Darkness falls / Kyle Mills.

Enhanced descriptions from Syndetics:

Erin Neal has been living a secluded life in the Arizona desert since the death of his girlfriend and he isn't happy when an oil company executive comes calling. A number of important Saudi wells have stopped producing and Erin is the world's foremost expert in resolving just these kinds of complications. As far as he's concerned, though, he's left that world behind. Not his problem. Homeland Security sees things differently. Erin quickly finds himself stuck in the Saudi desert, studying a new bacteria with a voracious appetite for oil and an uncanny talent for destroying drilling equipment. But worst of all is its ability to spread. It soon becomes clear that if this contagion isn't stopped, it will infiltrate the world's petroleum reserves, cutting the industrial world off from the energy that provides the heat, food, and transportation necessary for survival. Erin realizes that there's something eerily familiar about this bacteria. And that it couldn't possibly have evolved on its own.