What does a neutron density log measure?

In density logs, which measure electron density and transform it into bulk density, porosity is calculated by assuming the matrix density and fluid density. Neutron log measures the ratio of count rate from the rock, which is equivalent to how much hydrogen index it has.

What does a neutron log measure?

hydrogen concentration

The neutron log mainly measures hydrogen concentration in a formation. The logging device is a noncontact tool that emits neutrons from a source. Emitted neutrons collide with nuclei of the formation and lose some of their energy.

What does density log measure?

The density log measures electron density by detecting gamma rays that undergo Compton scattering. The intensity of scattered gamma rays is proportional to electron density. Electron density is the number of electrons in a volume of the formation. Electron density is proportional to bulk density.

What do neutron porosity logs actually measure and why?

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.

What is neutron density?

The neutron flux density, Ф, is the number of neutrons crossing through some arbitrary cross-sectional unit area in all directions per unit time. It is a scalar quantity, and it can be calculated as the neutron density (n) multiplied by neutron velocity (v).

How is neutron porosity measured?

Neutron porosity measurement employs a neutron source to measure the hydrogen index in a reservoir, which is directly related to porosity. The Hydrogen Index (HI) of a material is defined as the ratio of the concentration of hydrogen atoms per cm³ in the material, to that of pure water at 75 °F.

What is neutron porosity logs?

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.

What is density porosity?

It is defined as the ratio of the volume of the voids or pore space divided by the total volume. It is written as either a decimal fraction between 0 and 1 or as a percentage.

How do you find the porosity of a density log?

In density logs, which measure electron density and transform it into bulk density, porosity is calculated by assuming the matrix density and fluid density. Neutron log measures the ratio of count rate from the rock, which is equivalent to how much hydrogen index it has.

How do you find the density of a neutron?

=2.90×1017⋅kg⋅m−3 , which is fairly dense…….but then we expected it to be for a fundamental massive particle.

How does formation density log works?

A density-logging tool sends gamma rays into a formation and detects those that are scattered back. Typical logging sondes use a Cesium-137 source, which emits gamma rays of 0.66MeV. At this high energy level, Compton scattering dominates.

Which type of tools can be used to measure the density of the formation fluid at different depths?

Clarification: Nuclear Fluid Densimeter can be used to measure the density of the formation fluid. This Nuclear Fluid Densimeter logging tool uses a radioactive source and a detector.

What is well logging and its purpose?

A well log is a record of the formations and any events that are encountered in the well drilling process. It is also referred to as borehole logging. The main purpose of keeping a well log is to determine the suitability of the well for its intended use.

What do resistivity logs measure?

Resistivity logging is a method of well logging that works by characterizing the rock or sediment in a borehole by measuring its electrical resistivity. Resistivity is a fundamental material property which represents how strongly a material opposes the flow of electric current.

Why formation evaluation is important?

In petroleum exploration and development, formation evaluation is used to determine the ability of a borehole to produce petroleum. Essentially, it is the process of “recognizing a commercial well when you drill one”.

What does high resistivity mean?

A high resistivity means that a material does not conduct electric charge well. Electrical resistivity is defined as the relation between the electric field inside a material, and the electric current through it as a consequence: ρ=EJ.

Why Does Clay have low resistivity?

Clay minerals have a substantial negative surface charge that causes log resistivity val- ues to plummet. 2 This negative surface charge—the result of substitution in the clay lattice of atoms with lower positive valence —attracts cations such as Na+ and K+ when the clay is dry.

How soil resistivity is measured?

Soil resistivity is another name for the specific resistance of the soil. It is measured in ohm-meters or ohm-centimeters. An ohm-meter is that resistivity of the soil when it has a resistance of 1 ohm between opposite faces of a cube with one meter sides. Resistance is directly proportional to soil resistivity.

How does clay affect resistivity?

Electrical resistivity is also correlated with index properties. Soils with higher liquid limit or plasticity index, a greater percentage of fines or clay, or a smaller coarse fraction have lower electrical resistivity.

Why do we test soil resistivity?

Soil resistivity measurements have a threefold purpose. First, data is used to make sub-surface geophysical surveys as an aid in identifying ore locations, depth to bedrock and other geological phenomena. Second, resistivity has a direct impact on the degree of corrosion in underground pipelines.

What is the difference between soil resistivity and earth resistance?

The resistance of the earth varies from layer to layer. The lower layer of soil has more moisture and lower resistivity. If the lower layer contains hard and rocky soil, then their resistivity increases with depth.

What is Schlumberger method?

The Schlumberger method was developed to increase the voltage signal for the earlier, less sensitive instruments, by placing the potential probes closer to the current probes. The soil resistivity measurements will be affected by existing nearby grounded electrodes.

What is a good ground resistance value?

zero ohms resistance

Ideally a ground should be of zero ohms resistance. There is not one standard ground resistance threshold that is recognized by all agencies. However, the NFPA and IEEE have recommended a ground resistance value of 5.0 ohms or less.

What is a good earth ground reading?

The NFPA and IEEE recommend a ground resistance value of 5 ohms or less while the NEC has stated to “Make sure that system impedance to ground is less than 5 ohms specified in NEC 50.56. In facilities with sensitive equipment it should be 5ohms or less.”

How can you tell a good ground?

Set the voltmeter to read ohms (resistance) and probe the battery’s negative stud and ground connection on the accessory (the ground terminal on an amp, for example). If you have a reading less than five ohms, the ground is okay.