on similar assumptions: that oil fields are inherently dangerous, and that oilfield work was a “learn on the job” occupation. These claims were not untrue, but they were also inadequate. Neither could explain why death and injury rates were so much higher in North Dakota than in other oilfields. And both assumed that responsibility for workplace safety lay with workers, not employers; the problem wasn’t seen as inadequate training, or lack of workplace safety regulations and enforcement, but rather inadequate worker-to-worker mentoring. Both explanations also failed to ask how such high-risk environments were being produced in the first place and why workers were willing to accept such high levels of risk. To answer these questions, a political economic analysis, and not merely a demographic one, is required, albeit one that takes earth forces seriously. Stated in different terms, we will need to understand how in North Dakota ‘tight’ oil becomes ‘fast’ oil—a system of production in which the speed at which oil is extracted becomes of paramount importance. To understand this, we need to grapple with the specific qualities and dynamics of the underlying geological formation, not as the ultimate cause of these deaths, but as a constitutive, and thus irreducible, moment in the North Dakota oil production assemblage. We also need to understand how ‘tight oil’ differs from ‘conventional’ oil. What petroleum geologists call a ‘petroleum system’ consists of a source rock, a reservoir rock, a seal rock, and overburden. The source rock contains the original organic material from which oil and gas is formed. A reservoir rock (usually sandstone) is porous rock into which the oil and gas migrates from the source rock. Because oil and gas is less dense than water, it tends to migrate towards the earth’s surface, unless blocked by a ‘seal’ consisting of a layer of impermeable rock. If blocked, the oil and gas collects in ‘traps’, which are essentially the highest points in the reservoir rock. Overburden refers to the many layers of soil and rock above the seal that must be drilled through—or removed in the case of open pit mining—in order to reach the trapped oil. Conventional oil is relatively easy to access and relatively inexpensive to extract. Since the oil is pressurized beneath the impermeable
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