Severe Risk
High Risk
Medium Risk
Low Risk
6,500 ft
7,000 ft
Drilling Dynamics
Sensors and Optimization
Accurate, real-time measurements
for productive drilling
Drilling Dynamics Sensors and Optimization
■
Reduce shocks
■
Optimize ROP
■
Maximize bit performance
Avoid lost-in-hole and
NPT costs
■
Prevent fluid kicks
and fractures
■
Schlumberger drilling dynamics sensors
deliver accurate, real-time, downhole
measurements for productive drilling
reaching TD in less time.
S
chlumberger drilling dynamics sensors measure shock and
vibration, weight on the bit and torque at the bit, annular
pressure and temperature, and hole size. These measurements
enable drillers to optimize drilling parameters and minimize the
risk of drillstring fatigue, premature trips for failure, stuck pipe, kicks,
and lost circulation.
Real-Time Shock Outputs
Schlumberger MWD and LWD tools and PowerDrive* rotary steerable
systems all provide real-time and memory logs of the level and duration
of downhole shocks they are being subjected to (0 = no shocks,
1 = medium shock levels, 2 = high shock levels, and 3 = severe shock
levels). Shocks can be characterized in terms of counts per second
(cps), peak shocks, and cumulative shocks. The PowerPulse* MWD
telemetry system and the TeleScope* high-speed telemetry-whiledrilling service record the number of shocks greater than 50 g’s per
second as a moving average over a period of 100 s, transmit the answer
uphole as shock cps, and aid definition of shock risk level 0, 1, 2, or 3.
Our tools also measure stick/slip, indicated by variations in collar rpm
downhole over a specified time period. The variation measurement sent
uphole can be compared to surface rpm and reported as a stick/slip
level and risk 0, 1, 2, or 3.
These shock count and stick/slip measurements are basic outputs
that Schlumberger provides to help our engineers and customers
understand when potential BHA damaging shock levels are occurring,
allowing remedial action to be taken and enabling more efficient drilling.
Use real-time measurements to improve drilling efficiency
Rotational
Speed
Severe Risk
High Risk
c/min 200
Stick/Slip
Medium Risk
Indicator
Low Risk
0
c/min 200
Transverse
Surface
Collar
Torque
Rotational Speed RMS Vibration
gn
10 0
50 0 1,000 ft lbf 20 0
c/min 200 0
0
Depth,
ft
ROP Averaged
Over Last 5 ft
0
ft/h
500 0
Surface
WOB
1,000 lbf
Shock
Peak
gn
500
6,000 ft
Vibration levels
correspond with BHA
being in whirl
6,500 ft
7,000 ft
Track 5 of this depth log provides vibration risk level information.
Vibration levels
successfully mitigated
via a modification in
surface rpm, allowing
successful completion
of hole section
Shocks greater than 50 gn
Shock cps
0
100
Time, s
Shock cps
180
The shock cps provided by our MWD tools is a moving average.
Advanced Stick/Slip Measurement
Time, s
An advanced measurement to be used in conjunction with the standard
downhole stick/slip measurement is available from all Schlumberger
MWD tools to help evaluate the severity of stick/slip. This advanced
measurement is the percentage of time during a stick/slip cycle that
downhole string rotation is below 5 rpm. The measurement is split into
four levels (0 = 0%, 1 = 1% to 24%, 2 = 25% to 49%, and 3 = 50% or more).
Four-Axis-Shock Measurements
Adding an optional modular vibration chassis (MVC) to the PowerPulse
MWD telemetry system or TeleScope high-speed telemetry-while-drilling
service provides a real-time four-axis shock measurement that can be
used for more detailed analysis of drillstring dynamics. Because the
MVC is an integral component, no extra collars or connections are needed.
Stick/slip value
Downhole rpm
Variations in downhole collar rpm indicate stick/slip.
The MVC’s real-time four-axis shock measurement alerts the driller to
harmful downhole dynamic motions, such as bit bouncing, stick/slip, and
whirling, which, if undetected, can lead to poor drilling efficiency, bit
damage, and premature drillstring fatigue. Typically, the MVC is used in
conjunction with an IWOB* integrated weight on bit sub that provides
DWOB* downhole weight-on-bit and DTOR* downhole torque-at-thebit. This enables the driller to adjust weight on the bit, torque at the bit,
drillstring rotation speed, and other drilling parameters to reduce the
downhole shocks identified by the MVC, significantly improving ROP
and extending BHA life.
0
0
Depth,
ft
0
ROP
ft/h
Surface Torque
Surface Weight on Bit
lbf
40,000 0 ft.lbf 20,000 0
Lateral Vibration
gn
40 0
Shock Width
ms
3,000
Axial Vibration
gn
10 0
Shock Peak
gn
200
DownholeTorqueDownhole Drillstring Rotation Speed
Downhole Weight on Bit
c/min
300 0
50 0
lbf
40,000 0 ft.lbf 10,000 100
XX,320
XX,340
XX,360
Stick/slip threshold
weight
XX,380
These surface and downhole measurements were used to optimize drilling in a West Africa field.
Torsional Vibration
radian/s
3,000
Period with
downhole rpm
less than 5
Period with
downhole rpm
greater than 5
400
Downhole rpm
300
200
Surface rpm
100
0
0
1
2
3
Time, s
Advanced stick/slip measurement shows the duration of the stuck period during
a stick/slip cycle.
WOB, tons
30
20
10
0
WOB, tons
10
20
30
Time, s
40
50
30
20
10
0
Average WOB = 6.5 tons
0
10
20
30
Time, s
40
IWOB downhole measurements enable a driller to optimize ROP.
5
6
7
One axis—torque—is measured by strain gauges. The other three axes
are axial and radial shock measurements made by three mutually
perpendicular accelerometers. These accelerometers are axially
aligned with the direction and inclination (D&I) package in the center of
the collar to ensure that the shock measurements accurately represent
BHA vibration. Because the shock measurements are aligned with the
BHA axis, the driller can identify and correct poor drilling conditions
before the BHA experiences excessive fatigue.
Weight-on-Bit and Torque-at-the-Bit Measurements
Average WOB = 6.7 tons
0
4
50
The IWOB integrated weight on bit sub—an optional component
of the PowerPulse MWD telemetry system—provides real-time DWOB
downhole weight-on-bit (WOB) and DTOR downhole torque-at-the-bit
measurements. These direct dynamic measurements of the amount
of surface weight being transferred through the PowerPulse collar
to the bit and of the torque generated below the collar enable a driller
to optimize ROP by identifying downhole problems and correcting
or avoiding them.
IWOB measurements make it possible to distinguish drillstring effects—
BHA hanging on ledges, high friction coefficients, and BHA whirl—from
bit effects—stick/slip and locked cones. These measurements allow bit
usage to be maximized through continuous monitoring of bit condition,
and eliminate unnecessary trips to change bits because the driller can
tell whether a reduction in drilling efficiency is due to bit wear or to a
change in lithology. By detecting potential sticking problems, IWOB
measurements help avoid lost-in-hole and NPT costs, and help drillers
reach TD sooner.
Downhole torque, instantaneous - average
rms
Time, s
IWOB torsional vibration measurements show the rms magnitude of downhole
torque fluctuation.
Because the IWOB sub is an integrated component of the PowerPulse
collar, it eliminates the need for intersub wiring and electrical
connections. Actual downhole torque and WOB are measured and
transmitted to surface via MWD telemetry in real time. Advanced
downhole processing allows accurate interpretation of measurement
vibrations to identify stick/slip and other phenomena. A measurement of
the root mean square magnitude of downhole torque fluctuation at the
MWD tool also is available in real time. This measurement is a valuable
indication of drilling inefficiency and can be used to minimize the risk of
twistoff events and identify BHA whirl and other mechanisms.
IWOB downhole measurements are especially beneficial for optimizing
directional drilling with steerable mud motors. The real-time measurements
improve drilling efficiency by allowing swift correction of mud and hole
cleaning problems—such as cuttings buildup, mud gel strength, and
friction—so that TD can be reached faster with less BHA damage.
IWOB measurements eliminate much of the guesswork in determining
the forces acting on the drillstring. Combining these measurements
with MVC four-axis shock and APWD* annular pressure while drilling
measurements automatically removes interfering factors, such as
pressure, temperature, and bending. Quick identification of the sources
of ineffectiveness and potential problems enables the correct remedial
action to be taken, reducing cost and NPT.
A Shock & Vibration DVD box set, available free from Schlumberger,
discusses how shock and vibration slows ROP and adversely affects
BHA components and hole quality. To order a set, contact your local
Schlumberger representative.
Tool twist off (left) and impact damage to bit (right) resulted from shock and vibration.
Integrating downhole and surface measurements to optimize drilling
These examples show how drilling performance and efficiency can be improved by
integrating data from our downhole sensors with surface sensor measurements.
Bit on Bottom Flag
Block Position
0
ft
150
ROP
0 0
100
ft/h
Hook Load
100,000 lbf 500,000 0
Bit Depth Value
ft
0
Downhole WOB
lbf
60,000
Surface WOB
60,000
lbf
Vibration, X-Axis
gn
4
0400
Torsional
Vibration
0
4,000
Surface Torque
ft.lbf
30,000 Surface
–10,000 ft.lbf
Drillstring
Lateral Vibration
Rotation
gn
0
4
Speed
Downhole Torque
0
120
–10,000 ft.lbf
30,000 c/min
Total Pump 550
Flow
0
1,200
galUS/min 70
Turbine
RPM,
5,200
Real-Time
2,000 4,000
2,800
c/min
High lateral shocks
Increasing surface WOB reduces shocks
Increased WOB reduces lateral shocks
Increasing surface WOB reduced the lateral shocks detected by downhole sensors.
ECD
psi/1,000 ft
650
Annular Temperature
degC
150
Annular Pressure
psi
7,200
Standpipe Pressure
psi
4,400
0
0
Block Velocity
–2
ft/s
2 4
ROP
0 0
50
ft/h
Surface WOB
lbf
60,000
Hook Load
500,000
lbf
Vibration, X-Axis
gn
0
Bit Depth
Value
ft
0
0
Surface Torque
ft.lbf
20,000
Downhole torque
20,000
lbf
Torsional Vibration
Bit Depth
Downhole WOB
lbf
ft
0 4,000
500,000 0
0 4
Annular
Temperature
100
Lateral
Vibration
degF
12
300 0
Total
–9
Pump Flow
100
1,000
0 galUS/min 0
ECD
lbm/galUS
Annular Pressure
psi
5,000
Bit on Bottom
0.5
Standpipe Pressure
psi
5,000
Whirl started and was not
stopped after shutting down
for short period of time.
Whirl finally stopped
after longer period off bottom.
Off bottom for short time—
shocks return
Off bottom for short time—
shocks return
Off bottom for longer time—
shocks reduced
Two attempts to reduce BHA whirl by raising the bit off bottom to dissipate energy
were unsuccessful because the bit was not kept off bottom long enough. On the
third try, the bit was kept off bottom for a longer time, which reduced torsional and
lateral shocks when drilling resumed.
14
The APWD sensor provides accurate
measurements for
keeping pressure inside a narrow
operating margin
■
Annular-Pressure-While-Drilling Measurements
The APWD annular pressure while drilling sensor provides an accurate
real-time measurement of equivalent circulating density (ECD), equivalent
static density (ESD), and annular temperature. This enables the driller to
optimize drilling performance and minimize risk by improving practices
for hole cleaning, borehole stability, and well control, and to keep annular
pressure between tight limits in wells that have small margins between
fracture gradient and pore pressure.
While the pumps are on and drilling fluid is flowing, MWD telemetry
delivers APWD data in real time. During connections and leakoff tests
when the fluid is static, minimum, maximum, and average pressure
values are recorded downhole and transmitted to surface when the
pumps are turned on.
In deviated wells that require extensive drilling while sliding, and in
extended-reach and deepwater wells constricted by friction and barite
sag, APWD sensors near the bit can identify increased ECD due to
cuttings buildup or barite sag, lack of rotation, or poor hydraulics.
That allows corrective action to be taken before a stuck pipe occurs.
Near-bit APWD sensors can also detect small downhole fluid losses
or gains as they occur. This early detection can help a driller identify
potential well control issues before any indication of a fluid influx or
lost circulation is seen on surface, and allows the driller to maintain
a tight overbalance to optimize ROP without sacrificing safety. By
monitoring the effect of swab-surge on ECD, these near-bit sensors
allow tripping speeds to be optimized to prevent fluid influxes and fractures.
■
early detection of shallow water flow
■
optimizing tripping procedures
■
underbalanced drilling
■
monitoring barite sag
■
tracking motor performance
■
leakoff tests
■
discriminating influxes from sweeping
■
detecting kicks and influxes.
In addition, a driller can use APWD measurements to discriminate
a formation fluid influx from the harmless flow of mud over the bell
nipple—a common occurrence when circulation is stopped. Mistaking
the mud flow for an influx caused by increasing formation pressure
can result in a needless mud weight increase that slows ROP and may
cause lost circulation.
APWD sensors have been integrated into many Schlumberger MWD
and LWD tools and systems, some of which include an internal pressure
sensor in addition to the annular sensor. Annular and internal pressure
measurements, together with inferred motor torque and rpm, permit a
directional driller to continuously monitor motor performance and motor
wear, maximizing drilling performance while extending motor life by
preventing stalls.
Caliper Measurements
Ultrasonic and electrical caliper measurements
while drilling are not only important to petrophysicists
for LWD log quality control, but can also be crucial
to drilling success. Analysis of real-time caliper
information, especially in combination with APWD
measurements, can identify washouts, hole cleaning
problems and wellbore stability issues.
Schlumberger ultrasonic sensors measure standoff
accurately—up to 3 in beyond the drill collar—over a
wide range of mud weights and formation properties.
As the drillstring rotates, these measurements are
binned azimuthally, and can be transmitted, by
quadrant, in real time to make caliper images.
Azimuthal standoff measurements are useful for
understanding interpreted density responses and
making estimates of average hole size that can be
used to correct neutron porosity measurements.
A differential caliper inferred from density
measurements can be used as a quality control
on the ultrasonic caliper.
Our azimuthally averaged electrical caliper can be
used to quantify washouts in larger boreholes. This
caliper, available only in water-base muds (WBM)
with a resistivity of less than 0.5 ohm.m, provides hole
size estimates up to 36 in, and is accurate to less
than 0.5 in over most ranges of formation resistivity.
Because our azimuthally averaged electrical caliper
can be used to estimate hole size while tripping,
it allows a time-lapse picture of dynamic wellbore
conditions. A caliper measurement while tripping
is also valuable for cementing operations, because
total hole volume can be crucial information for
successful cementing.
Drilling optimization workflow
These workflow charts suggest remedial actions that can be taken to
mitigate axial, lateral, or torsional vibration.
Vibrations—Recognize
the Symptoms
Conventional Cures
While Drilling
SURFACE MEASUREMENT
OR SYMPTOM
LATERAL VIBRATION
(bit/BHA whirl)
Increased mean
surface torque
Increased delta
surface torque
Decrease rpm
by 10%
Increase
WOB by 10%
Reduced ROP
Increased mean
downhole torque
High-frequency downhole
shocks—10 to 50 Hz
Repeat three
times unless
WOB limit
is exceeded
Yes
No
Pick up off bottom and
allow string torque to
unwind
Restart drilling
with 70 rpm
Increase WOB
by 10% of original
Increase rpm
to original value
Increased torsional
acceleration
Loss of real-time
data/measurement
Increased shock count
No
Cutters/inserts damaged,
typically on shoulder
or gauge
Broken PDC blades
Worn hybrids (equivalents)
with minimal cutter wear
Overgauge hole
from calipers
One-sided wear
on stabilizers and BHA
BHA failure
Does
vibration
continue?
Yes
Increased lateral shocks
POSTRUN EVIDENCE
SURFACE MEASUREMENT
OR SYMPTOM
Topdrive stalling
Loss of toolface
DOWNHOLE
MEASUREMENT
Vibrations—Recognize
the Symptoms
Pick up off bottom
and allow string torque
to unwind
Restart drilling
with 70 rpm
Increase WOB
to original value
TORSIONAL VIBRATION
(stick/slip)
Place top drive in high gear;
ensure soft torque operational
Decrease
WOB by 5%
Increase
rpm by 10%
rpm/torque cycling
Loss of toolface
Reduced ROP
DOWNHOLE
MEASUREMENT
Increased delta
downhole torque
Increased torsional
acceleration
Repeat three
times unless
WOB limit
is exceeded
Yes
No
Pick up off bottom and
allow string torque to
unwind
Restart drilling
with 10%
increased rpm
Decrease WOB
15 to 20%
Downhole collar rpm greater
than surface rpm
Loss of real-time
data/measurement
Increased lateral shocks
Increased shock count
No
POSTRUN EVIDENCE
Cutters/inserts damaged,
typically on nose and taper
Overtorqued connections
Twist-offs and washouts
BHA failure
Does
vibration
continue?
Yes
Increased stick/slip indicator
Vibration
resumes?
Yes
Conventional Cures
While Drilling
Vibration
resumes?
Yes
Pick up off bottom and
allow string torque to
unwind
Restart drilling
with 70 rpm
Increase WOB
to 25% below
original value
Increase rpm to 25%
below original value
Gradually return
rpm to 15%
above original
CONTINUE
DRILLING
CONTINUE
DRILLING
Specifications
MWD Shocks & Stick-Slip
MeasurementRange
Resolution
Shock count
0 to 255 cps
1 cps
Shock peak
0 to 1,020 gn
4 gn
Stick/slip
0 to 381 rpm
3 rpm
Collar rotation speed
0 to 255 rpm
1 rpm
Shock and stick/slip risk
0 to 3
1
MVC Measurement
Range
Resolution
X-axis axial rms vibration
0 to 30.02 gn
0.125 gn
Y-axis lateral rms vibration
0 to 60.08 gn
0.25 gn
Z-axis lateral rms vibration
0 to 60.08 gn
0.25 gn
Lateral rms vibration
0 to 60.08 gn
0.25 gn
Torsional rms vibration
0 to 5,100 ft.lbf
5 ft.lbf
Shock peak level
0 to 1,020 gn
4 gn
Peak shock width
0 to 20.5 ms
20 us
IWOB Sensor
WOB
Torque
Measurement range
–65,000 to 190,000 lbf
–8,000 to 15,000 ft.lbf
Resolution
500 lbf
90 ft.lbf
Absolute accuracy
see table below
see table below
Scale factor
500 lbf/count
90 ft.lbf/count
Downhole Conditions
Error on WOB
Error on Torque
30,000 lbf WOB
(total electronics error) ± 2.85%
(cross talk) ± 2.85%
5,000 ft.lbf torque
(cross talk) ± 1,410 lbf
(total electronics error) ± 25 ft.lbf
± 50 psi differential pressure‡
± 885 lbf
± 7 ft.lbf
(sliding, worst orientation possible)
± 3,330 lbf
± 438 ft.lbf
Hydrostatic pressure
150 lbf/1,000 psi
5 ft.lbf/1,000 psi
Temperature
41 lbf/degF
4 ft.lbf/degF
IWOB Estimated Absolute Accuracy†
±15° dogleg§
† Accuracy depends on deviations of downhole conditions—such as applied WOB, running torque, sliding dogleg, hydrostatic pressure,
and temperature—away from the corresponding values at the last downhole rezero point.
‡ The effect of differential pressure (ΔP) will be eliminated by surface software based on standpipe pressure.
§The error due to dogleg exists when the MWD tool is in sliding mode. When the tool is in rotary mode, the error vanishes because of data filtering.
APWD Sensors (from EcoScope* multifunction LWD service†, arcVISION* array resistivity
compensated tools, or TeleScope service)
Resolution
1 psi
Accuracy
0 to 0.1% of full scale
Available ranges
0 to 5,000 psi
0 to 10,000 psi
0 to 20,000 psi
Annular temperature resolution
1 degC
Annular temperature accuracy
1 degC
Record rate
4-s minimum—average of 2-s samples
Real-time rate
programmable—typically every 80 s at 12 Hz—3 bps
Ultrasonic Caliper (from EcoScope service or adnVISION* azimuthal density neutron tools)
Frequency
250 kHz
Standoff range
3 in at maximum mud weight 10 lb/galUS and formation densities
above 2.2 g/cm3
1 in at maximum mud weight 16 lb/galUS and formation densities
above 2.5 g/cm3
Accuracy
± 1.5 ms transit time (± 0.1 inch in water)
Frequency
670 kHz
Standoff range
2 in at maximum mud weight 10 lb/galUS and formation densities
above 2.2 g/cm3
1 in at maximum mud weight 13 lb/galUS and formation densities
above 2.5 g/cm3
Accuracy
± 1.5 ms transit time (± 0.1 inch in water)
Drilling Dynamics Sensors and Optimization
www.slb.com/drilling
*Mark of Schlumberger
†Japan Oil, Gas and Metals National Corporation (JOGMEC), formerly Japan National Oil Corporation (JNOC), and
Schlumberger collaborated on a research project to develop LWD technology that reduces the need for traditional
chemical sources. Designed around the pulsed neutron generator (PNG), EcoScope service uses technology that
resulted from this collaboration. The PNG and the comprehensive suite of measurements in a single collar are key
components of the EcoScope service that deliver game-changing LWD technology.
Copyright © 2010 Schlumberger 10-DR-0169