Walking Beam and Horsehead of a Pumpjack in the Bakken

The horsehead and walking beam shown here are part of a beam pump, the standard mechanism used to bring crude oil to the surface across North Dakota's Bakken formation. A motor turns a crank below, which rocks the walking beam up and down; this motion pulls a polished rod and attached sucker rods inside the wellbore, drawing oil upward with each stroke. The counterweight opposite the horsehead offsets the load of the rod string, reducing the energy needed to lift fluid from depths that in the Bakken often exceed two miles. The Bakken shale, spanning parts of North Dakota, Montana, and southern Saskatchewan, became one of the largest U.S. oil-producing formations after horizontal drilling and hydraulic fracturing made its tight shale layers commercially viable starting in the mid-2000s. North Dakota's oil output, driven largely by Bakken wells, made it the second-largest oil-producing state in the country during the following decade.