Requires the drilling of small numbers of wells (usually vertical) to obtain core samples of the target rock formation. The location of these wells may be influenced by conducting seismic surveys or acquiring seismic data to determine where to drill. Horizontal drilling and a range of tests (including hydraulic fracturing, mini-fracks and other diagnostic procedures) may also be used.
Using the combined information from the exploratory drilling and seismic surveys, small number of new wells (or existing wells) are subjected to more testing to find out how much oil or gas can be extracted. These flow tests usually require gas to be flared on the sites producing airborne contamination and significant volumes of toxic and redioactive liquid waste.
Data from successful exploration and appraisal stages can then be used to produce a field development plan and begin the drilling of large numbers of production wells. Production requires massive additional infrastructure, including pipelines, compressor stations and gas processing plants. At production, fracking wells are drilled at high densities of up to 8 wells per square mile (or more). Production requires thousands of wells coating large areas.
Currently there are two companies that have been awarded concession licenses in Portugal - Australis and Portfuel. These companies undertaking the initial drilling in Portugal are however unlikely to have the resources necessary to drill the thousands of wells needed to take these project into full production. Meaning, that they will have to source partners.
The exploration and appraisal stages allow these companies to gather the data needed to attract large investors or to sell out to larger companies.
It is really important to understand that investors decisions will also be affected by non-geological and technical issues. Conspicuous, vocal opposition and resistance from local people is effective and extremely costly for companies, it can lead to the total abandonment of projects.
The Fracking industry is unlike manufacturing and conventional resource extraction industries.
Drilling into shale or coal seam will not necessarily produce large amounts of hydrocarbons. The reality is that the productivity of fracking wells varies massively.
The map of Texas Barnett Shale above shows gas well productivity. As you can see, the darker spots are surrounded by much larger numbers of wells which produce little gas. Even when the industry reaches the production phase, exploration and appraisal of new wells scattered over a wide area is required to locate and focus drilling on the best production wells (if they can be identified at all).