Dielectric Scanner

Multifrequency dielectric dispersion service

Measurements that speak volumes

The conventional approach to determining oil volume requires weeks or months for laboratory core analysis or accepting the uncertainty inherent in estimated Archie parameters. With Dielectric Scanner* measurements direct from your reservoir, the wait for accurate formation evaluation answers is over.

APPLICATIONS

Direct measurement of water volume independent of water resistivity (Rw) at a depth of investigation to 4 in [10 cm], solving for

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• Residual hydrocarbon volume in produced reservoirs • Hydrocarbon volume in low-resistivity or low-contrast shaly and laminated sand formations • Hydrocarbon volume and mobility in heavy oil reservoirs • Water salinity Continuous Archie mn exponent log from rock texture measurements in carbonates for determining saturations beyond the invaded zone

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Cation exchange capacity (CEC) to account for effect of clay volume in siliciclastics

RA4 RA3 RA2 RA1 PA

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High-resolution water-filled porosity for thin-bed analysis

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TA TB PB RB1 RB2 RB3 RB4

Dielectric Scanner pad antenna configuration. The blue dipoles define the longitudinal polarization and the red ones are the transverse polarization. The two coaxial electrical probes (PA and PB) are used for quality control of pad application and for determining the mud and mudcake dielectric properties at the frequencies of interest.

Dielectric Scanner service is the first in the industry to employ multifrequency dielectric dispersion science to accurately quantify residual hydrocarbon volume, the Archie mn exponent, and formation CEC. Parameters available previously only through core analysis or estimation are now delivered as continuous logs at the wellsite. The dielectric dispersion measurement constructs an accurate radial profile of the close-borehole region, providing new and unique information on rock properties and fluid distribution for advanced petrophysical interpretation. Used in conjunction with traditional logging measurements, Dielectric Scanner dielectric dispersion measurement enables developing a more accurate reservoir description for reservoir evaluation and management. Multispacing Operation

The heart of Dielectric Scanner service lies in its short, multispacing antenna array pad. Each of the cross-dipole antennas has collocated magnetic dipoles. The transmitters (TA and TB) are in the center and the receivers (RA1–4 and RB1–4) are placed symmetrically around them for optimal measurement accuracy and borehole compensation. To minimize environmental effects, the short, fully articulated antenna pad is applied firmly against the borehole wall by a hydraulically operated eccentering caliper to enable optimal pad contact, even in rugose boreholes. Electromagnetic waves are propagated into the formation at four frequencies and two polarizations for high-resolution, high-accuracy measurements of reservoir properties at up to 4 in from the borehole wall.

Dielectric dispersion science One of the revolutionary advances provided by the Dielectric Scanner tool is the continuous measurement of dielectric dispersion, which is the variation of formation dielectric properties as a function of the frequency. High-resolution measurements obtained with the different array spacings, each with two polarizations at four frequencies, are radially interpreted to obtain permittivity and conductivity at each frequency. Conventional dielectric tools make only a single-frequency measurement with limited applications, and its interpretation cannot account for textural effects, invasion, and unknown or variable water salinities. The Dielectric Scanner permittivity and conductivity measurements at each frequency are interpreted using a petrophysical model. The output parameters of the model are waterfilled porosity (hence water saturation if the total porosity is known), water salinity, and

Salinity Dielectric Scanner Salinity 0 ppt 100

Porosity Porosity Resistivity Resistivity 2-ft Array Induction 2-ft Array Induction Hydrocarbon Hydrocarbon Resistivity A90 Resistivity A90 0.2 ohm.m 2,000 ohm.m 2,000 Total Porosity Total Porosity 0 ppt 100 Invaded Zone Resistivity Invaded Zone Resistivity 3 3 fty.y /ft3 /ft x.x ft3x.x ohm.m 0.2 2,000 0.2 ohm.m 2,000 Dielectric Scanner Dielectric Scanner Dielectric Scanner Dielectric Scanner Water-Filled Porosity Water-Filled Porosity Invaded Zone Resistivity Invaded Zone Resistivity 3 3 3 3 /ft fty.y /ft 0.2 2,000ft x.x ohm.mx.x 0.2 ohm.m 2,000

textural effects in carbonates or CEC in shaly sands. Simultaneously fitting the permittivity and conductivity dispersions frees the waterfilled porosity from salinity effects. Rather, water salinity is an additional output of the analysis. For a well drilled with oil-base mud (OBM), the calculated water salinity is the formation water salinity. In carbonate reservoirs, the dielectric dispersion is driven mainly by the rock texture. In turn, Dielectric Scanner analysis provides a continuous in situ measurement of rock texture, presented as an mn exponent log. In shaly sand reservoirs, processing provides a continuous log of the CEC. In heavy oil reservoirs or in shallow-invasion situations, Dielectric Scanner measurements are made in both the invaded and non-invaded zones, to determine moveable hydrocarbon content.

Salinity

Salinity

Dielectric Scanner 0.2 Salinity

Dielectric Scanner Salinity y.y

y.y

0 ppt 100

Dispersion plots of the measured permittivity and conductivity at four frequencies and the fit to the petrophysical model with the estimated parameters.

Porosity Porosity Resistivity Resistivity 2-ft Array Induction 2-ft Array Induction Hydrocarbon Hydrocarbon Resistivity A90 Resistivity A90 ohm.m 2,000 0.2 ohm.m 2,000 Total Porosity Total Porosity 0 ppt 100 Invaded Zone Resistivity Invaded Zone Resistivity 3 3 x.x ft3x.x /ft3 fty.y /ft ohm.m 0.2 2,000 0.2 ohm.m 2,000 Dielectric Scanner Dielectric Scanner Dielectric Scanner Dielectric Scanner Water-Filled Porosity Water-Filled Porosity Invaded Zone Resistivity Invaded Zone Resistivity 3 3 3 3 /ft /ft fty.y 0.2 2,000 ohm.m 0.2 ohm.mx.x 2,000ft x.x Salinity

Dielectric Scanner 0.2 Salinity

X,000

X,000

X,000

X,000

X,050

X,050

X,050

X,050

X,100

X,100

X,100

X,100

X,150

X,150

X,150

X,150

X,200

X,200

X,200

X,200

X,250

X,250

X,250

X,250

X,300

X,300

X,300

X,300

X,350

X,350

X,350

X,350

X,400

X,400

X,400

X,400

X,450

X,450

X,450

X,450

X,500

X,500

X,500

X,500

X,550

X,550

X,550

X,550

X,600

X,600

X,600

X,600

y.y

y.y

Previous-generation singlefrequency electromagnetic propagation tools, emulated in the log on the left by single-frequency processing, cannot account for textural variation, resulting in the overestimation of invaded zone resistivity Rxo (Track 2). In the log on the right, Dielectric Scanner multifrequency mixing analysis correctly matches the water-filled porosity to the total porosity in this waterfilled sand in Track 3, as confirmed by the matching Rxo values of the Dielectric Scanner and resistivity tools in Track 2.

Case studies Dielectric Scanner measurements confirm 95% residual hydrocarbon saturation An operator in the Middle East wanted to improve understanding of the fluid saturations in a high-porosity carbonate reservoir where variability in the Archie m and n exponents increased the uncertainty in conventional log interpretation. The measurements were also ambiguous because the mud filtrate salinity was approximately 180,000-ppm [-ug/g] NaCl. The carbonate textural information provided by Dielectric Scanner service enabled accurate mn determination instead of relying on potentially incorrect estimations from conventional log analysis or waiting for laboratory core analysis. Having accurate values of the Archie exponents is important because they are the basis for calculating saturation values from resistivity. As shown by the porosity curves in Track 5, the significant difference between Dielectric Scanner water-filled porosity (blue curve) and the total porosity calculated from standard porosity measurements indicates a large volume of residual hydrocarbon in the formation. In Track 2 the Dielectric Scanner hydrocarbon saturation accounts for variation in the Archie exponents across the reservoir and confirms up to 95% residual hydrocarbon. Conventional saturation determination using constant values of the Archie mn exponents does not account for their variation, as shown by the difference shaded red where the conventional and Dielectric Scanner residual oil saturations do not match. Confirmation of the high residual saturation is in Track 4, where the Rxo measurements from Dielectric Scanner and conventional resistivity logging closely match each other.

It Speaks Volumes about Carbonates

Accurate hydrocarbon volume in carbonates from salinity-insensitive determination of water-filled porosity and rock texture factors

Caliper 6

in Epsilon Matrix from Lithology

0

10 Archie mn

1

Illite (dry)

Oil

Calcite

Difference

Dolomite

Archie 0

3.5

ft3/ft3

ft3/ft3

0.2 0.2 0.2

Bound Water

m3/m3

Dispersion Image Permittivity Conductivity

ohm.m

2,000

ohm.m

ELAN* Total Porosity 0.5

2,000

ohm.m

2,000

HRLA* True Resistivity 0.2

Porosity 1

Porosity Hydrocarbon

ohm.m

m3/m3

0

Dielectric Scanner Water-Filled Porosity

Dielectric Scanner Invaded Zone Resistivity 0.5

Oil

1

Resistivity Array Laterolog Resistivity Invaded Zone Resistivity

Water 1

Dielectric Scanner 0

Depth, m

Lithology

Residual Oil Saturation

16

m3/m3

0

Freq. 3 – Freq. 2

Freq. 0 – Freq. 1

Freq. 2 – Freq. 1

Freq. 1 – Freq. 2

Freq. 0 – Freq. 1

Freq. 2 – Freq. 3

2,000

0

X10

X20

X30

X40

X50

Confirmation of 95% residual hydrocarbon by Rxo match. The Rxo curve from Dielectric Scanner service in the carbonate reservoir agrees closely with the conventional Rxo measurement in Track 4, supporting the determination of 95% residual hydrocarbon saturation.

8

Caliper in

18

SP –100

mV Epsilon Matrix from Lithology

0

0

Residual Oil Moved Oil

Dielectric Scanner 10 Deep Water Saturation 0 ft3/ft3 1 Dielectric Scanner Shallow Water Saturation 0 ft3/ft3 1

Clay Resistivity Volume Standoff 0 .2 0 ft3/ft3 2 1 in 0 Density Standoff 1 in 0 0 .2

8-in Invaded Zone Resistivity ohm.m

Dielectric Scanner Deep Resistivity 0 .2

ohm.m

0 .2

ohm.m

0.015

T1 Cutoff

Water

0.5

0 .5

Dielectric Scanner Shallow Water-Filled Porosity ft3/ft3

0

0 .5

Dielectric Scanner Deep Water-Filled Porosity ft3/ft3

0

2,000

HRLA* True Resistivity

ft3/ft3

Moved Oil

2,000

Dielectric Invaded Zone Resistivity Scanner 0 .2 2,000 ohm.m Mudcake Thickness Dielectric Scanner Shallow Resistivity 1 in 0 0 .2 2,000 ohm.m Depth, ft

0

Array Laterolog Resistivity ohm.m

T2 Distribution

Residual Oil

2,000

2,000

ms

5,000

Total Porosity 0 .5

ft3/ft3

0

X,450

Sample at X,574 ft: Oil X,500

X,550

X,600

X,650

Sample at X,701 ft: Oil and water X,700

X,750

X,800

X,850

Moveable heavy oil confirmed by sidewall cores. Although the resistivity in Track 5 and NMR in Track 7 cannot readily distinguish between oil and formation freshwater below the oil-bearing interval from X,430 to X,500 ft, Dielectric Scanner measurements of fluid volumes (Track 6) and the resulting saturations (Track 2) clearly reveal significant moveable heavy oil down to X,720 ft, as confirmed by sidewall core analysis.

Thin Beds

Additional 150 ft of pay revealed by Dielectric Scanner dispersion measurements The production potential of a laminated reservoir in the Orinoco belt of Venezuela could not be fully determined with conventional logs. Thinly bedded shale and sand layers decreased resistivity measurements, masking pay zones and resulting in pessimistic interpretations of hydrocarbon volume. In this heavy oil reservoir, NMR logs measured a reduced apparent formation porosity, which in turn adversely affected fluid saturation determinations. An additional complication was the highly rugose borehole, as shown by the caliper in Track 1, but the pad of the Dielectric Scanner tool maintained good contact with the formation, and the measurements were not compromised. The high resistivity in Track 5 in the oil-bearing interval from approximately X,430 to X,500 ft had been observed in other wells in the area. However, resistivity values below this interval are uniformly low. Similarly, the NMR log in Track 7 has a strong oil signature in the upper interval, but the apparent porosity is reduced with increasing depth. The Dielectric Scanner log dispelled uncertainty about the reservoir quality of the lower interval, revealing moveable oil over a 150-ft section, from X,560 to X,650 ft and again from X,690 to X,720 ft. Sidewall samples confirmed the Dielectric Scanner measurements.

It Speaks Volumes about Thin Beds

High-resolution water-filled porosity and radial profiling delivered by multifrequency measurements without the errors introduced through the estimation of Archie formation factors

Weight percent bitumen quickly, accurately determined in Canadian oil sands Because the formation water salinity and resistivity vary in heavy oil reservoirs with thin-bedded shaly sections, Canadian operators had to wait several months for the results of Dean Stark core analysis. Without the analysis results to adjust conventional saturation calculations, using a constant Rw value led to errors in the water saturation determined for uncored intervals. With water-filled porosity calculated from Dielectric Scanner dispersion measurements, the weight percent of bitumen is accurately determined months in advance of laboratory core analysis turnaround. The operators can confidently consider a reduction in coring frequency and number of analysis points in their multiwell projects.

Washout 125

Caliper mm

90-in AIT Resistivity Depth, m 0.2 ohm.m 2,000 0.5

375

High-Resolution Gamma Ray 0

gAPI

0.5

150

0.5 0.5

Gas

Hydrocarbon

Total Porosity m3/m3 Neutron Porosity (Sand) m3/m3 Density Porosity (Sand) m3/m3 Dielectric Scanner Water-Filled Porosity (Sand) m3/m3

Dielectric Scanner Water Saturation m3/m3

0 0 0 0

T2 Distribution

Wt% Oil Archie 0

0.2

0

Core Wt% Oil 0 1 0 0.2 0.3 % Archie Water Saturation Wt% Oil Dielectric Scanner 3 3 0 0.2 m /m 0 1

m3/m3

0.3

T2 Cutoff ms

3000

ms

NMR Wt% Oil

Hydrocarbon

1 Core Wt% Oil NMR Water Saturation 0 0.2 % m3/m3 0 1 Dielectric Scanner Wt% Oil 0 0.2 Dielectric Scanner Water Saturation 0

m3/m3

0

1

X75

Y00

Y25

Accurate answers quickly. Water saturation and hydrocarbon volume calculated from Dielectric Scanner dispersion measurements provide higher resolution, more accurate answers than those derived from the Archie equation or nuclear magnetic resonance (NMR) data.

Core Photograph Dielectric Scanner Water Saturation 1

m3/m3

Depth, m

Facies

1:20

0

Fine Sand

X74

Muddy IHS

X75

IHS

Fine Sand

Depth, m

Washout 125

0

Caliper mm

375

High-Resolution Gamma Ray 150 gAPI

0.2

Neutron Porosity m3/m3 Density Porosity (Sand) m3/m3 0.5 Total Porosity v/v 0.5 Dielectric Scanner Water-Filled Porosity (Sand) m3/m3 0.5

90-in AIT Resistivity ohm.m 2,000 0.5

0 0 0

0 0

High-Resolution Wt% Oil Dielectric Scanner Core Wt% Oil %

0.2 0.2

HighCore HighHighResolution Resolution Photograph Resolution Static FMI* Water Water Image Saturation Saturation Dielectric Image Scanner 0

X76

m3/m3 1

0

X77

Sandy IHS

X75

X78

X79

Y00 X80

IHS

X81

Y25

X82

High vertical resolution. The high-resolution weight percent bitumen calculated from Dielectric Scanner measurements shows excellent agreement to the subsequent core analysis results in Track 4, even in the thin shale intervals identified in the core photograph by the lighter colors within the black bitumenrich core. IHS = inclined heterolithic stratification.

It Speaks Volumes about Heavy Oil

Heavy oil saturation and mobility from high-resolution measurements insensitive to oil viscosity and formation water resistivity

Medium Sand

Overlooked pay found in washed-out zones in heavy oil reservoir Washed-out borehole intervals in a heavy oil reservoir in Cymric field, California, USA, were adversely affecting logging. Washouts caused separation in the resistivity curves that could be confused with invasion, as shown at 700 and 745 ft in Track 2. Water-filled porosity measurements made with a conventional, mandrel-type, single-frequency electromagnetic propagation tool were suspect because the tool would not have been able to maintain good contact in these rugose conditions. Porosity and saturation calculated from Dielectric Scanner measurements in Tracks 5 and 3, respectively, correct the previous washout-impaired porosity, as confirmed by sidewall core analysis (black dots). With accurate porosity values, the pessimistically high water saturation value was corrected by 23%. Caliper 8.5

2-ft Array Induction Resistivity A90 Residual Hydrocarbon ohm.m 5,000 Invaded Zone Core Water Saturation Resistivity ft3/ft3 1 0.5 ohm.m 5,000 0 Dielectric Scanner Dielectric Scanner Invaded Zone Resistivity Water Saturation

Clay

in 18.5 0.5

Resistivity Standoff Density Standoff Resistivity Standoff 0 2.5 in Density Standoff 2.5 in 0

0.5

ohm.m

5,000

0

ft3/ft3

Residual Hydrocarbon Residual Hydrocarbon Dielectric Scanner Total Porosity Water-Filled Porosity ft3/ft3 0 0.5 ft3/ft3 0.5

Carbonate

Total Porosity

Irreducible Water Volume

1

0.5

0.5

Hydrocarbon

Depth, ft

Quartz Dielectric Scanner Water Saturation 1

500

600

700

Accurate resistivity and porosity measurements in a washed-out borehole. The articulated pad of the Dielectric Scanner tool is not affected by rugose hole conditions and obtained the actual Rxo measurement, proving that the difference between the other two resistivity curves in Track 2 was not caused by invasion. Similarly, the Dielectric Scanner porosity in Track 5 accurately measured water-filled porosity across washed-out intervals, unlike the previousgeneration mandrel tool.

800

ft3/ft3

ft3/ft3 Core Porosity

Clay-Bound Water Volume

0

ft3/ft3

0

Electromagnetic Propagation Porosity 0 0.5 0 ft3/ft3 Dielectric Scanner Water-Filled Porosity 0 ft3/ft3 0 0.5

Dielectric Scanner interpretation and quality control software Dielectric Pro* software provides quality control and advanced interpretation for Dielectric Scanner service. After preprocessing and applying quality control to the raw data, Dielectric Pro software performs a robust radial interpretation of the different spacing and polarization measurements to provide the dielectric dispersion data. A multimineral analysis for lithology and porosity that integrates measurements from different tools is performed in the same application to determine the total porosity and formation matrix permittivity. These outputs are used together with the dielectric dispersion in a final interpretation step, in which petrophysical models determine water-filled porosity, water salinity, and textural parameters.

Pore-fluid analysis ■ High-resolution residual saturation and invaded zone water salinity Hydrocarbon saturation profile in heavy oil reservoirs or shallow invasion environments

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Matrix analysis ■ Carbonates: mn log for cementation exponent estimation Shaly sands: high-resolution CEC for clay content

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Structural analysis ■ Thin-bed analysis Structural anisotropy in very thin beds

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Following a carefully engineered, efficient workflow, Dielectric Pro software delivers reliable petrophysical answers for complex environments in minimum time.

Picture to come

Dielectric Scanner Specifications Output Logging speed Vertical resolution† Depth of investigation Accuracy at the highest frequency Range of measurements at the highest frequency Combinability Max. temperature Max. pressure Outside diameter Borehole size—min. Borehole size—max. Minimum restriction Borehole fluid Length Weight Max. tension Max. compression§ Conveyance

Relative dielectric permittivity and conductivity at four frequencies 3,600 ft/h [1,097 m/h] 1 in [2.5 cm] 1 to 4 in [2.5 to 10 cm] Corresponding to 0.002-ft3/ft3 [0.002-m3/m3] water-filled porosity Permittivity: ±1% or ±0.1 Conductivity: ±1% or ±5 mS Permittivity: 1 to 100 Conductivity: 0.1 to 3,000 mS Platform Express* integrated wireline logging tool Most openhole tools 350 degF [177 degC] 25,000 psi [172 MPa] 4.77 in [12.12 cm] 5.5 in [14 cm] 22.0 in [55.9 cm] 5.25 in [13.3 cm] Both water- and oil-base muds‡ 11.27 ft [3.44 m] 262 lbm [119 kg] 50,000 lbf [222,411 N] 4,400 lbf [19,572 N] Wireline, TLC* tough logging conditions system, or tractor

† 1 in depending

on frequency mud under specific conditions; contact your Schlumberger representative § 8,000 lbf [35,586 N] with TLC stiffener kit ‡ Oil-base

www.slb.com/ds *Mark of Schlumberger Other company, product, and service names are the properties of their respective owners. Copyright © 2013 Schlumberger. All rights reserved. 13-FE-0010