What is Conventional Gas?
Natural gas is a hydrocarbon gas formed over thousands of years from the burying of dead plants and animals. The intense heat and pressure caused by the burying of this material triggers a reaction, which leads to the creation of natural gas, primarily methane (CH4)1.
Natural gas is referred to as ‘conventional’ when it can be extracted from the Earth either through naturally occurring pressure, or pumping mechanisms (CAPP). This is opposed to unconventional gas sources such as shale gas, tight gas, and coal bed methane which require novel technologies to unlock.
Four key components are required for conventional natural gas to form2:
- Source – This refers to the dead plants and animals that break down and become natural gas
- Migration – After the dead plants and animals break down, the newly formed natural gaswill move upwards through holes in the rock overlying the source
- Trap – The natural gas will continue to move upwards through the pores of rocks until it hits a rock that either does not have pores, or has pores that are not connected to one another. This rock is called a trap.
- Reservoir – The rock right below the trap that holds all the natural gas is called the reservoir. This is where natural gas is extracted from.
Production of conventional natural gas has four main phases:
- Exploration:Geological exploration is a series of technologies that are used by geologists and geophysicists to predict the location and extent of underground oil reservoirs.
- Drilling:Once a reservoir has been located with sufficient certainty, a drilling rig is used to bore a hole from the surface to the oil reservoir. Piping is then inserted, allowing the oil to be brought to the surface. Some of the oil in the reservoir will be produced using the natural pressure of the reservoir.
- Pumping:Gradually the pressure of the well will decrease as oil is produced. At this point a pump will be connected to allow the remaining oil to be extracted.
- Abandoning: After all the economically viable oil has been extracted from the well, the well is filled with cement to prevent any hydrocarbons from escaping and a special cap is placed over it to protect the area.
Conventional gas tends to be less expensive and complex to extract than unconventional gas due to the routine nature of the production techniques. Historically low natural gas prices have led to the popularity of its use for power and heating.
Generally, drilling and well abandonment are well-understood and regulated processes but there are always risks with such industrial operations. In drilling, pressure must be regulated carefully to avoid accidents and immediate environmental impacts like land disturbance. After abandonment, well leaks can occur if procedures were not carefully followed.
One of the greatest concerns regarding the use of any fossil fuel, including conventional natural gas, is the emission of greenhouse gases3.