How does porosity affect density?
Looked at from the porosity perspective, bulk density increases as pore space decreases. The relationship of bulk density and porosity is reciprocal. As one increases, the other decreases. Generally speaking, loose, rich in organic matter, well aggregated and porous soils have a low bulk density.
What is density porosity?
The porosity is an indicator of how much empty space is inside your rock that could be filled with water and/or hydrocarbon. In density logs, which measure electron density and transform it into bulk density, porosity is calculated by assuming the matrix density and fluid density.
What does a neutron porosity log measure?
The tool measures the size of the neutron cloud by characterizing the falloff of neutrons between the two detectors. Because neutrons penetrate considerably further than gamma rays, the design is much simpler than that of a density tool.
How do you determine porosity?
Porosity = ( ( Total Volume – Volume of the Solid ) / Total Volume ) x 100%. A larger percentage means that the rock has the ability to hold more water.
How do you calculate true porosity?
: All the pores ( open and sealed ) % True Porosity = Volume of all pores x 100 Total vol.
What is the porosity of heavy clay 100% clay particles?
Typical bulk density of clay soil is between 1.1 and 1.3 g/cm3. This calculates to a porosity between 0.58 and 0.51. This seems counterintuitive because clay soils are termed heavy, implying lower porosity.
What is density of neutron?
Neutron stars comprise one of the possible evolutionary end-points of high mass stars. They have densities of 1017 kg/m3(the Earth has a density of around 5×103 kg/m3 and even white dwarfs have densities over a million times less) meaning that a teaspoon of neutron star material would weigh around a billion tonnes.
How do you read density porosity logs?
Obtaining porosities from a density log
- Φ = porosity.
- ρma = matrix density (see table below)
- ρb = formation bulk density (log value)
- ρf = density of the fluid saturating the rock immediately surrounding the borehole—usually mud filtrate (use 1.0 for freshwater and 1.1 for saltwater mud)
How does neutron porosity work?
Referring to a log of porosity based on the effect of the formation on fast neutrons emitted by a source. Hydrogen has by far the biggest effect in slowing down and capturing neutrons. Since hydrogen is found mainly in the pore fluids, the neutron porosity log responds principally to porosity.
How to obtain correct porosities from density-neutron logs?
To obtain correct porosities from density–neutron logs when the two logs record different porosities for a zone, use one of the methods listed below. If density porosity is less than neutron porosity, such as in a sandstone with shale/clay content, the density log provides a reasonable approximation of formation porosity.
What is the effective porosity of a neutron Crossplot?
The density neutron crossplot porosity, PHIxdn, after all corrections are applied, is called the effective porosity, PHIe. or Gas zones with crossover. Chartbook solutions are provided above. Shale corrected data must be entered.
Why is the porosity of a gas greater than a neutron?
Crossover (density porosity is greater than neutron porosity) is due to the presence of gas in the formation. Recompute density porosity using Use gas density instead of water density.
When is the density-neutron Crossplot analysis ambiguous?
The density–neutron crossplot analysis can be ambiguous when the formation is of mixed mineralogies, like a dolomite-cemented sandstone. When gas is present, the situation is much more complicated.