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WELL
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MEASUREMENT WHILE
DRILLING (MWD), LOGGING
WHILE DRILLING (LWD) AND
GEOSTEERING
ADVANCED DRILLING ENGINEERING
PAB4333
LEARNING OBJECTIVES
Having worked through this session the students will be able to:
1. Describe the benefits of using and the general
principles behind the MWD, LWD and Geo-steering
concept.
2. Describe the applications of the MWD, LWD and
Geo-steering.
LEARNING CONTENTS
1. Introduction
2. Transmission System
3. Power Source
4. Sensors
5. Directional Tools
6. Gamma ray Tools
7. Transmission and Control Systems
8. Surface System
9. Future Development
INTRODUCTION
Concept
- Real Time data
Application
- Directional
- Petrophysical
- Drilling parameters
MWD CONFIGURATION
TOOLS CONFIGURATION
SENSOR DATA PRODUCED
Rate of Penetration Drilling Rate, ft/Min or ft/hr
Rotary or bit speed Revolution per minutes (RPM)
Mechanical Efficiency Log Monitor bit condition
Sticking pipe indicator Monitors friction losses
Strain gauge Weight on Bit, Torque, Bending Moment
Temperature Bottom Hole Mud temperature
Pressure Bottom Hole Hydrostatic mud Pressure
Gamma Ray Lithology Log
Resistivity Short Normal, Focused resistivity
Conductivity Induction, High-frequency Conductivity
Neutron Porosity Log
MWD AND LWD INSTRUMENT
SPECIFICATIONS
TOOLS FEATURE
OPERATING PARAMETERS
LOGGING IN DIRECTIONAL WELL
Gamma Ray Directional System Resistivity - Gamma Ray Directional System
Pulser Unit
Receives stored data and
converts it to high-frequency
pressure pulse in the mud
column, using mud pressure
differentials between the
inside and the outside drill
collar.
Pressure pulse travel through
the mud column to a sensitive
pressure detector at the
surface.
Surface equipment includes a
decoder to convert the
pressure pulse to electrical
pulses and digital type
displays and recorder.
Pressure Differential of Mud Pulser
Large varieties of sensors have been developed for evaluation
of the data. A pressure transducer installed in stand pipe
receives the signal, whic is further decoded. The weight of a
drilling fluid plays an important role in mud pulse telemetry. To
calculate Pressure differential of mud pulser used:
TELEMETRY TECHNIQUES
HARD WIRE
ELECTROMAGNETIC
ACCOUSTIC
MUD PULSE TELEMETRY
Pulses are sent to surface
TRANSMISSON SYSTEM
POSITIVE MUD PULSE
NEGATIVE MUD PULSE
CONTINUES WAVE (SIREN)
[FREQUENCY MODULATION]
TRANSMISSON SYSTEM
POSITIVE MUD PULSE
In the positive mud pulse system valve inside MWD tools partially closes, creating a
temporary increase in standpipe pressure.
NEGATIVE MUD PULSE
In all system, fluid must be circulating through the drillstring. In the negative mud pulse
system a valve inside the MWD tools opens and allows a small volume of mud to escape
from the drillstring into the annulus. The opening and closing of this valve creates a small
drop in standpipe pressure (50-100 psi), which can be detected by a transducer on
surface.
MUD SIREN
A standing wave is set up in the mud column by a rotating slotted disc. The phase of this
continuous wave can be reversed. The data is transmitted as a series of phase shifts.
TRANSMISSION TECHNIQEUS
POWER SOURCES
Directional Tools
All MWD use basically the same directional sensors for calculating Inclination, Azimuth
and Tool face.
The sensor package consists of 3 orthogonal accelerometer and 3 orthogonal
magnetometer.
Figure –A : Orientation of Sensors in Tool
C axis is aligned with the axis of tool, and B axis define the reference for the measuring
toolface angle.
Measuring Offset Toolface
The Locations of Sensors in The Inclinometer
Accelerometer
• Measure the component of earth’s gravitational field along the
axis. A test mass is suspended from a quartz hinge which restricts
any movement to along one axis only (See Figure).
• As the mass tends to move due to gravity acting along that axis, its
central position is maintained by an opposing electromagnetic
force. The larger the gravitational force, the larger pick-up current
required to oppose it.
• Accelerometer can calculate the angle of inclination and tool face.
•There must be enough non-magnetic drill collars above and below
the sensor to stop any such interference.
Accelerometer
Accelerometer
Magnetometer
A magnetometer is a instrument used to measure the strength
and/or direction of the magnetic field in the vicinity of the
instrument
The size of current is related to the direction of the coil with
respect to the direction of magnetic field.
As with the accelerometer the voltage is measured across a
resistor in the pick-up circuit of the magnetometer.
The voltage read each magnetometer can be used to
calculated the azimuth.
Magnetometer
Calculation for Inclination, Toolface and
Azimuth
Inclination ( ) – The angle between C
accelerometer and vertical. Looking at a vertical
cross-section:
Toolface ( ) – the angle between high side and B
accelerometer. Looking down the tool along the C
axis:
Eq. – 1
Calculation for Inclination, Toolface and
Azimuth
Eq. - 2
Note : This gives the toolface of the MWD tool itself. To measure the toolface of
the bent sub the offset angle must be included.
Azimuth ( ) - the angle between Z axis and magnetic North, when projected on
to the horizontal plane. Looking in the horizontal plane we define 2 vectors V1
and V2 where V1 lies along tool axis.
Calculation for Inclination, Toolface and
Azimuth
And substituting for a, b :
Eq. - 3
Example Calculation
The following data were obtained from the output of a MWD survey:
Accelerometer Voltage: Magnetometer Voltage
Ga = - 0.0132 Hx = 0.1062
Gb = 0.0157 Hy = 0.2510
Gc = 1.0141 Hz = 0.9206
The offset toolface = 0 and the magnetic declination = 7 W.
From this data calculate:
1. Inclination,
2. Azimuth
3. Gravity Toolface
Accuracy of MWD Surveys
Inclination : +/- 0.25
Azimuth : +/- 1.50
Toolface : +/- 3.00
Comparison of MWD and Wireline
Log
Comparison of MWD and Wireline
Log
LWD AND WIRELINE COMPARISON
WIRELINE LOG EXAMPLE
EXAMPLE LOGGING PROGRAM
EXAMPLE LOGGING PROGRAM
Geosteering
• In the process of drilling a well, geosteering is the act of adjusting the borehole position
(inclination and azimuth angles) on the fly to reach one or more geological targets. These
changes are based on geological information gathered while drilling.
• Used of information gained while drilling to make real time decision on the trajectory
of the well.
Geosteering is used in :
1. High-angle deviated wells in thin formations where productivity can be achieved
only if the wellbore remains in a thin permeable zone.
2. Horizontal wells where it is necessary to remain a fixed distance from either a fluid
contact or an overlying tight formation.
3. Closed proximity to a fault .
4. Drilling with a fixed orientation to a natural fracture.
1. http://chinookconsulting.ca/News/Remote-Geo-
Steering.html
2. http://www.makinhole.com/IMAGES/PDF/Stoner_
Technical%20Geosteering.pdf
Geosteering
Data produced:
1. Deviation
2. Cutting, including HC shows and gas reading.
3. Transmission of LWD tools in real time, typically
up/down GR, density, neutron and resistivity.
4. Drilling parameters such as: Losses, Kick ROP, and
torque.
Example of Up/Down Response as Borehole Crosses
Boundary from Above
Example of Up/Down Response as Borehole Crosses
Boundary from Above
Example of Up/Down Response as Borehole Crosses
Boundary from Above
Example of Up/Down Response as Borehole Crosses
Boundary from Above
Example of Up/Down Response as
Borehole Crosses Boundary from Above
Four Scenario of Wellbore Leaving a Formation
Example of geosteered Well
Landing a Horizontal Well Using
Geosteering
Source : http://www.makinhole.com/IMAGES/PDF/Stoner_Technical%20Geosteering.pdf
Example of Up/Down Response as
Borehole Crosses Boundary from Above
Q & A
Assignment (Due date 1 Sept 2010)
A. While drilling an 8 ½-in diameter hole at a deviation of 95 when the reservoir is existed. The offset between the up and down reading is 2 m, with the up reading responding first.
1. What is the relative dip between the bore hole and formation.
2. If the direction of dip of the formation is the same as the borehole, what is the absolute formation dip.
3. Suppose that it is known that the formation dip azimuth is at an angle of 40 to the borehole trajectory. What is now the true formation dip.
ASSIGNMENT (Due date 1 Sept 2010
B. Discuss the application of Gamma-Ray and resistivity Sensors in MWD tool that may be useful in drilling operations.
C. Discuss the relative merits of the two types of gamma-ray sensors that are presently used in MWD tools.
D. What Factors should be considered when comparing MWD gamma-ray logs with wire line gamma-ray logs?