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