Well treating composition and method

DETAILED DESCRIPTION We claim: 1.
In a method for fracturing a subterranean formation penetrated by a wellbore which comprises injecting down the wellbore and subjecting to fracturing pressure an essentially anhydrous mixture comprising liquid carbon dioxide and an alkanol of 1 to 3 carbon atoms gelled to a viscosity of at least 10 centipoises with a cellulose ether compound, the improvement which comprises employing as gelling agent a hydroxypropyl methylcellulose having a methoxyl D.
S.
of from about 0.
2 to about 1.
0 and a hydroxypropoxyl M.
S.
of at least about 1.
2 and wherein the sum of said D.
S.
and M.
S.
is at least about 1.
8.
2.
The method of claim 1 wherein the amount of hydroxypropyl methylcellulose is adjusted to produce a gelled alkanol having an apparent viscosity of from about 120 to about 300 centipoises.
3.
The method of claim 1 wherein the hydroxypropyl methylcellulose has a hydroxypropoxyl M.
S.
of from about 1.
2 to about 2.
2.
4.
The method of claim 3 wherein the hydroxypropyl methylcellulose has a methoxyl D.
S.
of from 0.
5 to 0.
95.
5.
The method of claim 1 wherein the alkanol is essentially anhydrous methanol.
6.
The method of claim 1 wherein the liquid carbon dioxide is combined with liquid petroleum gas.
7.
The method of claim 1 wherein the gelled alkanol carries a propping agent.
8.
The method of claim 7 wherein the propping agent is sand.
9.
An anhydrous composition for fracturing a subterranean formation which comprises liquid carbon dioxide and an essentially anhydrous alkanol containing 1 to 3 carbon atoms and gelled to a viscosity of at least 10 centipoises with a hydroxypropyl methylcellulose have a methoxyl D.
S.
of from about 0.
2 to about 1.
0 and a hydropropoxyl M.
S.
of at least about 1.
2 and wherein the sum of said D.
S.
and M.
S.
is at least about 1.
8.
10.
The composition of claim 9 wherein the hydroxypropyl methylcellulose has a hydroxypropoxyl M.
S.
of from about 1.
2 to about 2.
2 11.
The composition of claim 10 wherein the hydroxypropyl methylcellulose has a methoxyl D