Austin Chalk stratigraphic column in Texas

The Eagle Ford Group (also called the Eagle Ford Shale) is a

sedimentary Sedimentary rocks are types of rock formed by the cementation of sediments—i.e. particles made of minerals (geological detritus) or organic matter (biological detritus)—that have been accumulated or deposited at Earth's surface. Sedime ...

rock formation A rock formation is an isolated, scenic, or spectacular surface rock (geology), rock outcrop. Rock formations are usually the result of weathering and erosion sculpting the existing rock. The term ''rock Geological formation, formation ...

deposited during the

Cenomanian The Cenomanian is, in the International Commission on Stratigraphy's (ICS) geological timescale, the oldest or earliest age (geology), age of the Late Cretaceous epoch (geology), Epoch or the lowest stage (stratigraphy), stage of the Upper Cretace ...

and

Turonian The Turonian is, in the International Commission on Stratigraphy, ICS' geologic timescale, the second age (geology), age in the Late Cretaceous epoch (geology), Epoch, or a stage (stratigraphy), stage in the Upper Cretaceous series (stratigraphy), ...

ages of the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

over much of the modern-day state of

Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...

. The Eagle Ford is predominantly composed of

organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

-rich

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

iferous marine

shale Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of Clay mineral, clay minerals (hydrous aluminium phyllosilicates, e.g., Kaolinite, kaolin, aluminium, Al2Silicon, Si2Oxygen, O5(hydroxide, OH)4) and tiny f ...

s and

marl Marl is an earthy material rich in carbonate minerals, Clay minerals, clays, and silt. When Lithification, hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae. M ...

s with interbedded thin

limestone Limestone is a type of carbonate rock, carbonate sedimentary rock which is the main source of the material Lime (material), lime. It is composed mostly of the minerals calcite and aragonite, which are different Polymorphism (materials science) ...

s. It derives its name from

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth and other terrestrial planets. Features Outcrops do not cover the majority of the Earth's land surface because in most p ...

s on the banks of the West Fork of the Trinity River near the old community of Eagle Ford, which is now a neighborhood within the city of

Dallas Dallas () is a city in the U.S. state of Texas and the most populous city in the Dallas–Fort Worth metroplex, the List of Texas metropolitan areas, most populous metropolitan area in Texas and the Metropolitan statistical area, fourth-most ...

. The Eagle Ford

belt trends from the

Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...

border southward to

San Antonio San Antonio ( ; Spanish for " Saint Anthony") is a city in the U.S. state of Texas and the most populous city in Greater San Antonio. San Antonio is the third-largest metropolitan area in Texas and the 24th-largest metropolitan area in the ...

, westward to the

Rio Grande The Rio Grande ( or ) in the United States or the Río Bravo (del Norte) in Mexico (), also known as Tó Ba'áadi in Navajo language, Navajo, is one of the principal rivers (along with the Colorado River) in the Southwestern United States a ...

Big Bend National Park Big Bend National Park is a List of national parks of the United States, national park of the United States located in West Texas, bordering Mexico. The park has national significance as the largest protected area of Chihuahuan Desert topograph ...

, and the Quitman Mountains of

West Texas West Texas is a loosely defined region in the U.S. state of Texas, generally encompassing the desert climate, arid and semiarid climate, semiarid lands west of a line drawn between the cities of Wichita Falls, Texas, Wichita Falls, Abilene, Texa ...

.Denne, R. A., Breyer, J. A., Callender, A. D., Hinote, R. E., Kariminia, M., Kosanke, T. H., Kita, Z., Lees, J. A., Rowe, H., Spaw, J. M., and Tur, N. (2016). Biostratigraphic and geochemical constraints on the stratigraphy and depositional environments of the Eagle Ford and Woodbine Groups of Texas: "in" Breyer, J. A. (ed.), The Eagle Ford Shale: A renaissance in U.S. oil production, AAPG Memoir 110, pp. 1–86. It also occurs in the subsurface of

East Texas East Texas is a broadly defined cultural, geographic, and ecological region in the eastern part of the U.S. state of Texas that consists of approximately 38 counties. It is roughly divided into Northeast Texas, Northeast, Southeast Texas, Sout ...

and

South Texas South Texas is a geographic and cultural region of the U.S. state of Texas that lies roughly south of—and includes—San Antonio. The southern and western boundary is the Rio Grande, and to the east it is the Gulf of Mexico. The population of th ...

, where it is the

source rock In petroleum geology, source rock is a sedimentary rock which has generated hydrocarbons or which has the potential to generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sedim ...

for

oil An oil is any nonpolar chemical substance that is composed primarily of hydrocarbons and is hydrophobic (does not mix with water) and lipophilic (mixes with other oils). Oils are usually flammable and surface active. Most oils are unsaturate ...

found in the Woodbine, Austin Chalk, and the Buda Limestone, and is produced unconventionally in

and the "Eaglebine" play of

. The Eagle Ford was one of the most actively drilled targets for unconventional oil and gas in the United States in 2010, but its output had dropped sharply by 2015.Jennifer Hiller, "Hard Times Hit Eagle Ford," "

San Antonio Express-News The ''San Antonio Express-News'' is a daily newspaper in San Antonio, Texas, founded in 1865. It is owned by the Hearst Corporation and has offices in San Antonio and Austin, Texas. The ''Express-News'' is the third largest newspaper in the sta ...

," January 3, 2016, pp. 1, A20 By the summer of 2016, Eagle Ford spending had dropped by two-thirds from $30 billion in 2014 to $10 billion, according to an analysis from the research firm

Wood Mackenzie Wood Mackenzie, also known as WoodMac, is a global research and consultancy group supplying data, written analysis, and consultancy advice to the energy, chemicals, renewables, metals, and mining industries. In 2015, the company was acquired ...

. This strike has been the hardest hit of any oil fields in the world. As of 2016, the spending was, however, expected to increase to $11.6 billion in 2017. A full recovery was not expected any time soon.

Fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

s are relatively common in Eagle Ford rocks. Fossilized

Plesiosaurs The Plesiosauria or plesiosaurs are an Order (biology), order or clade of extinct Mesozoic marine reptiles, belonging to the Sauropterygia. Plesiosaurs first appeared in the latest Triassic Period (geology), Period, possibly in the Rhaetian st ...

mosasaur Mosasaurs (from Latin ''Mosa'' meaning the 'Meuse', and Ancient Greek, Greek ' meaning 'lizard') are an extinct group of large aquatic reptiles within the family Mosasauridae that lived during the Late Cretaceous. Their first fossil remains wer ...

s, Fish,

shark Sharks are a group of elasmobranch cartilaginous fish characterized by a ribless endoskeleton, dermal denticles, five to seven gill slits on each side, and pectoral fins that are not fused to the head. Modern sharks are classified within the ...

teeth,

crustacean Crustaceans (from Latin meaning: "those with shells" or "crusted ones") are invertebrate animals that constitute one group of arthropods that are traditionally a part of the subphylum Crustacea (), a large, diverse group of mainly aquatic arthrop ...

sea urchin Sea urchins or urchins () are echinoderms in the class (biology), class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal zone to deep seas of . They typically have a globular body cove ...

s, feather stars,

ammonite Ammonoids are extinct, (typically) coiled-shelled cephalopods comprising the subclass Ammonoidea. They are more closely related to living octopuses, squid, and cuttlefish (which comprise the clade Coleoidea) than they are to nautiluses (family N ...

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but no ...

s, clams, and other

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

shells have all been found there.Donovan, A. D., T. S. Staerker, A. Pramudito, W. Li, M. J. Corbett, C. M. Lowery, A. M. Romero, and R. D. Gardner (2012) The Eagle Ford outcrops of West Texas: Understanding heterogeneities within unconventional mudstone reservoirs: GCAGS Journal, v. 1, p. 162–185.

Depositional environment

The Eagle Ford rocks were created by the remains of sea life that dropped to the floor of an

inland sea An inland sea (also known as an epeiric sea or an epicontinental sea) is a continental body of water which is very large in area and is either completely surrounded by dry land (landlocked), or connected to an ocean by a river, strait or " arm of ...

(or epeiric sea) that covered much of modern-day

. The Texas shelf during the

was bounded by the Ouachita Uplift to the north, the Sabine Uplift to the East, relict reef margins of the Stuart City Formation and the Sligo Formation to the southeast, and the

Western Interior Seaway The Western Interior Seaway (also called the Cretaceous Seaway, the Niobraran Sea, the North American Inland Sea, or the Western Interior Sea) was a large inland sea (geology), inland sea that existed roughly over the present-day Great Plains of ...

to the west. The

and

regions were divided by an extension of the Llano Uplift known as the San Marcos Arch. Primary basins active during Eagle Ford deposition were the East Texas and Brazos Basins in East Texas and the Maverick Basin in South Texas. The bottom waters of the Eagle Ford sea were starved of oxygen when most of the Eagle Ford material dropped to the sea floor, and this is related to the global Oceanic

Anoxic Anoxia means a total depletion in the level of oxygen, an extreme form of hypoxia or "low oxygen". The terms anoxia and hypoxia are used in various contexts: * Anoxic waters, sea water, fresh water or groundwater that are depleted of dissolved ox ...

Event 2 (OAE2), or

Cenomanian-Turonian boundary event The Cenomanian-Turonian boundary event, also known as the Cenomanian-Turonian extinction, Cenomanian-Turonian Oceanic Anoxic Event ( OAE 2), and referred to also as the Bonarelli Event or Level, was an anoxic extinction event in the Cretaceous p ...

, although the Texas shelf became that way nearly two million years prior to OAE2. The low-oxygen conditions helped preserve the

that ultimately generated the

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

s associated with the Eagle Ford in the subsurface. Evidence for anoxia include the high amounts of organic matter, the lack of

s or

trace fossil A trace fossil, also called an ichnofossil (; ), is a fossil record of biological activity by lifeforms, but not the preserved remains of the organism itself. Trace fossils contrast with body fossils, which are the fossilized remains of part ...

s of the kind of creatures that live on the sea floor, and enrichment in the

redox Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is t ...

proxies

molybdenum Molybdenum is a chemical element; it has Symbol (chemistry), symbol Mo (from Neo-Latin ''molybdaenum'') and atomic number 42. The name derived from Ancient Greek ', meaning lead, since its ores were confused with lead ores. Molybdenum minerals hav ...

and

vanadium Vanadium is a chemical element; it has Symbol (chemistry), symbol V and atomic number 23. It is a hard, silvery-grey, malleable transition metal. The elemental metal is rarely found in nature, but once isolated artificially, the formation of an ...

. After the significant drop in

sea level Mean sea level (MSL, often shortened to sea level) is an mean, average surface level of one or more among Earth's coastal Body of water, bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical ...

(

marine regression A marine regression is a geological process occurring when areas of submerged seafloor are exposed during a drop in sea level. The opposite event, marine transgression, occurs when flooding from the sea covers previously-exposed land. Descript ...

) associated with deposition of the Woodbine during the Early Cenomanian, the sea level began to rise (

marine transgression A marine transgression is a geologic event where sea level rises relative to the land and the shoreline moves toward higher ground, resulting in flooding. Transgressions can be caused by the land sinking or by the ocean basins filling with water ...

), allowing for the deposition of Lower Eagle Ford organic-rich

s in South Texas and

s of the Terrell Member of the Boquillas Formation in

starting at about 96 million years ago. Gardner, R. D., M. C. Pope, M. P. Wehner, and A. D. Donovan (2013
“Comparative stratigraphy of the Eagle Ford Group in Lozier Canyon and Antonio Creek, Terrell County, Texas”
GCAGS Journal, v. 2, p. 42-52. Wehner, M., R. Gardner, M. M. Tice, M. C. Pope, A. D. Donovan, and T. S. Staerker (2015) Anoxic, storm dominated inner carbonate ramp deposition of Lower Eagle Ford Formation, west Texas: Unconventional Resources Technology Conference, San Antonio, Texas, USA 20-22 July 2015, doi:10.15530/urtec-2015-2154667 The rise in sea level eventually drowned the East Texas Woodbine

river delta A river delta is a landform, archetypically triangular, created by the deposition of the sediments that are carried by the waters of a river, where the river merges with a body of slow-moving water or with a body of stagnant water. The creat ...

s, initiating Eagle Ford deposition in East Texas.Denne, R. A., and Breyer, J. A. (2016) Regional depositional episodes of the Cenomanian-Turonian Eagle Ford and Woodbine groups of Texas: "in" Breyer, J. A. (ed.), The Eagle Ford Shale: A renaissance in U.S. oil production, AAPG Memoir 110, p. 87-135. The initial deposits, known as the Six Flags Limestone in Dallas and the Bluebonnet Limestone in Waco, are

calcarenite Calcarenite is a type of limestone that is composed predominantly, more than 50 percent, of detrital (transported) sand-size (0.0625 to 2 mm in diameter), Carbonate rock, carbonate grains. The grains consist of sand-size grains of either cor ...

s predominantly composed of disaggregated prisms of " Inoceramus" clams and

planktonic Plankton are the diverse collection of organisms that drift in water (or air) but are unable to actively propel themselves against currents (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they pro ...

foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

tests. Following deposition of the calcarenites, a river delta began to prograde from the Ouachita Uplift to the northern East Texas Basin. Although the

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

s and

siltstone Siltstone, also known as aleurolite, is a clastic sedimentary rock that is composed mostly of silt. It is a form of mudrock with a low clay mineral content, which can be distinguished from shale by its lack of fissility. Although its permeabil ...

s from this delta, known as the Templeton Member, were originally placed within the Woodbine Formation, the

s found within them indicate that they are better associated with the Eagle Ford. In areas unaffected by the Templeton Delta, depositional rates were low, producing a condensed section composed of organic-rich,

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

s, limestones, and

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...

beds in both South Texas and West Texas. The

microfossil A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, ...

s found within the marls are predominantly

coccolith Coccoliths are individual plates or scales of calcium carbonate formed by coccolithophores (single-celled phytoplankton such as ''Emiliania huxleyi'') and cover the cell surface arranged in the form of a spherical shell, called a '' coccosphere'' ...

s and

, whereas the limestones contain abundant

radiolaria The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ect ...

and calcispheres (calcareous

cyst A cyst is a closed sac, having a distinct envelope and division compared with the nearby tissue. Hence, it is a cluster of cells that have grouped together to form a sac (like the manner in which water molecules group together to form a bubb ...

s produced by some

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

s). '' Inoceramus'' fragments and

fish A fish (: fish or fishes) is an aquatic animal, aquatic, Anamniotes, anamniotic, gill-bearing vertebrate animal with swimming fish fin, fins and craniate, a hard skull, but lacking limb (anatomy), limbs with digit (anatomy), digits. Fish can ...

bones are also found in these deposits. During the Late Cenomanian the Sabine Uplift along the modern-day Texas/

Louisiana Louisiana ( ; ; ) is a state in the Deep South and South Central regions of the United States. It borders Texas to the west, Arkansas to the north, and Mississippi to the east. Of the 50 U.S. states, it ranks 31st in area and 25 ...

border became active, causing

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

of Eagle Ford and Woodbine

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

s and deposition within the Harris Delta complex. Clay from this delta reached as far south as

DeWitt County, Texas DeWitt County is a county located in the U.S. state of Texas. As of the 2020 census, its population was 19,824. The county seat is Cuero. The county was founded in 1846 and is named for Green DeWitt, who founded an early colony in Texas. Hi ...

. Towards the end of the Late Cenomanian, the bottom waters of the Texas shelf and the Western Interior Seaway became oxygenated,Eldrett, J. S., D. Minisini, and S. C. Bergman (2014) Decoupling of the carbon cycle during Ocean Anoxic Event 2: Geology, v. 42, p. 567–570. which may be related to the sea-level maximum associated with the Cenomanian-Turonian boundary event. Evidence for this oxygenation event, known as the "Benthonic Zone," include an increase in the abundance of benthic organism fossils and

bioturbation Bioturbation is defined as the reworking of soils and sediments by animals or plants. It includes burrowing, ingestion, and defecation of sediment grains. Bioturbating activities have a profound effect on the environment and are thought to be a ...

, a decrease in redox proxies

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

, molybdenum, and vanadium, and a reduction in organic matter.Denne, R. A., R. E. Hinote, J. A. Breyer, T. H. Kosanke, J. A. Lees, N. Engelhardt-Moore, J. M. Spaw, and N. Tur (2014) The Cenomanian-Turonian Eagle Ford Group of South Texas: insights on timing and paleoceanographic conditions from geochemistry and micropaleontologic analyses: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 413, p. 2-28.Boling, K. S. and Dworkin S. I. (2015) Origin of organic matter in the Eagle Ford Formation: Interpretation, v. 3, p. SH27–SH39. This oxygenation event marks the boundary between the Lower and Upper Eagle Ford in West Texas and the subsurface of South Texas. In general, Upper Eagle Ford rocks deposited during the Cenomanian-Turonian boundary event (OAE2) contain much less organic matter than Lower Eagle Ford rocks, which is the reverse of organic matter trends seen in the global ocean. An

unconformity An unconformity is a buried erosional or non-depositional surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. In general, the older layer was exposed to erosion for an interval ...

occurs throughout East Texas at this level, possibly due to a lack of sediments reaching the basin during the sea-level maximum. The sea-level began to drop after the Early

sea-level maximum; this is most obvious at

s near

Langtry, Texas Langtry is an unincorporated community in Val Verde County, Texas, United States. The community is notable as the place where Judge Roy Bean, the "Law West of the Pecos", had his saloon and practiced law. History Langtry was originally establi ...

, where water depths became shallower than 100 ft (30 m). This limestone-rich unit is known as the Langtry Member of the Boquillas Formation. It contains very little organic matter, and abundant

s. The Kamp Ranch Limestone is found above the unconformity in the Dallas area. It is similar to the older Six Flags and Bluebonnet Limestones, as it is predominantly composed of disaggregated prisms of '' Inoceramus'' clams and has

ripple marks In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water ( current or waves) or directly by wind. Defining ripple cross-laminae and asymmetric ripples * ''Current ripple ...

indicative of shallow-water deposition. As the sea level continued to fall during the Late Turonian, deltaic sediments originating from the Ouachita Uplift prograded into the northern East Texas region. These sandstones are known as the Sub-Clarksville Delta in the subsurface and the Bells Sandstone in

. In the South Texas subsurface, the age equivalent unit to the Langtry Member is more calcareous than the underlying Upper Eagle Ford rocks, making them difficult to distinguish from the limestones of the overlying Austin Chalk, although an unconformity is found between the Eagle Ford and the Austin Chalk in both South Texas and East Texas.

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 ~88 mya. A decrease in the effective elastic plate thicknesses caused the basin to subside as the uplift became increasingly elevated. As a result, an estimated 150 m 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 East Texas petroleum reservoir and the creation of a middle Cretaceous unconformity. Currently, the Sabine Uplift is in the subsurface, and the middle Cretaceous unconformity is not seen because it is buried below a massive wedge of

clastic Clastic rocks are composed of fragments, or clasts, of pre-existing minerals and rock. A clast is a fragment of geological detritus,Essentials of Geology, 3rd Ed, Stephen Marshak, p. G-3 chunks, and smaller grains of rock broken off other rocks by ...

sediments from the Late Cretaceous to the present.

Oil and natural gas production

Paul Basinski, the geologist who helped discover the Eagle Ford basin, has been called "one of the fathers of fracking". Petrohawk drilled the first well to unconventionally produce gas from the Eagle Ford in 2008, in LaSalle County, Texas. Oil companies quickly extended the productive area, which stretches from the Texas-

Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...

border in

Webb Webb may refer to: Places Antarctica *Webb Glacier (South Georgia) *Webb Glacier (Victoria Land) * Webb Névé, Victoria Land, the névé at the head of Seafarer Glacier * Webb Nunataks, a group of nunataks in the Neptune Range * Webb Peak (disa ...

and Maverick counties and extend 400 miles toward

. 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 A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

, which makes it brittle, and it is thus easier to use

hydraulic fracturing Fracking (also known as hydraulic fracturing, fracing, hydrofracturing, or hydrofracking) is a well stimulation technique involving the fracturing of Formation (geology), formations in bedrock by a pressurized liquid. The process involves the ...

to produce the oil or gas. The oil reserves in the Eagle Ford Shale Play were estimated in 2011 at 3 billion barrels. The U.S.

Energy Information Administration The U.S. Energy Information Administration (EIA) is a principal agency of the U.S. Federal Statistical System responsible for collecting, analyzing, and disseminating energy information to promote sound policymaking, efficient markets, and pub ...

(EIA) estimated that the Eagle Ford held 50.2 trillion cubic feet (TCF) of unproved, technically recoverable gas. The average well was estimated to recover 2.36 billion cubic feet (BCF) of gas. In 2011, the Eagle Ford produced an average of 1.14 BCF/day of gas and 211,000 barrels/day of oil and condensate. In 2012, the Eagle Ford produced an average of 2.43 BCF/day of gas and 566,000 barrels/day of oil and condensate. By the end of 2013, production had skyrocketed to well over 1,000,000 BOE/day. In 2013, the Eagle Ford produced an average of 3.73 BCF/day of gas and 975,000 barrels/day of oil and condensate. In 2014, the Eagle Ford produced an average of 4.85 BCF/day of gas and 1,376,000 barrels/day of oil and condensate. The large increase in tight oil production from the Eagle Ford is one of factors that led to the oil price drop of late 2014. Total production peaked in March 2015 at 2.62 million BOE/day (1.625 million BO/day and 5.75 BCF/day). Eagle Ford production has occurred in 27 counties in Texas. The large area of oil and gas operations of the Eagle Ford are visible on nighttime satellite photos of the United States, appearing as a diffuse bright patch about two hundred miles long, between the more concentrated lights of

Austin Austin refers to: Common meanings * Austin, Texas, United States, a city * Austin (given name), a list of people and fictional characters * Austin (surname), a list of people and fictional characters * Austin Motor Company, a British car manufac ...

Houston Houston ( ) is the List of cities in Texas by population, most populous city in the U.S. state of Texas and in the Southern United States. Located in Southeast Texas near Galveston Bay and the Gulf of Mexico, it is the county seat, seat of ...

, Victoria, Corpus Christi, Laredo, and neighboring cities.

Proven reserves (US)*

* US EIA, 2010: 2.5 trillion cubic feet (TCF) of gas * US EIA, 2011: 1.25 billion barrels of oil, 8.4 TCF of natural gas * US EIA, 2012: 3.37 billion barrels of oil * US EIA, 2019: 4.30 billion barrels of oil * US EIA, 2020: 3.25 billion barrels of oil * US EIA, 2021: 3.61 billion barrels of oil, 36.4 TCF of natural gas * US EIA, 2022: 3.82 billion barrels of oil, 39.6 TCF of natural gas *EIA estimate includes reserves in the basin in other overlying and underlying strata including the Austin Chalk, Olmos/San Miguel, etc.

Mexico

The Eagle Ford Formation extends into northern Mexico's Burgos Basin, where it is known as the Boquillas Formation and has an average thickness of . Total organic content (TOC) is estimated to average 5%. Technically recoverable hydrocarbons are estimated to be 343 trillion cubic feet of shale gas and 6.3 billion barrels of

tight oil Tight oil (also known as shale oil, shale-hosted oil or light tight oil, abbreviated LTO) is light crude oil contained in Unconventional (oil & gas) reservoir, unconventional petroleum-bearing formations of low Permeability (earth sciences), perme ...

. The national oil company

Pemex Pemex (a portmanteau of Petróleos Mexicanos, which translates to ''Mexican Petroleum'' in English; ) is the Mexico, Mexican State ownership, state-owned Petroleum industry, petroleum corporation managed and operated by the government of Mexico, ...

first began exploring in 2010. Pemex had an exploration program in progress until 2015. In April 2013, Pemex started producing the nation's first shale gas well, just south of the U.S. border. The well was completed in the equivalent of the Eagle Ford Formation. Gas drilling in the Burgos Basin, close to the U.S. border, has been hampered by drug gangs. One Mexican industry expert said that Mexico was unlikely to develop the Eagle Ford because of lack of pipeline infrastructure and lack of expertise and because the Mexican company Pemex was investing in oil deposits that yield a higher rate of return., Emily Pickrell
"Mexico unlikely to tap its Eagle Ford Shale, experts say"
''Houston Chronicle'', October 31 2013.

Decline in crude oil prices, 2015 onward

With the worldwide decline in crude oil prices in 2015, a sharp downturn swept through Eagle Ford play. In January 2015, there were 840 active

drilling rig A drilling rig is an integrated system that Drilling, drills wells, such as oil or water wells, or holes for piling and other construction purposes, into the earth's subsurface. Drilling rigs can be massive structures housing equipment used to ...

s in Texas as a whole; by the end of the year, 321. Within the Eagle Ford play, the decline during these twelve months was from 200 to 76 rigs. The oil price decline rendered it uneconomical to drill sub-optimal wells. Particularly hard hit in the decline were the oil-field workers in South Texas.

References

External links

The University of Texas at Dallas

Geosciences Department
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Eagle Ford Info
{{Shale gas Shale groups of the United States Upper Cretaceous Series of North America Cretaceous geology of Texas Geologic groups of Texas Cenomanian Stage Turonian Stage Oil fields in Texas Oil-bearing shales in the United States Marl groups Limestone groups of the United States Sandstone groups of the United States

Depositional environment

Eagle Ford unconformity

Oil and natural gas production

Proven reserves (US)*

Mexico

Decline in crude oil prices, 2015 onward

See also

References

External links