Widoczny [Schowaj] Abstrakt. Effect of water-table configuration and subsurface permeability variation. Water Resources Res. Quantitative interpretations. In: Managing common pool groundwater resources.
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Most of them are answered in this section. Considering the approach to delivery of operations that are associated with exploration and production of unconventional hydrocarbons shale gas , as well as existing available and commonly applied technologies, potential risks to the groundwater are expected to occur in the following stages:.
Gas-bearing shales occur In Poland at depths ranging from 3 to 5 km, in areas of different geology and hydrogeological conditions. The maximum depth of freshwater aquifer occurrence in Poland is estimated at approx. The depth may vary, depending on both regional and local factors. Moreover, mineral and thermal waters occur in the existing shale gas exploration areas.
The depths to mineral waters range from m below the ground near Torun to over m below the ground level for example north and northeast of Lublin. Thermal waters occur at a depth of approx. II, PGI, Due to the depth of gas-bearing shale occurrence, drilling wells have to pass through local aquifers that frequently are the only source of water supply to the local residents.
Drilling operations may potentially contaminate the aquifers as a result of:. At this stage, the risk of groundwater contamination is effectively eliminated by:.
The depth to gas-bearing shale rocks helps to eliminate the risk of groundwater contamination. A thick overburden of impervious rocks isolates freshwater aquifers that occur at depths of up to m from the ground level Fig. Hydraulic fracturing is a technical procedure which establishes a network of induced fractures in the shale formation. Interconnected fractures form a path of gas migration to the borehole and then to the surface. Normally, the range of hydraulically induced fractures is approx.
Fracturing Fig. The fracturing fluid is composed of water approx. Potential groundwater contamination risks from reservoir stimulation are associated with:. Gas may be produced for several decades from several tens of horizontal wells drilled out from a single site. Well abandonment and site reclamation is the final stage when gas production is discontinued. Its purpose is to restore the original intended use of the site area.
Exceptionally, well leakage and migration of reservoir gas to aquifers and the ground surface may occur following well abandonment. In that case the investor should prepare a recovery plan and cooperate with competent authority so as to minimize environmental impacts and restore integrity of the abandoned well.
Drilling stage Gas-bearing shales occur In Poland at depths ranging from 3 to 5 km, in areas of different geology and hydrogeological conditions. Drilling operations may potentially contaminate the aquifers as a result of: drilling fluid or gas migration — in the event of inadequate well construction, penetration of contaminants from the site surface e.
At this stage, the risk of groundwater contamination is effectively eliminated by: proper investigation of geological structure and hydrogeological conditions by the investor including seismic surveying. This makes it possible to design and construct a well that is safe to the groundwater Fig.
Seismic surveys do not represent a risk to groundwater quality, provided that they are performed according to applicable procedures, isolation of aquifers with casing strings cemented over the entire length Fig. Reservoir stimulation hydraulic fracturing stage Hydraulic fracturing is a technical procedure which establishes a network of induced fractures in the shale formation.
Potential groundwater contamination risks from reservoir stimulation are associated with: fracturing fluid or gas migration — if escape routes are formed in the local faults, other than expected fracture propagation — uncontrolled migration of gas or fracturing fluids, penetration of pollutants from site surface e.
At this stage, the risk of groundwater contamination is effectively eliminated by: seismic surveys made by the investor prior to drilling operations. Gas production stage Gas may be produced for several decades from several tens of horizontal wells drilled out from a single site.
At this stage potential risks to groundwater are: the duration of the production period. With time casing pipes may corrode and cement bonds fail. In that case penetration to the aquifers is possible, potential penetration of pollutants from the site surface, emergencies e. Well abandonment and site reclamation stage Well abandonment and site reclamation is the final stage when gas production is discontinued. If not delivered properly, well abandonment operations may involve: emissions of reservoir gas and groundwater contamination with gas.
At this stage the risk can be mitigated by: delivery of well abandonment operations in compliance with applicable regulations e. Sadurski red. English versions of environmental research reports are available. General Directorate for Environmental Protection made available online the English versions of the reports on the results of environmental studies delivered at shale gas exploration in Poland.
The U. Environmental Protection Agency published a report on the chemicals and water used in hydraulic fracture stimulation. Hydraulic fracturing companies use different chemicals in the process. Shale gas exploration has no significant effect on the environment. EPA: methane emission reduction the highest in hydraulically fracture stimulated wells. Waste Management - Part 3. The approach to the management of extractive wastes from shale gas exploration.
Shale gas exploration/production and the groundwater
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