Joint usage of s-waves and p-waves

In the method of reflected waves seismic exploration efficiency significantly increases when S-waves and P-waves are used jointly. Knowing speed of propagation for both types of waves provides for more reliable identification of deposition properties and composition, including such an important solution as determining nature of fluids filling rock pores. Such data bring seismic exploration to the frontline of searching for oil and gas, i.e. the final task of seismic exploration for hydrocarbons.

When directly searching for oil and gas just kinematical data, i.e. data on wave arrival times are not sufficient, and dynamic factors start to play the key role – shape and intensity of received waves, nature of wave shape change depending upon the wave trace in the medium. The most important now is to initiate elastic waves. Not only the source power but also a possibility to control parameters of generated by it oscillations becomes critical. This provides for conditions to determine such parameters of actual medium as absorption ratio.

Joint usage of S-waves and P-waves and determination of the medium absorption properties allow seismic exploration putting more and more complicated tasks not only when searching for oil and gas but also many others, including exploration of ore deposits.

Seismic noises

Seismic operations are known to be performed not in a lab but in the “field”. The “field” means clean field, taiga, desert, tundra, mountains or sea. All of them are filled with sounds, oscillations in the air and in the soil. How this circumstance results in seismic operations is easy to understand, if we take into account, that displacement of the soil on which seismographs are installed makes them very sensitive when a useful wave comes closer to the surface. Sources of such irregular interferences or noises, as a rule are weak, but being located close to seismic receivers, they can disguise arrival of even very intensive useful waves. Therefore, another problem arises – how to deal with noises and irregular waves. Suppressing to the needed extent these or those interferences, we will just come to the beginning of the acquisition process obtaining data on subsurface structure. However even at this stage of processing observation materials we have to use some kind of actual medium model. Otherwise we will never be able to distinguish the required useful signals.

The words to be memorized:

1. seismic exploration – сейсморазведка

2. reflection method –метод отраженных волн (MOB)

3. seismic noise –сейсмические помехи

4. arrivaltime– время вступления (волны)

5. Interference – помехи

6. Noise – шум

7. Absorption –адсорбция, адсорбционный

8. Hydrocarbons –углеводороды

9. Distinguish –различать

10. Propagation –распространение

11. Frontline –линия фронта

12. Absorption ratio– коэффициент поглощения

13. Elastic waves –упругие волны

14. Traveltime– время пробега (волны)

15. Receiver – сейсмоприемник

16. Reflection – отражение

17. Refraction –рефракция

18. Diffraction –дифракция

19. Anisotropic mediums – анизотропные среды

20. Multi-component mediums –многокомпонентные среды

21. Boundary –граница

22. Dissipation –разложение 

23. Thickness –мощность

EXERCISE 6 Answer questions about the text.

1. What does significantly increase seismic exploration efficiency in the method of reflected waves?

2. What does the knowledge of speed propagation for both types of waves provide for?

3. What is the final task of seismic exploration?

4. What factors start to play the key role searching for oil and gas?

5. What allowsdetermining the absorption ratio?

6. What does «field» mean?

7. How to solve the problem of noises and irregular waves?

EXERCISE 7 Connect the terms with their definitions.

Arrival time	a method of seismic exploration in which an excited seismic wave directly returns to the source.
Reflection method	interference during reception of seismic signal, can be coherent and incoherent.
Seismic exploration	an instrument that detects and records seismic vibrations.
Seismic noise	the use of seismic surveying and explosion seismology in prospecting for oil, gas or other mineral source.
Seismograph	the time that it takes a particular wave phase of seismic energy to travel from the shot to a reflector and back to the detector that records it during seismic exploration.

EXERCISE 8 Use the suitable nouns for adjectives and translate the word combinations.

Nouns: waves task operations interferences time deposits structure

Adjectives: seismic arrival reflected irregular final ore subsurface

EXERCISE 9 Give the English equivalents to the following word combinations.

1. Скорость распространения

2. Заключительная задача

3. Время вступления (волны)

4. Динамические факторы

5. Средний коэффициент поглощения

6. Рудные месторождения

7. Сейсмические операции

8. Шумы

9. Помехи

10. Подземная структуры

11. Средние модели

12. Полезные сигналы

EXERCISE 10 Read and translate the text.