Tertiary oil recovery process utilizing a preflush

Claim 1

A method of recovering petroleum from a porous, subterranean, petroleum-containing formation containing saline water which is penetrated by at least one injection well and at least one production well which comprises: (a) injecting an aqueous preflush fluid comprising a mixture of water, colloidal silica having a particle size ranging from about 7 to 15 millimicrons and a random, linear, water-soluble friction-reducing polymer of a monomer or monomers consisting essentially of from about 1 to 100 percent by weight of (3-acrylamido-3-methyl) butyl trimethyl ammonium chloride and from 0 to 99 percent by weight of acrylamide or partially hydrolyzed acrylamide wherein the said aqueous preflush fluid has a salinity less than the salinity of the formation water, into the formation, via an injection well, (b) injecting an aqueous surfactant solution into the formation via the injection well, and (c) recovering petroleum displaced by the said injections through a production well, wherein the said aqueous surfactant solution of step (b) comprises an aqueous solution of a surfactant composition selected from the group consisting of: (I) a polyethoxylated alkyl benzene sulfonate having the formula: ##STR11## wherein R is alkyl of from 8 to 22 carbon atoms, n is an integer of from 2 to about 10 and A is selected from the group consisting of hydrogen, sodium, potassium and the ammonium ion, a polyethoxylated alcohol sulfate having the formula: RO(CH.sub.2 CH.sub.2 O).sub.m SO.sub.3 A, wherein R and A have the same meaning as previously described and m is an integer of from 2 to about 18, or a polyethoxylated alcohol sulfonate having the formula RO(CH.sub.2 CH.sub.2 O).sub.m-1 CH.sub.2 CH.sub.2 SO.sub.3 A wherein R, m and A have the same meaning as previously described (II) a mixture of a polyethoxylated alkyl benzene sulfonate as described in (I) above together with an alkyl benzene sulfonate, and (III) a mixture of petroleum sulfonate and a polyethoxylated alkyl benzene sulfonate as described in (I) above.

Claim 2

A method of recovering petroleum from a porous, subterranean, petroleum-containing formation containing saline water which is penetrated by at least one injection well and at least one production well which comprises: (a) injecting an aqueous preflush fluid comprising a mixture of water, colloidal silica having a particle size ranging from about 7 to 15 millimicrons and a random, linear, water-soluble friction-reducing polymer of a monomer or monomers consisting essentially of from about 1 to 100 percent by weight of (3-acrylamido-3-methyl) butyl trimethyl ammonium chloride and from 0 to 99 percent by weight of acrylamide or partially hydrolyzed acrylamide wherein the said aqueous preflush fluid has a salinity less than the salinity of the formation water, into the formation, via an injection well, (b) injecting an aqueous surfactant solution into the formation via the injection well, and (c) recovering petroleum displaced by the said injections through a production well, wherein the said aqueous surfactant solution of step (b) comprises an aqueous solution of a surfactant composition selected from the group consisting of: (I) a polyethoxylated alkyl benzene sulfonate having the formula: ##STR11## wherein R is alkyl of from 8 to 22 carbon atoms, n is an integer of from 2 to about 10 and A is selected from the group consisting of hydrogen, sodium, potassium and the ammonium ion, a polyethoxylated alcohol sulfate having the formula: RO(CH.sub.2 CH.sub.2 O).sub.m SO.sub.3 A, wherein R and A have the same meaning as previously described and m is an integer of from 2 to about 18, or a polyethoxylated alcohol sulfonate having the formula RO(CH.sub.2 CH.sub.2 O).sub.m-1 CH.sub.2 CH.sub.2 SO.sub.3 A wherein R, m and A have the same meaning as previously described (II) a mixture of a polyethoxylated alkyl benzene sulfonate as described in (I) above together with an alkyl benzene sulfonate, and (III) a mixture of petroleum sulfonate and a polyethoxylated alkyl benzene sulfonate as described in (I) above.