Saturn Probe Delineates Contact in 12¼

Saturn Probe Delineates Contact in 12¼

CASE STUDY
Saturn Probe Delineates Contact in 12¼-in Wellbore in Low-Permeability Presalt Carbonate
Real-time identification of oil/water contact by obtaining low-contamination
samples from 0.03- and 0.06-mD/cP mobilities, deepwater Brazil
CHALLENGE
Accurately define the oil/water contact in a low-permeability zone of a 12¼-in
deepwater well where conventional probe
types returned only tight tests and the
expected longer station times would increase operational risk.
SOLUTION
Deploy the 9-in version of the Saturn* 3D
radial probe with the industry’s largest flow
area of its circumferential drain assembly
for readily inducing and sustaining flow in
large-diameter wells to measure pressure
and sample fluid.
RESULTS
Efficiently established the contact with realtime downhole fluid analysis (DFA) of lowcontamination water samples acquired at
stations with estimated mobilities of 0.03 and
0.06 mD/cP in only 3.5 and 6.5 h, respectively,
to save rig time and reduce risk.
Testing a low-permeability carbonate reservoir in a large-diameter well
An operator needed to accurately define the oil/water contact in a low-permeability zone of a presalt carbonate reservoir offshore Brazil. There were already concerns because of
the expected low mobility that conventional probe types would not be able to make pressure
measurements and obtain fluid samples in the water zone. Low mobility also implied that
excessively long pumping times—with higher attendant operational risk—would be required
to obtain representative pressure measurements and extract fluid with sufficiently low
contamination in the 12¼-in-diameter deepwater well. The operator needed a more efficient
approach that would reduce both operational risk and rig time for measuring pressure and
acquiring representative fluid samples.
Flowing fluid circumferentially with the 9-in radial probe
The new 9-in version of the Saturn 3D radial probe can effectively extract fluid even in largediameter wellbores and from low-permeability, low-mobility formations. The four self-sealing
elliptical ports of the Saturn probe have the industry’s largest surface flow area of 79.44 in2 to quickly establish and maintain 3D flow. Flowing fluid circumferentially instead funneling it to the single point of a conventional probe greatly reduces the time necessary for cleaning
up fluid samples and performing pressure measurements. The design of the Saturn probe also
minimizes the effects of storage volume on testing.
Efficiently sampling low-contamination fluid
The 9-in Saturn probe was deployed with
the MDT* modular formation dynamics
tester for conducting DFA on the extracted
reservoir fluid from the water zone. Although
a conventional probe had previously failed to
define the pressure gradient in the transition
and water zones, conducting only tight
tests, the 9-in Saturn probe reliably sealed
in the 12¼-in borehole to make multiple
valid pressure measurements in the lowpermeability carbonate reservoir.
Low-contamination water samples were
acquired by the 9-in Saturn probe at two stations
with estimated mobilities of 0.03 mD/cP and 0.06 mD/cP in only 3.5 and 6.5 h, respectively.
DFA confirmed the purity of the flowed fluid. The real-time pressure and fluid data acquired
with the 9-in Saturn probe efficiently achieved
the test objectives while reducing operational
time and the attendant risk.
Impressions of the Saturn probe’s inlet ports on
images logged by the UBI* ultrasonic borehole imager
demonstrate the probe’s circumferential coverage.
Formation Evaluation
Flowline resistivity, ohm.m
CASE STUDY: 9-in Saturn 3D radial probe flows fluid in 12¼-in wellbore, deepwater Brazil
Downhole resistivity and
optical monitoring of the fluid
extracted by the Saturn 3D
radial probe at a station with
0.06-mD/cP mobility confirmed
quick cleanup to low levels of
contamination in 3.5 h.
24
22
20
18
16
14
12
10
8
6
4
2
Oil-base-mud filtrate
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0
0.5
Water
1.0
1.5
Highly absorbing flag
2.0
2.5
3.0
Elapsed time, h
3.5
4.0
4.5
5.0
Free-Fluid
Volume
Capillary-Bound
Water
Tight Test
Dry Test
Dry Test
Tight Test
8,100
Washout
psi
NMR Porosity
9,100
0.3
Gamma Ray
0
gAPI
150
Bit Size
10
in
Water
20 0
in
V/V
0.2
Mud After
8,800
psi
10,000
Mud Before
Oil
1 8,800
psi
0.3
Depth,
m
Cable Tension
10,000 15,000 lbf
Dry test
V/V
Permeability
0
Drawdown Mobility
Free-Fluid
0.01
mD/cP
1,000
Volume Using
NMR Permeability
3-ms Cutoff
0 0.3
V/V
0 0.01
mD
ohm.m 2,000
Density Standoff Correction
g/cm3
0.2
ohm.m 2,000
Array Induction 2
2-ft
Resistivity A10
1,000 0.2
0.25
Standard-Resolution Formation
Photoelectric Factor
Array Induction
20
2-ft
Resistivity A90
0
Free-Fluid
Volume
InSitu Fluid
Analyzer
Fluid Fractions
20
Caliper
10
Array Induction
2-ft
-1
Resistivity A30
Clay-Bound
Water
Formation pressure
ohm.m 2,000 0.45
0
Standard-Resolution
Formation Density
g/cm3
3
Near/Array-Corrected
Limestone Porosity
V/V
–0.15
A conventional probe had
returned only tight, low-quality
pressure points (red) that were so
scattered that pressure gradients
and contacts across the lowpermeability water zone could
not be determined. The Saturn
3D radial probe obtained lowcontamination samples from the
zone that confirmed the presence
of water and delineated the
contact to the overlying oil zone.
X,550
Dry test
X,560
Dry test
Tight test
X,570
Lost seal
X,580
Dry test
Tight test
Lost seal
No seal
No seal
Lost seal
X,590
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