Kashagan, Caspian Sea, Kazakhstan

Discovered in July 2000, Kashagan has been described as the largest field found in the past 30 years, the largest outside the Middle East and with a projected output close to that of the Ghawar field in Saudi Arabia.

It is being developed by a group of partners including Shell, Exxon Mobil, Total, ConocoPhilips and Kazakh state-run oil company KazMunaiGas, and led by AgipKCO (Eni), which will pass its role as operator to the new North Caspian Operating Company in January 2009.

Geology

Kashagan is a carbonate platform of Late Devonian to middle Carboniferous age. The “reef” is about 75km long and 35km across, with a narrow neck joining two broader platforms (Kashagan East and Kashagan West). The top of the reservoir is about 4.5km below sea level and the oil column extends for more than 1km. The seal is middle Permian shale and late Permian salt.

The reservoir consists of limestones with low porosities and permeabilities. The oil is a light oil with 45º API gravity with a high gas-oil ratio and very high H2S content of 19%. The field is heavily overpressured, which presented a significant drilling challenge. The figures for oil in place range between 30 and 50 billion barrels with a common publicly quoted figure of 38 billion barrels, but because of the reservoir’s complexity the recovery factor is relatively low, about 15-25%.

The entire Caspian Sea is around 30m below sea level and while the mean water depth as a whole is 208m, this is considerably shallower to the north-east. The field, 75km SSE of Atyrau, lies in just 3.7m of water.

Temperatures can fall below -20°C in winter and a coating of ice, several metres thick, forms in this part of the Caspian Sea for many months of the year.

Discovery wells

The discovery well, Kashagan East 1, was a single vertical well, drilled in 2000 to a total depth of 5,200m. During tests the well flowed at a rate of 600m3 of oil per day and 200,000 m3 of gas per day on a 32/64” choke. Kashagan West 1 was the second discovery well. Discovered in 2001, tests showed that the well flowed at a rate of 3,400 bopd, while the oil gravity measured between 42º and 45º API.

Kashagan East 2 was discovered in late 2001, and was drilled to a depth of 4,142m and flowed at a rate of 7,400 bopd.

Dresser Services won the integrated drilling contract.

Because of the environmental conditions, icebreaking supply boats have to be used. Most icebreakers work by using the weight of the ship to crack the ice, but this will not work in the shallow waters of the Caspian, so shallow-draught Arcticaborg ice breakers from Finland’s Kvaerner Masa shipyards have been brought in to break the ice using specially designed propellers. Special tugs have also had to be designed to work in these waters, and arrived in the Caspian in September 2002.

Development

The development plan for the US$136bn project, approved in February 2004, foresees production developing in three phases for reserves of some 7 billion barrels, which could rise to 13 billion through the partial re-injection of gas. Production is forecast to start in late 2012, building up from 75,000 barrels/day to a peak by about 2021 of 1.5 million bpd – slightly more than Kazakhstan’s total current production.

The project design includes building production hubs on platforms and artificial islands to collect production. The oil, and any gas that is not re-injected, will be treated initially at the hubs before being sent in separate pipelines to new onshore treatment plans at Bolashak, near Atyrau. Here the oil will be further stabilised and purified, while the gas drawn for the removal of sulphuric acid will be used partly as fuel to supply the energy necessary for the production plants and partly marketed.

Under a Production Sharing agreement signed in October 2008, Shell will manage production operations after start-up of the first phase, with KazMunaiGas progressively assuming greater responsibility. During the second phase, Shell will run offshore development, Eni will be responsible for the onshore processing plant and ExxonMobil will be in charge of drilling.

Floating production vessel

The drilling programme at the Astrakhan yard in the Russian Federation has been being carried out by the Sunkar (which means 'falcon' in Kazakh) floating production vessel.

This converted swamp barge was re-designed and modified specifically for Caspian service, in a US$100 million engineering exercise, which included the installation of two 4m-high steel deflector tanks to protect the rig from the ice. The barge measures 85x53m and is 5.5m high - the largest of its type in the world. It weighs 6,000t and can hold up to 100 people.

In order to minimise supply operations, the platform design required storage-tank volumes that were as large as possible. The tanks include 19 ballast tanks (18,869m³), five drill water tanks (1,854m³), five fuel oil tanks (1,364m³), one pollution tank (516m³), four potable water tanks (513m³), one base oil tank for mud (385m³) and one brine tank (224m³).

Support facilities

Support facilities include a bacterial sewage unit, capable of handling 9.5m³ and two electrically driven Alfa Laval freshwater distillers, consisting of two units each capable of 33m³/day. Communication is maintained by radio and a satellite voice-and-data link, and there is a 19x19m helicopter deck. Power is provided by four 1,500kW power generators and one 860kW standby generator. Emergency power is available through the 420kW diesel-driven generator.

The rig barge sits on submerged limestone berms that stand less than a metre high. The berm is surrounded by 24 ice-resistant piles, each weighing 70t. They are 1.6m in diameter and 30m tall. These are used to break up ice sheets and reduce forces on the barge.

In October 2008, AgipKCO handed a $31m letter of intent for front-end engineering and design work on phase two of the development to a joint venture of Aker Solutions, WorleyParsons and CB&I. At the time, Aker Solutions and WorleyParsons were already engaged in executing phase one of the project, carrying out engineering services, fabrication and hook-up. The scope of the phase two FEED includes on- and offshore facilities, as well as pipelines.

Aker Solutions said the deal also includes options for services in the post-FEED phase, including early works, detail engineering and procurement services, technical assistance, and design/system integrity.