Chapter 4 Review Questions(1) PDF

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Chapter 4 Review Questions 1. What is meant by the term “offset wells”. 2. Where is the information relating to the offset wells stored? 3. Are oil companies required to share offset well data? 4. When is offset well data normally released to other oil companies? 5. Give an example of offset well data. 6. Compare and contrast well logs, wireline logs, and logs. 7. When are well logs run? 8. How far into the formation do the logs read? 9. What does the gamma ray log show? 10. What does the neutron/density log measure? 11. What does the sonic log measure? 12. What does the spontaneous potential log measure? 13. What does the resistivity log measure? 14. DST ____________ 15. What does the DST measure and why is it so important? 16. What information can be derived from chip samples? 17. What information can be derived from a core and nowhere else? 18. What other information can be derived form a core? 19. What is a structure map and why is it important? 20. What is an isopach map? 21. What are cross sections and what offset well information is used to construct them? 22. Name three types of geophysical information. 23. Why is geophysical information so valuable to the petroleum industry? 24. Explain “shooting seismic”. 25. What methods can be used for a sound source? 26. What is a “reflector”? 27. What are the limitations of seismic? 28. Is seismic required to be sent to the Board? 29. If an oil company wants to view and purchase seismic can they force the company that owns the seismic to allow viewing or to sell it?

Chapter 4 Solutions to Review Questions 1. Offset wells are wells that were drilled by oil companies over the years and are adjacent to the area that you are interested in. 2. EUB 3. Yes, they must give a copy of their information to the EUB. 4. In most cases the information is kept confidential for one year and then released to all oil companies. 5. Well logs, DST information, chip samples, core. 6. All are the same thing. 7. As soon as drilling is complete.

8. Six to ten inches 9. A gamma log will indicate the potential for reservoir rock. It will distinguish between shale and clastics/carbonates. 10. Porosity, recorded directly onto the log. 11. Porosity, derived from the log using published charts. 12. Permeability, not a quantitative value only as a possibility. 13. The resistivity log will give indication of the presence of hydrocarbon versus salt water. 14. Drill stem test 15. A DST uses pressure information to establish the size of the reservoir; it also, may obtain a fluid sample from the formation, and can get an estimate of permeability. It is important because completing a well (getting it ready for production) can be costly and it is poor practice to complete a well that will not produce long enough to reach payout and beyond. 16. Lithology (rock type), porosity, presence of oil, ballpark permeability. 17. A quantitative value (an actual number in Darcies) for permeability. 18. Environment of deposition. 19. A structure map shows the top surface, in map view, of a particular formation in the subsurface. It is important because oil companies need to know where the formation is highest as hydrocarbon moves updip. 20. An isopach map represents the thickness of the formation. 21. Cross sections are constructed from well logs and are a side view of the formation of interest. 22. Aeromagnetic survey, gravity survey, and seismic survey. 23. Because it allows the explorers a glimpse of the subsurface without the high cost of drilling a well. 24. Shooting seismic is the process of obtaining seismic information. The term “shooting” comes from shooting off charges of dynamite. 25. Dynamite and Vibroseis. 26. A reflector is a change in rock type usually marking a formation change. That causes a portion of a sound wave to be reflected back to the surface. 27. Acquisition can be difficult, seismic cannot resolve formations thinner than 30 ft (10 m), the sound will become weaker with depth, and seismic is highly interpretative. 28. No, seismic is considered proprietary data, meaning that the company who shoots it can keep is confidential forever. The EUB does not get a copy of seismic data. 29. No, if a company does not want to share (sell) their seismic they will not be required to do so....