The Cincinnati Post
The strong results, however, mask weakness in Chevron's core business: finding oil and gas. Last year, it pumped the equivalent of 2.5 million barrels of oil out of the ground every day. After factoring in asset sales, new discoveries and revisions to previous estimates, it didn't come close to adding that much in proven reserves. Its "replacement rate" was just 18 percent - one of the worst showings by a large oil company in recent years. If that continues, Chevron could eventually pump itself out of existence. That is why many in the oil patch see Chevron's acquisition of Unocal as a sign of weakness, not strength.
I remember reading somewhere that when oil becomes harder and harder to find and the cost of exploration and extraction increases, more companies will be merging. This is probably one example.