Schlumb_MWD LWD Basic v imp

4/23/2004

Example Exploration Well Plan

20” Normally pressured Schlumberger Public
16” clastics
13 3/8”
Pressure ramp
11 3/4”

9 5/8”

Reservoir Schlumberger Public

101 GR
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Now let’s imagine drilling an exploration well in a highly challenging
environment with the SeismicMWD tool.
The exploration basin is characterized by normally pressured clastics in
the shallow section, then a section with a severe pressure ramp and highly
over-pressured reservoirs.
To reach a deeper reservoir, the well must be geosteered accurately
through a step out section with an uncertain velocity profile.

To meet all of the objectives, wells in this region normally require flawless
planning, many casing strings and careful execution.
The well plan calls for a 20-, 13 3/8- and 9 5/8-in casing sequence and
contingent liners of 16 and 11 3/4-in. If needed, the contingent liners would
require underreaming and add considerable extra cost.

The key to success is to push the 20-in casing as deep as possible and to
set the 13 3/8-in casing exactly at the top of the pressure ramp that is an
obvious reflector on the surface seismic map but not easily recognizable
as a lithology change.

Drilling Office - Bit on Seismic Schlumberger Public4/23/2004

Time-Depth Surface
Curve and Seismic
Depth in Depth
Prediction
Schlumberger Public
Distance
to Target

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4/23/2004 Schlumberger Public

Schlumberger Public

Bit On Seismic

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4/23/2004

LWD-NMR

Schlumberger Public

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This is a picture of the tool taken while testing at RMOTC (Rocky Mountain Oilfield Test Center) in June 1999
this is actually a picture of the first generation tool, but the second generation is essentially identical in the
antenna region shown here. The only difference is in the new tool has a longer section of slick drill collar than
the original tool. The tools currently being deployed are second generation tools.

Describe picture

The spiral piece at the bottom is the field replaceable screw on stabilizer that is changed in the same way as a
drilling motor stabilizer.
Above this are antenna and wear bands.
The rest of the tool is slick.

Outline Presentation.
Questions rules (encourage interruption?)

4/23/2004

NMR While Drilling Schlumberger Public

„ Tools available to Schlumberger Public
measure T2 (or T1)
in real time

„ Measurement
complicated
compared to
wireline by tool
motion

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4/23/2004

LWD-NMR Outputs Schlumberger Public

Real Time Outputs Schlumberger Public
– Lithology Independent Porosity
– Bound Fluid Volume (BFV) / Free Fluid Volume (FFV)
– T2LM (Log mean of T2)
– Permeability
– Hydrocarbon from Multi-Wait Time Porosities

Additional Outputs from Recorded Mode
– Raw Echoes
– Full Data Re-Processing
– Full T2 Spectra
– Motion Data

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LWD-NMR Outputs

The tool performs downhole a T2 inversion and computes outputs for transmission in real
time. These real-time outputs could be used for GeoSteering, well placement, sidetrack
decisions, etc….

Direct hydrocarbon identification using porosities from multiple polarization times (examples
shown later) (see FAQ’s for description of hydrocarbon identification/characterization
methods)

Permeability is calculated uphole from the bound fluid free-fluid ratio using Coates-Timur
equation or from the SDR equation if T2LM is transmitted, coefficients and exponents for
these equations can be set by the user at the wellsite based on client desires.

The tool records the raw echoes and this data can be used to reprocess the data in the
IDEAL wellsite software. A more detailed (more components in T2 spectrum) can be
computed from the raw data. In addition, the tool records full accelerometer and
magnetometer data whose primary purpose is for QC of NMR data, but some interesting
drilling engineering applications will also be shown.

-------------------------------

Note that the downhole memory of the tool is obviously not unlimited. No “maximum footage
loggable” specification can be given as the tool records verses time. Currently the tool can
record around 104 megabytes of memory. Note that the tool only records while circulating.
Prior to the job during the planning stage the memory can be set up to record for longer
periods of time by stackking the raw echoes. As NMR data is inherently statistical and when
reprocessed the echoes are stacked anyway, there is no significant loss of information. In
this way, the memory can be programmed to last as long as required.

4/23/2004

Measurement & Motion

Resonant region Schlumberger Public

Borehole Wall Experiment
Region
Resonant
Region

107 GR Schlumberger Public
4/23/2004

The slide above shows the tool at first centered in the borehole at the beginning of
the measurement cycle. An experiment region is established with the 90degree
pulse, the 180 pulse should then be performed with a coincident resonant zone, i.e.
the tool should not move. The diagram on the right shows how the resonant region
stays at a fixed radius around the tool but the experiment zone is fixed in the
formation. In other words the experiment is now in error due to movement.

This is clearly a very great challenge with the drilling environment, either the
experiment has to be fast compared to the motion and or the tool should be
stabilized to reduce motion.

Also the slide demonstrates where the measurement is made. In a cylinder of a
particular thickness around the tool. It is where the magnetic field and the frequency
of the radio signal combine to produce a resonant effect in the hydrogen nuclei, this
is how only hydrogen is measured in the experiment. And also that no signal is
received from in front of or behind the resonant zone. In other words there is a well
defined and constant measurement region from this tool unlike other nuclear or
resistivity tools.

4/23/2004

Drilling Dynamics From Accelerometry

0.1 cm

Bit Whirling Schlumberger Public
&
Hole 1.0 cm
Enlargement

108 GR Schlumberger Public
4/23/2004

The above are examples of the kinds of whirling motion it is possible to resolve using the
tools capabilities.
Each graph shows the locus of lateral movement of the center of the tool, as it moves in the
bore hole. The scale is in meters, top left shows millimeter size whirl, top right sub millimeter
and bottom left shows centimeter range movement of about an inch that was constrained by
the tool hitting the borehole wall.

These motions are more or less damaging according to their shape and frequency of
oscillation. The lower left hand one may be particularly damaging as the oscillations are
much larger amplitude (6-7 cm) and the BHA is whirling around the outside of the borehole
contributing to borehole enlargement and possibly damaging formation by compressing mud
cake into the formation.

-------------------------------------------------------------------------
These were all recorded in one bit run in a shallow vertical hole with a rock bit at 500 ft/hr and
80-150 rpm parameters.

4/23/2004

Quality Control of Motion Effects

Lateral motion leads to Schlumberger Public
shortening of T2’s
Effects Understood
Accelerometers Æ lateral
motion velocity

QC from Accelerometry data.

QC from NMR data

109 GR Accelerometry Data Æ Maximum Measurable T2 Schlumberger Public
4/23/2004

Accelerometer Package is for QC Purposes

The motion data can be used for quality control of the log in recorded mode or real-time by
utilizing the lateral velocity of the tool, to compute the maximum T2 that can be resolved.
This is an example drilling through a gas sand. From the accelerometry package we can
calculate an average lateral velocity shown in track 1. This leads to the red line in the T2 track
that shows the limit of the T2 that could be resolved under the motion conditions experienced
by the tool while the measurements are made. You can see that the transition from shale to
the shaley gas sand sees the appearance of a second T2 peak that is to the left of the T2
maximum line. A separation from the line of about a decade indicates that there is probably
little or no motion shortening of the T2. Further down in the slightly better pay the T2 peak
increases in time to the right but is still to the left of the line so is certainly not noise, but
because it is a little closer to the line it will be somewhat shortened due to tool motion.

NMR standalone QC is also being investigated by looking only at the NMR data and
determining motion effects by looking at the NMR data itself.

4/23/2004

Formation Pressure While Drilling Draw Down Pump Schlumberger Public
Pressure Gauge
„ Measurement
principle identical to Sealing Element
wireline formation pressure System Volume
measurements
Schlumberger Public
„ Rely on direct contact with the
formation

„ Drill string movement must be stopped
„ A small area of the formation is sealed

off, and the pressure & mobility is tested
„ Dual packer type tools also exist

Tool shown is not a Schlumberger tool

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4/23/2004

GeoSteering -The full picture…

UDR Distance to boundary

Vision Res. Medium DOI Schlumberger Public

TT R

Base Balder GVR or VDN Real-Time Image

Gas injectors shall be
drilled near top reservoir

Top Heimdal

Producers shall be drilled 9 m above Base Heimdal Schlumberger Public
OWC or near base reservoir Top Chalk

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4/23/2004

Drilling Performance Sensors

Schlumberger Public

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VISION has a variety of Drilling performance sensors

Downhole weight, torque and multi-axis vibrations are not available on
VISION475.

PERFORM is a service which provides a Specialist Engineer who uses the
drilling performance sensors, surface indicators, offset well data,
knowledge database and local knowledge to improve the drilling process
to identify and reduce risk as well as improve overall ROP.

4/23/2004

Increase Drillstring and Bit Life

BHA whirling in vertical hole

Multi axis shocks
• Reduce drillstring fatigue
• Reduce borehole enlargement
• Increases ROP/bit life

Larger shocks result in more shock counts Schlumberger Public

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All of Anadrill’s MWD and LWD tools are designed with downhole shock
measurements.
In the MWD tools shock data is transmitted in real-time such that in the
event of high shocks drilling parameters can be adjusted and the effects
monitored.
Real-time shocks can reduce non productive time, as trips can be saved
by:
• reducing pipe fatigue
• failure of downhole components
• increasing bit life.
Multi axis shock measurements are also available (ie. Axial, lateral and
torsional) With this information it is possible to determine the type of
vibrations experienced (e.g. bit bounce, stick slip, resonance etc.) and
thus take appropriate action

The shock measurements are alsoused to track wear and tear on the tools
and the level of maintenance required on a tool is based upon the severity
of shocks experienced.
It should be noted that although the MWD/LWD electronics are the most
susceptible damage from shocks, failure of these components is not
catastrophic. Where as the effect of high shocks on BHA connections can
lead to catastrophic failures.

4/23/2004

Early Washout Detection

BHA whirling in vertical hole

Output Voltage vs. Flow Rate for 8-in. Turbine Schlumberger Public

114 GR Schlumberger Public
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The PowerPulse/Impulse MWD system uses a downhole turbine to
generate power. The output voltage from this turbine is directly
proportional to the flow rate passing through the tool and is thus a valuable
downhole flow meter which is sensitive to very small changes in flow.
As the example shows, any washout above the MWD tool is easily seen
from the turbine voltage, a lot earlier than it is seen at surface. Early
identification can help reduce non productive time for expensive fishing
trips. This can be set up as a smart alarm on the IDEAL system, thus
requiring no continuous interpretation of the data by the engineer.

4/23/2004

Stuck Pipe Avoidance

Schlumberger Public

Weight on Bit Torque

115 GR Schlumberger Public
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The PowerPulse tool can be configured to provide real-time
measurements of downhole weight on bit and torque. These
measurements are made based on strain gauges mounted in the MWD
tool.

The gauges for the weight on bit are aligned so that they are only sensitive
to the axial load (tension and compression on the drillstring). The torque
gauges are aligned so that they are only sensitive to the torsional effects
on the drillstring (I..e. not the axial forces)

These measurements are particularly valuable in deviated wells where
surface parameters of weight and torque can be unrepresentative of the
true downhole conditions. By using the downhole measurements the
performance of the bit can be optimized and premature damage of PDC
bits avoided.

By comparing both surface and downhole parameters a calculation of the
friction in the wellbore can be made and the onset of pipe.sticking
detected and action taken

The example shows how the sliding friction (drag) is increasing, indicating
the onset of a potential sticking problem. A wiper trip was made and the
log shows the impact of the corrective action. In this case it was
successful and drilling was resumed.

Thus using these measurements NPT an be reduced by optimizing bit
performance and avoiding stuck pipe.

The calculated friction factors are also a valuable input into the planning of
the next well.

4/23/2004

Accurate control of ECD

Modeled vs. Actual ECD

Schlumberger Public

• Key for Deepwater drilling Schlumberger Public
• Detect shallow water flows
• Detect cuttings loading and swab/surge effects
• Manage the pore pressure fracture grad window

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4/•23M/200i4nimize mud weight for optimum ROP

Anadrill can provide real-time annular pressure measurements in each
hole size. This measurement is used to calculate the true ECD (effective
circulating density) while drilling to ensure that the ECD remains higher
than the formation pore pressure, yet lower than the fracture gradient of
the formation.

Right hand diagram: shows the theoretical ECD (black). Without
downhole measurements this is the value used to define the mud weight
required to drill the well. The red curve shows the actual ECD as
measured by the downhole sensor and shows that there are major
fluctuations, compared to the modeled value, as a result of changing flow
rate and RPM. Other key factors that can effect the ECD are cuttings
loading pipe eccentricity, swab surge effects and temp/pressure effects. It
is clear therefore that in a well where there is a tight window between the
formation pore pressure and the fracture gradient to rely on a modeled
ECD value is dangerous and that real-time monitoring is crucial. This is
particularly true in the case of deepwater drilling where there can be a very
narrow window.

The ECD can also be calculated there is no circulation for accurate leak
off/formation integrity test measurements and to monitor swab/surge
effects

The APWD measurement has also proven to be a valuable tool for the
early detection of shallow water flows (a sharp increase is seen)

All annular pressure measurement can also be stored in the tools
downhole memory.

4/23/2004

Staying within the Pressure Window

Staying within the pressure window ISONIC example

Schlumberger Public

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Left hand diagram: shows a real-time plot of the real-time ECD
measurement plotted against the theoretical fracture gradient and a real-
time calculation of pore pressure based on LWD resistivity. The pore
pressure calculation is compared to the seismic pore pressure calculation
that was made prior to drilling the well.
Accurate monitoring of both the pore pressure and ECD are key. This is
particularly the case in deepwater wells were the window between fracture
gradient and pore pressure can be very narrow.
Right hand diagram:shows an example of how LWD sonic data can also
be used for real-time pore pressure evaluation. The normal compaction
trend of the formation would result in a gradual decrease in sonic transit
time. However, in overpressured formations we see that the formation
becomes less compacted and the sonic transit time diverges from its
normal trend and increases as a function of over pressure.

4/23/2004

Identification of Failure Modes

Shear Failure
Mud Weight too
Low

Schlumberger Public

Tensile Failure Stress Direction
Mud Weight too
High

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LWD images can be acquired from both the GVR
(GeoVISION Resistivity) and ADN (vision density).

As well as clearly showing the interbedding of the
formations and the dip of the beds, these images can
be used to define fractures. Both the direction of the
fractures and the failure mode can be determined.
When combined with Real time images, this will be very
valuable in refining or confirming wellbore stability
models and drilling practices.

But in the above example, the explanation shows that
the mud weight is too high AND too low. How can this
be--which is it?

Schlumberger Public 4/23/2004

Conclusion Schlumberger Public

MWD/ LWD has developed quickly compared to wireline
technology
The technique is widely used in deviated wells and where rig rates
are high
In vertical wells and low rig day rates wireline is more economical

– is there a need for RT data?

Almost all OH wireline measurements can be performed with LWD

– fluid sampling and high definition images are the significant
measurements not yet available

DEPTH control is the biggest single quality factor that
affects LWD measurements

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