The Sakhalin project

Gazprom Neft is developing a new offshore production cluster in the Sea of Okhotsk. In just three years, following the construction of two exploratory wells, the company has discovered two major fields at the Ayashsky license block, offshore from Sakhalin Island.


This oil and gas field, on the north—east of Sakhalin Island’s continental shelf, was discovered at the end of the 20th century. Seismic exploration undertaken over a period of three years by the then license holder, Gazprom, revealed the Ayashsky license block to contain mainly liquid hydrocarbons, so the license for its development was transferred to Gazprom Neft.

The Neptune and Triton fields
The Neptune and Triton fields

Production technologies

Exploratory drilling started in 2017, involving riserless-mud-removal (RMR) drilling used in Russia for the first time, speeding up well construction, improving well stability, and preventing potential gas emissions, as well as avoiding any possibility of drilling wastes entering the water — their being returned to shore for recycling.

The Neptune field

Exploratory drilling resulted in the discovery of a major field, named «Neptune» in honour of the Roman god of the sea. Reserves in place were initially estimated at 255 million tonnes of oil equivalent, but desk research allowed reserves to be estimated more precisely, resulting in initial expectations being significantly exceeded, at 415 million tonnes. By normal industry standards, this discovery was made in an exceptionally short time — all of the main work being completed within a year and a half. Petroleum consultants Wood Mackenzie included the Neptune fields among the world’s top-10 biggest oil and gas discoveries in 2017, with the Neptune field being ranked third by recoverable reserves.

The Triton field

A further field was discovered at the Ayashsky block in 2018, during drilling of an appraisal well at the Bautinsky formation. Reserves in place at this field — named the Triton field after the ancient sea god, son of Neptune — are estimated at more than 137 mtoe. Data from petroleum consultants WoodMackenzie places this field among the world’s most important oil and gas discoveries in 2018, ranked seventh by recoverable reserves.

Offshore from the Sea of Okhotsk Offshore from the Sea of Okhotsk
Offshore from the Sea of Okhotsk Offshore from the Sea of Okhotsk
Offshore from the Sea of Okhotsk Offshore from the Sea of Okhotsk
Offshore from the Sea of Okhotsk Offshore from the Sea of Okhotsk
More photos in Gazprom Neft Image Bank

Ecology and the environment

Gazprom Neft joined an ongoing project on monitoring the grey whale population in the Sea of Okhotsk on starting operations offshore from Sakhalin Island. Gazprom Neft subsidiary Gazpromneft-Sakhalin joined a collective programme being implemented by Sakhalin Energy and Exxon Neftegaz Limited in 2017.

The information obtained on the lifecycles of the Okhotsk—Korea grey whale population means any impacts on these animals and their habitats can be minimised — including, specifically, using low-noise vessels (and limiting their speed), and following routes some distance from whale feeding grounds.

Drilling of an exploration and appraisal well at the Triton field
Drilling of an exploration and appraisal well at the Triton field

Future plans

The discovery of two major fields means it is now possible to talk about developing an oil-production cluster offshore from Sakhalin, making the Russian Far East a new strategic region in Gazprom Neft’s asset map. Oil production at these fields is expected to start in 2025–2030, depending the surface-facilities strategy selected. The next few years will see further exploration at these fields, in line with the company’s geological prospecting plans.

Sakhain in figures

415 million tonnes Reserves in place at the Neptune field
137 million tonnes Reserves in place at the Triton field
500 km The field’s remoteness from Yuzhno-Sakhalinsk