Abstract: This invention relates to a process utilizing natural carbon-13 isotope for identification of early breakthrough of injection water in oil wells. All natural water sources are labeled by unique ratios of carbon isotopes (13C/12C). Following the requirements of the invention, the carbon isotope ratio for oil bearing formation water and for local aquifer water which is to be injected in to the oil reservoir rock is determined. The carbon isotope ratio of the produced water from the selected oil wells is then monitored periodically. When the carbon isotope ratio of the produced (oil well) water shows deviation from the formation water value and tends towards injection water value, then the early breakthrough phenomenon of injection water is identified. Thus the contrast in natural carbon isotope ratios of injection water, formation water and produced water from selected oil wells serve as tracer in the identification of “Early Breakthrough” phenomenon of injection water and its movement.

Abstract: This invention relates to a process utilizing natural carbon-13 isotope for identification of early breakthrough of injection water in oil wells. All natural water sources are labeled by unique ratios of carbon isotopes (13C/12C). Following the requirements of the invention, the carbon isotope ratio for oil bearing formation water and for local aquifer water which is to be injected in to the oil reservoir rock is determined. The carbon isotope ratio of the produced water from the selected oil wells is then monitored periodically. When the carbon isotope ratio of the produced (oil well) water shows deviation from the formation water value and tends towards injection water value, then the early breakthrough phenomenon of injection water is identified. Thus the contrast in natural carbon isotope ratios of injection water, formation water and produced water from selected oil wells serve as tracer in the identification of “Early Breakthrough” phenomenon of injection water and its movement.