1. Step 3: Resistivity Logs
ILD (deep)
Where do the resistivity logs give different values?
This indicates where the fluids in the rocks differ from the drilling fluid
In this case, it confirms the gas zone
Caliper
MSFL
NPHI
Gamma Ray
SFL
RHOB)
Shale
Siltstone
Gas
Formation Fluid
different from
Drilling Fluid
Sandstone
Formation Fluid
similar to
Drilling Fluid
SLIDE 13
Now we interpret the resistivity logs
For the bottom of the thick sand and the deeper sand, the medium and deep resistivity have similar values
That indicates that the drilling fluid is the same as the formation fluid
If the drilling fluid was an oil-based mud, then we have oil zones
If the drilling fluid was an water-based mud, then we have wet sands (pores filled with water)
There is a lot more that a log analyst can do – this is basic stuff that any geoscientist should be able to do
Water or Oil
Water or Oil
Siltstone
Sandstone
Water or Oil
Shale
Sandstone
Courtesy of ExxonMobil
L 4 - Well Log Data