Energy resources: Coal
Energy resources: Coal

Start this free course now. Just create an account and sign in. Enrol and complete the course for a free statement of participation or digital badge if available.

Free course

Energy resources: Coal

2.3.4 Geophysical methods — borehole logging

If a core is not recovered from a borehole, another way to assess the types of rock that it penetrates is to measure their physical properties. Mounting a string of electronic instruments behind the drill bit most conveniently does this: it allows the properties of the rock to be monitored as the borehole is drilled. An alternative is to lower instruments down the completed borehole by cable; hence the name wireline logging.

Such logging measures several physical properties of the rocks surrounding the borehole. These include the velocity at which sound travels through each rock type, their density and their emission of natural gamma radiation (from unstable isotopes of uranium, thorium and potassium that vary a great deal between different rock types). Because a single physical property cannot define a rock type, the logging geologist must compare a range of properties at each depth to interpret the rock type present.

As the location, quality and quantity of coal in a coalfield will affect the profitability of a mine, mining will not commence until the mining company and its financial partners are satisfied that these crucial parameters have been sufficiently constrained. Even after mining has commenced, further exploration (including the drilling of more boreholes) periodically allows initial estimates to be refined.

Skip Your course resources
S278_3

Take your learning further

Making the decision to study can be a big step, which is why you'll want a trusted University. The Open University has 50 years’ experience delivering flexible learning and 170,000 students are studying with us right now. Take a look at all Open University courses.

If you are new to University-level study, we offer two introductory routes to our qualifications. You could either choose to start with an Access module, or a module which allows you to count your previous learning towards an Open University qualification. Read our guide on Where to take your learning next for more information.

Not ready for formal University study? Then browse over 1000 free courses on OpenLearn and sign up to our newsletter to hear about new free courses as they are released.

Every year, thousands of students decide to study with The Open University. With over 120 qualifications, we’ve got the right course for you.

Request an Open University prospectus371