Wattenberg Gas Field

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Location of the Wattenberg Gas Field, Colorado Wattenberg Gas Field USA.png
Location of the Wattenberg Gas Field, Colorado

The Wattenberg Gas Field is a large producing area of natural gas and condensate in the Denver Basin of central Colorado, USA. Discovered in 1970, the field was one of the first places where massive hydraulic fracturing was performed routinely and successfully on thousands of wells. The field now covers more than 2,000 square miles between the cities of Denver and Greeley, and includes more than 23,000 wells producing from a number of Cretaceous formations. The bulk of the field is in Weld County, but it extends into Adams, Boulder, Broomfield, Denver, and Larimer Counties.

Natural gas fossil fuel

Natural gas, also called "Fossil Gas" is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly including varying amounts of other higher alkanes, and sometimes a small percentage of carbon dioxide, nitrogen, hydrogen sulfide, or helium. It is formed when layers of decomposing plant and animal matter are exposed to intense heat and pressure under the surface of the Earth over millions of years. The energy that the plants originally obtained from the sun is stored in the form of chemical bonds in the gas.

Natural-gas condensate, also called natural gas liquids, is a low-density mixture of hydrocarbon liquids that are present as gaseous components in the raw natural gas produced from many natural gas fields. Some gas species within the raw natural gas will condense to a liquid state if the temperature is reduced to below the hydrocarbon dew point temperature at a set pressure.

Denver Basin geologic basin in eastern Colorado

The Denver Basin, variously referred to as the Julesburg Basin, Denver-Julesburg Basin, or the D-J Basin, is a geologic structural basin centered in eastern Colorado in the United States, but extending into southeast Wyoming, western Nebraska, and western Kansas. It underlies the Denver-Aurora Metropolitan Area on the eastern side of the Rocky Mountains.

Contents

Geology

Stratigraphic column of the Wattenberg Gas Field. Oil and gas producing zones are in green; hydrocarbon source beds are in purple. Wattenberg Stratigraphy.png
Stratigraphic column of the Wattenberg Gas Field. Oil and gas producing zones are in green; hydrocarbon source beds are in purple.
East-West cross-section through the Denver Basin. The Wattenberg basin-centered field is shown in red. Denver Basin Cross Section.png
East-West cross-section through the Denver Basin. The Wattenberg basin-centered field is shown in red.

The reservoir rocks are Cretaceous sandstones, shales, and limestones deposited under marine conditions in the Western Interior Seaway.

Sandstone A clastic sedimentary rock composed mostly of sand-sized particles

Sandstone is a clastic sedimentary rock composed mainly of sand-sized mineral particles or rock fragments.

Shale A fine-grained, clastic sedimentary rock

Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments of other minerals, especially quartz and calcite. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility. It is the most common sedimentary rock.

Limestone Sedimentary rocks made of calcium carbonate

Limestone is a carbonate sedimentary rock that is often composed of the skeletal fragments of marine organisms such as coral, foraminifera, and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). A closely related rock is dolomite, which contains a high percentage of the mineral dolomite, CaMg(CO3)2. In fact, in old USGS publications, dolomite was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolomites or magnesium-rich limestones.

The gas and condensate is contained within Cretaceous formations in the deepest part of the Denver Basin, where the rocks were subject to enough heat and pressure to generate oil and gas from organic material in the rock. The field is a stratigraphic trap, basin-centered gas field. Most of the gas-producing formations are considered tight gas, having low natural permeability. Although the field today is in the deepest part of the basin, an unconformity at the base of the Pierre Shale shows that the field is on an early paleohigh active in the Middle Cretaceous. [1]

Tight gas

Tight gas is natural gas produced from reservoir rocks with such low permeability that massive hydraulic fracturing is necessary to produce the well at economic rates. Tight gas reservoirs are generally defined as having less than 0.1 millidarcy (mD) matrix permeability and less than ten percent matrix porosity. Although shales have low permeability and low effective porosity, shale gas is usually considered separate from tight gas, which is contained most commonly in sandstone, but sometimes in limestone. Tight gas is considered an unconventional source of natural gas.

Pierre Shale

The Pierre Shale is a geologic formation or series in the Upper Cretaceous which occurs east of the Rocky Mountains in the Great Plains, from Pembina Valley in Canada to New Mexico.

Discovery and development

Drilling in the Wattenberg Gas Field north of Denver, 2005. GasWellDenverBasinCO.jpg
Drilling in the Wattenberg Gas Field north of Denver, 2005.

Although numerous wells had drilled through the Wattenberg Field over the decades, and many drillers and wellsite geologists noticed gas “shows” (indications) in the "J" Sandstone and other strata, the "J" Sandstone and other gas-bearing formations had permeability too low to yield gas in commercial quantities. Core samples indicated the "J" Sandstone was similar to the Lower Cretaceous Dakota Sandstone reservoir in the San Juan Basin. This was supported with the Aug. 1967 discovery of the Roundup Field. Additionally, examination of outcrops and electrical logs showed the "J" Sandstone to be a delta-front sandstone. [2]

Core sample A cylindrical section of a naturally occurring substance, usually obtained by drilling with special drills into the substance.

A core sample is a cylindrical section of (usually) a naturally occurring substance. Most core samples are obtained by drilling with special drills into the substance, for example sediment or rock, with a hollow steel tube called a core drill. The hole made for the core sample is called the "core bowling". A variety of core samplers exist to sample different media under different conditions. More continue to be invented on a regular basis. In the coring process, the sample is pushed more or less intact into the tube. Removed from the tube in the laboratory, it is inspected and analyzed by different techniques and equipment depending on the type of data desired.

San Juan Basin geologic structural basin

The San Juan Basin is a geologic structural basin located near the Four Corners region of the Southwestern United States. The basin covers 7,500 square miles and resides in northwestern New Mexico, southwestern Colorado, and parts of Utah and Arizona. Specifically, the basin occupies space in the San Juan, Rio Arriba, Sandoval, and McKinley counties in New Mexico, and La Plata and Archuleta counties in Colorado. The basin extends roughly 100 miles N-S and 90 miles E-W.

Outcrop visible exposure of bedrock or ancient superficial deposits on the surface of the Earth

An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth.

Amoco geologist Pete Matuszczak noticed that all the wells drilled over a large area recorded noncommercial gas shows, with no water, through the "J" Sandsone (also called the Muddy Sandstone) on the mudlogs, cores, and drillstem tests. He suggested that the area might be made to produce large economic quantities if the wells were treated with the new method of massive hydraulic fracturing, which Amoco was using successfully in the San Juan Basin of New Mexico. [3]

Amoco former global chemical and oil company

Amoco Corporation, originally Standard Oil Company (Indiana), is a global chemical and oil company that was founded in 1889 around a refinery located in Whiting, Indiana, United States.

Drilling started in 1970, and wells were completed in the J Sandstone, at depths from 7350 to 8500 feet. Drilling deep gas also fortuitously found conventional oil in places in the shallower Terry and Hygiene sandstones. [4] The D Sandstone, another conventional reservoir, also produces in limited areas within Wattenberg.

Additional producing formations were added to the field. Starting in 1981, operators discovered that the Codell Sandstone would yield economic quantities of oil and gas if hydraulically fractured. Hundreds of new wells were drilled and completed in the Codell in the early 1980s; the Codell was often co-completed with the overlying Niobrara Formation. Additional wells were drilled and hydraulically fractured in the Plainview and Lytle formations, below the J Sandstone.

The initial spacing of one "J" Sandstone well per 320 acres was found insufficient to drain the reservoir, so the Colorado Oil and Gas Conservation Commission approved infill wells.

Gas wells in Wattenberg were drilled vertically until 2009, when operators discovered that horizontal wells drilled in the chalk of the Niobrara Formation yielded better quantities of gas and condensate, setting off a new round of drilling. [5]

Production and reserves

In 1973, the field was thought to contain 1.1 trillion cubic feet of recoverable gas. Through 2008, the Wattenberg Field had produced 2.8 trillion cubic feet of gas, [6] and an estimated 5.2 trillion cubic feet of recoverable gas remained. [7] In 2013, the US Energy Information Administration listed Wattenberg as the 9th largest gas field in the US in terms of remaining proved gas reserves, 4th in remaining proved oil/condensate reserves. [8] As of March 2018, the field was producing 1.92 billion cubic feet of gas and 331 thousand barrels of oil and condensate per day, from more than 23,000 active wells. [9]

More than 40 companies operate wells in Wattenberg. As of 2017, the five largest producers of oil and gas in the field were: Kerr-McGee, Noble Energy, PDC Energy, Extraction Oil and Gas, and SRC Energy. Together, the top five producing companies produced 84 percent of the total gas produced in 2017. [10]

Cited References

  1. R.J. Weimer and S.A. Sonnenberg, “Wattenberg field, paleostructure-stratigraphic trap, Denver Basin, Colorado,” Oil & Gas Journal, 22 Mar. 1982, p.204-210.
  2. Matuszczak, R.A. (1976). Braunstein, Jules, ed. Wattenberg Field, Denver Basin, Colorado, in North American Oil and Gas Fields. Tulsa: The American Association of Petroleum Geologists. pp. 136–144. ISBN   0891813004.
  3. "Reinventing Wattenberg," Oil & Gas Investor, July 2009, p.35-45.
  4. R.A. Matuszczak, “Wattenberg Field, Denver Basin, Colorado,” The Mountain Geologist, July 1973, v.10 n.3 p.99-105.
  5. Sharon Dunn, “Colorado’s Wattenberg growing in importance in oil, gas industry,” Denver Post, 13 Aug. 2012.
  6. American Petroleum Institute, Strategic energy resources: Denver-Julesberg Basin-Wattenberg Field, Colorado, Autumn 2008.
  7. Gargi Chakrabarty, “Wattenberg Field – a bottomless well?” Denver Rocky Mountain News, 18 Oct. 2008.
  8. US Energy Information Administration, Top 100 oil and gas fields, 2013 2013.
  9. Colorado Oil and Gas Conservation Commission, website
  10. Colorado Oil and Gas Conservation Commission, website

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Sirte Basin

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Piceance Basin

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Williston Basin structural basin

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Bakken Formation

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Haynesville Shale

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Montney Formation

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Cardium Formation

The Cardium Formation is a stratigraphic unit of Late Cretaceous age in the Western Canada Sedimentary Basin. It takes the name from the fossilized Cockle (Cardiidae) shells that it contains, and it was first described along the Bow River banks by James Hector in 1895. It is present throughout western Alberta and in northeastern British Columbia, and it is a major source of petroleum and natural gas.

Spraberry Trend oil field

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Shale gas in the United States

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Duvernay Formation

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Eagle Ford Group

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Hydraulic fracturing in Canada

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