Eagle Ford Shale

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The Eagle Ford Shale is a sedimentary rock formation from the Late Cretaceous age underlying much of South and East Texas in United States, consisting of organic matter-rich fossiliferous marine shale. It derives its name from the old community of Eagle Ford, now a neighborhood in West Dallas, where outcrops of the Eagle Ford Shale were first observed. Such outcrops can be seen in the geology of the Dallas–Fort Worth Metroplex, and are labeled on images with the label "Kef". The Eagle Ford Shale is one of the most actively drilled targets for both oil and gas in the U.S.

Gas production in Eagle Ford grew from very little in 2008 to about 2 bcf/day by mid-2012.

Water usage

From January 2011 through May 2013, fracking operators in the Eagle Ford Shale region of Texas used approximately 19 billion gallons of water for its 4,300-plus wells. That's was the highest water use of any fracking region in the country.

Pipeline proposed

In November 2013 it was reported that NET Mexico Pipeline Partners LLC, an affiliate of Houston-based NET Midstream, had obtained presidential approval to build a natural gas pipeline "to move Eagle Ford natural gas into Mexico, according to a statement from the company." Currently NET Mexico is planning to "build a 124-mile pipeline to move gas from nine points in Nueces County, Texas. The pipeline is anchored by a long-term gas transportation agreement for up to 2.1 billion cubic feet per day with MGI Supply Ltd., a subsidiary of the Mexican state-owned Pemex Gas y Petroquimica Basica, better known as PEMEX."

Depositional environment

Transgression (geology) continued to occur after complete deposition of the Woodbine around 92 million years ago ("mya"). Creation of the Colorado Group, which first created the Eagle Ford Shale, occurred between ~92 and 88 mya. The Eagle Ford is mostly confined within the subsurface but outcrops on west side of Dallas and continues at a 1 degree easterly prograding tilt. The Eagle Ford Shale had sea level depths about 100 meters or 330 feet, and deposited about 20-50 kilometers from the shore. The depositional environment in the lower beds was low energy and slightly Hypoxia (environmental). This anoxic setting of the deeper oceanic waters was a result of increased amounts of CO₂ during deposition in the Cretaceous. The lower section of the Eagle Ford consists of organic-rich, pyritic, and fossiliferous marine shales which mark the maximum flooding surface, or the deepest water during Eagle Ford deposition. The different fauna present in the Eagle Ford suggest the waters were calm and within the photic zone. A small member of the Eagle Ford that consists of a thin limestone unit between shales is known as the Kamp Ranch. A small regressive highstand formed this carbonate layer towards the top of the Eagle Ford, identifiable by high energy features, such as ripple marks from storm generated waves and interbedded carbonaceous siltstones. The overall thickness of the undivided Eagle Ford Group is 200–300 feet thick.

Eagle Ford unconformity

In the Cretaceous after the Woodbine and Eagle Ford formations were deposited, the Sabine Uplift started to become elevated again due to its reactivation ~88mya. A decrease in the effective elastic plate thicknesses caused the basin to subside, as the uplift became increasingly elevated. As a result, an estimated 150m of uplift over the Sabine region caused the eastern parts of the Woodbine and Eagle Ford formations to have a subaerial exposure, which eventually resulted in their easterly erosion. Deposition of the Austin Chalk after this erosional occurrence caused a sealing of the well known East Texas petroleum reservoir, and creation of a middle Cretaceous unconformity. Currently the Sabine Uplift is in the subsurface, and the middle Cretaceous unconformity is not seen since as it is buried below a massive wedge of Clastic rock sediments from the Late Cretaceous to the present.

Eagle Ford Group undivided

North of Hill County, Texas, shale, sandstone, and limestone; shale, bituminous, selenitic, with calcareous concretions and large septaria; sandstone and sandy limestone in upper and middle parts, platy, burrowed, medium to dark gray; in lower part bentonitic; hard limestone bed marks base in Ellis County, Texas and Johnson County, Texas Counties; locally forms low cuesta; thickness 200–300 feet.

Oil and natural gas

The Eagle Ford Shale is a hydrocarbon producing formation rich in oil field and natural gas fields. The shale Petroleum play area starts at the Texas-Mexico border in Webb County, Texas and Maverick County, Texas counties and extends 400 miles toward East Texas. The play is 50 miles wide and an average of 250 feet thick at a depth between 4000 and 12,000 feet. The shale contains a high amount of carbonate which makes it brittle and easier to use fracking to produce the oil or gas. The oil reserves are estimated at 3 billion barrels with potential output of 420,000 barrels a day.

Fines issued

It was reported in September 30, 2013 that "Texas air regulators fined 11 oil and pipeline companies for pollution violations in the fast-growing Eagle Ford Shale field in the last three years. An additional 188 operators were allowed to fix their violations without paying a fine, the Texas Commission on Environmental Quality said ... TCEQ issued a total of $78,684 in fines against 11 operators, according to documents the agency provided. Of that amount, $15,735 was deferred, meaning the companies involved could avoid paying it if they fixed the problem, according to documents provided by the commission."

Race and Class

A January 2016 article in American Journal of Public Health found that poor, heavily Hispanic neighborhoods disproportionately bear the brunt hydraulic fracturing wastewater burden in Texas' booming Eagle Ford Shale. Wastewater disposal wells in southern Texas are disproportionately permitted in areas with higher proportions of people of color and residents living in poverty. Of the more than 217,000 racial minorities living less than three miles from the Texas disposal well sites, 83% were Hispanic.

The study found [[hydraulic fracturing] slightly higher in white communities but wastewater wells higher in communities of color.

Dr. Jill Johnston, the lead author of the study told Environmental Health News, “A lot of people there [Eagle Ford area] are reliant on groundwater, putting this all underground is jeopardizing water sources.”

Resources

References

• Robert T. Ryder, Fracture Patterns and Their Origin in the Upper Devonian Antrim Shale Gas Reservoir of the Michigan Basin: A Review, US Geological Survey, Open-File Report 96-23, 1996, accessed 3 November 2009.

Related GEM.wiki articles

• United States and fracking
• Shale formations in the United States
• Texas and fracking

Wikipedia also has an article on Eagle Ford Shale. This article may use content from the Wikipedia article under the terms of the GFDL.