Doctor Neutron has added a .pdf image of his latest
paper entitled "PORE SIZE, ORIENTATION AND SHAPE;
LAMINAE; AND FRACTAL DIMENSION EFFECTS ON THE
RESPONSE OF SEVERAL NUCLEAR LOGGING TOOLS".

This paper was first published in the Proceedings
of the 2009 SPWLA Annual Logging Symposium,
The Woodlands, Texas, as Paper Y.

For the laminae examples, small formal effects on
formation sigma were observed and much larger effects
on neutron porosity.  Some interesting results are
predicted for open hole bulk densities in sand-shale
laminae.  These heterogeneous predictions are based
on non-linear mixing of the gamma ray linear attenuation
coefficients with the result that gamma transmission
n the two media becomes interdependent.

The insensitivity of a new cased hole bulk density
measurement to Montmorillonite laminae intrusion into
an oil sand needs further investigation using both
the new Transmission Probability Method and Monte
Carlo modeling.  These same methods can also be used
to continue study of the impact of pore size, laminae,
and fractal dimension on direct measurement of the
thermal neutron diffusion coefficient from the Chappell
Hill Logging multi-detector pulsed neutron logging tool.


-----------------------------------------------------------------------------------

Periodically this site will present fresh new examples with
LVPM concerning the impact of pore size and laminae properties
on bulk density, Pe, dual-spaced neutron porosity, thermal
neutron diffusion coefficient, and neutron capture cross section.

In particular, the density and Pe computations no longer utilize
Filippov's method. Instead, a new and very accurate
interpolation scheme based more directly on the NIST data tables
of Hubbell and Seltzer is used. As in the previous Filippov
formulation, the new LVPM calculations still account for energy
losses during gamma ray propagation, corrections for multiple
scatterings, and the gamma detector energy-dependent counting
efficiency.

One new feature has been added to the LVPM Program Internals
Output Pane: Material 1 and Material 2 MCNP5 Mass Fractions.

In the XY plot shown further on, the impact of fractal
dimension variations on neutron-density crossplots is
illustrated using concepts presented in the 2009 SPWLA
Annual Logging Symposium, Paper Y.

As the fractal dimension increases, pore size dramatically
decreases.  Since scattering and diffusing neutrons tend to
avoid water, when the fractal dimension is low and the pores
are larger, they don’t “see” some water internal to these
larger pores and they propagate more in the rock matrix and
the sensed neutron porosity is lower.  But then, as the pores
are reduced in size with higher fractal dimensions, the neutrons
“find” all the water present, they are more spatially confined,
and the sensed neutron porosity is higher.

Conversely, gamma rays attempt to avoid the higher density
of the matrix and tend to propagate in the lower density
fluid, reporting relatively more water than matrix when the
fractal dimension is low, and inversely.