Flashcards in Chapter 3 - Natural Gas Overview Deck (31):
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?
The nonydrocarbons that must be removed from raw natural gas
What is added to natural gas to give it an identifiable smell?
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?
Gas in geopressurized zones
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?
Eagle Ford (Texas)
What are the major oil plays in Canada?
Horn River/Muskwa (northeast BC)
Colorado Group (west-central Saskatchewan/south-central 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.
Touch on recoverable methane hydrate.
Estimates of the worldwide methane hydrate resource vary from 7,000 to more than 73,000 tcf; however, these numbers are far from certain. Sumstantial additional research is needed to assess how hydrates form, interact with surrounding materials, behave during extraction operations, and potentially affect the environment.
Define Liquefied Natural Gas (LNG)
LNG is not a naturally occurring gas resource. Rather, it is created by deeply cooling natural gas (typically to 260F below zero)
Define the LNG process.
The process transforms natural gas from gaseous to liquid form-increasing its energy density (Btu per cubic foot) by a factor of about 600-and makes possible the cost-effective shipment of the LNG in insulated tanker ships from gas production regions to major market regions.
Touch on the LNG unloading process.
The LNG is then unloaded from the tankers and regasified (i.e. warmed to convert it back into the gaseous state), treated to bring its composition to compliance with market specifications, and then distributed to users through conventional pipeline networks.
Touch on the projected trends in gas production
Looking to the future, gas resources from a variety of sources are expected to keep world markets well supplied at relatively low prices for the period from 2007 to 2035, according to EIA. The major increase in production is expected from the Middle East, Africa, and Russia. EIA projects that Iran and Qatar alone will increase production by a combined 12 tcf by 2035-nearly one-fourth of the total growth in global production.
How are tight sands, gas-bearing shales and coal beds going to effect gas production?
Tight sands, gas-bearing shales, and coal beds are expected to make major contributions to growth in gas production-and not just in the United States. For example, these three resources are expected to account for 63% of total domestic production in Canada and 56% in China in 2035.