Sakhalin-I

The Sakhalin-I (Russian: Сахалин-1) project, a sister project to Sakhalin-II, is a consortium for production of oil and gas on Sakhalin Island and immediately offshore. It operates three fields in the Okhotsk Sea: Chayvo, Odoptu, and Arkutun-Dagi.

In 1996, the consortium completed a production-sharing agreement between the Sakhalin-I consortium, the Russian Federation and the Sakhalin government. The consortium was managed and operated by Exxon Neftegas Limited (ENL), a unit of ExxonMobil, until Exxon's withdrawal in March 2022 following the 2022 Russian Invasion of Ukraine. The Russian government froze Exxon's investment in August 2022 and ordered its transfer to a newly created Russian company the following October.

Since 2003, when the first Sakhalin-1 well was drilled, six of the world's 10 record-setting extended reach drilling wells have been drilled at the fields of the project, using the Yastreb rig. It has set multiple industry records for length, rate of penetration and directional drilling. On 27 August 2012, Exxon Neftegas beat its previous record by completing Z-44 Chayvo well. This ERD well reached a measured total length of 12,376 meters (40,604 ft), making it the longest well in the world. In November 2017, the record well reached 15 kilometers (49,000 ft) long.

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.

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 meters (490 ft) oil column. This provided the certainty that the field was commercially viable in the hostile environment with a potential to be a 1-billion-barrels (160×10^⁶ m³) field.

In 2007, the project set a world record when extended-reach drilling (ERD) well Z-11 reached 11,282 meters (37,014 ft). That record was broken in early 2008 with extended-reach well Z-12 reaching 11,680 meters (38,320 ft). Both extended-reach wells are in the Chayvo field and reach over 11 kilometers (6.8 mi). As of early 2008^[update], the Chayvo field contains 17 of the world's 30 longest extended-reach-drilling wells. 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 meters (40,318 ft) including a record horizontal reach of 10,902 meters (35,768 ft) in 36 days.

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 meters (40,502 ft) and a horizontal displacement of 11,475 meters (37,648 ft). Exxon Neftegas completed the well in 60 days.

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 meters (40,604 ft).