Hydrocarbon gels useful in formation fracturing

Liquid hydrocarbons are gelled by the introduction of a phosphate ester and a crosslinking agent. Gelling times and viscosities are improved through the use of an enhancer which is, preferably, an oxyalkylated amine or a blend of an oxyalkylated amine with another amine or a non-nitrogen-containing component. Preferred phosphate esters are ether phosphate esters.

FIELD OF THE INVENTION 
Generally, the present invention is directed to the improved gellation of 
hydrocarbons liquids for a variety of applications. The present invention 
is specifically directed to an enhancer for improving the gelling of 
hydrocarbon liquids when treated with phosphate esters and crosslinking 
agents. 
BACKGROUND OF THE INVENTION 
In order to maximize the amount of oil derived from an oil well a process 
known as hydraulic pressure stimulation or, more commonly, formation 
fracturing is often employed. Generally, a fluid is pumped under high 
pressure down the wellbore through a steel pipe having small perforations 
in order to create or perpetuate cracks in the adjacent rock. The fluid 
employed must be able withstand exceptionally high shear forces. Gelled 
liquids, particularly gelled hydrocarbons, are often employed. In gelling 
the hydrocarbon on-site it is also preferred that gellation occur as 
quickly as possible. 
Rapid gellation of hydrocarbon liquids is also required when tanks or 
vessels containing such liquids are damaged during transit to avoid or 
reduce spillage and the resultant damage to the environment. 
A variety of other applications exist which require the rapid gellation of 
hydrocarbon liquids. Therefore, several means for gelling hydrocarbon 
liquids are disclosed in the prior art. 
U.S. Pat. No. 5,417,287 to Smith et al. is directed to a method for 
fracturing a subterranean formation which involves adding to a hydrocarbon 
liquid (a) an organic phosphate of the formula HPO.sub.4 RR' where R is an 
alkyl or alkaryl group having from 6 to 18 carbon atoms and R' is hydrogen 
or an aryl, alkaryl, or alkyl group having from 1 to 18 carbon atoms; and 
(b) a ferric salt. 
European Patent Application No. 551021A1 to McCabe et al. is directed to 
gelling a hydrocarbon liquid by adding thereto an at least partially 
neutralized alkyl orthophosphate acid ester, a C.sub.8 -C.sub.18 surface 
active amine and a C.sub.2 -C.sub.4 monohydric alcohol. The surface active 
amine employed includes alkyl and alkanol amines having from about 8-18 
carbon atoms, N-heterocyclic amines, alkyl substituted derivatives of such 
heterocyclics and mixtures thereof. Amines having more than one nitrogen 
group are preferred and imidazoline such as that prepared from the 
reaction of a tall oil fatty acid with diethylenetriamine is most 
preferred. 
U.S. Pat. No. 4,316,810 to Burnham is directed to a fracturing composition 
which is an aluminum salt of an oxaalkyl phosphate in an oil base liquid. 
Surface active agents are not disclosed. 
U.S. Pat. No. 4,153,649 to Griffin is directed to the reaction product of a 
hydroxy ether and a pentavalent phosphorus compound and an alcohol. The 
hydroxy ether has the formula ROR.sub.1 OH wherein R is a C.sub.1 to 
C.sub.6 alkyl group, R.sub.1 is a C.sub.2 or C.sub.3 alkylene group and 
the total carbon atoms of R.sub.1 and R range from 3 to about 8. The 
disclosed reaction product may be employed in the gelling of hydrocarbon 
liquids when used with a compound containing a multivalent metal cation. 
U.S. Pat. No. 5,271,464 to McCabe is directed to a method of plugging or 
sealing a subterranean formation by introducing a rapidly gelling 
hydrocarbon thereto. To the hydrocarbon is added a first component which 
is an at least partially neutralized alkyl orthophosphate ester and a 
second component which is the reaction product of an aqueous source of 
aluminum or ferric ions and a C.sub.8 -C.sub.18 surface active amine in 
the presence of a water miscible organic solvent. The surface active amine 
is as defined above for European Pat. Application No. 551021A1, also to 
McCabe. The water miscible organic solvent is generally a monohydric 
alcohol. 
U.S. Pat. No. 3,494,949 to Monroe et al. is directed to an additive for 
improving the viscosity of motor oils which is generally an aluminum salt 
of an alkyl orthophosphate. 
U.S. Pat. No. 2,983,678 to Pellegrini et al. is directed to an additive for 
lubricating oils which is generally a rare earth metal salt of a diester 
phosphate. 
While a variety of systems are available for gelling hydrocarbon liquids 
for the applications discussed above, there exists a clear need in the art 
for a means of improving the known systems to achieve decreased gelling 
times and improved viscosity. 
SUMMARY OF THE INVENTION 
Therefore, it is one object of the present invention to provide such a mean 
s for improving known gellation systems. 
It is a further object of the present invention to provide a novel 
gellation system exhibiting decreased gelling times and improved 
viscosity. 
It is yet another object of the present invention to provide a composition 
for decreasing gelling time and improving viscosity for use in 
conventional methods of gelling hydrocarbon liquids. 
These as well as other objects are achieved by providing an enhancer for 
improving the gelling of hydrocarbon liquids with phosphate esters and 
crosslinking agents, said enhancer comprising an oxyalkylated amine. 
Such objects are also achieved by providing a method of gelling hydrocarbon 
liquids which involves adding to a hydrocarbon liquid (a) a phosphate 
ester; (b) a crosslinking agent; and (c) an enhancer comprising an 
oxyalkylated amine. 
Such objects are further achieved by providing a method of gelling 
hydrocarbon liquids which involves adding to a hydrocarbon liquid (a) an 
ether phosphate ester; (b) a crosslinking agent; and (c) an enhancer which 
is a C.sub.2 -C.sub.22 amine. 
Such objects are still further achieved by providing an enhancer for 
improving the gelling of hydrocarbon liquids with ether phosphate esters 
and crosslinking agents, said enhancer comprising a C.sub.2 -C.sub.22 
amine.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Generally, the present invention is related to an enhancer for use in the 
gelling of hydrocarbon liquids when such a liquid is treated with a 
phosphate ester and a crosslinking agent. Specifically, the present 
invention is directed to the gel which results from adding to a 
hydrocarbon liquid a phosphate ester, a crosslinking agent and an 
enhancer. 
Hydrocarbon liquids which are appropriate for use in accordance with the 
present invention include kerosene, diesel oil and crude oil, gasoline and 
other aliphatic and aromatic hydrocarbons such as octane, heptane, 
paraffinic oils and lubricating oils. Generally, kerosene is the 
preferred; but, the hydrocarbon liquid chosen for use in accordance with 
the present invention will depend on the end-use application. 
The crosslinking agent or activator employed is generally the salt of a 
multivalent cation, preferably the salt of a multivalent metal cation. 
Although a wide variety of metal salts, such as aluminum salts and rare 
earth metal salts, are within the scope of the present invention, ferric 
salts are generally preferred. Preferred ferric salts include ferric 
nitrate and ferric sulfate. 
The phosphate ester of the present invention is generally the reaction 
product of a pentavalent phosphorus compound and an alcohol. It is 
preferred that an oxyalkene such as oxyethylene, oxypropylene or 
oxybutylene is also present as a reactant in order to yield an ether 
phosphate ester. Accordingly, the term "phosphate ester" as used herein 
includes ether phosphate esters such as described below. The phosphate 
ester of the present invention will thus contain one or more of the 
following structures: 
##STR1## 
wherein R, R.sub.1, and R.sub.2 are independently C.sub.1 -C.sub.18 alkyl, 
C.sub.6 aryl, C.sub.1 -C.sub.12 alkyl or dialkyl C.sub.6 aryl, C.sub.1 
-C.sub.18 alkyl ether, C.sub.6 aryl ether, or C.sub.1 -C.sub.18 alkyl or 
dialkyl C.sub.6 aryl ether where any R, R.sub.1, or R.sub.2 C.sub.1 
-C.sub.18 alkyl ether or C.sub.6 aryl ether group has the following 
structures, respectively 
EQU --(CHR'CH.sub.2 O).sub.n --C.sub.1 -C.sub.18 alkyl 
and 
EQU --(CHR'CH.sub.2 O).sub.n --C.sub.6 aryl 
wherein R' is hydrogen, methyl or ethyl and n is an integer from 1 to 100. 
Generally, it is preferred that the phosphate ester of the present 
invention is non-neutralized. However, depending on the enhancer employed, 
it is also within the scope of the invention to at least partially 
neutralize the phosphate ester. 
The enhancer of the present invention is generally an amine and is 
preferably an oxyalkylated amine. The following structures are within the 
scope of the enhancer of the present invention: 
##STR2## 
where R, R.sub.1, and R.sub.2 are independently hydrogen, C.sub.1 
-C.sub.18 alkyl, C.sub.5 -C.sub.6 cycloalkyl, or 
EQU --(CHR'CH.sub.2 O).sub.n -- 
wherein R' is hydrogen, methyl or ethyl and n is an integer from 1 to 100; 
##STR3## 
where R is C.sub.1 -C.sub.18 alkyl, R.sub.1 is hydrogen, C.sub.1 alkyl or 
EQU --(CHR'CH.sub.2 O).sub.n -- 
wherein R' is hydrogen, methyl or ethyl and n is an integer from 1 to 100, 
R.sub.2 is hydrogen or 
EQU --(CHR'CH.sub.2 O).sub.n -- 
wherein R' is hydrogen, methyl or ethyl and n is an integer from 1 to 100 
and R.sub.3 is C.sub.3 alkyl; or 
##STR4## 
where R is C.sub.6 -C.sub.18 alkyl, R.sub.1 is hydrogen or 
EQU --(CHR'CH.sub.2 O).sub.n -- 
wherein R' is hydrogen, methyl or ethyl and n is an integer from 1 to 100, 
and R.sub.2 is C.sub.3 alkyl. 
Thus, preferred oxyalkylated amines include oxyalkylated alkyl amines such 
as ethoxylated alkyl amines having from 1 to about 100 moles of ethylene 
oxide per mole of amine and ethoxylated alkyl amines having from about 4 
to about 18 carbon atoms in the alkyl group; polyoxypropylene alkyl amine 
having from 1 to about 100 moles of propylene oxide per mole of amine; and 
polyoxybutylene alkyl amine having 1 to about 100 moles of butylene oxide 
per mole of amine. Also within the scope of the oxyalkylated alkyl amines 
of the present invention are oxyalkylated dialkyl amines such as 
ethoxylated dialkyl amines having from 1 to about 100 moles of ethylene 
oxide per mole of amine; polyoxypropylene dialkyl amine having from about 
1 to about 100 moles of propylene oxide per mole of amine; and 
polyoxybutylene dialkyl amine having from about 1 to about 100 moles of 
butylene oxide per mole of amine. Also within the scope of the 
oxyalkylated amines of the present invention are oxyalkylated diamines. 
Oxyalkylated aryl amines are also within the scope of the present 
oxyalkylated amines. 
Blends are also appropriate for use as the enhancer of the present 
invention. Preferred blends include at least one oxyalkylated amine as set 
forth above with a further amine or with a non-nitrogen containing 
component. It should be noted that blends containing more than two 
components are also within the scope of the present invention. A further 
amine appropriate for use in the enhancer blend may be chosen from 
oxyalkylated amines such as those set forth above or alkyl amines such as 
C.sub.2 -C.sub.22 alkyl amines, dialkyl amines, alkyl diamines, dialkyl 
diamines, or dialkyl aminoalkylamines. Non-nitrogen containing components 
which are appropriate in the present blend include oxyalkylated ethers, 
oxyalkylated glycerides, oxyalkylated esters and oxyalkylated alcohols as 
well as non-oxyalkylated alcohols and phenols. 
The following examples set forth in Table I are representative of gelling 
systems in accordance with the present invention. For each of the examples 
below, 200 milliliters of kerosene was placed in a 500 ml Waring blender 
having a standard stirring assembly. The blender was plugged into a 
rheostat set at 30% output. The blender was started. The type and amount 
of activator and phosphate ester and system enhancer set forth below were 
added to the kerosene. Where a system enhancer was employed in accordance 
with the present invention, 0.21 milliliters were added. The blender was 
stirred until the vortex created from the agitator closed. If the vortex 
had not closed after 120 seconds, the blender was stopped at that point. 
The kerosene gel was then poured into a Marsh funnel viscometer. The time 
required for 100 milliliters of the gelled kerosene to flow through the 
viscometer is set forth for each example, below. 
The specific components employed in each of the following examples are: 
Enhancers: 
Am-1: an ethoxylated C.sub.16 -C.sub.18 alkyl amine having two moles of 
oxyethylene per mole of amine; 
Am-2: an ethoxylated C.sub.8 alkyl amine having two moles of oxyethylene 
per mole of amine; 
Am-3: an ethoxylated di-C.sub.4 alkyl amine having one mole of oxyethylene 
per mole of amine; 
Am-4: an ethoxylated C.sub.12 -C.sub.14 alkyloxy C.sub.3 alkyl amine having 
three moles of oxyethylene per mole of amine; 
Am-5: N,N-di-C.sub.1 alkyl C.sub.16 alkyl amine; 
Am-6: N,N-di (C.sub.1) alkyl C.sub.18 alkyl amine; 
Am-7: C.sub.16 -C.sub.18 imidazoline prepared from tall oil fatty acid and 
diethylenetriamine; 
Am-8: an alkoxylated C.sub.16 -C.sub.18 alkyl amine having six moles of 
oxypropylene per mole of amine; 
Am-9: an ethoxylated di-C.sub.4 alkyl amine having ten moles of oxyethylene 
per mole of amine; 
Am-10: an alkoxylated C.sub.16 -C.sub.18 alkyl diamine having three moles 
of oxypropylene per mole of diamine; 
Am-11: N,N-di-C.sub.4 alkyl amine; 
Am-12: an alkoxylated C.sub.16 -C.sub.18 alkyl amine having two moles of 
oxybutylene per mole of amine; 
Am-13: an alkoxylated di-C.sub.4 alkyl amine having one mole of oxybutylene 
per mole of amine; 
Am-14: an alkoxylated di-C.sub.4 alkyl amine having one mole of 
oxypropylene per mole of amine; 
Am-15: dimethylaminopropylamine; 
Am-16: aminomethylpropanol; 
Am-17: an ethoxylated aniline having two moles of oxyethylene per mole of 
benzamine; 
Gl-1: an ethoxylated tri-C.sub.18 alkyl glyceride having five moles of 
oxyethylene per mole of glyceride; 
Et-1: an ethoxylated C.sub.12 -C.sub.14 alkyl ether having three moles of 
oxyethylene per mole of ether; 
Es-1: an ethoxylated unsaturated C.sub.16 -C.sub.18 fatty acid having three 
moles of oxyethylene per mole of fatty acid; 
Ph-1: phenol; 
Ph-2: C.sub.5 di-tertiary-alkyl phenol; 
Al-1: isodecyl alcohol. 
Phosphate Esters: 
PE-1: C.sub.2, C.sub.8, C.sub.10 alkyl phosphate; 
EP-1: C.sub.2, C.sub.8, C.sub.10 alkyl, C.sub.6 aryl ether (one mole of 
oxyethylene per mole of C.sub.6) phosphate ester having an alkyl/aryl 
composition of 31% C.sub.2, 25% C.sub.8, 30% C.sub.10, 14% ethoxylated 
aryl. 
Crosslinking Agents: 
Fe3+: a 60% solution of ferric sulfate; 
Al3+: an aluminum chloride solution in accordance with U.S. Pat. No. 
5,271,464. 
TABLE I 
______________________________________ 
EXAMPLES 
Closure 
Viscosity 
Ex. Enhancer Phosphate 
Salt secs. mins. 
______________________________________ 
1 none PE-1 Fe3+ &gt;120 0.6 
Comp. (1 ml) (1 ml) 
2 Am-1, Am-3 PE-1 Fe3+ 3 32.5 
(80%/20%) (1 ml) (0.79 ml) 
3 Am-1, Am-3 EP-1 Fe3+ 2 150 
(80%/20%) (1 ml) (0.79 ml) 
4 none EP-1 Fe3+ &gt;120 1.28 
Comp. (1 ml) (1 ml) 
5 none PE-1 Al3+ 79 2.28 
Comp. (0.77 ml) 
(1 ml) 
6 Am-1, Am-3 PE-1 * Fe3+ 45.7 39 
(80%/20%) (0.77 ml) 
(0.79 ml) 
7 none PE-1 * Fe3+ &gt;120 8.5 
Comp. (1 ml) (1 ml) 
8 Am-2, Am-3 PE-1 Fe3+ 30 95 
(80%/20%) (1 ml) (0.79 ml) 
9 Am-8, Am-9 EP-1 Fe3+ &gt;120 5 
(80%/20%) (1 ml) (0.79 ml) 
10 Am-3, Am-10 
EP-1 Fe3+ &gt;120 15.5 
(80%/20%) (1 ml) (0.79 ml) 
11 Am-1, Am-11 
EP-1 Fe3+ 3.7 &gt;210 
(80%/20%) (1 ml) (0.79 ml) 
12 Am-12, Am-3 
EP-1 Fe3+ &gt;120 &gt;150 
(80%/20%) (1 ml) (0.79 ml) 
13 Am-3, Gl-1 EP-1 Fe3+ &gt;120 74 
(80%/20%) (1 ml) (0.79 ml) 
14 Am-3, Et-1 EP-1 Fe3+ 90 52 
(80%/20%) (1 ml) (0.79 ml) 
15 Am-1, Am-13 
EP-1 Fe3+ 4 52 
(80%/20%) (1 ml) (0.79 ml) 
16 Am-1, Am-14 
EP-1 Fe3+ 3 240 
(80%/20%) (1 ml) (0.79 ml) 
17 Am-3, Es-1 EP-1 Fe3+ 90 88 
(80%/20%) (1 ml) (0.79 ml) 
18 Am-4, Am-3 EP-1 Fe3+ 4.8 360 
(80%/20%) (1 ml) (0.79 ml) 
19 Am-3, Am-5 EP-1 Fe3+ 2 900 
(80%/20%) (1 ml) (0.79 ml) 
20 Am-3, Ph-1 EP-1 Fe3+ &gt;120 60 
(80%/20%) (1 ml) (0.79 ml) 
21 Am-3, Al-1 EP-1 Fe3+ 95 35 
(80%/20%) (1 ml) (0.79 ml) 
22 Am-3, Am-15 
EP-1 Fe3+ 90 300 
(80%/20%) (1 ml) (0.79 ml) 
23 Am-3, Ph-2 EP-1 Fe3+ &gt;120 37 
(80%/20%) (1 ml) (0.79 ml) 
24 Am-3, Am-6 EP-1 Fe3+ 3 720 
(80%/20%) (1 ml) (0.79 ml) 
25 Am-1, Am-16 
EP-1 Fe3+ 7.5 180 
(80%/20%) (1 ml) (0.79 ml) 
26 Am-1, Am-17 
EP-1 Fe3+ 10.7 240 
(80%/20%) (1 ml) (0.79 ml) 
27 Am-7 EP-1 Fe3+ &gt;120 0.12 
Comp. (1 ml) (0.79 ml) 
______________________________________ 
The asterisk (*) in the phosphate column of Example 6 and Comparative 
Example 7 indicates that the phosphate esters of those examples were 
partially neutralized. 
Generally, gelling systems in accordance with the present invention 
demonstrate increased gelling speeds as compared to prior art systems. Of 
the comparative examples set forth hereinabove only Comparative Example 5 
has a gel closure time of less than 120 seconds. Only about one fourth of 
the examples of the invention required more than 120 seconds to achieve 
gel closure. 
However, the more dramatic difference between the examples of the present 
invention and those of the prior art can be seen in the viscosity of the 
gels. None of the prior art examples exceeded a viscosity of 10 as 
measured in minutes required for 100 milliliters of gel to pass through a 
Marsh funnel. In fact, of the four prior art examples given four were of 
such a low viscosity that less than three minutes were required for 100 
milliliters of gel to pass through the funnel. Of the present examples of 
the invention, however, only one demonstrated a viscosity requiring less 
than 10 minutes for 100 milliliters of gel to pass through the funnel and 
nearly half of the inventive examples demonstrated a viscosity requiring 
in excess of 100 minutes for 100 milliliters to pass through the funnel. 
The foregoing description of preferred embodiments of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed, and modifications and variations are possible in light of the 
above teachings or may be acquired from practice of the invention. The 
embodiments were chosen and described in order to explain the principles 
of the invention and its practical application to enable one skilled in 
the art to utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated. It is 
intended that the scope of the invention be defined by the claims appended 
hereto, and their equivalents.