5. Fill in the gaps with the words and expressions:

layers samples logging rock formation

cuttings data porosity

Standard (1)___________ consists of examining and recording the physical aspects of a well. For example, the drill (2)__________ are all examined and recorded, allowing geologists to physically examine the subsurface rock. Also, core (3)___________ are taken by lifting a sample of underground rock intact to the surface, allowing the various layers of rock and their thickness to be examined. These cuttings and cores are often examined using powerful microscopes that can magnify the rock up to 2,000 times. This allows the geologist to examine the porosity and fluid content of the subsurface rock, and to gain a better understanding of the earth in which the well is being drilled.

Electric logging consists of lowering a device used to measure the electric resistance of the rock (4)__________ in the 'down hole' portion of the well. This is done by running an electric current through the (5)____________ and measuring the resistance that it encounters along its way. This gives geologists an idea of the fluid content and characteristics. A newer version of electric logging, called induction electric logging, provides much the same types of readings, but is more easily performed and provides (6)_________ that is more easily interpreted.

6. Read the second part of the text and answer the questions:

When and where should different means of exploration be used?

Which means are more typical for Russian exploration?

Computer Assisted Exploration. One of the greatest innovations in the history of petroleum exploration is the use of computers to compile and assemble geologic data into a coherent 'map' of the underground. Use of this computer technology is referred to as 'CAEX', which is short for 'computer assisted exploration'.

Computer allows processing of very large amounts of data. There are three main types of computer-assisted exploration models: two-dimensional (2-D), three-dimensional (3-D), and most recently, four-dimensional (4-D). These imaging techniques, while relying mainly on seismic data acquired in the field, are becoming more and more sophisticated. Computer technology has advanced so far that it is now possible to incorporate the data obtained from different types of tests, such as logging, production information, and gravimetric testing, which can all be combined to create a 'visualization' of the underground formation. Thus geologists and geophysicists are able to combine all of their sources of data to compile one clear, complete image of subsurface geology.

3 -D Seismic Imaging. Three-D imaging utilizes seismic field data to generate a three dimensional 'picture' of underground formations and geologic features. This allows the geophysicist and geologist to see a clear picture of the composition of the Earth's crust in a particular area.

Although this technology is very useful, it is also very costly. Three-D seismic imaging can cost hundreds of thousands of dollars per square mile. The generation of 3-D images requires data to be collected from several thousand locations. As such, 3-D imaging is a much more involved and prolonged process.

4-D Seismic Imaging. One of the latest breakthroughs in seismic exploration and the modeling of underground rock formations is the introduction of four-dimensional (4-D) seismic imaging. This type of imaging is an extension of 3-D imaging technology. However, instead of achieving a simple, static image of the underground, in 4-D imaging the changes in structures and properties of underground formations are observed over time. The fourth dimension in 4-D imaging is time.

Various seismic readings of a particular area are taken at different times, and this sequence of data is fed into a powerful computer. The different images are amalgamated to create a 'movie' of what is going on under the ground. By studying how seismic images change over time, geologists can gain a better understanding of many properties of the rock, including underground fluid flow, viscosity, temperature and saturation.