Chapter 3 - Natural Gas Overview Flashcards
What is the simplest hydrocarbon molecule?
One carbon atom bonded to four hydrogen atoms (CH4) – Methane
Raw natural gas may contain other hydrocarbons, as well as?
Water Carbon Dioxide Oxygen Nitrogen Hydrogen Sulfide Helium
Define inerts.
The nonydrocarbons that must be removed from raw natural gas
What is added to natural gas to give it an identifiable smell?
Mercaptan
Natural gas also may contain heavier hydrocarbons in the gaseous state, such as pentane, hexane, and heptane. At surface conditions, what happens?
These will condense out of the gas to form natural gas condensate, often shortened to condensate.
Define Conventional Natural Gas.
The term conventional generally used to describe natural gas produced from well-understood geologic formations known through experience to hold natural gas.
Where has the greatest U.S. natural gas reserves historically have been concentrated around?
Texas and the Gulf of Mexico, with substantial amounts also found in the Rocky Mountain West.
Define associated gas.
Conventional gas that is produced during the extraction of crude oil
Define nonassociated gas
A formation targeted specifically for extraction of natural gas
Define unconventional natural gas.
Unconventional natural gas is a gas that cannot be economically produced unless one or more technologies are used to stimulate the gas-bearing formation and to expose more of the formation to the wellbore.
What did the Natural Gas Policy Act of 1978 provide?
The act provided incentives for searching for and extracting unconventional natural gas and spurred investment into deep exploration and development drilling.
What are the six main categories of unconventional natural gas?
Deep gas Tight gas Shale gas Coal-bed methane Gas in geopressurized zones Methane hydrate
Define Deep Gas.
Deep gas is typically found 15,000 feet or deeper underground, consider deeper than conventional gas. Therefore, deep gas is relatively expensive to find and produce.
Define Tight gas.
Tight gas is trapped in unusually impermeable hard rock or in sandstone or limestone that is highly nonporous (tight sand). Extraction of gas from tight formations typically requires expensive techniques such as fracturing and acidizing.
Define Shale gas.
Natural gas can also exist in deposits of shale, a fine-grained and soft sedimentary rock that breaks easily into thin, parallel layers. Gas is typically found in sections where two thick, black shale deposits “sandwich” a thinner area of shale.
What are the major shale plays in the US?
Marcellus (Appalachia) Haynesville (Louisiana/Texas) Barnett (Texas) Fayetteville (Arkansas Woodford (Oklahoma) Eagle Ford (Texas) Antrim (Michigan)
What are the major oil plays in Canada?
Horn River/Muskwa (northeast BC)
Colorado Group (west-central Saskatchewan/south-central Alberta)
Montney (Alberta)
Touch on the productivity of shale gas wells
There is an emergy debate about how rapidly production from a typical shale well is likely to decline and whether that decline rate flattens out over time.
If the curve flattens out slowly, then shale wells will rpduce gas at a reasonably high rate and low cost over a long period of time. By Contrast, if the curve declines more sharply and rapidly, then the ultimately recovered gas reserves from a shale formation could be significantly lower and the production costs could be higher.
For this reason, some experts argue that better models are needed to guide the commitment of financial resources to the continued development of gas-bearing shales.
Define Coal-bed Methane
Historically, methane was a nuisance and a safety hazard in the coal-mining industry. Today, however, coal-bed methane has become a popular form of unconventional natural gas, with many projects put in place around the world to extract and market it.
Touch on the recoverable coal-bed methane. USA.
In April 2011, the Potential Gas Committee (PGC) estimated that about 158.6 trillian cubic feet of technically recoverable (probably, possible, and speculative) coal-bed methane existed in the United States at the end of 2010.
Touch on recoverable coal-bed methane. Australia.
In eastern Australia, coal-bed gas reserves (proved plus probable) grew from about 6 tcf in 2006 to about 27 tcf in 2010, according to Resource and Land Management Services, a consultancy based in Brisbane.
Define Geopressurized Gas.
Natural geologic formations in which the pressure is higher than would be expected for a given depth are said to be geopressurized. In these zones, layers of clay have been deposited and compacted quickly on top of sand or silt. The water and natural gas present in the clay have been squeezed out by the compression of the clay and have entered the more porous sand or silt deposits. Owing to this compression, the natural gas in the sand or silt is under very high pressure.
Touch on recoverable geopressurized gas.
Geopressurized zones are typically quite deep, usually 10,000-25,000 geet below the surface of the Earth. In the United States, they are located chiefly in the Gulf Coast region. It has been estimated that U.S. geopressurized zones could hold anywhere from 5,000 to 49,000 tcf of natural gas.
Define Methane Hydrate.
Another unconventional gas resource under evaluation for potential production in the longer term is methane hydrate. Hydrate is typically a cold, slushlike, crystalline structure consisting of methane molecules trapped in a lattice of water molecules. Such hydrates are abundant in the Arctic (where they were first discovered) and in the marine sediments, below the seabed.
