Geoscience Scale of Investigation
This graphic illustrates the scales involved in geoscience and engineering measurements that are routinely made, and the technical specialties that use those measurements. One can see that differences in interpretation of the subsurface can arise on the basis of those scale differences alone, as well as on the basis of the experience and viewpoint of each interpreter. Note that each specialty covers several orders of investigative magnitude. In the specialty of Petrophysics/Log Analysis one must consider the investigation scale, through the vertical resolution and depth of investigation (away from the borehole), of each measurement used in an interpretation.

Sizes of Molecules and Pore Throats in Siliciclastic Rocks
This graphic (Nelson 2009) focuses on the size of the material being investigated; in particular, the size of pore throats in sandstones and shales. The lower left corner of the graphic also infers that the measurement of porosity and permeability may be affected by the fluids (gases and liquids) used in the laboratory, through the molecule sizes of those fluids as compared to the molecule sizes of the fluids occupying the rock in the subsurface.

History of Wireline Companies
This graphic shows the general history of the four major wireline companies. Dashed lines indicate uncertainties in when the companies existed or the existence of the company prior to acquisition, or after sale, of the wireline part of the company. Name changes along the same line indicate a company name change, while right angle changes in the lines indicate purchase or sale of the company. The graphic is intended to help people understand the source of old logs encountered in files, and may help the user direct questions about those logs to the proper company which now exists.

Shaly Sand Basic Petrophysical Definitions
Shaly sands are a complex physical mixture of solid and liquid components. This complexity is increased by the differences in the definitions of those components, especially in the historical literature; e.g., `clay` vs `shale`. The diagonally shaded parts of some of the definitions and of the porosity measurements indicate that there are discrepancies in how various sources describe the rock components and uncertainties in the log and core measurements.