Density and viscosity of tight oil from Yanchang Formation, Ordos Basin, China and the geochemical controls

For assessing the density and viscosity of tight oil and their geochemical controls, 47 tight oil samples across the Ordos Basin were analyzed. The oil density and viscosity lay in the ranges of 0.81–0.88 g/ml and 1.9–13.36 mPa·s, which are low in overall. The average saturated hydrocarbon content is higher than 80%. The molecular compositions suggest a source dominated organic matter by lacustrine type I/II with minor input of terrestrial type III kerogen. The oils were mainly generated at relatively high maturities. Fractionation during the oil expulsion may also result in the depletion of heavy-ends compounds. These are the main controlling factors for the overall good quality of the Ordos tight oil.