Evolution of H-O Isotopes from Fracturing Flowback Fluids for Shale Gas Wells: A Case Study in Chongqing, China

Abstract The hydrogen and oxygen isotopes of the fracturing flowback fluids from 3 wells in the Longmaxi Formation in Dazu area of western Chongqing, China provides insights into the source of the flowback fluids. We use the valued of δ2H and δ18O, combined with concentrations of ions to discuss the changing rule of H and O isotopes throughout the flowback period. The values of δ2H and δ18O for Z2 and Z5 wells show different changing trends. But he values of δ2H and δ18O for Z2 and Z5 wells have similar changing trends. There is no obvious correlation between hydrogen and oxygen isotopes for 3 wells. The fracturing fluids, formation brines, meteoric water, and water-rock reaction can change the H and O isotopes for flowback fluids from shale gas wells.