Schlumb_MWD LWD Basic v imp

Schlumberger Public 4/23/2004

400 KHz Measurement Schlumberger Public

Depth of investigation:
„ Deeper in conductive formations
„ Similar in resistive formations

Advantages:
„ Better signal in conductive formations (< 1 Ohm.m)
„ Less sensitive to eccentering

Limitation:
„ Less accurate at higher resistivity (low PS & ATT sensitivity to
Rt)

51 GR
4/23/2004

4/23/2004

Depth Of Investigation Comparison

Schlumberger Public

52 GR Schlumberger Public
4/23/2004

4/23/2004

Blended (Best) Resistivity

2MgHz Phase Shift Schlumberger Public
400KHz Phase Shift
2MgHz Attenuation
400KHz Attenuation

Eccentering Effect

53 GR Schlumberger Public
4/23/2004

Sorry about the quality--
This log shows a log that has been severely affected by eccentering. 2-MHz tools are severely affected by
eccentering when there is a large Rt/Rm contrast or a large Rm/Rt contrast. In this case the blue curves in
track two are the 2-MHz phase shift outputs and the black curves in track three are the attenuation curves.
Both are affected by eccentering that has been exaggerated by a washout. In this case the environment
had a large Rm/Rt contrast (OBM and a Rt of less than 1 ohmm.
One of the biggest advantages of the 400-kHz outputs is the immunity to eccentering. To take advantage
of the deeper reading 400-kHz at low resistivity and the immunity to eccentering as well as take advantage
of the higher signal to noise ratio and better vertical resolution of the 2-MHz a new output was created. It
is called the blended or best resistivity (P16B--Phase shift 16 -in spacing /blended output). The 400kHz
curve is presented below 1 ohmm, the 2MHz output is presented above 2 ohmm and the output is a
weighted average between 1 & 2 ohmm. This will be the standard presentation for the commercial version
of IDEAL 6.1 The blended outputs are the red and green curves. Note that they are very well behaved.

4/23/2004 Schlumberger Public

4/23/2004

Polarization Horn Effect

Schlumberger Public

55 GR Schlumberger Public
4/23/2004

4/23/2004

Polarization Horn Effect

Schlumberger Public

56 GR Schlumberger Public
4/23/2004

4/23/2004 Schlumberger Public

Schlumberger Public 4/23/2004

VISION Schlumberger Public
Resistivity

vs. AIT

58 GR
4/23/2004

The VISION resistivity log is extensively used for formation evaluation. It has a similar
response to the Array Induction Tool. Here five PS curves are plotted against the AIT. At low
resistivities, PS curves have about a one foot vertical resolution. The resolution is not
constant like the AIT, as the PS resolution degrades to 2 feet at 50 ohmms.
The attenuation curve resolution is severely affected by an increase in resistivity. The
attenuation curve has a resolution of 2 feet at 1 ohmm but 8 feet at 50 ohmms.
The curve mnemonics are also different from that of an AIT.
For a VISION curve:
•1st letter denotes the curve--either P for Phase Shift or A for attenuation
•second two numbers represent the spacing (10,16,22,28,34, or 40 -inch)
• Unlike the AIT this is not the constant depth of Investigation!!!
•The last letter is either “H” for High frequency (2-MHz) or “L” for low frequency (400-kHz)
Note that the IMPulse currently does not have the 400-kHz option but will be modified latter in
2000 that will provide it with increased memory to 50 MB, dual frequency, digital electronics
and simultaneous acquisition.

4/23/2004

GeoVISION Resistivity Tool

Schlumberger Public

59 GR Schlumberger Public
4/23/2004

4/23/2004

GeoVISION Resistivity

GVR Azimuthal Button Resistivity Measurements

Schlumberger Public

Schlumberger Public

4/23/2004

GeoVISION Current Focusing

Schlumberger Public

61 GR Schlumberger Public
4/23/2004

4/23/2004

Ring Resistivity Principle

Schlumberger Public

62 GR Schlumberger Public
4/23/2004

4/23/2004 Schlumberger Public

4/23/2004

WL dual laterolog Resistivity response

Schlumberger Public

64 GR Schlumberger Public
4/23/2004

4/23/2004

GVR focused Ring Resistivity response

Schlumberger Public

65 GR Schlumberger Public
4/23/2004

4/23/2004

GRV Imaging: Break-outs and Schlumberger Public
Button Averaging
Schlumberger Public
66 GR
4/23/2004

4/23/2004

GVR Azimuthal Caliper

Schlumberger Public

67 GR Schlumberger Public
4/23/2004

Caliper data can be acquired from several sources using LWD data.
• A real-time ultrasonic caliper is made with the Vision675 density tool
• resistivity caliper from the CDR, ARC and RAB in WBM
Today the resistivity calipers are only available in memory but should be available in real-time
by the end of the year (99).
The caliper data provides a picture of the shape of the bore hole, indicating the severity of
formation breakout and the primary directions of failure
The diagram above shows caliper data from the Geovision resistivity tool at different depths,
highlighting that breakout has occurred long the north-west / south-east plane.
The resistivity image data from the same tool over the same interval clearly shows the areas of
breakout along that plane
The caliper data can also be used to potential hazardous areas while tripping, running tubulars
or wireline

4/23/2004

GVR and FMI Comparison

Azimuthal Resistivity for Geological and Fracture Analysis

Schlumberger Public

68 GR Schlumberger Public
4/23/2004

• Fracture presence and orientation are often key parameters to

drilling successful horizontal wells.
• This examples compares a wireline FMI Formation Micro-
Imager (left image) to a GeoVISION resistivity image (right
image) acquired during the drilling process.
• Note the fracture in the middle of each image. This sine wave
has a different orientation to the bedding planes.

4/23/2004

GeoVISION Real Time Images

Real Time Image Recorded Mode Image

70 ft Schlumberger Public

69 GR Schlumberger Public
4/23/2004

Ref.: SPE - 71331

This is an example of a compressed and decompressed image compared
to a recorded mode image straight from the tool memory (I.e. retrieved
when the tool was on the surface. Although the resolution of the
compressed and decompressed image is poorer the main feature of
cutting up through a thin conductive bed can clearly be seen.

4/23/2004

Density Neutron Measurement Schlumberger Public

Wireline density tools Schlumberger Public
typically use a skid mounted
source & detector to obtain
good contact with borehole

LWD tools use different
methods to record density
data with the lowest
standoff as the tool rotates

Neutron porosity
measurements can be
corrected for mud standoff

70 GR
4/23/2004

4/23/2004

Vision Azimuthal Density Neutron (VADN) Schlumberger Public

-AmBe neutron source
-He3 detecNtoerustron
-Thermal nSeeuctrtoionns
-C137 Gamma ray source
-Two gain-Dsteanbsiliitzyed Nal
scintillationSdeectteiocntors

71 GR Schlumberger Public
4/23/2004

4/23/2004

Density Borehole Compensation

RHOmc < RHOb
DRHO > 0

RHO ls Schlumberger Public

RHOmc > RHOb
DRHO < 0

RHO ss
RHOb = RHO ls + DRHO

DRHO = f (RHO ls - RHO ss)

“SPINE & RIBS” algorithm Schlumberger Public

RHOb compensates up to 1” stand-off

72 GR RHOmc
4/23/2004

4/23/2004 Schlumberger Public

Schlumberger Public

73 GR
4/23/2004

4/23/2004

ADN Dual Source Assembly

Assembly Schlumberger Public

Density Source

Neutron Source

74 GR Schlumberger Public

4/23/2004 Schlumberger Public

Schlumberger Public

75 GR
4/23/2004

4/23/2004

CLAMP-ON STABILISER

Schlumberger Public

BUILT-IN STABILISER

76 GR Schlumberger Public
4/23/2004

4/23/2004

ADN Images Theory

AAzziimmuutthhaall ssoouurrccee aanndd ddeetteeccttoorrss

AADDNN DDeennssiittyy IImmaaggee Schlumberger Public

CCoolloorr
ssccaallee

QQuuaaddrraanntt aarrrraayyss Schlumberger Public

77 GR
4/23/2004

4/23/2004

Image Resolution

(Relative pixel sizes)

Schlumberger Public

One inch Pef GVR UBI FMI
scale

Density Schlumberger Public

78 GR
4/23/2004

Despite this coarseness of image, density images can prove invaluable.
They can be acquired in oil and water based muds. Using LWD allows
measurements in complex shaped wells that would require risky TLC runs
if they are possible at all.

Furthermore many of these wells are logged at high angles, where even
thin bed are seen over many feet within the borehole.

As with any imaging tool a contrast in the medium being measured is
required to identify beds.

4/23/2004

Image resolution Limitation6 in Schlumberger Public

8.5 in Schlumberger Public

35°

™The sinusoids are not
resolved for apparent dips of
less than 35 Degrees

4/23/2004

VADN Images PowerDrive - 2D Images

Ultrasonic Schlumberger Public
Pef
RHOS Schlumberger Public
RHOB (quad.) ROSI
RHOB (sect.) ROIM
RHOL

80 GR
4/23/2004

4/23/2004

Comparison Real Time vs. Memory Image

RTI RMI

Schlumberger Public

81 GR Schlumberger Public
4/23/2004

LWD Calipers 4/23/2004

Ultrasonic Caliper direct Derived

Density Caliper

Phase Caliper from Propagation Tool Schlumberger Public

Caliper from multiple DOI Resistivity

Neutron Caliper

82 GR Schlumberger Public
4/23/2004

4/23/2004

Ultrasonic Caliper Measurement

Schlumberger Public

Borehole spiraling Schlumberger Public

83 GR
4/23/2004

4/23/2004

Advantages of the Ultrasonic Caliper Schlumberger Public

• Direct and Azimuthal Measurement Schlumberger Public
• Works in OBM and WBM
• Good Precision (0.1 –0.2 in.)
• Available in Real Time

Factors that Affects Accuracy

Acoustic Impedance Contrast between Mud and Formation
Signal Attenuation in Heavy Mud
Standoff Range up to 2.5 in.
Hole Rugosity / Target Alignment

84 GR
4/23/2004

VADN/FMS Schlumberger Public4/23/2004

Image Comparison Drilling Schlumberger Public
down
85 GR sequence
4/23/2004
parallel to
bedding

Drilling
down
sequence

4/23/2004

Schlumberger Public

VADN VADN Schlumberger Public

Density Pef
Dynamic Dynamic

Image Image

4/23/2004

Azimuthal Density Reveals Filtrate Drape Schlumberger Public

Azimuthal Formation Evaluation - Gravity Segregation of Fluids

Gas

filtrate

87 GR Schlumberger Public
4/23/2004

• This is a quadrant density presentation from a horizontal well in a high

permeability gas zone.
• All quadrant densities (top, bottom, left and right) are “crossed-over” the neutron in
the characteristic gas signature.
• The quadrant densities themselves do not agree in the homogeneous formation.
The bottom density has the highest reading. The top density is the lightest.
• This is due to filtrate drape - gravity segregation to the bottom of the wellbore.
This generally occurs in high permeability gas zones due to the buoyancy force.
•Note the difference that this may make on resistivity measurements - GVR would
be useful in this case to compute quadrant water saturations.

4/23/2004

Azimuthal Porosity GeoSteering

Schlumberger Public

88 GR Schlumberger Public
4/23/2004

This example illustrates the benefit of azimuthal density geosteering. A gas zone is overlain by a shale. In
zone A, all four quadrants measure low densities and crossover the neutron, indicating a gas zone. The
top quadrant has a lower density than the bottom quadrant. This may be a result of “filtrate drape”, which
is gravity segregation of filtrate invasion toward the low side of this horizontal well.
The drillpipe is sliding for a short section, until zone B. The density measurement for the top of the
wellbore has increased as it is now measuring the shale bed above the wellbore. The other three
quadrants (bottom, left and right) still indicate gas. With the azimuthal measurement, you would now make
a decision to turn down, away from the shale boundary. However, with an average density, it may not
even be recognized that the wellbore was approaching a shale boundary.
The tool and drill pipe slides again to zone C. Now the wellbore is further into the shale section. Only the
bottom density indicates gas. Only now, would an average density reading indicate that a steering
decision would need to be made, but it still would not provide a direction.

Schlumberger Public 4/23/2004

Sonic while drilling Schlumberger Public

transmitter Receivers

Receivers

Attenuator

Transmitter

89 GR
4/23/2004

Bottom Hole Assembly - ISONIC

The ISONIC8 is combinable with any 8-in. LWD measuring device and is
traditionally run with LWD triple combo tools (e.g. CDR/RAB and CDN).
Similarly, the ISONIC6 can be run with all 6 3/4-in. collar LWD/MWD tools.
Both tools can be run with all bit types. Pictured is a typical quad-combo bottom
hole assembly. In such a configuration, the ADN/CDN will always be at the top
of the BHA to allow for source retrieval. The ISONIC would be typically next,
but it can be placed anywhere in the string, above or below the MWD tool, even
just above the bit in “low noise” environments (e.g. rotary drilling - not hard
rocks).

The ISONIC can be run with or without a downhole motor or geosteering
assembly.

4/23/2004

ISONIC-Array Sonic While Drilling

Schlumberger Public

90 GR Schlumberger Public
4/23/2004

4/23/2004

Recorded Mode Data

Schlumberger Public

91 GR Schlumberger Public
4/23/2004

4/23/2004

ISONIC Vs. Wireline Sonic

Schlumberger Public

92 GR Schlumberger Public
4/23/2004

4/23/2004

Delta-T in Overpressure Zone

Schlumberger Public

93 GR Schlumberger Public
4/23/2004

4/23/2004

ISONIC Applications

Real-time Schlumberger Public

Porosity measurement Schlumberger Public
Lithology identification
Seismic correlation real-time input for synthetic seismograms
Pore pressure trends while drilling
Real-time decision making

Recorded mode

Porosity measurement
Lithology identification
Mechanical properties (hard rocks)
Improved quality sonic measurements

„ Formation alteration (shales) & invasion
„ Hole enlargement

94 GR
4/23/2004

ISONIC Applications

ISONIC applications can be divided into two groups - real time and recorded mode
applications . Real time measurements provide the client with unique opportunities for
better drilling decisions. The two main applications are real time seismic correlation and
pore pressure indication.

Real Time Seismic Correlation

From real time ISONIC compressional slowness measurements, real time synthetic
seismograms can be computed. These seismograms can be used to correlate the client’s
surface seismic data to driller’s depth. The client will learn where the bit is located on his
seismic section. This gives the client the opportunity to re-evaluate his drilling operation
before he reaches total depth.

Pore Pressure Indication

In most sand/shale sequences, compaction increases with depth due to increasing
overburden with depth. Sound travels faster through sand/shale sequences the more
compacting occurs. Therefore, compressional delta-t lessens with depth at relatively
constant rate. When overpressured formations occur, pore space is greater than normal
and the delta-t value increases above the expected trend. Therefore, slow delta-t values
above the compacting trend indicate overpressured formations.

Recorded Mode

The major recorded mode application is wireline sonic replacement. Seismic tie and
sonic porosity (computed from delta-t and used as an input to the petrophysical
evaluation (i.e. lithology, porosity, etc.) are the primary customer objectives for sonic data.
When running ISONIC in fast rocks, shear slowness can be acquired from the recorded
data. Combining shear with compressional slowness allows for mechanical property
computations such as IMPact*, MechPro* and Frachite*.

ISONIC compressional data is gathered well before wireline data can be acquired. This
means that the measurements are made before formation alteration, stress relief,
invasion and increasing hole enlargement can occur. The result is that ISONIC slowness
measurements may be a truer representation of the formation properties than subsequent
wireline sonic measurements.

4/23/2004

LWD Shear Measurement Schlumberger Public
in Slow Formations

The presence of drill collar requires an alternative to
standard wireline-like technology.

A Dipole measurement requires a very large
dispersion correction

R&D programs led to the starting of development
work in quadrupole technology for LWD

95 GR Schlumberger Public
4/23/2004

4/23/2004

Why Quadrupole? Borehole
with collar
Empty
borehole

Dipole Borehole mode Strong collar Schlumberger Public
Formation Shear interference

More sensitive Less sensitive Collar mode
to shear to shear
Small collar
Borehole mode interference
Formation Shear
Collar mode
Quadrupole

96 GR Schlumberger Public
4/23/2004

Shear slowness in slow formations is derived from the measurement of
dipole or quadrupole modes. Both of these modes are dispersive. They
propagate at the shear slowness at low frequencies. As the frequency gets
higher sensitivity to the shear slowness decrease and sensitivity to mud
slowness and other environmental parameters increase. Therefore, one
would like to make the measurement at as low frequency as possible.
However, for the dipole mode the presence of the drilling collar in the
borehole interferes with the formation dipole wave at the low frequencies
making it very difficult to extract formation shear information if at all
possible. The quadrupole collar mode on the other hand is cut-off at low
frequencies and interferes very little with the formation quadrupole wave.
In summary quadrupole measurement is much better suited to shear
logging in slow formations in LWD environment.

4/23/2004

Seismic While Drilling Principle

Surface System

MWD telemetry Source Surface source Schlumberger Public
sea floor Downhole receivers
Waveforms recorded in
LWD Tool
downhole memory
97 GR Downhole processing
4/23/2004 Real-time check-shot

via MWD telemetry
Look-ahead imaging

seismic reflector Schlumberger Public

4/23/2004

SeismicVision System Surface System

Downhole Tool

Schlumberger Public

Rugged LWD technology Triangular cluster (450 in3)
Multiple sensors (3 Geophones, 1 Bottled air supply
Special control system
Hydrophone)
Processor, memory, telemetry Schlumberger Public

98 GR
4/23/2004

SPE71365

The SeismicMWD system has two main components, a downhole tool and
a surface system.

The downhole tool was constructed of typical rugged LWD technology. It
was configured with multiple sensors including geophones, hydrophones
and accelerometers. In addition, it has a processor for downhole
computations, memory for storing data and a telemetry system for
transmitting data to the surface.

The surface system for these tests included a triangular airgun cluster with
a total volume of 450 cu in. A bottled air supply was used to reduce
maintenance for the long “while-drilling” operation. A specially developed
control system was used to activate the source in a manner that would be
synchronized with the downhole recordings.

Schlumberger Public 4/23/2004

Check shot data from Seismic While Drilling Schlumberger Public

Wireline

99 GR
4/23/2004

First field test in Wyoming.
Traces in top section acquired while tripping down.
Bottom trace acquired while drilling at connection time.
Wireline VSP was run after the test. Very good match in
che-ckshot times.

4/23/2004

Applications Schlumberger Public

Real-time check-shot Schlumberger Public

„ Put the bit on seismic map
„ Update seismic velocities for PPP
„ Optimize ECD boundaries and drilling parameters
„ Update velocities for seismic reprocessing

Real-time salt proximity
Seismic look-ahead, 500+ ft (2003)
Replace intermediate wireline check-shot, save

rigtime

100 GR
4/23/2004