Yukos Oil bought a 10 percent stake in Kvaerner ASA in an effort to help the struggling company to avoid bankruptcy. Kvaerner shares jumped 30 percent as investors expected that the company, which plans a $230 million rights offering to stay afloat, has found a backer. Even after the gain, the stake is worth just $16.3 million. Kvaerner was once valued at $5 billion. Yukos, which pumps almost as much oil as Opec member Indonesia, needs new technologies to raise production from aging fields in western Siberia. With world oil prices almost double those in Russia, Yukos boosted oil sales in the first half by 17 percent, part of a plan to lift output some 50 percent by 2005. Yukos is a major Kvaerner client and hopes that its orders can help alleviate Kvaerner's financial troubles.