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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