Tight gas

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An illustration of tight gas compared to other types of gas deposits. (Non) Conventional Deposits.svg
An illustration of tight gas compared to other types of gas deposits.

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. This natural gas is trapped within rocks with very low permeability, in other words, they are sealed in very impermeable and hard rocks, making their formation "tight". These impermeable reservoirs which produce dry natural gas are also called "Tight Sand". [1] Tight gas reservoirs are generally defined as having less than 0.1 millidarcy (mD) matrix permeability and less than ten percent matrix porosity. [2] [3] 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. But they are much older than the Conventional gas. Tight gas was formed 248 million years ago in Paleozoic formations. Cementation and recrystallization changed a conventional gas reserve which reduced the permeability of the rock and natural gas was trapped within these rock formations. Horizontal and directional drilling is used to extract tight gas deposits as they run along the formation which in turn allows more natural gas to enter the well that was dug. Numerous wells can be drilled to access the gas. Hydraulic fracturing is one of the main methods to access the gas which requires breaking apart the rocks in the formation by pumping fracking fluids in to the wells. This increases permeability and allows gas to flow easily, feeing it from the trap. After that deliquifaction is used to help in the extraction.

Contents

Rock with permeabilities as little as one nanodarcy, reservoir stimulation may be economically productive with optimized spacing and completion of staged fractures to maximize yield concerning cost. [4]

Examples

Some examples of tight gas reservoirs are:

See also

Related Research Articles

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Tight oil is light crude oil contained in petroleum-bearing formations of low permeability, often shale or tight sandstone. Economic production from tight oil formations requires the same hydraulic fracturing and often uses the same horizontal well technology used in the production of shale gas. While sometimes called "shale oil", tight oil should not be confused with oil shale, which is shale rich in kerogen, or shale oil, which is oil produced from oil shales. Therefore, the International Energy Agency recommends using the term "light tight oil" for oil produced from shales or other very low permeability formations, while the World Energy Resources 2013 report by the World Energy Council uses the terms "tight oil" and "shale-hosted oil".

Hydraulic fracturing Well-stimulation technique in which rock is fractured by a hydraulically pressurized liquid

Hydraulic fracturing, also called fracking, fracing, hydrofracking, fraccing, frac'ing, and hydrofracturing, is a well stimulation technique involving the fracturing of bedrock formations by a pressurized liquid. The process involves the high-pressure injection of "fracking fluid" into a wellbore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine will flow more freely. When the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants hold the fractures open.

Wattenberg Gas Field

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.

The Mansfield Natural Gas Field is located west of Mansfield, Ohio, within the Appalachian foreland basin. The field is 1.5 miles long by 1.4 miles wide and is in a general oval shape, stretching northward. This field, although small, is an analog for many of the natural gas fields that occur within the Appalachian Basin. It was first discovered by the Pan American Petroleum and Transport Company in the early 1930s. It is part of the Utica – Lower Paleozoic system, which is estimated to make up 15 to 20 percent of the total hydrocarbon abundance of the Appalachian Basin.

Halibut Oil Field

The Halibut Field, is an oil field, within the Gippsland Basin. The oil field is located approximately 64 km offshore of southeastern Australia. The total area of this field is 26.9 km2 and is composed of 10 mappable units.

Fault zone hydrogeology

Fault zone hydrogeology is the study of how brittlely deformed rocks alter fluid flows in different lithological settings, such as clastic, igneous and carbonate rocks. Fluid movements, that can be quantified as permeability, can be facilitated or impeded due to the existence of a fault zone. This is because different mechanisms that deform rocks can alter porosity and permeability within a fault zone. Fluids involved in a fault system generally are groundwater and hydrocarbons.

References

  1. "Tight Gas – an overview | ScienceDirect Topics". www.sciencedirect.com. Retrieved 2021-04-25.
  2. Ben E. Law and Charles W. Spencer, 1993, "Gas in tight reservoirs-an emerging major source of energy," in David G. Howell (ed.), The Future of Energy Gasses, US Geological Survey, Professional Paper 1570, pp. 233–252.
  3. Ali Sharif, Tight gas resources in Western Australia, Western Australia Department of Mines and Petroleum, Sept. 2007.
  4. McCoy, Mark; W. Neal Sams (2007). "Tight Gas Reservoir Simulation: Modeling Discrete Irregular Strata-Bound Fracture Networks and Network Flow, Including Dynamic Recharge from the Matrix" (PDF). National Energy Technology Laboratory . Retrieved 27 October 2011.CS1 maint: discouraged parameter (link)
  5. Alan Petzet, "Wintershall starts Dutch North Sea tight gas flow," Oil and Gas Journal, 6 Mar. 2012.