It is the simplest and oldest type of cement sensors.
This type of sensor is lowered as a full set into the well and includes:
(CBL , VDL , GR , CCL )
Whereas:
- CBL : cement bond log
- VDL : Variable Density log
- GR: Gamma Ray (used for depth correction)
- CCL : casing collar locator (determination of the boundary between bushings)
The CBL and VDL sensors have one transmitter and two receivers.
(CBL) the arrival time of a wave at a distance of three feet (3 ft) from the transmitter and records the amplitude of the first arrival wave (mv).
(VDL) is the waves traveling through casing and formation and are in the form of black and white colored bands and also record the “second arrival time in ms” where the evaluation of cement according to VDL is from two sides: the first is the bonding of cement between the lining and cement (casing and cement) and the second is the bonding of cement between cement and formation
CBL can be lowered in Kisink size (13.375, 9.625, 7, 6.625).