What are the major types of Unconventional Natural Gas Resources?
There are three major types of unconventional natural gas resources:
This is natural gas extracted from shale gas formations. The shale is acting as the source, reservoir and the trap for the natural gas. These kinds of natural gas formations have very low porosity and permeability in the Nano-Darcy range.
This is natural gas trapped in formations that are generally not permeable and porous. They are trapped in reservoirs with permeability in the Milli Darcy range.
Coalbed Methane (CBM):
This is natural gas found in coal seams.
In addition to the above three major types of unconventional gas resources, Coal-to-Gas (produced by destructive distillation of coal) and methane hydrates (formed from mixture of water and natural gas in permafrost and deep marine sediments)are often referred to as unconventional gas resource .
How are these Unconventional Natural Gas resources extracted?
As mentioned earlier, unconventional gas resources are found in unusual geological locations and therefore require special extraction technologies. Notwithstanding this, the combination of two independent technologies of horizontal drilling and hydraulic fracturing (cracking of rock by pumping in highly pressurized liquid) made their exploitation possible.
Is Hydraulic Fracturing safe?
The question of how safe is hydraulic fracturing has been a topic of debate amongst government regulators, environment groups, scientists and other technical experts of recent. Some of the concerns being raised and debated is whether hydraulic fracturing can lead to underground water contamination, deterioration of air quality due to release of gases & chemicals to the surface during the drilling activities, induced seismicity etc. To address the issues raised, the oil and gas industry, working together with some governments and other stakeholders are developing innovative technologies, policies and regulations to ensure that the hydraulic fracturing is conducted in a less destructive manner.