1. Dipping layer reflection events and the common midpoint gather
Environmental and Exploration Geophysics II
Dipping layer reflection events and the common midpoint gather
tom.h.wilson
Department of Geology and Geography
West Virginia University
Morgantown, WV
Tom Wilson, Department of Geology and Geography

2. Dipping Layer Reflection Event with Offset Apex
Tom Wilson, Department of Geology and Geography

3. How do you find depth h, velocity V and dip ?
Tom Wilson, Department of Geology and Geography

4. If you could not see the direct arrival then you could solve for V using either expressions for t0 or tapex.
Tom Wilson, Department of Geology and Geography

5. Tom Wilson, Department of Geology and Geography

6. Tom Wilson, Department of Geology and Geography

7. Tom Wilson, Department of Geology and Geography

8. Tom Wilson, Department of Geology and Geography

9. This is referred to as a stacking chart
This is referred to as a stacking chart. The significance of the name will become apparent later on.
Tom Wilson, Department of Geology and Geography

10. Bring questions to class on Tuesday
For next week at this time construct a stacking chart for a symmetrical split spread consisting of 12 geophones arranged 6 on each side of the source.
Bring questions to class on Tuesday
Tom Wilson, Department of Geology and Geography

11. Tom Wilson, Department of Geology and Geography

12. Tom Wilson, Department of Geology and Geography

13. Tom Wilson, Department of Geology and Geography

14. Tom Wilson, Department of Geology and Geography

15. Tom Wilson, Department of Geology and Geography

16. Tom Wilson, Department of Geology and Geography

17. Tom Wilson, Department of Geology and Geography

18. Tom Wilson, Department of Geology and Geography

19. The effect of the moveout correction on the traces in the common midpoint (CMP) gather is to create a composite normal incidence trace that effectively shares a coincident source and receiver at the midpoint shared by all the traces in the gather. We’ll discuss CMP data in more detail in a couple lectures.
Tom Wilson, Department of Geology and Geography

20. Stages of development: Sediments pile up and dip into the Gulf
Stages of development: Sediments pile up and dip into the Gulf. Mass wasting of the shelf proceeded under the pull of gravity
Tom Wilson, Department of Geology and Geography

21. Faults rise to the surface in the landward direction as the sediments take a sled ride into the Gulf. These faults accommodate extension at a slow (creeping) but steady pace. Time is always available in excess for the geologist.
Tom Wilson, Department of Geology and Geography

22. From Seismic to reservoir image
Tom Wilson, Department of Geology and Geography

23. Seismic acquistion to subsurface imaging
Tom Wilson, Department of Geology and Geography

24. Note the roll-over into the glide zone, synthetic and antithetic faults
Tom Wilson, Department of Geology and Geography

25. Tom Wilson, Department of Geology and Geography

26.
Tom Wilson, Department of Geology and Geography

27. Complex traps and cap rock
Tom Wilson, Department of Geology and Geography

28. Questions about the Exploration Project
The Main Fault
Tom Wilson, Department of Geology and Geography

29. At a minimum you should have digitized the main (synthetic fault – light blue) and the antithetic fault that cuts back into the main fault (antithetic fault- light green)
Tom Wilson, Department of Geology and Geography

30. On Monday we went through the horizon digitization procedures
Tom Wilson, Department of Geology and Geography

31. Just as with the fault your picks can be displayed in map view by double clicking the horizon or by dragging over the Amplitudes or Times from the horizon list in the project tree
Project tree
Tom Wilson, Department of Geology and Geography

32. For the remainder of the class work in pairs as you complete your horizon interpretation
Note the presence of fault gaps in your horizon picks. This is where you will draw in a fault polygon.
The gap at left is produced by the intersection of the main synthetic fault with the interpreted horizon
Tom Wilson, Department of Geology and Geography

33. Fault Gap
We’re running a little bit behind but I think we need to take the time to be sure you have the basics down. So we will conclude this exercise next Monday
Tom Wilson, Department of Geology and Geography

34. Homework
Construct a stacking chart for a symmetrical split spread consisting of 12 geophones arranged 6 on each side of the source (see handout).
Bring questions to class next Monday. Chart is due next Wednesday.
Complete your reading of Chapter 4. Dipping layer reflection events are covered on pages , with additional discussion on pages The idea of common depth point sorting is discussed on pages We’ve talked tangentially about resolution ( ) and velocity analysis ( ). We will be talking about stacking of CDP gathers ( ) and migration ( ). Discussions of migration will come later but it is helpful to be aware of the issues early on.
Look over problems 4.1, 4.4 and 4.8.
Tom Wilson, Department of Geology and Geography