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?