Cbl-vdl tool

Therefore, another important use of natural gamma logging is for stratigraphic correlation. In the cement bond logging, the main purpose of natural gamma logging tool is to regulate the depth. CCL logging is used to determine the location of casing collar.

Share on: Facebook Twitter Pinterest. Related Products. Product Catalog. Model No. Total 10 Related Items. Product Description. Predicted cement tops for the lead and tail cements. Casing and centralizer report to determine where casing eccentering may occur. Openhole logs with a caliper and lithology. An understanding of fluid type or gas in the formation pore space. Radial-CBL: Radial-CBL tools were developed to overcome some limitations of conventional CBL tools and to permit more accurate evaluation of cement distribution by providing the precise location of partial bond and channeling.

Bookmark the permalink. Properly run and interpreted, cement-bond logs CBL provide highly reliable estimates of well integrity and zone isolation. Just as filtrate invasion and formation alteration may produce changes in formation acoustic properties, and thus variation in acoustic logs over time, [6] [7] [8] so too, cement-bond logs may vary over time as the cement cures and its properties change.

Modern acoustic cement-evaluation bond devices are comprised of monopole axisymmetric transmitters one or more and receivers two or more. They operate on the principle that acoustic amplitude is rapidly attenuated in good cement bond but not in partial bond or free pipe. These cased-hole wireline tools measure:. Conventional CBL tools provide omnidirectional measurements, while the newer radial cement-evaluation tools provide azimuthally sensitive measurements for channel evaluation.

Amplitude, measured directly or as an attenuation ratio, is the primary bond measurement and is used to provide:. Tool response depends on the acoustic impedance of the cement, which, in turn is function of density and velocity. On the basis of empirical data, the log can be calibrated directly in terms of cement compressive strength. However, in foamed cements or when exotic additives are used, these calibrations can be inaccurate.

In these situations, users are advised to consult with the logging service company regarding the appropriate calibrations. Presentation of the full acoustic waveform assists in resolving bond ambiguities arising from use of an amplitude measurement alone and provides qualitative information about the cement-to-formation bond. Variable density is a continuous-depth time display of full-waveform amplitude presented as shades of black and white. Positive waveform amplitudes are shown as dark bands and negative amplitudes as gray or white bands; contrast is proportional to amplitude.

On a variable-density log, free pipe and fluid arrivals if present are easily identified as straight dark and light lines indicating homogenous acoustic properties at either side of the display Fig. The zigzag, wavy, or chevron pattern between these two arrivals is the formation signal indicating varying acoustic transit time.

The height of the collar disturbance is a function of measurement TR spacing amplitude, 3-ft interval; variable density, 5-ft interval courtesy of Baker Atlas. Early CBL designs s used a single transmitter and single receiver for an amplitude measurement. In an evolution similar to that of openhole acoustic logs, new designs were subsequently introduced that measured signal amplitude at a near receiver and a full waveform from a far receiver. Eventually, borehole-compensated devices using dual transmitters and dual receivers were introduced in the s, and today most commercial devices use multiple transmitters and receivers in a variety of arrangements to provide compensated measurements.

These devices measure the attenuation between two transmitters and receivers as a way of eliminating, or at least minimizing, the effects of:. In addition to specialized cement-bond devices, modern openhole array tools are designed to also provide conventional cement-evaluation measurements in cased hole. The cement-bond instrument sleeve is typically slotted to suppress and delay the tool signal that might otherwise be confused with the important casing signals. TR spacing typically ranges from 3 to 5 ft.

The shorter spacing e. This separation allows for easier analysis of the formation-signal strength and is used to monitor cement-to-formation bonding. These tools typically operate at higher frequencies than conventional openhole tools—between 20 and 30 kHz.

The attenuation in each segment is measured in two directions using a pair of acoustic receivers and two transmitters. The two measurements are combined to form a result that compensates for:. Transmitting elements and the firing sequence are controlled to direct steer and enhance the acoustic-energy output of both the pad transmitters and the VDL transmitter. This has the effect of improving the signal strength of both the casing and cement-to-formation arrivals, respectively.

The use of new high-performance low-density, foam, and complex cements is increasing. However, the presence of gas in cement slurries, as an inert component or as contamination, may seriously affect ultrasonic-tool interpretation. New interpretation methods integrate ultrasonic and attenuation measurements from conventional tools to provide improved cement evaluation in these conditions. Interpretation techniques combining these different measurements provide improved evaluation in lightweight cements, especially in the annulus, beyond the casing-cement bond.

Conventional cement-bond logs CBLs comprise a pulsed transmitter and several receivers of acoustic energy positioned as a vertical array of transducers.

The signal is received, processed, and displayed as a microseismogram. The recorded waveforms are presented together with the travel time and a casing-amplitude curve, which displays the amplitude of the acoustic signal that has traveled through the casing but not through the knterpretation and formation.

The waveform and amplitude data allow two bonds to be investigated. These are the bond between casing and cement and, to a lesser extent, that between cement and formation. Intrrpretation in the acoustic display are interpreted as indicating the presence of bonded cement.

However, they are not reliable as indicators of hydraulic sealing by the cement, because they cannot detect small channels therein.

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