All about Density Log; an Important Cased-Hole logging Tool


Well, logging is a continuous recording of geophysical properties in the borehole, where the value of the measurement is continuously plotted against the depth of the wellbore.

It helps in the investigation of the underground materials.

Well logging is the essential part for oil and gas industry. It provides complete information related to the physical and chemical properties of underground fluid or rocks. It is divided into two parts that are open-hole logging and cased-hole logging to get the complete knowledge on well formation or integrity.

Open-hole logging is done before the completion of the wellbore; it helps you to dig a precise and wellhole that help you completely in your motive. However, cased-hole logging helps you with the casing of well, measuring the properties of fluid like density, porosity, conduction, etc.

Cased-hole logging tools provide the accurate and exact information of downhole activities that will help you in maintaining the well.


Usually in moving down in depth the density increases and porosity decreases due to the rise in pressure at downhole. The density log can measure the electron density of the well formation and help in oilfield pipe recovery. Density gives the information of material with which rock is formed. Also, density is the primary indication of porosity. Density log is a source of gamma rays, it emits these rays into them, and they collide with electrons of the formation. At every collision, gamma rays lose some energy to the neutrons, and finally, the scattered gamma ray reaches the detector and is counted as an indication of density. As the denser the formation, the more neutrons are present at the detector.

Electrical resistivity

Electrical resistivity is the measure of abstraction to current flow; it is opposite to the conductivity. Rock matrix does not conduct electricity, although the little conductivity is due to the presence of fluid in them. Resistivity can be affected by porosity and lithology of formation in well. Resistivity measurement gives you the information about the saturation of hydrocarbons in the wellbore.

To measure the resistivity, a current is passed between the electrodes on the logging tool, and the amount of potential difference between them provides the resistivity. As rock is non-conducting hence the value of conductivity is results of liquid pore space in the rocks. Therefore electrical resistivity also measures the porosity of formations.


Porosity is the void in rocks as compared to total area of rocks. Cased-hole porosity log helps you to determine the porous property of well formation and mud. High range of porosity indicates that rocks may have more liquid which can be useful and hence give rise to your oilfield business. There are three types of porosity logs like sonic, neutron and density log that will help you to measure the porosity in down hole. The density and neutron logs use nuclear theory for measurement.

Lower down the tools with wire line services into the testing area, and recognize the above mention properties of fluid as well as of well formations. All these properties will help you to judge the area for drill the borehole for oilfield or wireline work. If you feel that you are not able to perform the logging task by yourself, then you may hire the expert professionals, as they are expert in handling measuring and logging tools. Proper inspection and maintenance of well bore provides you good well and also increase its lifetime with production. Directly or indirectly it will be a great benefit for your business.


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