Shale gas is a type of natural gas, it consists mainly of methane and is concentrated in shale.
Shales are rocks that are composed of several layers of parallel low-temperature minerals (chlorite, sericite, actinolite, muscovite, etc.).
These rocks are characterized by the ability to easily split into plates, forming spaces (reservoirs) between which shale gas accumulates.
Individual reservoirs are not rich in gas reserves, but, nevertheless, they are quite enough to organize industrial production.
Shale deposits are found on all continents, which can make any country non-volatile, providing the necessary resources.
The production of such gas at cost is large due to the fact that initially it was associated with the opening of large areas using hydraulic fracturing (hydraulic fracturing) and the constant drilling of long wells in large quantities, creating cracks in them for pumping gas.
Gas production
The first commercial gas production from the shale field was carried out in the United States.
Later, the technology was improved by combining vertical and horizontal drilling, which allowed to reduce the cost of gas production.
Today, shale gas is produced by drilling vertical and horizontal wells using multi-taps at the same depth and multi-stage wells (horizontal) with a tapping length of up to three kilometers.
Shale gas production technology involves pumping into a drilled well a mixture of water, chemicals and sand. There is a water hammer, which destroys the walls of gas reservoirs, which allows pumping all available gas to the surface.
Horizontal drilling technology uses the innovative 3DGEO seismic modeling technique, which combines geological exploration and mapping with computer processing of information, including visualization.
Drilling a horizontal well should be carried out with strict observance of all the rules, for example, the correct drilling angle should correspond to the angle of inclination of the slate formation.
Shale gas as a commodity
The cost of gas production is determined by such indicators:
- the content of clay in hard sands, which is able to absorb the energy of hydraulic fracturing, which increases the amount of chemicals used and affects the cost;
- sulfur dioxide content (lower sulfur dioxide inclusion increases the price of gas during sale);
- kerogen content;
- the cost of production in thick and thermally strong shales belonging to the Paleozoic and Mesozoic period;
- an indicator of the content of silicon dioxide (the higher it is, the more fragile shale and lower cost).
Mining benefits
- development of oil shale deposits using hydraulic fracturing can be carried out in densely populated areas;
- direct proximity of shale gas fields to end consumers;
- Production takes place without the release of greenhouse gas.
disadvantages
- with hydraulic fracturing technology requires large reserves of water near the deposits, the fluid is contaminated and difficult to dispose of;
- shale wells are less durable in operation than conventional ones;
- drilled wells reduce production very quickly - by 30-40% per year;
- In order to produce shale gas, approximately 85 toxic agents are used, although the exact numbers are confidential;
- methane is significantly lost during gas production, which enhances the greenhouse effect ;
- profitability of production is advisable only if there is a high gas price and demand for it;
- ancient shale deposits have a high level of gamma radiation, which increases the background radiation as a result of hydraulic fracturing.
Ecology and shale gas production
With existing technology, shale gas cannot be a worthy alternative to natural.
However, with careful environmental monitoring, gas production from shale is possible in sparsely populated areas.