, and 
in the results reported in Tables I-IV, the procedure was to employ a 
laboratory Waring blender with a voltage regulator set at 25. 300 ml of 
Diesel oil was placed in the blender and the power turned on. The 
phosphate ester preparation was first added and after it was blended, the 
ferric salt solution was introduced by pipette. The time was recorded from 
the initial introduction of the ferric compound to the gel point, 
determined by a concave shape of the material in the blender. Blending was 
continued to determine the time required to reach maximum gel, which was 
estimated to be the first sign of conversion of the shape of the material 
to convex instead of concave. The blending was then stopped and the 
material transferred to a sample container, observing the consistency of 
the gel. Brookfield viscosity readings were then taken as shown in the 
Table I. 
In the examples below, Composition M is about two-thirds phosphate ester of 
the above formula HPO.sub.4 RR', together with 10% triethanolamine, and 
solvent. Composition L contains about two-thirds phosphate ester HPO.sub.4 
RR', together with 10% triethylamine, and high flash aliphatic solvent. 
Composition K is two-thirds of the same phosphate ester and 15.5 g 45%KOH, 
also with a solvent. Composition F contains about 27% ferric sulfate, 
together with ethylene glycol, mixed surfactants, 10% triethanolamine, and 
water. In each case, the amounts of composition M shown were added first 
to the Diesel oil and blended; then the amount shown of Composition F was 
added and blended. Results are presented in Table I. 
TABLE I 
__________________________________________________________________________ 
Ex M F X-link 
Invers 
Spindl 
5 min 
30 min 
60 min 
__________________________________________________________________________ 
1 3 ml 3 ml 
20 sec 
30 sec 
#3 2500 
-- 3890 
2 3 ml 3 ml 
20 sec 
30 sec 
#3 2300 
-- 3460 
3 3 ml 3 ml 
25 sec 
35 sec 
#3 2375 
-- 3400 
4 3 ml 3 ml 
30 sec 
60 sec 
#4 6360 
11000 
13800 
5 3 ml 3 ml 
30 sec 
55 sec 
#4 7320 
12300 
13500 
6 3 ml 3 ml 
45 sec 
none at 180 sec 
7 2 ml 2 ml 
60 sec 
150 sec 
#4 -- -- -- 
8 3 ml* 
3 ml 
20 sec 
55 sec 
#3 10000.sup.& 
-- 13000.sup.& 
9 6 ml* 
3 ml 
15 sec 
30 sec 
#4 -- -- 21500.sup.& 
10 2 ml.sup.$ 
3 ml 
20 sec 
35 sec 
#4 13650.sup.& 
-- 13850.sup.& 
__________________________________________________________________________ 
*Composition L used instead of M 
.sup.$ Composition K used instead of M 
.sup.& rotation at 10 rpm 
Persons skilled in the art will recognize from Table I that the 
formulations make excellent gels. 
In a separate experiment, it was shown that the order of addition of the 
phosphate ester solution (sometimes herein called the gellant) and the 
ferric sulfate component (activator) is not important. In this experiment, 
6.16 g deionized water and 1.3 g ferric sulfate were added to 85.95 g 
Diesel oil and mixed with the blender; then 0.4 ml of phosphate esters of 
the formula HPO.sub.4 RR' was added and inversion took place in about one 
minute. 
The data in Table II demonstrate that our hydrocarbon gel former will 
operate in the presence of significant amounts of water; indeed the 
viscosity increases with increasing amounts of water. In this experiment, 
an initial mixture was made as above with 4 g of gellant and 10 g of 
activator in about 250 g of Diesel oil. Water was then added incrementally 
and the viscosity measured immediately. 
TABLE II 
______________________________________ 
Cumulative Viscosity 
Water, % (511 sec.sup.-1) 
______________________________________ 
0.65% 1 cp 
1.27% 6 cp 
2.16% 12 cp 
2.78% 19 cp 
3.50% 26 cp 
4.18% 29 cp 
5.06% 30 cp 
6.17% * 
7.58% * 
8.38% * 
10.41% * 
14.78% * 
20.2% * 
______________________________________ 
* Dial bouncing and unreadable; excellent lipping gel observed. 
Additional tests were made as shown in Table III, which records the 
viscosities achieved by various combinations within our invention. 
TABLE III 
______________________________________ 
ml M ml F cps ml other comment 
______________________________________ 
3 3 13,800 
3 3 13,500 
2 2 (bouncing dial) 
a 3 13,000 
b 3 21,500 6 TEA* 
c 3 13,900 2 KOH 
3 3 15,000 
3 3 16,000 
d 3 5,800 low acid value PE 
e 3 9,400 high acid value PE 
f 3 20,800 KOH 
g 3 11,300 1/2 KOH 
3 3 7,000 3/4 KOH 
3 3 8,600 no TEA in F 
3 3 8,700 KOH in M; no TEA in F 
3 3 14,500 KOH in M; no TEA 
3 3 13,400 
3 3 -- 4400 cps @ 20 rpm 
i 3 9,300 
j 3 20,400 
2 ml 3 12,700 
2 ml 1.5 8,300 
k 1.5 10,000 
1 1.5 12,500 2 ph est; KOH; 1.5 Fe 
3 3 14,700 
m 3 20,000 
3 3 23,000 0.25 g Na.sub.2 CO.sub.3 
n 3 21,000 
o 3 18,400 0.25 g NA.sub.2 CO.sub.3 
3 3 19,500 0.5 g CaCl.sub.2 
p 3 13,800 0.5 g CaCl.sub.2 
2 3 7,000 
q 3 11,600 
r 3 12,100 
3 3 10,500 
3 3 10,500 Fe Citrate 
3 3 9,700 
3 3 6,800 Fe Citrate 
u 3 8,200 
v 3 18,400 Na.sub.2 CO.sub.3 
w 3 21,000 Na.sub.2 CO.sub.3 
x 3 10,000 
y 3 11,000 
aa 2 6,700 
bb 1 780 
cc 4 12,300 
dd 3 13,000 
ee 4 12,200 
ff 5 12,000 
gg 6 11,500 
hh 7 12,300 
ii 9 11,500 
jj 11 11,400 
kk 13 13,300 
ll 17 11,800 
mm 3 10,900 
nn 3 14,700 
oo 2 14,900 
pp 4 14,900 
qq 6 12,500 
rr 8 12,700 
ss 11 10,400 
tt 15 7,600 
______________________________________ 
In Table III, the following notes apply to the column headed "ml Other": 
______________________________________ 
a triethylamine with phosphate ester of M - 3 ml 
b triethylamine with phosphate ester of M - 6 ml 
c KOH with phosphate ester of M - 2 ml 
d triethanolamine with varied phosphate 
ester - 3 ml 
e triethanolamine with varied phosphate 
ester - 3 ml 
f KOH with phosphate ester of M - 3 ml 
g same as f with half as much KOH - 3 ml 
h same as g with half as much KOH - 3 ml 
i, m, n, o, p 
KOH with phosphate ester of M - 3 ml 
k, l KOH with phosphate ester of M - 2 ml 
q, r, s KOH with varied phosphate ester - 2 ml 
t, u, v, w, x, y 
no alkali; phosphate ester of M - 3 ml 
aa 3 ml non-neut phosphate ester; 2 ml F 
bb 3 ml non-neut phosphate ester; 1 ml F 
cc 3 ml non-neut phosphate ester; 4 ml F 
dd 3 ml KOH-treated phosphate ester; 3 ml F 
ee 3 ml KOH-treated phosphate ester; 4 ml F 
ff 3 ml KOH-treated phosphate ester; 5 ml F 
gg 3 ml KOH-treated phosphate ester; 6 ml F 
hh 3 ml KOH-treated phosphate ester; 7 ml F 
ii 3 ml KOH-treated phosphate ester; 9 ml F 
jj 3 ml KOH-treated phosphate ester; 11 ml F 
kk 3 ml KOH-treated phosphate ester; 13 ml F 
ll 3 ml KOH-treated phosphate ester; 17 ml F 
mm 3 ml non-neut phosphate ester; 3 ml F 
nn 3 ml non-neut phosphate ester; 2 ml F 
oo 3 ml M; 4 ml F 
pp 3 ml M; 6 ml F 
qq 3 ml M; 8 ml F 
rr 3 ml M; 11 ml F 
ss 3 ml M; 15 ml F 
* 6 ml of triethanolamine instead of 3 ml 
______________________________________ 
From the above table III, it is apparent that a broad range of ferric 
salts, neutralizing agents, and other additives such as breakers, and 
other materials are not detrimental to the gelling abilities of our 
invention. In addition, it may be seen that triethanolamine and 
triethylamine are useful in concentrations of about one-half molar 
equivalent (3 ml in the above table) to about 1 molar equivalent (6 ml) 
with respect to the phosphate ester. We may use the low molecular weight 
amines in amounts from about one-fourth molar equivalent to about 1.5 
molar equivalent or more. 
In the following Table IV, ferric salts as shown were used in combination 
with a standard 3 ml concentration of phosphate ester solution, some with 
KOH and some without, in 300 ml oil. The viscosity was measured with a #4 
spindle at 10 rpm unless otherwise noted. 
TABLE IV 
______________________________________ 
Iron salt ml Fe Viscosity Comment 
______________________________________ 
Fe Citrate 3 6,800 
Fe Citrate 1 8,800 
Fe Citrate 3 16,700 
Fe Citrate 3 7,000+ 
Fe Citrate 2 8,000 
Fe Citrate 2.5 3,300 #3 spndl; 10 rpm 
Fe Citrate 2.5 3,200 " 
Fe Citrate 2.5 3,200 " 
Fe Citrate 2.5 2,700 " 
Fe Amm Sulf 1 13,000 
Fe Amm Sulf 1 3,500 (20 rpm) 
Fe Amm Sulf 1.5 14,700 
Fe Amm Sulf 1.5 15,000 
Fe Chloride 3 6,200 
Fe Chloride 2 7,600 
Fe Sulfate 1 9,700 
Fe Sulfate 1.5 14,000 
Fe Sulfate 1 7,000 
Fe Amm Citrate 
3 12,000 
Fe Gluconate 
3 4,600 
______________________________________ 
Additional tests and demonstrations were made on combinations of ferric 
sulfate and low molecular weight amines. In the runs shown in Table V, 
Fann viscosity readings were taken on various gellant preparations 
including low molecular weight amines. For Table V, a solution (TC-23C) of 
67% phosphate ester, 15% KOH and 18% solvent was prepared; this was mixed 
with a composition (TC-23E) comprising 54.4% ferric sulfate (40% solution) 
15.9% triethanolamine, 18.7% ethylene glycol, 3% ammonium cumene sulfate, 
a surfacant (ACS) and 8% water. The shear rate in the Fann viscosimeter 
was maintained at 100.+-.0.1. The temperature was elevated as shown in the 
table. The gel achieved a remarkably stable viscosity after about 30 
minutes of shear. 
TABLE V 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
______________________________________ 
0 70.1 0 71 
3 123.8 348 94 
8 133.7 376 181 
13 124.4 350 224 
18 100.7 283 251 
23 89.5 252 268 
28 81.5 229 279 
33 77.1 217 288 
38 76.0 214 295 
41 75.1 211 299 
46 74.6 210 301 
51 75.1 211 301 
55 74.6 210 300 
60 74.6 210 300 
65 74.8 210 299 
69 75.1 211 299 
74 74.8 210 299 
79 74.9 210 299 
99 74.9 211 299 
______________________________________ 
Table VI shows results using the same materials, in which the pressure was 
maintained at 240 psig (.+-.2) throughout. The shear rate was 100.+-.0.1 
as in Table V. 
TABLE VI 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
______________________________________ 
0 77.1 0 109 
4 120.6 339 144 
9 126.9 357 168 
14 138.1 388 185 
19 150.9 424 196 
24 157.8 444 203 
29 157.2 442 210 
34 152.0 427 216 
39 145.4 409 222 
44.5 139.4 392 227 
47.5 136.4 384 229 
52.5 133.9 377 230 
57.5 130.8 368 231 
61.5 111.6 314 231 
66.5 86.8 244 230 
______________________________________ 
A third series of results was obtained on the same preparation, as shown in 
Table VII: 
TABLE VII 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY PRESS 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
(psig) 
______________________________________ 
0 77.4 0 81 259 
1 144.5 406 90 259 
11 174.5 491 136 261 
21 214.8 604 155 263 
31 213.6 601 168 264 
24 201.5 567 177 265 
29 197.2 554 179 266 
58 196.7 553 180 266 
68 198.7 559 179 267 
86 200.5 563 179 268 
109 200.8 564 180 269 
______________________________________ 
These also were highly stable after a prolonged period. In Table VIII, a 
gellant was prepared by mixing two components--the first was 67% phosphate 
ester, 6% KOH, and 27% solvent; the second was 54.4% ferric sulfate, 20.9% 
triethanolamine, 18.7% ethylene glycol, 3% ammonium cumene sulfate (a 
surfactant) and 3% water. These two components were mixed into Diesel oil 
at a concentration of 2 components of 1%. The resulting gelled hydrocarbon 
was tested in the Fann (model 50), viscometer in a manner similar to the 
above. For the series reported in Table VIII, the pressure increased 
gradually from 259 to 267 psig. 
TABLE VIII 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
______________________________________ 
0 70.6 0 130 
5 191.1 538 151 
10 194.7 547 160 
15 197.6 555 167 
20 201.2 566 172 
25 202.8 570 177 
28 202.2 569 179 
33 199.2 560 181 
38 194.5 547 182 
55 182.2 512 181 
100 173.4 488 179 
______________________________________ 
The same compositions used for Table VIII were run again for the results in 
Table IX. In this case, the pressure was maintained at 244-245 psig. 
TABLE IX 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
______________________________________ 
0 74.2 0 105 
1 172.0 484 129 
5 159.8 449 183 
9 124.9 351 218 
16 92.6 260 255 
24 78.2 220 277 
32 74.8 210 290 
38 73.9 208 298 
46 73.9 208 300 
52 73.9 208 300 
56 73.9 208 300 
82 73.8 208 299 
112 73.8 208 299 
______________________________________ 
The same compositions used for Tables VIII and IX were used for Table X. In 
Table X, the pressure dropped gradually from 240 psig to 237 psig. As in 
all Tables V-IX, the shear rate was maintained at 100.+-.0.1. 
TABLE X 
______________________________________ 
ELAPSED SHEAR 
TIME STRESS VISCOSITY 
Min. LB/100 F.sup.2 
(cP) TEMP. .degree.F. 
______________________________________ 
0 72.3 0 103 
4 179.0 503 143 
8 172.0 484 164 
12 162.3 456 179 
16 149.2 420 190 
20 136.4 384 198 
24 124.2 349 206 
28 114.7 322 212 
32 105.2 296 218 
36 102.0 287 219 
40 96.4 271 223 
44 92.6 260 228 
48 91.3 257 231 
52 90.0 253 233 
56 90.1 253 233 
60 89.8 252 233 
77 92.8 261 233 
92 94.8 267 229 
107 96.3 271 229 
122 98.0 276 229 
______________________________________ 
Excellent gels have also been made using the techniques recited below: 
In this procedure, 55 g ferric sulfate was blended with 11 g monoisopropyl 
amine 
##STR2## 
for a period of about an hour, then blended into Diesel oil containing a 
previously prepared mixture consisting of 67% phosphate ester, 15% KOH, 
and 18% solvent. The ferric sulfate-containing blend and the phosphate 
ester blend each comprised about 0.5 percent of the final fracturing 
fluid. The fracturing fluid was found to make a good gel overnight. A 
similar experiment substituting monobutyl amine provided an excellent gel 
overnight.