EVALUACIÓN DE CEMENTO

Bond log showing cement top

Typical Cement Bond

Log presentation

Good Formation Bond

Free pipe

CBL-VDL in free pipe (no cement). Notice straight line and high amplitude pattern on

VDL pipe arrivals (railroad track pattern). Travel

Time curve is constant and amplitude curve reads

high. Note casing collar anomalies on travel time

and amplitude curves, and more weakly on VDL display.

Casing is still unbonded (high amplitude

Railroad tracks on early arrivals on VDL), Railroad tracks on early arrivals on VDL),

Amplitude curve reads high, BUT late arrivals on VDL have “shape” and track

porosity log shape. This indicates free

pipe laying on side of borehole and

Touching formation. The VDL arrivals with “shape” are the Formation arrivals.

Better casing Centralization should be

used on the next well. A cement squeeze

will improve the scene but will probably

not provide isolation on the low side of

the pipe.

Well bonded pipe (low amplitude on

early arrivals on VDL, good bond to formation (high amplitude late arrivals with “shape”). Mud arrivals

would have high amplitude but no “shape”.

VDL on left shows poor bond but formation signal is fairly strong. When casing is put under pressure,

bond improves (not a whole lot) as seen on lower amplitude early arrivals on right hand log. This is

called a micro-annulus. Under normal oil production, the micro-annulus is not too big a problem unless

bottom hole pressure is very low. Micro-annulus is caused by dirty or coated pipe, pressuring casing

before cement is fully cured, or ridiculous pressures applied during stimulation.

When there is no CBL-VDL made

under pressure, the un-pressured

version can be used to interpret

micro-annulus. High amplitude

early arrivals (normally

Indicating poor bond) actually

Indicate good bond (with

micro-annulus) IF formation

signals are also strong.

The travel time curve is lower than baseline

(shaded areas, Track 1) indicating fast formation

arrivals. If you see fast formation, you have a

good bond to pipe and to formation. However,

you cannot use the amplitude curve (labeled

“Casing Bond” on this example) to calculate

attenuation, compressive strength, or bond

index, because the amplitude is measured on

the formation arrivals, not the pipe arrivals.

• Centralización

• Pozos con gas

• Microanillo

Tracks 8 to 16 provide 5 segmented curves from the impedance image broken into 9 segments around the wellbore. High activity indicates solids, and low activity indicates fluid. In the zone F notice how the curves have both low impedance and low activity compared to the data immediately above it in zone C.

Track 6 (DZ) is the variance of the impedance map which highlights the differences between solids

Track 3 contains a standard CBL waveform display (WMSG).

Track 2 presents the amplitude (AMP), amplified amplitude (AAMP), filtered cement bond index (FCBI), as well as the computed cement bond index (FCEMBI).

Track 1 presents correlation data (GR), quality control (ECTY), and the average impedance (ZAVG) which provides a quick interpretation of the cement placement.

Track 7 (CEMT) shows the result of both the impedance and variance in determination of solids vs. fluids. Fluids are designated as blue, while cement is indicated by the brown color.

the differences between solids (cement) and liquids.

The ultrasonic impedance map (ZP) is presented in Track 5, which indicates the impedance of the material behind pipe.

Track 4 is the total CBL waveform (WMSGT) which is the ACE™ processing which highlights the collar response.

waveform display (WMSG).