MWD vs. LWD
LWD vs. Wireline Decision Making
Signal Transmission Methods
MWD System Components
What is MWD?
Measurement While Drilling (MWD) systems measure
formation properties (e.g. resistivity, natural gamma
ray, porosity), wellbore geometry (inclination, azimuth),
drilling system orientation (tool face), and mechanical
properties of the drilling process.
MWD vs LWD
Logging while drilling (LWD) is closely related to MWD.
LWD provides formation measurements, while MWD
provides drilling mechanics and survey measurements.
• Inclination, azimuth, tool face
• Rotational speed of the drill string
• Smoothness of that rotation
• Type and severity of
any vibration downhole
• Downhole temperature
• Torque and weight on bit
• Mud flow volume
• inclination at the drill bit (NBI)
• magnetic resonance
• formation pressure
Wireline vs. LWD
small, light and delicate
since the 30s
high data speeds
good borehole contact
powered through cable
problem at high deviation
susceptible to hole
big, heavy and tough
since the 70s
subject to drilling
batteries and mud turbine
can log in any direction
more capable in tough
Real-time Surveys for
• Inclination is the angle between a
vertical line and the path of the
well bore at that point.
• An inclination of 0° is a vertical
• An inclination of 90° is a
• Azimuth is the angle between
North Reference and a
horizontal projection of the
current Survey position.
• A hole drilled due North has
an azimuth of 0°.
Magnetic North and True North
• The Flow of liquid Iron(Fe) in the
earth’s outer core generates electric
currents, which in turn, produce
• Originates at the poles
• The northernmost point on the earth
that lies at the top axis of rotation.
Also called geographic North.
ToolFace is the angle which describes where the bend of the
motor is pointing.
Toolface angle = 0° - the bent
sub or steerable motor is
pointing upwards, the azimuth
should remain steady.
Toolface angle = 90°- the hole
azimuth should turn to the right
Toolface angle = 270°- the hole
azimuth should turn to the left
• The sensors used in steering tools and MWD/LWD tools
are solid-state electronic devices known as
magnetometers and accelerometers which respond to
the earth's magnetic field and gravitational field
The MWD Surface System
Surface sensors for measuring surface drilling parameters,
as well as the well’s depth.
A transducer at the surface to receive the measurement
signals from the MWD tool.
A computer for decoding downhole
data at the surface.
A computer for processing, storing,
and using all of the data.
How the Data is Transferred
Mud Pulse Telemetry Electromagnetic Telemetry
Mud Pulse Telemetry
Positive mud pulse telemetry (MPT) uses
hydraulic poppet valve to momentarily restrict
mud flow through an orifice to generate
increase in the pressure in form of positive
pulse which travel back to the surface to be
Negative MPT uses a controlled valve to
vent mud momentarily from the interior
of the tool into the annulus .
This process generates a decrease in the
pressure in the form of a negative pulse
which travels back to the surface .
Mud Pulse Telemetry
The EM does not use the drilling
mud to send pressure waves.
The tool sends either a magnetic
pulse or electrical current through
the ground to the surface.
On the surface the data is received
through ground antennas and the
data is processed.
EM systems are significantly faster
(10x) than conventional mud pulse
EM & MPT
EM systems have no moving parts and does not create
significant restrictions in the drill string.
As a result, it is more reliable and there is less damage
from erosion caused by drill solids.
EM tools have depth limitations which are a function
of how much power can be supplied by batteries for the
duration of the drilling interval, and at higher power
settings the battery costs may be significant.
Geosteering is the science, or art, of maintaining a
near horizontal well bore within a pre-defined
geological layer (payzone).
Real-time decision making and well steering
Effective placement of a well
Maximize reservoir exposure
Collect available offset wells data
Build Pre-drilling geological model
Monitor the real time data and
MWD/LWD technology is showing tremendous potential
to replace open hole wireline logging
The MWD/LWD will continue its growth by using
technology to increase the efficiency and decrease the
cost of drilling and evaluating wellbores.
Geosteering enhances early production by maximizing
Geosteering is proved technology for successful drilling
Baker Hughes. (1997). Baker Hughes INTEQ's Guide to Measurement While
Drilling. Information Guide, 1-142.
Cathedral Energy Services. (2014, March 10). MWD, Electromagnetic.
Choudhary, D. (2011, July 5). Directional Drilling Technology. Retrieved from
Basic Terminologies Related to Directional Drilling:
Crain, E. R. (2014). Geosteering With MWD Data. P. Eng.
Lamont-Doherty Earth Observatory. (February 2008). An Introduction to
Logging While Drilling. Seminar to Marine Geophysics, 1-5.
Middle East Technical University. (n.d.). Chapter 4, Measurement While
Mottahedeh, R. (2014). Horizontal Well Geo-Navigation: Planning,
Monitoring, and Geosteering.
Schlumberger. (2007). Schlumberger Logging School. Houston.
Schlumberger. (2014, March 10). Oilfield Glossary. Retrieved from Gravity