Identifying oil and gas reservoirs with oxygen isotopes

摘要

Carbonate samples are received from a wellbore formed in a geologic formation. An oxygen isotope ratio and carbon isotope ratio present within each of the carbonate samples are determined. A mineral composition of each of the carbonate samples is determined. A plot showing the determined oxygen isotope ratios versus a depth from where within the wellbore each of the carbonate samples was obtained is created. One or more negative oxygen isotope shifts are identified based on the plot. Natural carbonate cement levels within one or more of the plurality of carbonate samples that correspond to the one or more negative oxygen isotope shifts identified in the plot are determined. One or more production sweet spots are determined based on the identified negative oxygen isotope shifts and the determined natural carbonate cement levels.