Geology Reference
In-Depth Information
4.5
Exercises
4.5.1
Interpretation of Thickness in a Well
Based on the data in Table 2.2, what is the isocore thickness of the Smackover? What
is the true thickness of the Smackover given its attitude of 12, 056 from the dipmeter
log and the orientation of the well from Exercise 2.9.1? Discuss the significance of the
difference between the isopach and isocore thickness.
4.5.2
Thickness
Given a bed with dip vector 10, 290, and a measured thickness of 75 m in a vertical
well, use the universal-thickness equation to determine its true thickness.
4.5.3
Thickness from Map
Use the map of the Blount Springs area (Fig. 2.27) to answer the following ques-
tions. What is the thickness of the Mpm between the structure contours using the
map-angle equations and the pole-thickness equation? Are the results the same? If
they are different, discuss which answer is better. What is the difference between
the true thickness and the vertical thickness of the Mpm? What is the thickness of
the Mpm in its northeastern outcrop belt, assuming that the dip is 28° at its
northwestern contact and the value determined above occurs at its southeastern
contact? Use the concentric fold model and the dip-domain model. Discuss the
effect of changing the location of the axial surface on the thickness computed
with the dip-domain model. Measure the thickness of the Mpm at 5-10 loca-
tions evenly distributed across the map. Measure thicknesses between structure
contours where possible. Construct an isopach map from your thickness measure-
ments. Is the unit constant in thickness? What would be the apparent thickness of
the Mpm in a north-south, vertical-sided roadcut through the northwestern limb
of the anticline?
4.5.4
Isopach Map
Make an isopach map of the sandstone thicknesses on the map of Fig. 4.19. The
thickest measurements form a trend that could be a channel or the limb of a
monocline. If the thickness anomaly is due to a dip change, what is the amount?
If the thickness anomaly is due to paleotopography, what is the maximum topographic
slope?
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