Colby Cooper-Formation of the Barnett Shale

The Shale was formed by the intermixing of clay with organic materials, a process that repeated itself for millions of years, piling up one layer on top of another until hundreds of feet of organically enriched sediment built up. This massive and regionally widespread rock layer, known as the Barnett Shale, is so rich in organic materials that it ranks as one of the ten most prosperous petroleum-generating systems in the world.

Importantly, after the Barnett Shale was deposited, a thick, impermeable layer of limestone known as the Marble Falls formation was deposited on top, effectively sealing the Barnett Shale below. Later, the ancient basin was filled with alternating layers of sandstone, clay, shale, and limestone. As additional layers of sediment were piled on top, the more deeply buried formations were subjected to increasing pressure and temperature. The original seawater trapped within the Barnett Shale was expelled, further compressing the rock. Over time, the organic material began thermally to crack into oil and gas. As gas pressures within the Barnett Shale began to increase, the highly porous and brittle rock fabric fractured. This process continued until the Barnett Shale became a self-sourcing reservoir rock capable of generating, storing, and mobilizing hydrocarbons. Driven by gas expansion, huge amounts of oil and gas were expelled from the rock and migrated through faults and other permeable conduits, stopping only when trapped by other reservoir formations. The Barnett Shale formation lies at a depth of one to two miles below the surface. Current measuring techniques have concluded that the thickness of the Barnett Shale averages between 500 and 1,000 feet. Due to its thickness, the Barnett Shale can produce multiple pay zones within one well with various potential pay zones being accessed at a relatively minor cost. The Barnett Shale can be divided into an upper and lower unit, separated by the Forestburg Limestone. However, the Barnett Shale is generally assessed as one single unit.

Since September of 2002, the industry has been moving towards innovative techniques, including slick water fracture stimulation. In general, horizontal drilling in the area has resulted in an even greater amount of production, with significant production improvements of 300-400% and only a 40-50% increase in drilling costs. Wells are considered to be so valuable in the Barnett Shale that fracturing wells is quite common after several years, which restores many wells to initial or even higher production.