but if it does it can be solved as stated above the process of the present invention generally requires quantitative measurement of the tracer content of produced waters the testing methods required to make such quantitative analysis of the known useful tracer are well known in the art and such tests are available on a commercial basis although such quantitative measurement is preferred in the process of the present invention it is not absolutely required for example in many cases of tracing water flow alcohols such as methanol and isopropynol may be used as these tracers the content of such tracers can be analyzed accurately using well known gas chromatograph equipment while the outputs of such gas chromatographs are usually calibrated to provide absolute quantitative output readings they can provide the basic ratio information needed in the present inventions without such calibration a sample containing for example both methanol and isopropynol can be analyzed on a gas chromatograph to provide the concentration ratio of the two tracers in a single test without calibration for absolute concentrations the measurement of absolute concentration is preferred though since it provides additional information relating to the total quantities of water from each injection well which is reaching the production well the present invention is not limited to the injection of a single combination of tracers in a single injection well for example in some oil recovery projects a number of different banks of materials are injected into each injection well in sequence for example a preflush slug may.