BAKER HUGHES - Drilling Fluids Reference Manual

PRESSURE PREDICTION AND CONTROL
• Shale stringers within massive sand sections tend to exhibit high, unreliable readings.
• Avoid shale readings immediately above a known gas sand. These readings will characteristically
display high, unreliable values.
• If available, the caliper survey should be scanned for excessive hole enlargement. Excessive
enlargement can create a skip in signal on sonic logs and lead to erroneous data.
• Avoid plotting silty or limey shales by inspecting the SP curve. Minimum SP values will result in
more reliable data.
• Scan log prior to plotting for scale changes or error in tie-back on subsequent log runs.
• Utilize available well data to verify predicted pressures (formation tests, “d” exponent plots, well
kick data, etc.).
Factor
Salinity changes
Swelling clays
Hole enlargement
Limey shales
Resistivity markers
Age change
Bentonite clays
Improper calibration
Tool malfunction
x = Affected
s = Sometimes Affected
Short
Normal
x
x
x
x
x
x
s
s
Conductivity
x
s
x
x
x
s
s
Transit
Time
Table 12 - 3 How Variables Affect Logs
x
x
x
x
s
s
Bulk
Density
x
x
x
x
s
s
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 12-10