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Similarly to other formations, the hydrocarbons (due to low density) migrate upwards within the formation until trapped by a cap rock such as sandstone. If this happens, it creates a conventional reservoir that can be drilled to create a production well. However, many shale reservoirs are classified as unconventional. This essentially means the reservoir has low permeability and requires stimulation for production.
Shale gas has significant obstacles to overcome in terms of production. Since there is a quantity of gas trapped within pore spaces of rock, it is sometimes inaccessible. In recent years, the combination of horizontal drilling and hydraulic fracturing methods ...

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Cover of Shale Oil and Gas Handbook

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