History
Sakhalin I's fields Chayvo, Arkutun-Dagi and Odoptu were discovered by the Soviets some 20 years before the Production Sharing Agreement of 1996. However, these fields had never been properly assessed and a reevaluation of the commercial viability had to be carried out. To do this, factors such as the reservoir quality, producibility and well locations had to be found. 3-D seismic is the most common way to determine much of this however shallow gas reservoirs interfered with the seismic signals and blurred the images somewhat.[1]
Two campaigns of 3-D seismic were carried out along with a number of appraisal wells into the Arkutun-Dagi and Chayvo fields. The results were initially average from the appraisal wells with hydrocarbons being successfully tested, but there was still a large amount of uncertainty involved with the project. However, in late 1998, a revaluation of the 3-D seismic data using the most advanced seismic-visualization techniques then available indicated that the hydrocarbon depth on the edge of the field could be significantly deeper than first thought. In 2000, the Chayvo 6a delineation well confirmed what was suspected, a 150 m oil column. This provided the certainty that the field was commercially viable in the hostile environment with a potential to be a 1 Goilbbl field.[1]
In 2007, the project set a world record when extended-reach drilling (ERD) well Z-11 reached 11282 m.[5][6] That record was broken in early 2008 with extended-reach well Z-12 reaching 11680 m.[6] Both extended-reach wells are in the Chayvo field and reach over 11 km.[6] As of early 2008, the Chayvo field contains 17 of the world's 30 longest extended-reach-drilling wells.[6] However, in May 2008, both world records of ERD well were surpassed by the GSF Rig 127 operated by Transocean, which drilled the ERD well BD-04A in the Al Shaheen oil field in Qatar. This ERD well was drilled to a record measured length of 12,289 m including a record horizontal reach of 10,902 m in 36 days.[7]
On 28 January 2011, Exxon Neftegas, operator of the Sakhalin-1 project, drilled the then world's longest extended-reach well. It has surpassed both the Al Shaheen well and the previous decades-long leader Kola Superdeep Borehole as the world's longest borehole. The Odoptu OP-11 Well reached a measured total length of 12,345 m and a horizontal displacement of 11,475 m. Exxon Neftegas completed the well in 60 days.[8]
On 27 August 2012, Exxon Neftegas beat its own record by completing Z-44 Chayvo well. This ERD well reached a measured total length of 12,376 m.[9]
Since the start of drilling in 2003 to 2017, Sakhalin-1 has drilled 9 of the 10 longest wells in the world. Since 2013, the project has set five records for drilling wells with the deepest depths in the world. In April 2015, the O-14 production well was drilled, with length of 13.5 km, in April 2014 the Z-40 well was completed with a length of 13 km, in April and June 2013 - the Z-43 and Z-42 wells 12.45 km and 12.7 km long, respectively. In November 2017 the record well reached 15 km long.[10][11]
Production from Sakhalin 1 halted in May 2022, when operator Exxon Neftegaz declared force majeure at the project in response to international sanctions imposed on Russia after the Russian invasion of Ukraine in February. In October 2022 Vladimir Putin instructed authorities to disband Exxon Neftegaz and transfer the project and all of its assets and equipment to a new operator, in which the government will hold a controlling 80% shareholding for an initial period of one month. The Exxon Neftegaz shareholding may be sold at an auction to a third party if authorities discover any damage to the development.[12] By November the new operator of the project Sakhalin 1 LLC was owned 30% by Exxon Mobil, 20% by India’s Oil and Natural Gas (ONGC), 30% by Japan’s Sakhalin Oil and Gas Development (SODECO), Rosneft subsidiary Sakhalinmorneftegaz-Shelf who manages the project was given 11.5% and JSC RN-Astra 8.5%.[13]
After handing over operations of Sakhalin 1 to the Rosneft subsidiary, production was re-established with an output of 140000 oilbbl/d-150000 oilbbl/d expected to rise to 220000 oilbbl/d eventually.[14]
