Meteoric Water Incursion, Crude Oil Degradation and Calcite Cementation of an Upper Cretaceous Reservoir in the Zagros Foreland Basin (Kurdistan Region of Iraq)

Field observations, together with the results of gas chromatography–mass spectrometry (GC-MS) and stable carbon isotope analysis bitumen, coupled fluid inclusion microthermometry analyses closely associated vug- fracture-filling columnar calcite in Upper Cretaceous Bekhme Formation, Kurdistan Region Iraq, suggest that degradation crude oil was caused by regional incursion meteoric waters. This incursion, which is interpreted to have occurred during tectonic uplift Zagros Orogeny, evidenced by: (i) depletion n-alkanes acyclic isoprenoid alkanes (pristane phytane) bitumen; (ii) low δ13CVPDB values (−8.5‰ −3.9‰) δ18OVPDB (−22.9‰ −15.0‰), more radiogenic Sr isotopic ratios (0.70771–0.70772) compared seawater; (iii) salinity temperatures (20 40 °C) inclusions calcite. study demonstrates water into sedimentary basins can be linked accompanied cementation events carbonate reservoirs.