Well logging, also known as borehole logging is the practice of making a detailed record (a well log) of the geologic formations penetrated by a borehole. The log may be based either on visual inspection of samples brought to the surface (geological logs) or on physical measurements made by instruments lowered into the hole (geophysical logs). Well logging can be done during any phase of a well’s history; drilling, completing, producing and abandoning. Well logging is performed in boreholes drilled for the oil and gas, groundwater, mineral and geothermal exploration, as well as part of environmental and geotechnical studies.
Techniques and typical logging objectives are as follows:
- Optical Televiewer ( OPTV – OBI ) delineate fracture patterns and orientations and other structural features
- Acoustic Televiewer (BHTV- OBI ) delineate fracture patterns and orientations and other structural features
- Sonic-access casing cement bond; P-wave velocity correlations
- P & S wave Suspension Logger-determine compressional and shear wave velocities
- Gamma ray
- Caliper
- Resistivity logging(SPR) Spontaneous Potential (SP)-define stratigraphy and stratigraphic correlations
- Deviation-determine borehole verticality
- Temperature-Differential Temperature Fluid Conductivity-determine groundwater inflow and outflow depth locations
- Flowmeter
- Heat-Pulse Flowmeter-measure vertical groundwater flow