geoelectrical insitu test

7/24/2019 Geoelectrical Insitu Test

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CO2 Storage:

4D Geophysical Monitoring

Geoelectrical Measurements

Conny Schmidt-Hattenberger


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OUTLINE:

Brief description of the method & practicalworkflow.

How it works for monitoring of CO2 storage ?

Practical example: Geoelectrical measurementsat the Ketzin test site.


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Resistivity method and its application

The method is based on the

resistivity contrasts of subsurface

materials.

R of the material depends on:

Horizontal and vertical discontinuities can be studied in a variety offields:

Hydrogeology and underground water prospection

Engineering & construction site investigation

Waste and pollutant investigations Glaciology, permafrost

Archaeological investigations

Underground storage operations CO2 storage

GeoEn Summer School, Potsdam, 24-28 September 2012


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Background theory of DC resistivity

method (I) employs very low-frequency alternating currents as source signals

magnetic properties can usually be ignored

displacement currents and induction effects are negligible Maxwells equation reduce to

Poisson equation for electrostatic fields

Ohms law

Potential due to single point source forthe homogeneous half-space

E-field



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Background theory of DC resistivity

method (II)

r1r4 distances between A, B, M and N

K geometric factor

Four-electrode measurement:

apparent resistivity

Schematic illustration of a four-electrode arrangement afterKndel et al., (1997). Current flow lines (solid) andequipotential lines (dashed) are given for a two-layer casewith higher resistivity in the first layer.



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Rock texture has influence on resistivity

(Ward, 1990)

Basalt is a typicalexample of a highporosity rock withlow conductivity dueto its lowpermeability(unconnected or

dead-end porespace).



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Resistivity of different materials in nature

(Ward, 1990)

destilled water > 104 m

sea water ~ 0.25 m

brine


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SurveysDesign:

Depth of investigation characteristic:

Experimental techniques :

electric profiling or areal mapping

vertical electric sounding (VES)

2D and 3D imaging

(after Szalai et al., 2009)



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Geoelectric modeling

Forward modeling

Inversion

CurrentVoltage

MODEL DATA

(modified after Marescot, 2010)



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Sensitivity analysis

The sensitivity matrixSijindicates how changes in themodel domain elementmj do change the data domainelementfi .

Examples of 2D sensitivity distributions of a homogenoushalf-space for various arrays (modified after Friedel, 2000):

Asymmetric Schlumberger Wenner

Measurement i Cell j



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Which steps form our workflow?

&

&

&

&

&

.

&

()

()



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How to apply ERT for CO2 storage

monitoring?

at intermediate and high gassaturation (above 20 %) geoelectricalmethods are more sensitive thanseismic methods

geoelectrical measurements arerelatively easy to deploy

higher repetition rates and cost-efficiency,

but: lower structural resolution

P-wave velocity and resistivity

versus CO2 saturation- measured at Nagaoka test site (Japan)by X. Zue et al., SPE 126885, Nov. 2009.

Our motivation:



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Available reservoir data support feasibilitystudy

Reservoir properties:The aquifer resistivity is calculated using Archies law (Archie, 1942)and assuming:

-Salinity of formation water ~ 230 g/l-Reservoir temperature of about 36 C (from T-logs)-Resistivity of 20 wt-% brine @ 36C = 0.05 m-Mean porosity of 23 %

= A w -m Sw

-n

(SCO2 = 1-Sw)

- Archie parametersA = 1.0 and m, n = 2.0 assumed in a first rough model.

- Typical CO2 saturation scenario of 50% ( 2.8 m).

}Ketzin data



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Lab data

before CO2

Lab data

after CO2

difference

Ktzi202_B2-3b

[m] 0.52 1.75 +240%

Ktzi202_B3-1b

[m] 0.47 1.40 +200%

Available lab data indicate a bulk

CO2 saturation of 50% which

corresponds to a resistivity increase

of +200% to +240% (~ factor 3).

Results from laboratory

flow-through experiments:

(Kummerow et al., 2011)

CO2formation fluid

formation fluid ~ 0.52 m formation fluid

t [h]

CO2 ~ 1.7 m

Laboratory experiments



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The Ketzin project Europes longest-operating

on-shore CO2 storage site Located in the North East German Basin

~ 25 km west of Berlin, at the SE flank

of a double anticline

Storage reservoir: saline aquifer of the

Stuttgart Fm.

Project start 2004, well completion 2007,

start of injection 2008



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An interdisciplinary monitoringconcept is applied @ Ketzin site

Start of CO2 injection:

30.06.2008

CO2 sources and quality:Primary source: food-gradeCO2 (Linde), purity > 99.9 %

Secondary source (limitedtime): Schwarze Pumpe pilotplant (Vattenfall),purity > 99.7 %

Injection rates:

24 to 77 t/day(currently ~ 1 kt CO2/month)

03.06.2012: 61,402 t CO2injected



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Electrical Resistivity Tomography (ERT) systems

in CCS projects Nagaoka

(logging tool /non-permanent )

Regular induction logs

as alternative solution

Cranfield(permanent array)

Deepest ERT array in

CCS operationworld-wide

Ketzin(permanent array)

First ERT array in

CCS operationworld-wide

., 2010 ., 2010 ., 200



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The Ketzin ERT concept: combination ofcrosshole & surface-downhole measurements

Permanent installation of Vertical Electrical ResistivityArray (VERA) in the three Ketzin wells (at insulatedcasing)

Concentric circles with 16 surface dipoles & crossedprofiles for enlargement of observation area, dipolelength: 150 m, r1 = 800 m, r2 = 1500 m )

In cooperation with:



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Design details of the Ketzin permanent ERT array

(1) Stainless steel ring-shaped electrodeswith multi-conductor cables (15 wires)

(2) Centralizer & Protector Tool(3) Casing: 5.5steel casing, coated with

insulating layer along the ERT array area

(1) (2)

(3)



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(Photos: Courtesy of University Leipzig)

(Photos: Courtesy of GFZ)

current: 2.5 A max. channels: 15

(for potential registration) measured voltage: 50 V to 100 mV

signal period: 8 s

current: 4 10 Avoltage: 500 1300 V

signal period: 16 sLength of time series ~ 1 h

Insulated casing

Stainless-steelelectrode

MeasurementUnit (ZONGE)

Electric power sourceTSQ-4 (SCINTREX)

Electrode ensemblefor current injection

Data logger (TEXAN-125)

Site-specific Customization ofSurface and Downhole

Equipment.



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Field installation: Casing assembly

Photos: Silvio Mielitz



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Field installation: Casing assembly




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Field installation: Cable management




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Field installation: Sensor mounting


electrode

centralizer

cable



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Data QC and PreProcessing of the field data

Due to time constraints bythe acquired manifold ofelectrode configurations andto obtain transient effects

Only two signal cycles havebeen recorded

(each cycle T= 8s).

No regular reciprocialmeasurements, but forindividual data sets only.

Individual error estimation

from the cycles, and RMSestimation from the adaptedpreprocessing scheme.

QC

PP

EE

Day of injection

ABMN: 3-2-18-17



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Inversion Strategy

Test of various program codes :EarthImager, ERTLab, BERT

Deployment of constraints,e.g. resistivity logs andlaboratory results

Predefinition of most essentialparameters:-regularization ,z- geometrical weight,E- error weight

Separate investigation of 2D inversion results for two observation planes.

0.5 - 5 m low-res. environment small resistivity contrasts moderate resistivity changes thin target reservoir zone

(Gnther & Rcker, 2006)



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2D Time-lapse results Gravity driven upward

migration (funnel-likeshape) was observedsince middle of August2008.

steady-state situation

reached in December2008.

Attenuated resistivityprofiles in the

observation planeKtzi200-Ktzi201for phases of significantreduced injection rate(March August 2010).

Good coverage of theinjection start phase byfrequently measureddata sets given.

Ktzi201 Ktzi200 Ktzi201 Ktzi200 Ktzi201 Ktzi200 Ktzi201 Ktzi200

August 18, 2008 December 03, 2008 March 15, 2010 April 02, 2011

Ratio

(monitor/baseda

ta)

Inversion(

monitordata)

(Schmidt-Hattenberger et al., 2012)



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3D Time-lapse results

Consistent results of the 2D inversion and the full 3D inversion for the individualobservation planes Ktzi200-Ktzi201 and Ktzi200-Ktzi202.

Significant volume effectnecessary in order to detect the CO2 arrival at both

observation wells (Ktzi200 / Ktzi202) in the inverted data.Assumption: limited 3D effect since Nov 2009 (degradation detected by contact

resistance checks) critical electrodes: some of them have to be excluded frominterpretation, and some of them even from the inversion procedure.

3D ViewZ-slice @ 630 m

Ktzi201 Ktzi200

z=620 m

201 200

202

z=635 m

201 200

202 z=640 m

201 200

202

201200

202

Data set from July 2010


C h ki f t d i d li


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Cross-checking of measurements and inverse modelingensures data reliability

Zonge Engineering equipment

Multi-Phase Technologies equipment

Data inversion byopen-source codeBERTwith unstructured

tetrahedral grids.www.resistivity.net

Data inversion byERTLabwhich providedvery fast on-siteresults.www.ertlab.com

Survey: April 2011



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Surface-downhole results

Operating range: extended wellbore area

(Bergmann et al., 2012)



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()

CO2 signature has been detectedwith sufficient spatial resolution.

Data sets are consolidated now,

updated petrophysical results areavailable.

Evaluation & Outlook

Contribution to data integration.(in progress)(Lth et al., 2011)

, , 242 2012


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Electrical and electromagnetical monitoring

on various scalesRegional scale

Magnetotellurics (MT) &

Controlled-SourceElectromagnetics (CSEM)

see presentation by K.M.Bhatt

Sub-regional scale

Electromagnetics (EM)

Local scaleElectrical ResistivityTomography (ERT)



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References:

Archie, G.E. (1942). The electric resistivity log as an aid in determining some reservoir characteristics. Trans. Am. Inst. Miner.

Met. 146,5462.Bergmann, P. et al. (2012). Surface-downhole electrical resistivity tomography applied to monitoring of CO2 storage atKetzin, Germany. Geophysics 77 (2012), B253-B267.Carrigan, C. R. et al. (2009). Application of ERT for tracking CO2 plume growth and movement at the SECARB Cranfield site.8th Annual Conference on Carbon Capture & Sequestration, Pittsburgh, PA, United States, 4-7 May, 2009.Friedel, S. (2000). ber die Abbildungseigenschaften der geoelektrischen Impedanztomographie unter Bercksichtigung vonendlicher Anzahl und endlicher Genauigkeit der Medaten. Ph.D. thesis, Fakultt fr Physik und Geowissenschaften, UniversittLeipzig, Germany.Gnther et al. (2006). Three-dimensional modelling and inversion of dc resistivity data incorporating topographyII.Inversion. GJI 166, 506517.Kiessling, D. et al. (2010). Geoelectrical methods for monitoring geological CO2 storage, First results from crosshole andsurface-downhole measurements from the CO2SINK test site at Ketzin (Germany). International Journal of Greenhouse GasControl 4 (2010), 816-826.Kndel, K., Krummel, H., Lange, G. (1997). Handbuch zur Erkundung des Untergrundes von Deponien und Altlasten, Band 3- Geophysik. Bundesanstalt fr Geowissenschaften und Rohstoffe, Springer Verlag, 1063 S.Kummerow and Spangenberg (2011). Experimental evaluation of the impact of the interactions of CO2-SO2, brine, andreservoir rock on petrophysical properties: A case study from the Ketzin test site, Germany: Geochemistry Geophysics

Geosystems, 12, 5, Q05010.Lth et al. (2011). Time-lapse seismic surface and down-hole measurements for monitoring CO2 storage in the CO2SINKproject (Ketzin, Germany). Energy Procedia, Volume 4, 3435-3442.Marescot, L. (2010). http://tomoquest.com/attachments/File/Marescot_Intro_to_Inversion_UNIFR_19042010.pdf, Script onIntroduction to Inversion in Geophysics.Xue, Z. et al. (2009). Detecting and monitoring CO2 with P-wave velocity and resistivity from both laboratory-and field scales.In:SPE126885,SPE International Conference on CO2 Capture, Storage, and Utilization, SanDiego, CA, USA, November24.Schmidt-Hattenberger, C. et al. (2012). A modular geoelectrical monitoring system as part of the surveillance concept inCO2 storage projects. Energy Procedia 23 (2012), 400-407.

Szalai, S. et al. (2009). Depth of Investigation and Vertical Resolution of Surface Geoelectric Arrays, Journal of Environmental& Engineering Geophysics, 14, 15-23.Ward, S. H. (1990). Geotechnical and Environmental Geophysics, Chapter Resistivity and Induced Polarization Methods,pages 147189. Investigations in Geophysics No. 5. Soc. Expl. Geophys.


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