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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

Cased Hole Form ation Resist iv i ty

(CHFR)

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

CHFR Cased Hole Formation Resistivity Tool

Stationary formation resistivity measurementsbehind casing

Applications

Primary resistivity evaluation in wells with no

openhole measurements

Identification of bypassed hydrocarbons

Identification of fluid contacts

Measurement of residual oil saturation

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

Dif ferences in Respon se of

Resist iv i ty tools :

Laterolog devices (including

CHR) measure Rt in series.

Induction devices measure

resistivities in parallel.

Laterolog and InductionMeasured Resistivities

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

CHFR identifies

hydrocarbon and water

bearing zones through

casing

Illustration of CHFRusage in old and new

wells benefits

Remaining unswept

reserves identified,

extending economic

field lifeResistivity measured

despite conditions

preventing acquisition of

open hole data

CHFR Applications

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

The CHFR tools introduce current to the

casing so that extremely small amounts

escape into the formation.

The voltage drop caused by this phenomenon,expressed in nanovolts (10 9V, or 1 trillionth

of a volt), is measured by tool electrodes and

used to determine formation resistivity.

The CHFR tool design incorporates four levels

of three electrodes spaced 120 apart.

This 12-electrode configuration allows fast

operations and provides redundant

measurements in case of casing corrosion

or in the presence of perforations.

CHFR Operation

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

The CHFR tool works by injecting current

into the casing,

The amount that leaks out over a 1.2 m

interval of casing is measured using very

accurate differential voltage sensors.The higher the current leakage, the lower

the resistivity of the formation outside the

casing.

Stationary measurements are made to

ensure good electrical contact with the

casing and to improve the signal quality.

The measurement range is 1-100 ohm-m,

and the effective logging speed is

approximately 40 m/hour.

CHFR Operation

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

Low frequency AC passes up the pipe

to the surface

AC also passes down the pipe

through the formation to a return at

the surface

The tool measures the voltage

difference: l in downgoing currentbetween pairs of voltage electrodes.

At every station 3-electrodes

contribute to the measurement

With 4 sets of electrodes, twomeasurements are made at every

stationary point.

V0=casing voltage, V1and V2are

voltages measured in the formation

between two pairs of electrodes. Rc=

casing resistance.

CHFR Operation

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

CHFR Calibrations:

Current is passed from upper to lower

electrodes

DRcis measured

This is the resistance of casing

between the 2 contact points.

CHFR Calibrations

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

CHFR and CHDT services

were run to acquire data in

this well-Pressure and sampling data

could not be obtained in open

hole.

CHFR data overlaid deep-

reading openhole resistivity,

CHDT tester acquired

formation pressures and fluid

samples, allowing the well to

be completed successfully.

Example-1Perforation Selection

CHFR and Sampling

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

This log from a well in

a water-injection

project demonstratesthe value of the

CHFR technology in

identifying bypassed

paytop 60 ft.

Abandoned in 1998,the well was

producing 300 BOPD

in 2001 after it was

logged and perforated

again.

Example-2By-Passed Oil

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Cased Hole Evaluation

CHFR >>Cased Hole Formation Resistivity (CHFR)

It was not possible to

obtain Open hole data inthis example.

The CHFR tool was used

Determine that the

uppermost sand had not

been produced.

Perforated the zone and

benefited and produced

dry oil: 600 B/D.

Example-3

Locating

Producing Zone