DPHI
Schlumberger%Density Porosity
Porosity computed from bulk density given an assumed matrix and fluid density. It is not an independent measurement — RHOB re-expressed as porosity — and it forms one half of the neutron-density gas crossover.
- Property
- Density Porosity
- Apparent Porosity
- Quantity
- dimensionless
- % · GEuc · ppm · mEuc · cEuc · MEuc · nEuc · pEuc · kEuc · ppk · fEuc · µEuc · dEuc · EEuc · TEuc · Euc
- Typical range
- ~0–21.6 PU
- porosity units, matrix-dependent
Logging tool
No logging tool is associated with this curve.
Service company
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How it's measured
Derived, not measured: φD = (ρma − ρb) / (ρma − ρf). The chosen matrix density (2.65 sandstone, 2.71 limestone, 2.87 dolomite) sets the porosity zero.
How it's used
Neutron-density crossplot porosity and gas detection, where density porosity reads above neutron porosity across gas. A quick-look porosity when the matrix is known.
Common gotchas
Entirely dependent on the assumed matrix and fluid — the wrong matrix biases every value. It inherits all of RHOB's borehole problems (washouts, mudcake), so check DRHO and the caliper, and remember gas makes it read too high.
In LAS files
Recorded as DPHI (or DPOR, PHID) in v/v or %. The matrix assumption is often encoded in the mnemonic suffix (e.g. DPHI_LS).
Also seen with DPHI in real logs
Curves that appear alongside DPHI in the same wells across the public corpus.