OIL companies rarely soil their hands with the business of extracting the hydrocarbons that are their lifeblood. The job of drilling, and constructing and maintaining wells is largely delegated to oilfield-services firms. In a deal agreed on November 17th Halliburton, the second-largest of these in the world, by market capitalisation, is set to buy Baker Hughes, the third-largest, for $38 billion in cash and shares.