On 11 September 2018, Gazprom Neft reported that the State Commission for Reserves (GKZ) approved the revision of reserves for the Neptune discovery offshore Sakhalin. After integration of seismic data and drilling results, Gazprom Neft generated a new geological model of the discovery increasing its 3P reserves up to 3.035 Bbbl in-place and 911 MMbbl of recoverable.  Background Information  On 4 October 2017, Gazprom Neft reported an oil discovery in the Ayashskiy license offshore Sakhalin. Wildcat Ayashskaya 1, spudded in mid-June 2017, was drilled to 2,700 m by contractor Japan Drilling Co using semi-submersible Hakuryu-5. It is understood that oil flows were tested from four reservoirs in the Nutovo Formation (Miocene) at a depth range of 2,000-2,700 m. The operator estimated 3P reserves of the Ayashskoye discovery at 500-580 MMbbl of oil. The new discovery is located some 55 km from the Sakhalin coast. A water depth in the drilling location is 62 m. In mid-October, it was decided to re-name the discovery to Neptune due to some difficulties with pronunciation of the original name for non-Russian speakers. Also, Gazprom Neft announced its plan to drill a wildcat at the Bautinskiy prospect in 2018 at the same license.Â Â    The Ayashskiy block covers 4,294 sq km east of Sakhalin and encompasses several structures. Gazprom obtained a long-term license (a part of the Sakhalin-3 project) in 2009 and, by 2016, completed several seismic surveys in the area including acquisition of 2,150 sq km of 3D data. In January 2017, the rights were transferred to Gazpromneft-Sakhalin (license ShOM16292NR). It may indicate that, based on analysis of new acquired data, the area was considered as mainly oil-prone and it is more convenient for Gazprom Neft, Gazpromâs oil branch, to continue the exploration. According to Gazprom, hydrocarbon resources of the Ayashskiy prospect were estimated at 4.9 Tcf of gas and 1,022 MMbbl of oil and condensate.
Gazprom Neft reported that the GKZ approved the revision of reserves for the Neptune discovery. After integration of seismic data and drilling results, Gazprom Neft generated a new geological model of the discovery increasing its 3P reserves up to 3 035 Bboe in-place and 911 MMboe of recoverable.