Improving Confidence in Cement Evaluation
Pablo Estrada
Wireline Well Integrity Domain, North Sea
Offshore Well Integrity Conference, North Sea
Aberdeen 27th-28th Feb. 2013
Agenda
Cementing Objectives
Why Cement Evaluation?
Cement Evaluation Measurements
– CBL/VDL
– Traditional Ultrasonic Technology
– Enhanced Ultrasonic Technology
High quality cementing objectives
Support the pipe in place
– Further drilling
– Production
Protect the pipe in place
– Corrosive formation fluids
Hydraulic isolation
– No communication between different formation fluids
– No migration of formation fluids to surface
– No loss of production to thief zones
Cements ranges widely in property
– Foam to high density cements
– Contaminated cements
Cement placement quality depends on
– Well construction
– Cement design and execution
– Formation pressure, fracture gradient & fluid migration behavior
Annulus geometry varies
– Casing centralization
Challenges in Cement Evaluation
Confirm vertical
continuity of cement
placement to isolate
zones
Confirm the azimuthal placement of
cement and absence of channels
Identify cement placement challenges
Confirm adequate pipe centralization (where possible)
Resolve ambiguity through
multiple measurements
Address the wide range of cements that could
be potentially placed
Norsok D-10 Rev 3.0
Cement Evaluation: Reducing uncertainty
Cement evaluation measurements
Presence of the cement – CBL – amplitude / attenuation
– VDL – formation arrivals
– Acoustic Impedance
– Flexural attenuation
– Third Interface Echo
Cement azimuthal placement – Acoustic impedance
– Flexural attenuation
– Third Interface Echo
Isolation Scanner
Sonic (CBL-VDL)
Ultrasonic
3ft receiver - Amplitude 5ft receiver - Waveform (VDL)
Good
Bond
No
Cement
Cement Bond Log (CBL) & Variable Density Log (VDL)
Free Pipe
Well cemented Pipe
?
Sonic Tools (CBL/VDL) – Too simplistic and subjective
Strengths
– Work well in most well fluids, tolerate corrosion
– Qualitative cement-formation bond from VDL
Limitations
– Omni directional measurement
– High CBL amplitude can be ambiguous
– Microannulus & Channels
– Contaminated or Light cement
– Sensitive to fast formation
Traditional Ultrasonic Technology (USI)
Single Tx-Rx configuration rotating at 7.5 rps
72 azimuthal measurements
1.2 in (30mm) resolution
Excitation of thickness mode of the casing
Inversion for the acoustic impedance
Measurements:
– Cement evaluation (Acoustic Impedance)
– Casing corrosion and wear
Echo amplitude
Internal casing
condition
Transit time
Internal radius
Resonance
Thickness
Resonance
Cement acoustic
impedance
Cement Casing Mud
Transducer
Formation
1st Interface 2nd Interface 3rd Interface
USI azimuthal cement evaluation
USIT Strengths
– High azimuthal & vertical resolution
– Quantitative measurement
– Less sensitive to microannulus
– Pipe diameter & thickness measurement
Benefits
– Azimuthal cement map
– Channel identification
– Pipe inspection with cement evaluation
Value to Operators
– Reduced uncertainty on cement placement
– Efficiency – Cement and Pipe Evaluation
Gas Cement Liquid Acoustic
impedance
8
6
4
2
0
Light
Contaminated
cement
Incr
easi
ng
con
tam
inat
ion
Neat USI
GAS SOLID 0.3 Mrayls
(Default)
2.6 Mrayls
(Class-G)
8 Mrayls
(Class-G)
Traditional ultrasonic challenges
– Low mud-cement contrast
– Subjective light/contaminated
cements
– Cement evaluation limited to
pipes with thickness <0.6”
– High attenuation logging fluids
Enhanced Ultrasonic technology (Isolation Scanner)
Service built on USI Ultrasonic hardware
Combines USI measurement with 2nd flexural
attenuation measurement:
– Used with USI cement acoustic impedance to
characterize SLG (Solid-Liquid-Gas) model
Improved evaluation of Light Weight and
contaminated cements
Circumferential imaging, up to formation or
second casing
Fle
xura
l
Aco
ustic
Impe
danc
e
Far
Near
Tx
USI
Isolation Scanner - Material identification in annulus
Independent measurements to define annulus material in 1 of 3 SLG (Solid-Liquid-
Gas) states, limiting reliance on thresholds
SLG = Acoustic Impedance + Flexural Attenuation
Isolation Scanner increases cement evaluation confidence Isolation Scanner strengths
– Retains USIT answers
– Adds flexural attenuation measurement
– Improved sensitivity to light and contaminated cements
– Extends cement evaluation to pipe thickness up to 0.8”
Benefits
– Quantitative & azimuthal cement map (S-L-G)
– Annulus velocity, pipe centralization
– Identify presence of channels and impact to zonal isolation
– Pipe inspection with cement evaluation
Value to operators
– Reduced uncertainty on cement placement and zonal isolation decisions
IPTC 10546
Cement Casing Mud
Transducer
Formation
Isolation Scanner - Third Interface Echo (TIE)
1st Echo
3rd Echo
Estimated wave velocity - confirm the SLG map
and better understand cement placement
Physical measurement of casing standoff in %
Cement sheath pseudo-thickness
3D annular geometry imaging - improved zonal
isolation determination
Support for improved completion, kickoff, CSG
retrieval and remedial strategy
Requires the ability to
– Confirm vertical continuity of cement for zonal isolation
– Confirm adequate pipe centralization
– Confirm azimuthal cement and absence of channels
– Resolve ambiguity through multiple measurements Acoustic impedance, Flexural attenuation
3rd interface echo (TIE) annulus velocity and thickness
(SPE-120061)
Casing standoff
measurement
indicates a
value of 60-80%
SLG map discriminates
more solids compared
to USIT image
Annulus cross-section shows a
marginally thinner cement on one
side, but still confirms the presence
of a solid cement sheath
Reducing uncertainty in hydraulic isolation – Isolation Scanner
Thank You