Hello everyone,
I have a question please.
How I can modify or arrange between well log porosity and core porosity.
I have one printed well log data which held neutoron porosity, density porosity and gamma ray and 3 point core porosity on interested zone.

But, well logging porosity is very different compared to core porosity.

Actually, core porosity is less than well logging one.

How can I analyze these differences?

Also is ok to calculate using NPHI/DPHI Method?
Total porosity of well logging data using NPHI/DPHI (for example two-third method ... ) is accurate? or not?

And, what is the major different between NPHI(Sandstone matrix) and NPHI(Limestone or Dolomite matrix)

if my interesting zone comprise mainly of sandstone and a bit of limestone, in this case I have to use
NPHI(sandstome matrix) and DPHI(sandstone matrix) or not.
Please guide me.

Soman