Rosneft has started drilling at its maiden exploration well targeting a deep a unconventional oil formation in Russia's Orenburg region, as it seeks to prove up new commercial reserves outside of its main area of operations in West and East Siberia.

The well is being drilled into the tight, low permeability Domanik formation on the Kutuluksky block, with the state-controlled company aiming to confirm its preliminary estimate of in-place resources for the formation at 510 million barrels of oil and 23 billion cubic metres of gas.