March 17-18, 2008 4th Wellbore Integrity Meeting

CCP2 Well Integrity SurveyAnalysis Program and Way ForwardAnalysis Program and Way Forward

Walter CrowBP Alternative Energy (CCP2 Representative)

Bill CareyLos Alamos National Laboratory

CO2 Capture Project 2LA-UR-07-8437

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CCP2 Wellbore Integrity Field StudyCO Capture Project 2

Objectives

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mat

ion

CCP2 Wellbore Integrity Field Study

• Establish the extent of alteration in CO2 experienced wells• Model the impact of documented alteration on long-term performance of the

well barrier system.• Develop appropriate engineering solutions to improve well integrity 35

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Com

mun

ica

Methodology• Sample and analyze well materials• History match well materials alteration to well life a

larg

er $

3/ P

olic

y / C

y• Forward simulate long-term well alteration in CO2 charged environments

Deliverables• 2 to 3 well studies with analyses of obtained fluid and solid samples p

art o

f a/ S

tora

ge /

2 to 3 well studies with analyses of obtained fluid and solid samples• Past and forward alteration scenarios• Outline of engineering solutions

This

is 1

Cap

ture

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Well Selection Criteria for Integrity Survey

• Clastic reservoir• At least 10 years CO2 exposure• Casing integrity largely intact• 7” casing required for survey tool deployment• Geologic production and well construction data • Geologic, production and well construction data

to complete analysis

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CO2 Production Well Timeline

30 ear ell lifeFresh Water

No history of annulus pressure30 year well life

TOC: 3050’

CIPB: 4640 with TOC at 4570 (set after survey)

1976 1984 1986 1997 2006/2007Actual Well HistoryActual Well History

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Well Integrity Survey

• Mechanical integrity – caliper surveySurvey Components Analytical Purpose

Mechanical integrity caliper survey

• Cement conditioncement bond log

lt i / t l

Barrier assessment

ultrasonic/scanner tools

• Pulse test of cement sheath (in-situ perm)

• Gas saturation / spectroscopy - behind casing

• Fluid/gas samples and pressure survey

Signs and effectof CO2 migration

Fluid/gas samples and pressure survey

• Sidewall cores through casing

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Stratigraphy and Location of Core Samples

10 sidewall cores taken in Survey #2

6 sidewall cores taken in Survey #1y

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CO2 and the Wellbore BarrierShaleCasing

Grout-CasingInterface

Hydrated Cement

Grout-ShaleInterface

Migration Pathways and MechanismsAlong Cement Barrier

P diff ti l b t

Fractured CementFlow

• Pressure differential between zones• Matrix flow limited by capillary

propertiesCementMatrix Flow

• CO2 diffusion along cement sheath

Potential Effects of Carbonation Interface Flow Interface FlowPotential Effects of Carbonation• Beneficial:

Decrease in porosity, decrease in permeability, and increase in strength• Harmful:

Interface Flow Interface Flow

Reduction of pH of pore fluid leading to corrosion of casingCarbonation-induced shrinkage leading to cracksReduction of casing/cement and/or cement/caprock interface integrityL f t t l i t it t lti t b ti t tLoss of structural integrity at ultimate carbonation state Important factors controlling rates of carbonation

Water/cement ratio, age of cement, capillary properties

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Study Design

• Assess wellbore conditionC t l ti l ( i / lt i ) li• Cement evaluation logs (sonic / ultrasonic), caliper

• Effective permeability of wellbore outside of the casing• Look for evidence of CO2 migrationLook for evidence of CO2 migration

• Cement mineralogy• Fluid sample chemistry

• Determine any consequences of CO2 migration• Corrosion in casing• Hydrologic and mechanical properties of cement• Hydrologic and mechanical properties of cement

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Analytical ApproachExterior face

To caprockTo casing

• X-ray diffraction, optical microscopy, and scanning electron microscopy of cement to assess presence of carbonatesmicroscopy of cement to assess presence of carbonates

• X-ray tomography • Mechanical properties (moduli, acoustic velocity)Mechanical properties (moduli, acoustic velocity)• Permeability, porosity, capillary pressure, and formation factor• Compare with fresh cement laboratory samples p y p• Compare with cement sheath pulse test

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Sample Recovery

• Cement recovery uneven with complete casing-cement-rock samples rareS f• Samples generally separate from casing when recovered

• Interfaces (at separation) can be re-assembled, suggesting tight bondsgg g g

• Recovered cement is physically intact and spans the casing-rock annulus

Core from Bottom of caprock Core from Top of caprockCore from Bottom of caprock Core from Top of caprock

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Preliminary Observations

• Casing (and tubulars) in excellent conditionCasing (and tubulars) in excellent condition• Cement and interface condition indicate annular space intact and

capable of limiting fluid movement• Cement shows evidence of reaction with CO2 to form calcium carbonate• The extent of carbonation appears to decrease up the wellbore but has

not yet been fully quantifiednot yet been fully quantified• Cement permeability decreases by 1-2 orders of magnitude from the

bottom of the caprock to the top of the caprockp p p

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CCP2 Well Integrity Study

Key Messages• Core samples have varying degrees of alteration but are intact• Existing logging technology is capable of assessing well integrity

Way Forward• Complete the sample / data analysis and report the results• Complete the sample / data analysis and report the results• Create model to history match well conditions• Forward-project barrier life and conditionForward project barrier life and condition• Engineer solutions that are fit-for-purpose to maintain barrier integrity

Acknowledgements:

CO2 Capture Project Member Companies & Associates