Borehole geophysics involves lowering a geophysical instrument, such as a downhole camera, acoustic televiewer, or downhole geophysical logging tool, into a borehole to collect data on the physical and chemical properties of the rock formations and fluids in the borehole. The data collected can be used to determine the lithology, stratigraphy, porosity, permeability, and water content of the subsurface formations.
Some of the commonly used borehole geophysical methods include:
- Acoustic and ultrasonic methods: These methods involve transmitting and receiving acoustic or ultrasonic signals in the borehole to measure the velocity and attenuation of the signals, which can provide information on the lithology, porosity, and fracturing of the formations.
- Electrical methods: These methods involve measuring the electrical properties of the formations, such as resistivity and conductivity, by introducing an electric current into the borehole.
- Nuclear methods: These methods involve introducing a radioactive source into the borehole and measuring the gamma radiation emitted by the formations, which can provide information on the lithology and mineral content of the formations.
- Magnetic methods: These methods involve measuring the magnetic properties of the formations, such as susceptibility and remanence, which can provide information on the lithology and mineralogy of the formations.
Borehole geophysics can provide valuable information for various applications, such as mineral exploration, groundwater studies, environmental assessments, and geotechnical investigations.