Formation Evaluation Exercise

1
Formation Evaluation Exercise For Subsurface
Methods Geology Course 4233 By Richard
Andrews March 5, 2009
2
Cromwell Sandstone
GR SP RESISTIVITY 2 Rxo/Rt - 0.5
1 10 100 1K
Calculate Sw in this zone every 2 ft.
SP
GR
deep
Rxo/Rt
shallow
3
Cromwell Sandstone
GR Cal Density Neutron F 6
in 16 30 20 10 0
Calculate Sw in this zone every 2 ft.
Note This log is shifted down 2 ft from
resistivity log.
4
GR CAL Density Neutron Porosity
0 API 150 30 20 10
0 6 in. 16
Red Fork Sandstone (3670-3690)
3700
Bartlesville Sandstone (3758-3792)
3800
5
GR SP RESISTIVITY 0 API
150 1 10 100 1k
Red Fork Sandstone (3670-3690)
3700
Bartlesville Sandstone (3758-3792)
3800
6
GR SP RESISTIVITY 0 API
150 1 10 100 1k
Mississippian Limestone zone
GR CAL Density Neutron Porosity
0 API 150 30 20 10
0 6 in. 16
Calculate Sw every 2 ft in this zone
(6190-6260).
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• Questions for formation evaluation
  exercise
• Identify zones having hydrocarbon potential
  throughout the designated intervals in all wells.
  Calculate Sw every 2 feet in the indicated zones
  using Excel spreadsheet.
• Identify the expected type of hydrocarbon in each
  of the 4 zones.
• In the Red Fork Bartlesville sandstones
• a. How clean are they??
• b. What is the GR log profile telling you about
  the depositional setting and areal distribution
  of these two sandstones deposits?
• c. Explain the behavior of the density and
  neutron porosity logs across these two intervals.
• 4. In the Cromwell sandstone
• a. Why is the density-neutron separation
  different in the top of the interval versus the
  bottom?
• b. Identify zones having permeability.
• c. Why is there no separation between the
  shallow and deep resistivity recordings from
  6172-6206?
• d. Explain the behavior of the Rxo/Rt log in
  detail.
• e. If this well was drilled using 9-pound mud
  and the virgin reservoir pressure was 2500 psi,
  was this well drilled over or under-balanced?.
  Would you expect invasion in a permeable
  formations?