Somervell County…Part of the Barnett Shale Growth

Approximately 345 million years ago in a sea covering thousands of square miles of the State of Texas fine grained clay carried to the shore by rivers and distributed by oceanic currents slowly began to accumulate on the sea floor. At the time, microscopic organisms thrived in the sea above and as countless generations went through their life cycle, dead organisms literally rained onto the ooze below. The intermixing of clay with organic materials repeated itself for millions of years, piling one layer on top of another until hundreds of feet of organically enriched sediment built up. This massive and regionally widespread rock layer, called the Barnett Shale, is so rich in organic materials that it ranks as one of the 10 richest petroleum generating systems in the world.

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 layers 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 and the rock was further compressed. Over time, the organic material began to thermally crack into oil and natural gas. As the gas pressures within the Barnett Shale continued to increase, the highly porous and brittle rock fabric fractured. This process continued until the Barnet 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 until they were trapped in other reservoir formations. Today, the bulk moveable hydrocarbon remaining in the Barnett Shale is natural gas and the estimated volumes are astonishing. According to recent study, the Barnett Shale is estimated to contain upwards of 10 trillion cubic feet of recoverable natural gas.

Thousands of wells have been drilled and the field outline encompasses over 400,000 Texas acres. It is currently producing at a rate of 21.8 billion cubic feet per month. The success rate is close to 100% and thousands of infield locations are yet to be drilled. In a period of only a few years, the field evolved from an economically marginal petroleum resource to the largest onshore field in Texas.

Many enterprising companies began exploring for Barnett Shale production far outside what was the established trend. These step out exploratory tests resulted in a multitude of new field discoveries. The most recent edition of the current Barnett Shale Play Map, published by Geomap Company, now displays thirty such fields and the list is expected to continue growing.

Today, Somervell County sits right in the center of a drilling hotbed in the Barnett Shale. Surrounded by Johnson, Hood, Erath, Hill, Bosque and Comanche counties, Somervell County is positioned in an area that is experiencing unprecedented natural gas production.