The firm says making crude extraction from Kamennoye economically viable was particularly challenging as the geology is more complicated than at any of its more recent developments.

Since 2004, TNK-BP has invested $600 million in Kamennoye and plans to invest $700 million more in 2009—13, including $250 million in 2009. These costs look rather low compared with other new projects — possibly because it saved on exploration outlay by using Soviet-era data, Solid brokerage’s Denis Borisov says.

Kamennoye’s complicated geology impeded development during Soviet times. In the 1970s and 1980s, 100 exploration wells were drilled, but most did not yield high enough flow rates to justify large-scale development. The field was abandoned and resources diverted to other west Siberian fields that were easier to develop. A second effort to develop Kamennoye in the 1990s also failed, after 30pc of the 200 wells drilled proved dry. Those that were not dry only yielded 3—5 t/d.

The field’s main difficulty is its complex reservoir structure — typical of other Krasnoleninsk group fields, including Talinskoye and Em-Yoga. A significant proportion of reserves are focused in the transition zone — the area above the oil-water contact, but below the pure water level. This complicates hydraulic fracturing and the drilling of horizontal wells, TNK-BP says. The firm has had to adjust standard horizontal drilling and fracturing techniques, which were proving inefficient.

There are 320 producing wells at Kamennoye, with a combined output of 4,000 t/d. Production is expected to peak at 84,000 b/d in 2013, by when the firm plans to have added 250—300 more wells. More than 40pc of the 2009 investment TNK-BP has allocated for Kamennoye will be spent on infrastructure, with the remainder going on drilling, the firm says. It will also focus on rehabilitating idle wells, which now only constitute 10pc of the total, down from 45pc before.

In 2006—07 Kamennoye produced 16,000 b/d. This year, output is due to grow by 40pc to 36,000 b/d, from the 26,000 b/d produced in 2008. The field’s lower horizons hold significant reserves, but these are not presently profitable to exploit, TNK-BP says. Partly situated in a protected floodplain, Kamennoye is environmentally sensitive. Only minimal infrastructure is permitted, while well management, processing and metering are all automated.