Permian Basin map

Underground the region is not one basin but three features side by side. The Midland Basin is the eastern bowl, under Midland, Martin, Glasscock, Upton and Reagan counties. The Delaware Basin is the western bowl, deeper and younger in its productive rock, under Loving, Reeves, Ward and Winkler counties and on into New Mexico. Between them runs the Central Basin Platform, a buried block of older rock that stood up as a shoal while sediment piled into the basins on either side; Ector, Andrews and Crane counties sit on top of it.

The one place you can see the edge of all this at the surface is 100 miles west, where the Capitan Reef — the limestone rim that once ringed the Delaware Basin — has been tilted up and exposed as the Guadalupe Mountains. Everywhere else the Permian rock is a mile or more down and known only from drill cuttings, seismic lines and the names on the leases: Spraberry and Wolfcamp in the Midland Basin, Bone Spring and Wolfcamp in the Delaware.

The surface is high plain, 2,300 to 3,000 feet, sloping down toward the Pecos River. The northern boundary is the Llano Estacado escarpment below Lamesa, where the South Plains and its cotton begin. The southern boundary is I-10 and the Glass Mountains, past which the country becomes Big Bend. West of the Pecos the basin runs into the Trans-Pecos deserts of West Texas; east of Big Spring it fades into the rolling plains around Abilene.

Midland and Odessa sit 20 miles apart on I-20 with the region's airport between them, and the two of them hold about 247,000 of the region's 483,000 people. Midland was named for sitting midway between Fort Worth and El Paso on the Texas and Pacific Railway, which is the most literal place name in West Texas.

The modern basin dates from 28 May 1923, when a well called Santa Rita No. 1 came in on University of Texas land in Reagan County. The royalties from that lease and the ones that followed built the Permanent University Fund. Big discoveries followed fast — the Yates field in Pecos County and the Hendrick field in Winkler County, both in 1926 — and by the 1930s the region was a mature oil province. It was written off as a declining one by the 1990s, then horizontal drilling and hydraulic fracturing reopened the Spraberry and Wolfcamp after 2010 and made it the largest oil-producing region in the United States.

You can see the consequences on any map at large scale. The public road network is a plain section grid, but the lease roads and gathering lines woven through it are far denser, so a satellite image shows a mesh of tracks and rectangular well pads that no road atlas carries. Gas flares burn in enough places that the basin shows up in satellite night-light imagery as a bright smear across otherwise dark country. Towns swell and shrink with the price of crude: Reeves and Ward counties gained work camps and RV parks in the 2010s that were not there a decade earlier.

Some of it changes the ground itself. In Winkler County two sinkholes opened near Wink, one in 1980 and another in 2002, where salt beds dissolved around decades-old boreholes. Disposal of produced water into deep wells has been linked to small earthquakes around Pecos and Midland, monitored by a state seismic network. Meanwhile Scurry County's SACROC unit has had carbon dioxide pumped into it since the 1970s to push out oil the first pass left behind — one of the oldest projects of its kind anywhere.