Introduction to MWD

Introduction to MWD Revised: 10/2/98 Printed: 10/2/98 Page 1 of 55

Source: SLC IntroToMWD.doc Revised:2-Oct-98

Introduction to Measurement While Drilling(MWD)

Subject Matter Expert: Jan Morley

An asterisk (*) is used throughout this module to denote a mark of Schlumberger.

ObjectivesIn this module you will learn how Measurement While Drilling (MWD) system componentswork, their function and what they do. You will also learn about the major components ofAnadrills six MWD tools.

Study Questions

This module contains study questions. As you come across the questions, try to answer themwithout looking back at the lesson. Look if you need to. Answers are provided in the last part ofthis module.



1 IntroductionTechnological advancements in drilling haveresulted in more cost-effective proceduresand improved drilling techniques. One areathat has benefited from the improvedtechnology has been the measurements whiledrilling program. MWD provides real-timedata from measurements made near the drillbit during the drilling of a well, allowingadjustments to be made while the drilling is inprogress.

The MWD tools in use today are able to provide datafor a variety of measurements such as real-time formation measurement (shown here) data

for correlation and pore pressure analysis, includingresistivity, density and porosity measurements of theformation,

real-time surveys, including inclination, azimuth, andtoolface, allowing the driller to steer the well fordirectional control, and

real-time drilling mechanics data for drillingefficiency, including downhole weight-on-bit anddownhole torque-at-bit.

While drilling is taking place, the drillingfluid, or "mud", is pumped through drillpipeconnecting the surface equipment to thebottomhole assembly (BHA).



Data from some of the MWDtools is transmitted uphole to thesurface by mud pulse telemetry,while other tools transmit data tothe surface electronically via awire and are referred to aswireline MWD systems. The pulses are converted toelectrical voltages at the surfaceby a transducer mounted in themud pump discharge piping. Thesurface equipment thendecodes the information, whichrepresents measurements madeby the tool.

Logging while drilling (LWD) isclosely related to MWD. LWDprovides formationmeasurements, while MWDprovides drilling mechanics andsurvey measurements.

Both MWD and LWD data aretransmitted in real time to thesurface. However, LWDprovides better resolution thanMWD because the LWDmeasurements are commonly

stored in downhole memory. The MWD measurements have data transmissionlimitations, which hinder the resolution of the measurement values.

LWD will be covered in another module, while this module concentrates on the MWDtools and systems.



What Do You Think?

What type of measurements does MWD provide that LWD does not?

Circle all the correct answers.

1.Formation measurements

2.Drilling mechanics

3.Survey measurements



2 MWD System Components

In this lesson you will learn to identify the components of an MWD system.

MWD System Components

Anadrill manufactures a range ofMWD tools and systems to meetthe requirements of itscustomers. All of the MWDtools are made up of the samemajor surface and downholecomponents even though eachtype of tool is designed to meet aspecific need.

The MWD surface systemcomponents consist of: surface sensors for measuring

surface drilling parameters, aswell as the wells depth,

a transducer at the surface toreceive the measurementsignals from the MWD tool,

a computer for decodingdownhole data at the surface,and

a computer for processing,storing, and using all of thedata.



The MWD downhole toolcomponents consist of: a component to supply the

power needed to makedownhole measurements,

one or more components formaking downholemeasurements, and

a component for producingand transmitting themeasurement signals to thesurface.



Exercises

1. Each MWD tool is made up of which of the following downhole components?Circle all the correct answers.

1.A component for producing and transmitting the measurement signals to the surface

2.A transducer for receiving the measurement signals at the surface

3.A component to supply the power needed to make downhole measurements

4.One or more components for making downhole measurements

2. Each MWD surface systems is made up of which of the following surfacecomponents?Circle all the correct answers.

1.A component for communicating with other wellbores

2.Surface sensors for measuring surface drilling parameters, as well as the wells depth

3.A component for estimating the cost of production

4.A computer for decoding downhole data at the surface



3 MWD System Component Functions

In this lesson you will learn to match the components of an MWD system with a description ofwhat each component does.

3.1 Power Supply

Batteries, or downholealternators, supply power to thetools. The batteries allow thetools to operate without the flowof mud, but the operating timeand sensor power output islimited. The alternators needmud flow to generate theirpower and can work in a widerange of flow rates.

3.2 Measurement

All MWD systems measure thedirection and inclination (D&I)of the wellbore. Themeasurements are used toaccurately map the well so thedriller can guide the bit to itsultimate or intermediate targets,as well as avoid other wells. Thewell being drilled may requirespecific turn and build rates. TheMWD tool may also have theability to make secondarymeasurements,such as downhole weight on bitand annular temperature.



3.3 Signal Production

The tools measuring deviceproduces data signals that needto be sent to the surface.Because the MWD tool isremote from the driller, it isnecessary to transmit the data byway of a signal from the tool tothe driller. This must be done ina manner that maximizes datatransmission and reliability andminimizes the impact on drillingoperations.

3.4 Transmitting andTelemetry

MWD systems use mud pulsetelemetry to transmit survey datato the surface. Analog signalsproduced by the tool measuringdevices are converted intodigital signals (1 and 0). Thedigital signals are then convertedinto pressure pulses that carrythe data to the surface throughthe column of drilling fluid.



What Do You Think?

Write in the correct term to complete the following sentence.

MWD systems use _______________________ pulse telemetry to transmit survey data to thesurface.



3.4.1 Mud Pulse Telemetry Downhole

Information is transmitted to the surface through the mud by way of a data signal createddownhole. The surface equipment decodes the data signals of the measurements so that thedriller can make adjustments. The three common types of signals generated are positive pulsetelemetry, negative pulse telemetry and continuous wave telemetry.

Positive Pulse Telemetry

A flow restrictor produces positive pulses asillustrated in the graphic.



Negative Pulse Telemetry

A diverter valve produces negative pulses asillustrated in the graphic.



Continuous Wave Telemetry

Rotating plates produce continuous waves asillustrated in the graphic.



3.4.2 Wireline Telemetry

Data can also be sent to the surface through a wire attached to theMWD tool. This method was common with older types of tools(called steering tools). However, with an attached wire, thedrillstring cannot be rotated. Today, wireline is used in conjunctionwith coiled tubing, where the drillstring is a continuous length ofmetal pipe fed into the wellbore from a drum and so cannot berotated.

3.5 Receiving and Decoding

A transducer (or sensor) at thesurface receives the pressurepulses and converts them toelectrical signals. A surfacesensor is not necessary for thewireline type of MWD.

Surface computers decode theelectrical signals from thetransducer and turn the digitalinformation into engineeringvalues and survey computations.



3.6 Data Processing and Usage

An important function of thesurface computer is to processthe data of the local conditions,such as hole size and depth.

The data produced by the MWDtool is processed and used toprovide information about thewell. This information is used tomake critical decisions about thedrilling process, such as the welldirection.

An important function of thesurface computer is to processthe data of the local conditions,

such as hole size and depth.

The data produced by the MWD tool is processed and used to provide information about thewell. This information is used to make critical decisions about the drilling process, such as thewell direction.

3.7 Display

Monitors display data in real-time on the drillfloor so that thedriller can make well steeringdecisions. Displays are used inthe Anadrill unit to allow forproduction of logs (a plot of dataagainst depth) and makingformation-evaluationinterpretations. With remote datalinks, displays located at theclients office allow them toview MWD data from thewellsite.



3.8 Control Downhole

MWD allows the driller tocontrol downhole drilling in realtime. Directional information issent to the surface continuouslyso that course corrections can bemade. MWD tools makeapplications like geosteeringpossible. The driller can use themeasurement data to maximizethe productive length of awellbore within a reservoir.



Exercises

1. Write the name of the MWD system component that performs each function listedbelow.

1.Supplies power to the tool ______________________________

2.Measures direction and inclination ______________________________

3.Produces data signals to be sent to the surface ______________________________

4.Sends wellbore data to the surface ______________________________


1.Receives pulses and converts them into electrical signals ________________________

2.Decode electrical signals and turns them into digital information __________________

3.Processes data of the local conditions ________________________


1.Used to view data in real time on the drill floor ________________________

2.Allows the driller to control drilling in real time ________________________

3.Provides information that is used to make critical decisions about the drilling process

________________________



4. Identify each telemetry signal in the picture below.

_______________________ pulse

________________________ pulse

________________________ pulse



4 How MWD Components Work

In this lesson you will learn about the components of a MWD system and descriptions of howeach component works.

4.1 Power Supply

Power is supplied to the tools bybatteries or alternators. The batteriesgive power without the need for mudflow. An alternator uses mud flow toturn a turbine. The turbine generatesenough current to power the MWDtools.

MWD tools are able to provide a varietyof measurements, including wellboreinclination and direction.Accelerometers are used to measure theearths gravitational field to get theinclination of the wellbore.Magnetometers are used to measure theearths magnetic field to get thedirection. Magnetometers are used inconjunction with accelerometers to give

azimuth. The specific details on how the downhole sensors work to measure geologicalcharacteristics are covered in a separate module.



What Do You Think

Match each of the MWD system components with its description. Write the letter of thecomponent that matches each description in the spaces provided.

1.Uses mud flow to generate current _____________

2.Measures the inclination of the wellbore _____________

3.Measures the direction of the wellbore _____________

A. MagnetometerB. AlternatorC. Accelerometer



4.3 Signal Production, Transmitting, and Telemetry

Survey data, collected by the MWD tool, is transmitted to the surface by mud pulse telemetry.The next four sections will explain how the three types of signals are generated and transmittedto the surface.

Positive Pulse Telemetry

Positive pulse telemetry uses a flow restrictor (orplunger mechanism) that closes to increasestandpipe pressure when activated. As the mudflows through the pipe, the pressure fluctuates asthe plunger mechanism opens and closes. Thehighs and lows of pressure, as sensed by atransducer on the standpipe, are transmitted to thesurface as ones or zeros and are decoded as data.

Negative Pulse Telemetry

Negative pulse telemetry uses a diverter (orflapper) valve. When the flapper valve is open thedrilling fluid is diverted to the annulus, creatingnegative pulses as the pressure fluctuates. Thepressure changes are identified and decoded at thesurface as data.

Standing or Continuous Wave Pulsers

Standing or continuous wave pulsers, also knownas mud sirens, are a type of positive pulsetelemetry. Rotating baffled plates are used totemporarily interrupt mud flow, creating apressure wave in the standpipe. A carrier wave isformed, allowing information to be embeddedwithin the carrier wave by changing the wavesphase or frequency. The information carried bythe wave is identified at the surface and decoded.



Wireline Telemetry

Wireline telemetry uses a cable to transmit data to the surface fromthe downhole systems. The VIPER tool uses a wireline cable totransmit the data to the surface as shown in the graphic.



What Do You Think?

Complete the following sentence.

Standing or continuous wave pulsers are also known as _____________ _____________.



4.4 Receiving and Decoding

Pressure pulses are received andconverted to electric voltages bya transducer installed in the mudpump discharge piping.

The surface computers thenperform the pressure pulsedecoding and surveycomputations to convert the datainto useful measurements.

4.5 Data Processing

Anadrills Integrated Drilling Evaluation and Logging(IDEAL*) system combines downhole directional drilling,drilling mechanics, and petrophysical data measurementswithin a few feet of the bit and transmits the data to thesurface in real time.

Downhole data is merged with relevant surfacemeasurements and is automatically checked and translatedinto useful information. The information can be displayedsimultaneously on the rig floor, in the surface unit, and inthe company representatives office.

Real-time formation evaluationmeasurements enable the steering teamto keep the wellpath in the productiveformation, even when there areunexpected changes in the formation.



Exercises

1. Match each of the MWD system components with the description of how it works.Write the letter of the system in on the line below the description that matches it.

1.Batteries give power without mud flow. An alternator uses a turbine to generate current.

__________

2.Accelerometers measure the earths gravitational field to get the inclination.

__________

3.Pressure pulses are received and converted to electric voltages by a transducer.

__________

4.The surface computers perform the pressure pulse decoding to convert the data into usefulmeasurements.

__________

A. DecodingB. MeasurementC. Power supplyD. Receiving


1.Uses a flow restrictor to generate a pulse _____ A. Negative pulse telemetryB. Wireline

2.Uses a diverter valve to generate a pulse _____ C. Continuous wave telemetryD. Positive pulse telemetry

3.Uses rotating plates to generate a pulse _____

4.Uses a cable to carry the signal _____



3. Write the name of the type of telemetry associated with the equipment shown ineach picture.

1. ______________________________

2. ______________________________

3. ______________________________



5 MWD Tools

In this lesson, you will learn about the market need for Anadrills MWD tools.

Advancements in technological innovations have resulted in the development of new andimproved MWD tools. As a well is being drilled, the MWD tool makes measurements andgathers data so the driller can make adjustments as soon as possible.

This section provides reasons for developing the following Anadrill MWD tools:

1. VIPER*,2. Slim 1*,3. SHARP*,4. M3*,5. PowerPulse*,and6. IMPulse*.

5.1 VIPER

The VIPER tool was developed because there was a need for an integrated device that wouldwork with coiled tubing for slimhole and reentry operations. The VIPER tool is a 2 7/8-in.,steerable BHA tool that uses a wireline to transmit data to the surface.

The VIPER can measure direction and inclination (D&I), gamma ray (GR), external pressure,internal pressure, casing joint detection, and motor stall indication.

5.2 Slim 1

The Slim 1 tool was developed because there was a need for a low cost retrievable,reconfigurable tool that could be used with a wide variety of collar sizes (2 7/8-in. to 9 5/8-in.).

The Slim 1 can measure inclination, azimuth, gravity, or magnetic tool face, as well as formationgamma ray.



5.3 SHARP

The SHARP tool was developed as a portable, low cost replacement for the Slim 1. SHARPstands for Slim Hole Adaptable Retrievable Platform. It has many of the same parts as the Slim1, but the SHARP has improved signal detection and greater programming flexibility. TheSHARP is retrievable and reconfigurable and has the capability of a higher data rate than theSlim 1.

The SHARP tool can be used in drill collars varying from 4 3/4-in. to 9 5/8-in. or even as smallas 2 7/8-in., but it is not retrievable or resettable at this size. The SHARP can measureinclination, azimuth, gravity or magnetic toolface and natural gamma ray.

5.4 M3

The M3 tool was designed and developed as a replacement for the older M1 tool and is directlycompatible with all LWD tools. The modulator and the telemetry cartridge were redesignedbecause there was a need for improved signal generation and detection as well as increasedflexibility and reliability.



5.5 PowerPulse

The PowerPulse (M10*) tool was designed and developed because there was a need for a toolwith improved reliability, decreased maintenance costs, increased data rate, and as a replacementfor the M3. Other design advantages of the PowerPulse include reduced length, no collar wiring,variable operating frequencies, higher shock and vibration resistance, larger flow range andhigher maximum flow rate.

5.6 IMPulse

The IMPulse tool is a smaller version of the PowerPulse tool. It was designed and developed toaddress MWD and LWD in slim holes. Design improvements of the tool include beingcompatible with other slim hole LWD tools.



Exercise

Match each MWD tool with the reason it was developed. Write the letter of the market need inthe space beside the name of the tool.

1. VIPER ___________ A. An integrated device that works withcoiled tubing

2. Slim 1 ___________ B. Designed to address MWD and LWDin slim holes

3. SHARP ___________ C. A portable, low cost replacement forthe Slim 1 with improved signaldetection and greater programmingflexibility

4. M3 ___________ D. A low cost retrievable, resettable toolthat could be used with a wide varietyof collar sizes

5. PowerPulse ___________ E. Replacement for the older M1 anddirectly compatible with all LWDtools

6. IMPulse ___________ F. Replacement for the M3 withimproved reliability



6 Anadrill MWD Tool Components

In this lesson, you will learn about the major downhole components of Anadrills MWD tools.

The Anadrill MWD tools covered in this section include:

1. VIPER,2. Slim 1,3. SHARP,4. M3,5. PowerPulse, and6. IMPulse.

This section illustrates the major components of each tool. The function and operation of thecomponents are covered in the module on each individual tool.

6.1 VIPER

The VIPER tool uses a wire to transmit data to the surface. The graphic illustrates the majorcomponents of the VIPER system, including the: coiled tubing and wireline, telemetry and power section, gamma ray sensor (GR), and direction and inclination sensor (D&I).



6.2 Slim 1

The Slim 1 tool uses positive pulse telemetry to transmit data to the surface. The graphicillustrates the major components of the Slim 1 system, including the:

pulser (SMA), gamma ray sensor (GR), direction and inclination sensor (D&I), electronics module (SEA), centralizer module, and battery module.

6.3 SHARP

The SHARP tool uses positive pulse telemetry to transmit data to the surface. The graphicillustrates the major components of the SHARP system, including the:

pulser (SMA), direction and inclination sensor (D&I), gamma ray sensor (GR), electronics assembly (SHEC), battery assembly (SHBA), and orienting assembly (SHOA).



6.4 M3

The M3 uses continuous wave telemetry to transmit data to the surface. The graphic illustratesthe major components of the M3 system, including the:

M3 collar, telemetry cartridge assembly (TCA), sensor cartridge assembly (SCA), gamma ray assembly (GRTM), turbine alternator assembly (TAA), and modulator (MOD).

6.5 PowerPulse

The PowerPulse uses continuous wave telemetry to transmit data to the surface. The graphicillustrates the major components of the PowerPulse system, including the:

M10 drill collar (MDC), modulator assembly (MMA), direction and inclination sensor (D&I), gamma ray sensor (GR), electronics assembly (MEA) and turbine assembly (MTA).



6.6 IMPulse

The IMPulse uses continuous wave telemetry to transmit data to the surface. The graphicillustrates the major components of the IMPulse system, including the:

gamma ray detector (GR), direction and inclination sensor (D&I), power and telemetry section, and resistivity antennas.



Exercises

1. Identify the components of the VIPER. Write the number of each component on theline next to its name.

_______ Direction and inclination sensor _______ Telemetry & power

_______ Coiled tubing & wireline _______ Gamma ray sensor

2. Identify the components of the Slim 1. Write the number of each component on theline next to its name.

_______ Centralizer module _______ Electronics module

_______ Pulser _______ Battery module

3. Identify the components of the SHARP. Write the number of each component on theline next to its name.

_______ Pulser _______ Battery assembly

_______ Electronics assembly _______ Orienting assembly



4. Identify the components of the M3. Write the number of each component on theline next to its name.

_______ Sensor cartridge assembly _______ Turbine alternator assembly

_______ Telemetry cartridge assembly _______ Gamma ray assembly

5. Identify the components of the PowerPulse. Write the number of each componenton the line next to its name.

_______ Modulator assembly _______ M10 drill collar

_______ Electronics assembly _______ Turbine assembly

6. Identify the components of the IMPulse. Write the number of each component onthe line next to its name.

_______ Power and telemetry section _______ Gamma ray detector

_______ Direction and inclination sensors _______ Resistivity antennas



7 Summary

Technological advancements with MWD tools have led to improved and more effectivemeasurements. MWD tools are essential to making measurements near the bit during drilling soa driller can make adjustments when needed.

In this module you have learned to:

Identify the components of a MWD system. Match the components of a MWD system with a description of what the component does. Match the components of a MWD system with a description of how the component works. Match each tool with the reason it was developed. Identify the major downhole components of Anadrills MWD tools.



8 Answers to Study Questions

Correct answers are shown as bold or typed on the lines provided.Part 1

What Do You Think?

What type of measurements does MWD provide that LWD does not?

Circle all the correct answers.

1.Formation measurements

2.Drilling mechanics

3.Survey measurements

Part 2

Exercises

1. Each MWD tool is made up of which of the following downhole components?Circle all the correct answers.

1.A component for producing and transmitting the measurement signals to the surface

2.A transducer for receiving the measurement signals at the surface

3.A component to supply the power needed to make downhole measurements

4.One or more components for making downhole measurements

2. Each MWD surface systems is made up of which of the following surfacecomponents?Circle all the correct answers.

1.A component for communicating with other wellbores

2.Surface sensors for measuring surface drilling parameters, as well as the wells depth

3.A component for estimating the cost of production

4.A computer for decoding downhole data at the surface



Part 3

What Do You Think?

Write in the correct term to complete the following sentence.

MWD systems use ____________mud________ pulse telemetry to transmit survey data to thesurface.

Exercises


1.Supplies power to the tool ___power supply________________

2.Measures direction and inclination ___measurement________________

3.Produces data signals to be sent to the surface ___signal production_____________

4.Sends wellbore data to the surface ___transmitting_________________


1.Receives pulses and converts them into electrical signals ___receiving and decoding__

2.Decode electrical signals and turns them into digital information ___receiving and decoding__

3.Processes data of the local conditions __data processing and usage_


1.Used to view data in real time on the drill floor __display________________

2.Allows the driller to control drilling in real time __control downhole________

3.Provides information that is used to make critical decisions about the drilling process

__data processing and usage_____



4. Identify each telemetry signal in the picture below.

____positive______________ pulse

____negative_____________ pulse

____continuous___________ pulse



Part 4

What Do You Think

Match each of the MWD system components with its description. Write the letter of thecomponent that matches each description in the spaces provided.

1.Uses mud flow to generate current _____B________

2.Measures the inclination of the wellbore _____C________

3.Measures the direction of the wellbore _____A________

A. MagnetometerB. AlternatorC. Accelerometer

What Do You Think?

Complete the following sentence.

Standing or continuous wave pulsers are also known as _____mud_____ ____siren___.



Exercises


1.Batteries give power without mud flow. An alternator uses a turbine to generate current.

____C______

2.Accelerometers measure the earths gravitational field to get the inclination.

____B______

3.Pressure pulses are received and converted to electric voltages by a transducer.

_____D_____

4.The surface computers perform the pressure pulse decoding to convert the data into usefulmeasurements.

_____A_____

A. DecodingB. MeasurementC. Power supplyD. Receiving




1.Uses a flow restrictor to generate a pulse __D__ A. Negative pulse telemetryB. Wireline

2.Uses a diverter valve to generate a pulse __A__ C. Continuous wave telemetryD. Positive pulse telemetry

3.Uses rotating plates to generate a pulse __C__

4.Uses a cable to carry the signal __B__

3. Write the name of the type of telemetry associated with the equipment shown ineach picture.

1. ____positive pulse______________

2. ____negative pulse______________

3. continuous pulse or standing wave_



Part 5

Exercise

Match each MWD tool with the reason it was developed. Write the letter of the market need inthe space beside the name of the tool.

7. VIPER _____A______ G. An integrated device that works withcoiled tubing

8. Slim 1 _____D______ H. Designed to address MWD and LWDin slim holes

9. SHARP _____C______ I. A portable, low cost replacement forthe Slim 1 with improved signaldetection and greater programmingflexibility

10. M3 _____E______ J. A low cost retrievable, resettable toolthat could be used with a wide varietyof collar sizes

11. PowerPulse _____F______ K. Replacement for the older M1 anddirectly compatible with all LWDtools

12. IMPulse _____B______ L. Replacement for the M3 withimproved reliability

Part 6

Exercises

1. Identify the components of the VIPER. Write the number of each component on theline next to its name.

___4____ Direction and inclination sensor ___2____ Telemetry & power

___1____ Coiled tubing & wireline ___3____ Gamma ray sensor

2. Identify the components of the Slim 1. Write the number of each component on theline next to its name.



___3____ Centralizer module ___2____ Electronics module

___1____ Pulser ___4____ Battery module

3. Identify the components of the SHARP. Write the number of each component on theline next to its name.

___1____ Pulser __3_____ Battery assembly

___2____ Electronics assembly ___4____ Orienting assembly

4. Identify the components of the M3. Write the number of each component on theline next to its name.

___2____ Sensor cartridge assembly __4_____ Turbine alternator assembly

___1____ Telemetry cartridge assembly ___3____ Gamma ray assembly



5. Identify the components of the PowerPulse. Write the number of each componenton the line next to its name.

___1____ Modulator assembly ___2____ M10 drill collar

___3____ Electronics assembly ___4____ Turbine assembly

6. Identify the components of the IMPulse. Write the number of each component onthe line next to its name.

___3____ Power and telemetry section ___1____ Gamma ray detector

___2____ Direction and inclination sensors ___4____ Resistivity antennas

Documents

Introduction to MWD