- Title : Handbook of Natural Gas Transmission And Processing by Saeid Mokhatab William A.Poe James G Speight
- Publish : Gulf Professional Publishing is an imprint of Elsevier
- Type Document : pdf
- Release : December 2006
- Total Page : 672 Page
- Size : 8.36 Mb
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Decrypted Contents
GAS SOURCES
Natural gas produced from geological formations comes in a wide array of compositions. The varieties of gas compositions can be broadly categorized into three distinct groups: (1) nonassociated gas that occurs in conventional gas fields, (2) associated gas that occurs in conventional oil fields, and (3) continuous (or unconventional) gas. Some types of unconventional gas resources include “tight gas” or “tight sands gas,” which is found in low-permeability rock; “coalbed methane (CBM),” which is natural gas that has been formed along with the geological processes that formed coal; “natural gas from geopressurized aquifers,” which refers to gas dissolved under high pressure and at high temperatures in brines located deep beneath the Earth’s surface; “gas hydrates,” which are ice-like structures of water and gas located under the permafrost; and “deep gas,” which is found at levels much deeper than conventional gas.
Although there is no scientific consensus, some believe deep gas originated from inorganic sources and that it exists everywhere as a result of the geological processes that formed the earth. Of the unconventional gas sources, the one most important to the gas transportation industry is coal bed methane.
Natural gas produced from geological formations comes in a wide array of compositions. The varieties of gas compositions can be broadly categorized into three distinct groups: (1) nonassociated gas that occurs in conventional gas fields, (2) associated gas that occurs in conventional oil fields, and (3) continuous (or unconventional) gas. Some types of unconventional gas resources include “tight gas” or “tight sands gas,” which is found in low-permeability rock; “coalbed methane (CBM),” which is natural gas that has been formed along with the geological processes that formed coal; “natural gas from geopressurized aquifers,” which refers to gas dissolved under high pressure and at high temperatures in brines located deep beneath the Earth’s surface; “gas hydrates,” which are ice-like structures of water and gas located under the permafrost; and “deep gas,” which is found at levels much deeper than conventional gas.
Although there is no scientific consensus, some believe deep gas originated from inorganic sources and that it exists everywhere as a result of the geological processes that formed the earth. Of the unconventional gas sources, the one most important to the gas transportation industry is coal bed methane.
1.4.1 Non-associated Gas
Nonassociated gas (sometimes called “gas well gas”) is produced from geological formations that typically do not contain much, if any, higher boiling hydrocarbons (gas liquids) than methane. Nonassociated gas can contain nonhydrocarbon gases such as carbon dioxide and hydrogen sulfide. Nonassociated gas is directly controllable by the producer; one just turns the valves. The gas flows up the well under its own energy, through the wellhead control valves, and along the flow line to the treatment plant. Treatment requires the temperature of the gas to be reduced to a point dependent upon the pressure in the pipeline so that all liquids that would exist at pipeline temperature and pressure condense and are removed.
1.4.2 Associated Gas
Associated gas is produced during crude oil production and is the gas that is associated with crude oil. Crude oil cannot be produced without producing some of its associated gas, which comes out of solution as the pressure is reduced on the way to and on the surface. Properly designed crude oil well completions and good reservoir management are used to minimize the production of associated gas so as to retain the maximum energy in the reservoir and thus increase ultimate crude oil recovery. Crude oil in the reservoir with minimal or no dissolved associated gas is rare and as dead crude oil is often difficult to produce as there is little energy to drive it.
After the production fluids are brought to the surface, they are separated at a tank battery at or near the production lease into a hydrocarbon liquid stream (crude oil or gas condensate), a produced water stream (brine or salty water), and a gaseous stream. The gaseous stream is traditionally very rich (rich gas) in natural gas liquids (NGLs). Natural gas liquids include ethane, propane, butanes, and pentanes and higher molecular weight hydrocarbons (C+6 ). The higher molecular weight hydrocarbons product is commonly referred to as natural gasoline.
Associated gas is produced during crude oil production and is the gas that is associated with crude oil. Crude oil cannot be produced without producing some of its associated gas, which comes out of solution as the pressure is reduced on the way to and on the surface. Properly designed crude oil well completions and good reservoir management are used to minimize the production of associated gas so as to retain the maximum energy in the reservoir and thus increase ultimate crude oil recovery. Crude oil in the reservoir with minimal or no dissolved associated gas is rare and as dead crude oil is often difficult to produce as there is little energy to drive it.
After the production fluids are brought to the surface, they are separated at a tank battery at or near the production lease into a hydrocarbon liquid stream (crude oil or gas condensate), a produced water stream (brine or salty water), and a gaseous stream. The gaseous stream is traditionally very rich (rich gas) in natural gas liquids (NGLs). Natural gas liquids include ethane, propane, butanes, and pentanes and higher molecular weight hydrocarbons (C+6 ). The higher molecular weight hydrocarbons product is commonly referred to as natural gasoline.
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