Enhanced Oil Recovery (EOR)
A number of methods can enhance oil recovery. Further crude oil production can be obtained by injecting water ("water flooding") or natural gas to maintain reservoir pressure and push oil out of the rock. This is called secondary recovery. More advanced methods are referred to as tertiary recovery.
The most common tertiary recovery method for light and medium crude oil is miscible flooding. In this procedure, natural gas liquids (methane) are injected into special injection wells. When dissolved, these liquids reduce the surface tension and viscosity to help release the oil from the reservoir rock.
Carbon dioxide has been used as a viable method for miscible floods. This has the added advantage of using a greenhouse that would otherwise be released into the atmosphere. Two such projects are in operation in Alberta and Saskatchewan. One of the projects was designed by Enviro Energy International technical partner Alberta Innovates – Technology Futures. Some reservoirs are more amenable to this technique than others. Research is continuing on the injection of carbon dioxide into underground formations, another possible use is to stimulate production of natural gas from coal deposits (CBM)
Coalbed Methane (CBM)
Coalbed methane (CBM), is simply the natural gas formed and trapped in coalbeds. CBM is generated during the coalification process that transforms organic material such as peat bogs into coal. In coal seams, the methane can occur as "dry" gas or be associated with saltwater or freshwater. The most common production method uses wells drilled into the naturally fractured coal seams. Dry gas can be produced like conventional natural gas. If the gas is associated with water, the wells initially remove water from the coal, but eventually methane is freed from the coal as the pressure and surface tension are lowered. The disadvantage is the long time period before significant gas production begins and the need to dispose of the water, usually by injection into deep wells beneath existing groundwater aquifiers. Researchers are investigating other means of freeing the methane from the coal, including the injection of carbon dioxide (ECBM), which could also provide a way to reduce greenhouse gas emissions.
Enhanced Coalbed Methane (ECBM)
Enhanced coalbed methane recovery is a method of producing additional coalbed methane from a coal, similar to enhanced oil recovery applied to oil fields. Carbon dioxide injected into a bituminous coalbed would occupy pore space and also adsorb onto the carbon in the coal at approximately twice the rate of methane, allowing for potential enhanced gas recovery. This technique may be used in conjunction with carbon capture and storage in mitigation of global warming where the carbon dioxide that is sequestered is captured from the output of fossil fuel power plants.
Coal Mine Methane (CMM)
Coal mine methane (CMM) is methane released from coal seams during coal mining. CBM is methane trapped within coal seams that have not, or will not, be mined. CMM is a greenhouse gas that is over 20x more potent than carbon dioxide. Though emitted in much smaller quantities, methane is the second-most harmful greenhouse gas after carbon dioxide. The capture and use of CMM will benefit the local and global environment by mitigating greenhouse gas emission and utilizing an otherwise wasted clean energy source.