Well logging provides continuous downhole records of different properties of the subsurface, measured by a range of instruments. Since this technique is used in boreholes, it is not restricted to the maximum depths typical of other methods of continuous vertical data acquisition, such as cone penetration testing, which range from about 60 to 100 metres. Instead, it can provide records to depths of several kilometres.
Borehole logging was first employed in France by the brothers Conrad and Marcel Schlumberger, in 1927. It enables the collection of detailed, quantitative information on the subsurface, including the associated natural resources. The method is very useful when comparing and interpolating among boreholes, and over time has become increasingly popular and sophisticated.
Globally, the biggest end user of well logs is the oil and gas industry, including multinationals like Shell, BP and ExxonMobil. The service companies that do most of the measurements include Schlumberger, Baker Hughes and Halliburton. In addition, many logs are produced for the minerals market (coalbed methane, coal, metals, minerals, etc.) and for the water-supply industry. Customers for shallow borehole logs (up to 500 metres deep) are water-supply companies, project developers for geothermal energy, drilling firms, provinces, large industrial water users and geological surveys.
Well logs on the map
Logs can be found on the map under Subsurface research, sub-heading Well logs.