The conventional gas reservoirs are largely consist of porous sandstone formations capped by impermeable rock, where the natural resources are trapped. It is easier to access and extract compared to unconventional.
The resources that can be extracted from conventional petroleum reserves include crude oil, condensate and natural gas. The products that can be refined include liquefied petroleum gas, fuel oils, petrol, diesel, kerosene, asphalt base and others.
The resources are extracted by drilling down through the ‘cap’ rock and allowing petroleum to flow up the well through the well pressure.
The unconventional gas is produced by complex geological systems which significantly limit the production rate. Previously, it was uneconomical due to difficulties in extraction and low production rates, however, recent advances in the oil and gas technology has made it feasible.
The unconventional gas is divided into:
- Shale gas;
- Tight gas; or
- Coal seam gas.