Method of using tracer fluids for enhanced oil recovery

In a method of recovering oil from a subterranean, petroleum-containing formation penetrated by an injection well and a production well, comprising injecting an aqueous, surfactant-containing fluid into the formation via the injection well to displace petroleum through the formation to the production well, from which it is recovered to the surface of the earth, said surfactant fluid containing a tracer amount of a tracer material which is susceptible to bacterial attack, wherein the improvement for inhibiting bacterial degration of the tracer comprises:

• incorporating in the surfactant and tracer containing fluid from 10 to 2000 parts per million of an aromatic compound having the following formula:
• ##STR3## wherein R.sub.1, R.sub.2, and R.sub.3 are each hydrogen, methyl or C.sub.2 to C.sub.5 alkyl, the total number of carbon atoms in R.sub.1, R.sub.2, and R.sub.3 being from 0 to 5.

In a method of recovering oil from a subterranean, petroleum-containing formation penetrated by an injection well and a production well, comprising injecting an aqueous, polymer-containing fluid into the formation via the injection well to displace petroleum through the formation to the production well, from which it is recovered to the surface of the earth, said polymer fluid containing a tracer amount of a tracer material which is susceptible to bacterial attack, wherein the improvement for inhibiting bacterial degration of the tracer comprises:

• incorporating in the polymer and tracer containing fluid from 10 to 2000 parts per million of an aromatic compound having the following formula:
• ##STR4## wherein R.sub.1, R.sub.2, and R.sub.3 are each hydrogen, methyl or C.sub.2 to C.sub.5 alkly, the total number of carbon atoms in R.sub.1, R.sub.2, and R.sub.3 being from 0 to 5.