Resource Insights: What is Saudi Arabia not telling us about its oil future?: "If the Saudis are acting now to cripple U.S. and Canadian production for the reasons my friend suggests, it means world oil supplies are going to be much more problematic after 2020 than many people suppose. It implies that at some point in the next 10 years OPEC will cease to be able (rather than cease to be willing) to balance world oil supplies. And, it suggests that no one else will be ready to act in that role when the time comes."
Over 30% of what comes up from Saudi oil fields is water that was injected to bring up the oil. The oil is running out, getting more expensive. They are desperately trying to gain market share by putting rivals out of business with low prices. This just makes the oil under Kirkuk more important to the US.