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86-591: As of 2007, some experts suggested that the Barnett Shale might have the largest producible reserves of any onshore natural gas field in the United States . The field is thought to have 2.5 × 10 ^  cu ft (71 km) of recoverable natural gas, and 30 × 10 ^  cu ft (850 km) of natural gas in place. Oil also has been found in lesser quantities, but sufficient (with high oil prices) to be commercially viable. The Barnett Shale

172-521: A geological mapping expedition, scientists noted a thick black organic-rich shale in an outcrop close to the stream. The shale was consequently named the Barnett Shale. The Barnett shale has acted as a source and sealing cap rock for more conventional oil and gas reservoirs in the area. Gas wells producing from the Barnett Shale of the Fort Worth basin are designated as the Newark, East Gas Field by

258-607: A 100% success rate on completed wells. An experimental vertical well is being drilled in McLennan County (near Waco ) to assess the potential for drilling along the Ouachita Fold , a geological barrier which defines the southern limit of the Barnett Shale. Although horizontal wells are now the norm, as of early 2013, some vertical wells were still being drilled in the Barnett. Hydraulic fracturing carried out in

344-581: A 25% royalty for homeowners in Ryan Place, Mistletoe Heights, and Berkley on Fort Worth's south side, and $ 22,500 per acre and a 25% royalty for a group of homeowners in south Arlington . More recent articles in the Fort Worth Weekly report that many signed lease agreements have not been honored, with lessors alleging that they were paid significantly less than promised or were not paid at all. Oil industry advocates claim that by 2015

430-469: A January 2011 Texas Railroad Commission (TRRC) hearing, TRRC staff concluded that, based on chemical composition, the gas in the water wells came from the shallow Strawn Formation, rather than the deeper Barnett Shale, in which the Range wells were completed. They also concluded that pressure tests by Range showed mechanical integrity of the casing. EPA and the two homeowners were invited to present evidence at

516-445: A cap rock) is a fundamental part of the trap that prevents hydrocarbons from further upward migration. A capillary seal is formed when the capillary pressure across the pore throats is greater than or equal to the buoyancy pressure of the migrating hydrocarbons. They do not allow fluids to migrate across them until their integrity is disrupted, causing them to leak. There are two types of capillary seal whose classifications are based on

602-406: A consequence, oil and natural gas are often found together. In common usage, deposits rich in oil are known as oil fields, and deposits rich in natural gas are called natural gas fields. In general, organic sediments buried in depths of 1,000 m to 6,000 m (at temperatures of 60 ° C to 150 °C) generate oil, while sediments buried deeper and at higher temperatures generate natural gas. The deeper

688-407: A few, very large offshore drilling rigs, due to the cost and logistical difficulties in working over water. Rising gas prices in the early 21st century encouraged drillers to revisit fields that previously were not considered economically viable. For example, in 2008 McMoran Exploration passed a drilling depth of over 32,000 feet (9754 m) (the deepest test well in the history of gas production) at

774-587: A gravity higher than 45 API. Gas cycling is the process where dry gas is injected and produced along with condensed liquid. Devon Energy Devon Energy Corporation is a company engaged in hydrocarbon exploration in the United States. It is organized in Delaware with operational headquarters in the 50-story Devon Energy Center in Oklahoma City , Oklahoma . Its primary operations are in

860-482: A pace that Mitchell could not match. In 2001, for the first time, Mitchell completed fewer than half the Barnett Shale wells (258 wells, versus 260 by other operators). George Mitchell sold Mitchell Energy to Devon Energy in 2002. Helped by better drilling technology, the difficulties of drilling near populated areas, and higher gas prices in the 2000s, horizontal wells became more economic and practical, and in 2005 new horizontal wells outnumbered new vertical wells in

946-471: A result of changes in the structure of the subsurface from processes such as folding and faulting , leading to the formation of domes , anticlines , and folds. Examples of this kind of trap are an anticline trap, a fault trap, and a salt dome trap. They are more easily delineated and more prospective than their stratigraphic counterparts, with the majority of the world's petroleum reserves being found in structural traps. Stratigraphic traps are formed as

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1032-435: A result of lateral and vertical variations in the thickness, texture, porosity, or lithology of the reservoir rock. Examples of this type of trap are an unconformity trap, a lens trap and a reef trap. Hydrodynamic traps are a far less common type of trap. They are caused by the differences in water pressure, that are associated with water flow, creating a tilt of the hydrocarbon-water contact. The seal (also referred to as

1118-502: A significantly higher displacement pressure such that the pressure required for tension fracturing is actually lower than the pressure required for fluid displacement—for example, in evaporites or very tight shales. The rock will fracture when the pore pressure is greater than both its minimum stress and its tensile strength then reseal when the pressure reduces and the fractures close. Unconventional (oil & gas) reservoirs are accumulations where oil and gas phases are tightly bound to

1204-428: Is an economic benefit worthy of commercial attention. Oil fields may extend up to several hundred kilometers across the surface, meaning that extraction efforts can be large and spread out across the area. In addition to extraction equipment, there may be exploratory wells probing the edges to find more reservoir area, pipelines to transport the oil elsewhere, and support facilities. Oil fields can occur anywhere that

1290-402: Is analogous to saying that the oil which can be extracted forms within the source rock itself, as opposed to accumulating under a cap rock. Oil sands are an example of an unconventional oil reservoir. Unconventional reservoirs and their associated unconventional oil encompass a broad spectrum of petroleum extraction and refinement techniques, as well as many different sources. Since the oil

1376-403: Is being pursued at a higher rate because of the scarcity of conventional reservoirs around the world. After the discovery of a reservoir, a petroleum engineer will seek to build a better picture of the accumulation. In a simple textbook example of a uniform reservoir, the first stage is to conduct a seismic survey to determine the possible size of the trap. Appraisal wells can be used to determine

1462-452: Is best to manage the gas cap effectively, that is, placing the oil wells such that the gas cap will not reach them until the maximum amount of oil is produced. Also a high production rate may cause the gas to migrate downward into the production interval. In this case, over time the reservoir pressure depletion is not as steep as in the case of solution-based gas drive. In this case, the oil rate will not decline as steeply but will depend also on

1548-426: Is called the stock tank oil initially in place . As a result of studying factors such as the permeability of the rock (how easily fluids can flow through the rock) and possible drive mechanisms, it is possible to estimate the recovery factor, or what proportion of oil in place can be reasonably expected to be produced. The recovery factor is commonly 30–35%, giving a value for the recoverable resources. The difficulty

1634-490: Is contained within the source rock, unconventional reservoirs require that the extracting entity function as a mining operation rather than drilling and pumping like a conventional reservoir. This has tradeoffs, with higher post-production costs associated with complete and clean extraction of oil being a factor of consideration for a company interested in pursuing a reservoir. Tailings are also left behind, increasing cleanup costs. Despite these tradeoffs, unconventional oil

1720-456: Is created in surrounding rock by the presence of high heat and pressure in the Earth's crust . Reservoirs are broadly classified as conventional and unconventional reservoirs. In conventional reservoirs, the naturally occurring hydrocarbons, such as crude oil ( petroleum ) or natural gas , are trapped by overlying rock formations with lower permeability , while in unconventional reservoirs

1806-487: Is known as an unconventional "tight" gas reservoir, indicating that the gas is not easily extracted. The shale is very impermeable, and it was virtually impossible to produce gas in commercial quantities from this formation until oil and gas companies learned how to effectively use massive hydraulic fracturing in the formation. The use of horizontal drilling further improved the economics, and made it easier to extract gas from under developed areas. Future development of

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1892-431: Is more accurate to divide the oil industry into three sectors: upstream ( crude oil production from wells and separation of water from oil ), midstream (pipeline and tanker transport of crude oil) and downstream ( refining of crude oil to products, marketing of refined products, and transportation to oil stations). More than 65,000 oil fields are scattered around the globe, on land and offshore. The largest are

1978-649: Is shared between Iran and Qatar . The second largest natural gas field is the Urengoy gas field , and the third largest is the Yamburg gas field , both in Russia . Like oil, natural gas is often found underwater in offshore gas fields such as the North Sea , Corrib Gas Field off Ireland , and near Sable Island . The technology to extract and transport offshore natural gas is different from land-based fields. It uses

2064-413: Is that reservoirs are not uniform. They have variable porosities and permeabilities and may be compartmentalized, with fractures and faults breaking them up and complicating fluid flow. For this reason, computer modeling of economically viable reservoirs is often carried out. Geologists, geophysicists, and reservoir engineers work together to build a model that allows simulation of the flow of fluids in

2150-940: Is usually necessary to drill into the Earth's crust, although surface oil seeps exist in some parts of the world, such as the La Brea Tar Pits in California and numerous seeps in Trinidad . Factors that affect the quantity of recoverable hydrocarbons in a reservoir include the fluid distribution in the reservoir, initial volumes of fluids in place, reservoir pressure, fluid and rock properties, reservoir geometry, well type, well count, well placement, development concept, and operating philosophy. Modern production includes thermal , gas injection , and chemical methods of extraction to enhance oil recovery. A virgin reservoir may be under sufficient pressure to push hydrocarbons to

2236-724: The Barnett Shale STACK formation in Oklahoma , Delaware Basin , Eagle Ford Group , and the Rocky Mountains . In 2023, the company was ranked 216th on the Fortune 500 and 445th on the Forbes Global 2000 . As of December 31, 2023, the company had proved reserves of 1,817 million barrels of oil equivalent (1.112 × 10  GJ), of which 43% was petroleum , 28% was natural gas liquids , and 29%

2322-1137: The Fayetteville Shale in Arkansas , the Marcellus Shale in Appalachia, the Woodford Shale in Oklahoma, the Ohio Shale in Kentucky and West Virginia and the Haynesville Shale in Louisiana and East Texas. 33°N 98°W  /  33°N 98°W  / 33; -98 Natural gas field A petroleum reservoir or oil and gas reservoir is a subsurface accumulation of hydrocarbons contained in porous or fractured rock formations. Such reservoirs form when kerogen (ancient plant matter)

2408-634: The Ghawar Field in Saudi Arabia and the Burgan Field in Kuwait , with more than 66 to 104 billion barrels (9.5×10 m ) estimated in each. In the modern age, the location of oil fields with proven oil reserves is a key underlying factor in many geopolitical conflicts. Natural gas originates by the same geological thermal cracking process that converts kerogen to petroleum. As

2494-605: The Texas Railroad Commission . From 2002 to 2010 the Barnett was the most productive source of shale gas in the US; it is now third, behind the Marcellus Formation and the Haynesville Shale . In January 2013, the Barnett produced 4.56 billion cubic feet per day, which made up 6.8% of all the natural gas produced in the US. The field was discovered in 1981 when Mitchell Energy drilled and completed

2580-560: The aquatic ecosystem , which is usually a sea but might also be a river, lake, coral reef, or algal mat , the formation of an oil or gas reservoir also requires a sedimentary basin that passes through four steps: Timing is also an important consideration; it is suggested that the Ohio River Valley could have had as much oil as the Middle East at one time, but that it escaped due to a lack of traps. The North Sea , on

2666-407: The buoyancy forces driving the upward migration of hydrocarbons through a permeable rock cannot overcome the capillary forces of a sealing medium. The timing of trap formation relative to that of petroleum generation and migration is crucial to ensuring a reservoir can form. Petroleum geologists broadly classify traps into three categories that are based on their geological characteristics:

Barnett Shale - Misplaced Pages Continue

2752-678: The Barnett Shale Energy Council (an industry advocacy group) has said that he believes regulation will increase under the Obama administration; as of 2012, this has not been the case. A 2011 study for the Fort Worth Chamber of Commerce concluded that the Barnett Shale development was responsible for 119,000 jobs in Texas, 100,000 of them in the Fort Worth region. An expanded gas pipeline network for transporting

2838-536: The Barnett Shale allege that companies have reneged on promised lease payments, altered agreements after the fact, or failed to meet their commitments to lessors of land in the shale. The profit potential of the Barnett Shale gas play has spurred companies to search for other sources of shale gas across the United States . Other shale gas prospects in the United States include the Antrim Shale in Michigan ,

2924-399: The Barnett Shale is done by pumping a mixture of water, sand, and various chemical additives (to affect viscosity , flow rates, etc.) into the well bore at a sufficient pressure to create and propagate a fracture in the surrounding rock formation down hole. This is crucial in low permeability rock as it exposes more of the formation to the well bore and greater volumes of gas can be produced by

3010-457: The Barnett Shale may be responsible for more than 108,000 jobs. Critics say that tax revenues may be offset by cleanup costs for toxic byproducts of gas drilling, such as benzene and naturally occurring radioactive material (NORM). Environmental groups have pressured state regulators to begin forcing cleanups. The San Juan Citizens Alliance has sued to force the EPA to tighten regulations. Ed Ireland, of

3096-449: The Barnett Shale, the gas uses fractures to move out of the rock and into the wellbore . The fractures may be natural or induced (see below). A horizontal well exposes more rock (and therefore more fractures) to the wellbore because it is usually designed with the horizontal portion of the well in the productive formation. In 2005–2007 horizontal drilling in the Barnett Shale extended south into Johnson , Hill , and Bosque counties, with

3182-579: The Barnett Shale. Mitchell is widely credited with personally making a success of the Barnett Shale, and thus creating the gas production boom in the Barnett, and, when other companies imitated his techniques, many other shale-gas and tight-oil successes in the US and other countries. Incrementally, Mitchell Energy found ways to increase production. Early on, Mitchell abandoned the foam frac, which had been used with some success in Appalachian Basin shales, and found that gel fracs worked better in

3268-402: The Barnett for the first time. In 2008, 2901 horizontal wells were completed in the Barnett, versus just 183 vertical wells. It was thought that only a few of the thicker sections close to Fort Worth would be able to support economic drilling, until new advances in horizontal drilling were developed in the 1980s. Techniques such as fracturing, or "fracking", wells, used by Mitchell Energy, opened

3354-466: The Barnett where water use for hydraulic fracturing could compete with other uses such as drinking and agriculture. The process of hydraulic fracturing generates significant criticism. Opponents allege that it is inadequately monitored and poses significant threats to water and air quality in surrounding areas, and cite a growing number of incidents of methane in nearby water wells. As of September 2008, gas producers said that bonuses paid to landowners in

3440-455: The Barnett. In 1986, Mitchell Energy applied the first massive hydraulic frac, a gel frac, to the Barnett Shale. In 1991, Mitchell Energy, with a subsidy from the federal government, drilled the first horizontal well in the Barnett, but the experiment was not considered a success. It was not until 1998 that Mitchell drilled two more horizontal wells; they were technical successes, but economic failures. Mitchell's fourth and last horizontal attempt

3526-620: The Blackbeard site in the Gulf of Mexico. ExxonMobil 's drill rig there had reached 30,000 feet by 2006, without finding gas, before it abandoned the site. Crude oil is found in all oil reservoirs formed in the Earth's crust from the remains of once-living things. Evidence indicates that millions of years of heat and pressure changed the remains of microscopic plants and animals into oil and natural gas. Roy Nurmi, an interpretation adviser for Schlumberger oil field services company, described

Barnett Shale - Misplaced Pages Continue

3612-644: The C. W. Slay #1 near Newark, Texas , in Wise County . The well was drilled vertically, completed with a nitrogen foam frac, and did not produce enough gas to cause any excitement. Despite the low production rate, Mitchell Energy owner George P. Mitchell was convinced that he could find a better way to produce gas from the Barnett. Mitchell persevered for years in the face of low production rates in his initial wells, low gas prices, and low profitability. Industry commentators have written that few, if any, other companies would have continued drilling well after well in

3698-523: The Core area where the shale is thicker and the uncertainty is reduced. This allows for the wells to be drilled at slightly lower gas prices than those in Non-core areas. Operators, such as EOG Resources , Gulftex Operating, Inc , and Devon Energy , stated in public reports in mid-2005 that they estimate that one third to one half of the land in the counties that contain the Barnett Shale, including

3784-715: The TRRC hearing, but did not. In March 2012, the EPA dropped its order against Range. The mayor of DISH, Texas complained that air pollution from a natural gas compressor station was sickening his family. However, in May 2010, The Texas Department of State Health Services released air quality results for DISH, including tests of blood and urine samples from 28 DISH residents that were tested for volatile organic compounds (VOCs). The agency concluded: “The information obtained from this investigation did not indicate that community-wide exposures from gas wells or compressor stations were occurring in

3870-410: The actual capacity. Laboratory testing can determine the characteristics of the reservoir fluids, particularly the expansion factor of the oil, or how much the oil expands when brought from the high pressure and high temperature of the reservoir to a "stock tank" at the surface. With such information, it is possible to estimate how many "stock tank" barrels of oil are located in the reservoir. Such oil

3956-499: The early years of the field. In 1995, for instance, Mitchell completed 70 Barnett wells, while all other operators combined completed three. This was largely because the Barnett was marginal economically: according to a former CEO, Mitchell had invested about $ 250 million in the Barnett from 1981 to 1997, and had not recouped its costs. But after 1997, competitors realized that Mitchell had discovered how to extract gas profitably, they, too started buying leases and drilling Barnett wells, at

4042-400: The end of 2011 were 32.6 trillion cubic feet of gas and 118 million barrels of oil or condensate. Two key developments in well design and completions have fostered development of the Barnett Shale. These are horizontal drilling, and hydraulic fracturing. Horizontal drilling has increased the potential of the Barnett Shale as a major source of natural gas . Horizontal drilling has changed

4128-478: The field will be hampered in part by the fact that major portions of the field are in urban areas, including the rapidly growing Dallas-Fort Worth Metroplex . Some local governments are researching means by which they can drill on existing public land (e.g., parks) without disrupting other activities so they may obtain royalties on any minerals found, whereas others are seeking compensation from drilling companies for damage to roads caused by overweight vehicles (many of

4214-402: The gas bubbles drive the oil to the surface. The bubbles then reach critical saturation and flow together as a single gas phase. Beyond this point and below this pressure, the gas phase flows out more rapidly than the oil because of its lowered viscosity. More free gas is produced, and eventually the energy source is depleted. In some cases depending on the geology the gas may migrate to the top of

4300-546: The gas to market is being sought. The completion of a 42-inch (1,100 mm) natural gas transmission pipeline through Hill County may open up new areas for drilling. According to the Texas Railroad Commission , as of 2012 there were 235 operators (companies which manage producing wells) in the Barnett Shale. In terms of gas volumes produced, the top ten operators, in order of decreasing gas production, were: The Barnett Shale has been classified into "Core" and "Non-Core" areas of production. To date production has concentrated in

4386-407: The geology of the underlying rock allows, meaning that certain fields can be far away from civilization, including at sea. Creating an operation at an oil field can be a logistically complex undertaking, as it involves the equipment associated with extraction and transportation, as well as infrastructure such as roads and housing for workers. This infrastructure has to be designed with the lifespan of

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4472-468: The increased surface area. Without hydraulic fracturing, the wells would not produce at an economically feasible rate. In 1997, Nick Steinsberger, an engineer of Mitchell Energy (now part of Devon Energy ), applied the slickwater fracturing technique, using more water and higher pump pressure than previous fracturing techniques, which was used in East Texas in the Barnett Shale of north Texas. In 1998,

4558-434: The liquid sections applying extra pressure. This is present in the reservoir if there is more gas than can be dissolved in the reservoir. The gas will often migrate to the crest of the structure. It is compressed on top of the oil reserve, as the oil is produced the cap helps to push the oil out. Over time the gas cap moves down and infiltrates the oil, and the well will produce more and more gas until it produces only gas. It

4644-438: The location of oil-water contact and with it the height of the oil bearing sands. Often coupled with seismic data, it is possible to estimate the volume of an oil-bearing reservoir. The next step is to use information from appraisal wells to estimate the porosity of the rock. The porosity of an oil field, or the percentage of the total volume that contains fluids rather than solid rock, is 20–35% or less. It can give information on

4730-440: The most heavily prospected counties like Johnson and Tarrant, will get wells. There have been few dry holes drilled, because technology like 3D Seismic allows operators to identify potential hazards before they drill and avoid bad areas. Some of the hazards include faults and karst features (sinkholes). Faults may divert hydraulic fracturing, reducing its effectiveness, and karst features may contain abundant water that limits

4816-568: The new technique proved to be successful when the first 90 days gas production from the well called S.H. Griffin No. 3 exceeded production of any of the company's previous wells. Scientists at the Jackson School of Geosciences at the University of Texas at Austin , who have worked closely with producing companies to develop the Barnett play, also see potential for conflict in some parts of

4902-438: The oil and form a secondary gas cap. Some energy may be supplied by water, gas in water, or compressed rock. These are usually minor contributions with respect to hydrocarbon expansion. By properly managing the production rates, greater benefits can be had from solution-gas drives. Secondary recovery involves the injection of gas or water to maintain reservoir pressure. The gas/oil ratio and the oil production rate are stable until

4988-436: The oil field in mind, as production can last many years. Several companies, such as Hill International , Bechtel , Esso , Weatherford International , Schlumberger , Baker Hughes and Halliburton , have organizations that specialize in the large-scale construction of the infrastructure to support oil field exploitation. The term "oilfield" can be used as a shorthand to refer to the entire petroleum industry . However, it

5074-724: The other hand, endured millions of years of sea level changes that successfully resulted in the formation of more than 150 oil fields. Although the process is generally the same, various environmental factors lead to the creation of a wide variety of reservoirs. Reservoirs exist anywhere from the land surface to 30,000 ft (9,000 m) below the surface and are a variety of shapes, sizes, and ages. In recent years, igneous reservoirs have become an important new field of oil exploration, especially in trachyte and basalt formations. These two types of reservoirs differ in oil content and physical properties like fracture connectivity, pore connectivity, and rock porosity . A trap forms when

5160-406: The placement of the well with respect to the gas cap. As with other drive mechanisms, water or gas injection can be used to maintain reservoir pressure. When a gas cap is coupled with water influx, the recovery mechanism can be highly efficient. Water (usually salty) may be present below the hydrocarbons. Water, as with all liquids, is compressible to a small degree. As the hydrocarbons are depleted,

5246-490: The possibility of more large scale production. Even with new techniques, significant drilling did not begin until gas prices increased in the late 1990s. As of 2012, the Newark, East Field extended into 24 counties, with permits issued for wells in a 25th county, Hamilton . The field had more than 16,000 producing wells. Gas production in 2011 was 2.0 trillion cubic feet. The field was the largest gas producer in Texas, and made up 31% of Texas gas production. Proved reserves as of

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5332-431: The preferential mechanism of leaking: the hydraulic seal and the membrane seal. A membrane seal will leak whenever the pressure differential across the seal exceeds the threshold displacement pressure, allowing fluids to migrate through the pore spaces in the seal. It will leak just enough to bring the pressure differential below that of the displacement pressure and will reseal. A hydraulic seal occurs in rocks that have

5418-429: The pressure. As the reservoir depletes, the pressure falls below the bubble point , and the gas comes out of solution to form a gas cap at the top. This gas cap pushes down on the liquid helping to maintain pressure. This occurs when the natural gas is in a cap below the oil. When the well is drilled the lowered pressure above means that the oil expands. As the pressure is reduced it reaches bubble point, and subsequently

5504-485: The process as follows: Plankton and algae, proteins and the life that's floating in the sea, as it dies, falls to the bottom, and these organisms are going to be the source of our oil and gas. When they're buried with the accumulating sediment and reach an adequate temperature, something above 50 to 70 °C they start to cook. This transformation, this change, changes them into the liquid hydrocarbons that move and migrate, will become our oil and gas reservoir. In addition to

5590-401: The production of gas. Several groups in communities in which gas wells have been located have complained of high risk of catastrophic accidents, and some allege that accidents have already occurred, including several resulting in fatalities. Some environmental groups and north Texas residents have expressed concern about the effects of drilling on air and water quality in the areas surrounding

5676-491: The reduction in pressure in the reservoir allows the water to expand slightly. Although this unit expansion is minute, if the aquifer is large enough this will translate into a large increase in volume, which will push up on the hydrocarbons, maintaining pressure. With a water-drive reservoir, the decline in reservoir pressure is very slight; in some cases, the reservoir pressure may remain unchanged. The gas/oil ratio also remains stable. The oil rate will remain fairly stable until

5762-408: The reservoir pressure drops below the bubble point when critical gas saturation is reached. When the gas is exhausted, the gas/oil ratio and the oil rate drops, the reservoir pressure has been reduced, and the reservoir energy is exhausted. In reservoirs already having a gas cap (the virgin pressure is already below bubble point), the gas cap expands with the depletion of the reservoir, pushing down on

5848-409: The reservoir, leading to an improved estimate of the recoverable resources. Reserves are only the part of those recoverable resources that will be developed through identified and approved development projects. Because the evaluation of reserves has a direct impact on the company or the asset value, it usually follows a strict set of rules or guidelines. To obtain the contents of the oil reservoir, it

5934-553: The roads are rural and not designed for use by heavy equipment). In addition, drilling and exploration have generated significant controversy because of environmental damage including contamination to the ground water sources. The formation is named after John W. Barnett , who settled in San Saba County during the late 19th century, where he named a local stream the Barnett Stream. In the early 20th century during

6020-410: The rock fabric by strong capillary forces, requiring specialised measures for evaluation and extraction. Unconventional reservoirs form in completely different ways to conventional reservoirs, the main difference being that they do not have "traps". This type of reservoir can be driven in a unique way as well, as buoyancy might not be the driving force for oil and gas accumulation in such reservoirs. This

6106-419: The rocks have high porosity and low permeability, which keeps the hydrocarbons trapped in place, therefore not requiring a cap rock . Reservoirs are found using hydrocarbon exploration methods. An oil field is an area of accumulated liquid petroleum underground in multiple (potentially linked) reservoirs, trapped as it rises to impermeable rock formations. In industrial terms, an oil field implies that there

6192-605: The sample population. This conclusion was based on the pattern of VOC values found in the samples. Other sources of exposure such as cigarette smoking, the presence of disinfectant by-products in drinking water, and consumer or occupational/hobby related products could explain many of the findings.” Texas environmental regulators and the EPA have ordered the Texas Commission on Environmental Quality to begin investigating drilling complaints on-site within 12 hours of reception. Numerous lawsuits against companies operating in

6278-442: The slickwater frac, Mitchell Energy not only lowered the cost of completing wells by $ 75,000 to $ 100,000, but also dramatically increased the recovery of gas. Mitchell tried to buy more leases in the area before word spread, but soon many other operators started buying leases and drilling Barnett wells, in what had been until then essentially a Mitchell Energy play. Mitchell Energy had a near-monopoly in drilling Barnett Shale wells in

6364-410: The source, the "drier" the gas (that is, the smaller the proportion of condensates in the gas). Because both oil and natural gas are lighter than water, they tend to rise from their sources until they either seep to the surface or are trapped by a non-permeable stratigraphic trap. They can be extracted from the trap by drilling. The largest natural gas field is South Pars/Asalouyeh gas field, which

6450-566: The southern counties ranged from $ 200 to $ 28,000 per acre ($ 500–69,000/ha), the higher prices being paid by Vantage Energy in the fall of 2008. Royalty payments in the 18–25% range. One lease in Johnson County now has 19 wells permitted. A Fort Worth Star-Telegram article reported more than 100,000 new leases were recorded in Tarrant County in 2007. Terms of recent leases have included $ 15,000 per acre ($ 37,000/ha) and

6536-454: The structural trap, the stratigraphic trap, and the far less common hydrodynamic trap . The trapping mechanisms for many petroleum reservoirs have characteristics from several categories and can be known as a combination trap. Traps are described as structural traps (in deformed strata such as folds and faults) or stratigraphic traps (in areas where rock types change, such as unconformities, pinch-outs and reefs). Structural traps are formed as

6622-452: The surface. As the fluids are produced, the pressure will often decline, and production will falter. The reservoir may respond to the withdrawal of fluid in a way that tends to maintain the pressure. Artificial drive methods may be necessary. This mechanism (also known as depletion drive) depends on the associated gas of the oil. The virgin reservoir may be entirely semi-liquid but will be expected to have gaseous hydrocarbons in solution due to

6708-407: The water begins to be produced along with the oil, the recovery rate may become uneconomical owing to the higher lifting and water disposal costs. If the natural drives are insufficient, as they very often are, then the pressure can be artificially maintained by injecting water into the aquifer or gas into the gas cap. The force of gravity will cause the oil to move downward of the gas and upward of

6794-431: The water reaches the well. In time, the water cut will increase, and the well will be watered out. The water may be present in an aquifer (but rarely one replenished with surface water ). This water gradually replaces the volume of oil and gas that is produced out of the well, given that the production rate is equivalent to the aquifer activity. That is, the aquifer is being replenished from some natural water influx. If

6880-442: The water. If vertical permeability exists then recovery rates may be even better. These occur if the reservoir conditions allow the hydrocarbons to exist as a gas. Retrieval is a matter of gas expansion. Recovery from a closed reservoir (i.e., no water drive) is very good, especially if bottom hole pressure is reduced to a minimum (usually done with compressors at the wellhead). Any produced liquids are light-colored to colorless, with

6966-485: The way oil and gas drilling is done by allowing producers access to reservoirs which were otherwise too thin to be economically viable through vertical drilling. Much of the gas in the Barnett Shale is beneath the City of Fort Worth . The new technology has attracted a number of gas-production companies. In addition to extended reach, horizontal drilling drastically increases production. In "tight" rock (low permeability) like

7052-754: The well was capped. Devon contributed over $ 1 million in each of the last 3 U.S. election cycles, almost entirely to organizations and individuals affiliated with the Republican Party . After agreeing with the Obama administration to install systems to control the illegal emission of hazardous chemicals, Devon backed out of such agreements during the Trump administration due to rollbacks of environmental regulations. Devon and its lobbyists have been noted to have close ties to government officials. In 2014, an investigation by The New York Times uncovered that

7138-628: The wells and pipelines. In 2010, the Environmental Protection Agency (EPA) issued an emergency order against Range Resources , stating that the company's drilling activities in Parker County, Texas had contaminated at least two residential drinking water wells. The company denied the allegations, and said the presence of methane was a result of naturally occurring migration, and had shown up in nearby water wells long before Range drilled its gas wells. However, after

7224-564: Was natural gas . Devon was founded in 1971 by John Nichols (1914-2008) and his son, J. Larry Nichols . In 1988, the company became a public company via an initial public offering . In October 2012, the company completed construction of its current headquarters, the 50-story Devon Energy Center in Oklahoma City , Oklahoma and closed its office in the Allen Center in Downtown Houston . In August 2015, Dave Hager

7310-512: Was made in 2000, but ran into drilling problems and was abandoned. The largest breakthrough in the Barnett came in 1997, when Mitchell Energy petroleum engineer Nick Steinsberger suggested that a slickwater frac, which was being successfully used by other companies in wells to the Cotton Valley Sandstone of east Texas, might work better in the Barnett Shale than the gel fracs. By going against conventional wisdom and switching to

7396-576: Was named president and chief executive officer of the company. In February 2016, Devon announced plans to lay off 1,000 employees, including 700 in Oklahoma City, and cut its dividend as part of a cost-cutting effort due to low prices of its products. In November 2019, a blowout at a Devon natural gas well prompted authorities to seal off thousands of acres of land near the Eagle Ford Shale towns of Yorktown and Nordheim until

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