Source-rock and petrophysical evaluation of the Late Cretaceous Haymana Formation, Haymana Basin, Central Anatolia, Turkey

This study investigates the petroleum potential of mudstones of the Late Cretaceous Haymana Formation in the Haymana Basin, Turkey. The lithofacies, pore structure and source-rock characteristics of the mudstones are examined using stratigraphic, sedimentological, petrophysical and organic geochemical methods along four stratigraphic sections and other sampling sites. The depositional model presents a facies distribution within a submarine fan system. According to the bulk mineralogy, the identified lithofacies are mixed mudstone, mixed siliceous mudstone, marl, mixed carbonate mudstone, argillaceous/siliceous mudstone and clay-rich siliceous mudstone. XRD and mercury intrusion measurements suggest that the macropores (>50 nm) of the mudstones formed by dissolution of calcite, while mesopores (2–50 nm) developed around the clay–quartz/feldspar. Of the analysed samples, no lithofacies class is distinct with any specific range of porosity or permeability, which suggests a strong heterogeneity in pore throat size, mineral content and grain size. The black shale from the NW of the basin with a total organic carbon (TOC) content of 1.19%, S1 value of 0.07 mg g −1 , S2 value of 1.01 mg g −1 and a T max value of 441°C is a relatively more mature source rock, although it still exhibits a poor petroleum potential. Overall, the TOC values (average of 0.38%) of the mudstones suggest organic-poor rock characteristics for the Haymana Formation in the studied parts of the Haymana Basin.