Mwd Manual

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DIRECTIONAL DRILLING

INDUCTION MANUAL

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DIRECTIONAL DRILLING

INDUCTION MANUAL-01

Issue/Revision : JIN-DD-MWD.IND.MANUAL-01

Compiled By

Kamlesh Unadkat / Vaishali Sali

Base Coordinator

Reviewed By

Umesh Thakur / Satish Jawanjal

GM (Directional Drilling)

Approved By

Dr. I N Chatterjee Director

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1. INTRODUCTION

This is the official “Jindal Drilling MWD Training Guide.” This manual is designed to help novice and seasoned oilfield worker make the transition into becoming an MWD Engineer specializing in the use of probe based positive pulse telemetry MWD system.

This manual is intended to be used with your in-field training to give you the best possible chance for success.

The only dumb question is the one you didn‟t ask and should have. By not asking a question you may inadvertently miss an important point that could cause trouble in field and cost thousands of dollars.

Guide to Safety

You must take adequate precautions before you start working on any operations. A health and safety introduction will be conducted before you can go to any rig

sites.

You‟ll be shown current handling and cleaning methods for all equipment that your job requires you to use.

Ensure your equipment is in good working order to prevent accidents from happening.

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In case of an accident, report it to management immediately.

PERSONAL PROTECTIVE EQUIPMENT

When working on an oil rig, appropriate attire, coverall is required. Any clothing underneath the coverall should be fire retardant or at very least breathable and slow burning.

The uniform should be clean and in good repair when you go to a job site. You should look professional when at any jobsite.

For safety reasons your hair must be cut short. If you have longer hair it must be tied back or put in a pony tail and you should come clean shaven for work.

MWD uniforms consist of:

 Fire retardant coveralls

 CSA approved Hard hat

 CSA approved steel toed Boots

 Hearing protection

 Gloves

TAKE PRIDE IN YOUR WORK AND WHERE YOU WORK!

You are responsible for maintaining your equipment.

Ensure all tools and equipment is clean and in good working order, ensure your toolboxes have adequate supplies to complete a job professionally – all the time.

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Please keep any living/work area clean for yourselves and your co-workers. Ensure you clean up any shacks properly before leaving a job site.

Work Smart – Work Safe

MWD ENGINEER RESPONSIBILITIES

 The MWD Engineer must know how a rig operates as the rig operations affect the working of the MWD tool. In this knowing the BHA( bottom hole assembly) in hole is a must.

 An MWD Engineer must know how the different components of an MWD string operate and how they contribute to drilling.

 An MWD Engineer must reduce the problems and downtime.

 An MWD Engineer must always remember that they are representing their company in front of the client hence proper behavior is expected of the operator always in their shift.

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2. Oil exploration & Drilling

2.1 Forming oil

Oil comes from organic matter that died and sank into the sand at the bottom of the sea.

Over the years, the organisms decayed in the sedimentary layers. In these layers, there was little or no oxygen present so microorganisms broke the remains into carbon-rich compounds that formed organic layers which formed the source rock. As new sedimentary layers were deposited, they exerted intense pressure and heat on the source rock. The heat and pressure distilled the organic material into crude oil and natural gas. The oil flowed from the source rock and accumulated in thicker, more porous limestone or sandstone, called reservoir rock. Oil and natural gas in the reservoir rocks got trapped between layers of impermeable rock, or cap rock.

The different types of trap systems are:

Structural traps

Folds - Horizontal movements press inward and move the rock layers upward

into a fold.

Faults - The layers of rock crack, and one side shifts upward or downward.

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Pinch out - A layer of impermeable rock is squeezed upward into the reservoir

rock.

2.2 Locating Oil

Searching for oil over water using seismology

Whether employed directly by an oil company or under contract from a private firm, geologists are the ones responsible for finding oil. Their task is to find the right conditions for an oil trap -- the right source rock, reservoir rock and entrapment. Modern oil geologists also examine surface rocks and terrain, with the additional help of satellite images. However, they also use a variety of other methods to find oil. They can use sensitive gravity meters to measure tiny

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changes in the Earth'sgravitational field that could indicate flowing oil, as well as sensitive magnetometers to measure tiny changes in the Earth's magnetic field caused by flowing oil. They can detect the smell of hydrocarbons using sensitive electronic noses called sniffers. Finally, and most commonly, they use seismology, creating shock waves that pass through hidden rock layers and interpreting the waves that are reflected back to the surface.

In seismic surveys, a shock wave is created by the following:

 Compressed-air gun - shoots pulses of air into the water (for exploration

over water)

 Thumper truck - slams heavy plates into the ground (for exploration over

land)

 Explosives - detonated after being drilled into the ground (for exploration

over land) or thrown overboard (for exploration over water)

The shock waves travel beneath the surface of the Earth and are reflected back by the various rock layers. The reflections travel at different speeds depending upon the type or density of rock layers through which they must pass. Sensitive microphones or vibration detectors detect the reflections of the shock waves hydrophones over water, seismometers over land. Seismologists interpret the readings for signs of oil and gas traps.

Once geologists find a prospective oil strike, they mark the location using GPS coordinates on land or by marker buoys on water.

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2.3 Oil Drilling Preparation

Once the site has been selected, scientists survey the area to determine its boundaries, and conduct environmental impact studies if necessary. The oil company may need lease agreements, titles and right-of way accesses before drilling the land. For off-shore sites, legal jurisdiction must be determined.After the legal issues are settled, the crew goes about preparing the land:

1. The land must be cleared and leveled, and access roads may be built. 2. Because water is used in drilling, there must be a source of water nearby.

If there is no natural source, the crew drills a water well.

3. The crew digs a reserve pit, which is used to dispose of rock cuttings and drilling mud during the drilling process, and lines it with plastic to protect the environment. If the site is an ecologically sensitive area, such as a marsh or wilderness, then the cuttings and mud must be disposed of offsite -- trucked away instead of placed in a pit.

Once the land has been prepared, the crew digs several holes to make way for the rig and the main hole. A rectangular pit called a cellar is dug around the location of the actual drilling hole. The cellar provides a work space around the hole for the workers and drilling accessories. The crew then begins drilling the main hole, often with a small drill truck rather than the main rig. The first part of the hole is larger and shallower than the main portion, and is lined with a large-diameter conductor pipe. The crew digs additional holes off to the side to temporarily store equipment -- when these holes are finished, the rig equipment can be brought in and set up.

Depending upon the remoteness of the drill site and its access, it may be necessary to bring in equipment by truck, helicopter or barge. Some rigs are built

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on ships or barges for work on inland water where there is no foundation to support a rig (as in marshes or lakes).

In the next section, we'll look at the major systems of an oil rig.

2.4 Oil Rig Systems

PARTS OF A RIG

No diagram can ever explain a drilling rig completely unless you don‟t see one for yourself but in trying to familiarize you with the different parts here is a rig schematic.

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One can divide the rig into three major sections:

a) Power system

 Large diesel engines - burn diesel-fuel oil to provide the main source of power

 Electrical generators - powered by the diesel engines to provide

electrical power

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 Hoisting system - used for lifting heavy loads; consists of a mechanical winch (draw works) with a large steel cable spool, a block-and-tackle pulley and a receiving storage reel for the cable.

 Turntable - part of the drilling apparatus

c) Rotating equipment - used for rotary drilling

 Swivel - large handle that holds the weight of the drill string; allows the

string to rotate and makes a pressure-tight seal on the hole

 Kelly - four- or six-sided pipe that transfers rotary motion to the turntable

and drill string

 Turntable or rotary table - drives the rotating motion using power from

electric motors

 Drill string - consists of drill pipe (connected sections of about 30 feet (10

meters) and drill collars (DC) and heavy weight drill pipes

(HWDP) (larger diameter, heavier pipe that fits around the drill pipe and

places weight on the drill bit which helps in drilling)

 Drill bit - end of the drill that actually cuts up the rock; comes in many

shapes and materials (tungsten carbide steel, diamond) that are specialized for various drilling tasks and rock formations.

A few other parts are:

 Derrick - support structure that holds the drilling apparatus; tall enough to allow new sections of drill pipe to be added to the drilling apparatus as drilling progresses

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CIRCULATORY SYSTEM

The mud pump is like the heart of the rig whereas the mud is like the blood that flow through the system. Pumps drilling mud (mixture of water, clay, weighting material and chemicals, used to lift rock cuttings from the drill bit to the surface) under pressure through the kelly, rotary table, drill pipes and drill collars A diagrammatic representation of the circulatory system is:

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 Pump - sucks mud from the mud pits and pumps it to the drilling apparatus

 Pipes and hoses - connects pump to drilling apparatus

 Mud-return line - returns mud from the hole

 Shale shaker - shaker/sieve that separates rock cuttings from the mud

 Shale slide - conveys cuttings to the reserve pit

 Reserve pit - collects rock cuttings separated from the mud

 Mud pits - where drilling mud is mixed and recycled

 Mud-mixing hopper - where new mud is mixed and then sent to the mud pits

Blowout preventer - high-pressure valves (located under the land rig or on

the sea floor) that seal the high-pressure drill lines and relieve pressure when necessary to prevent a blowout (uncontrolled gush of gas or oil to the surface,

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2.5 Testing For Oil

Drilling continues in stages: The crew drills, then runs and cements new casings, then drills again. When the rock cuttings from the mud reveal the oil sand from the reservoir rock, the crew may have reached the well's final depth. At this point, crew members remove the drilling apparatus from the hole and perform several tests to confirm this finding:

 Wire line logging – lowering nuclear, density, sonic and various other

tools to take measurements of the rock formations there

 Drill-stem testing - lowering a device into the hole to measure the

pressures, which will reveal whether reservoir rock has been reached

 Core samples - taking samples of rock to look for characteristics of

reservoir rock

On confirming the presence of oil the major steps involved in oil production are:

a) Perforation: A perforating gun into the well to the production depth. The

gun has explosive charges to create holes in the casing through which oil can flow. a) After the casing has been perforated, they run a small-diameter pipe (tubing) into the hole as a conduit for oil and gas to flow up through the well. A device called a packer is run down the outside of the tubing. When the packer is set at the production level, it's expanded to form a seal around the outside of the tubing. Finally, they connect a multi-valve structure called a Christmas tree to the top of the tubing and cement it to the top of the casing. The Christmas tree allows them to control the

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flow of oil from the well. After the well is completed, the crew must start the flow of oil into the well. For limestone reservoir rock, acid is pumped down the well and out the perforations. The acid dissolves channels in the limestone that lead oil into the well.

For sandstone reservoir rock, a specially blended fluid

containing proppants (sand, walnut shells, aluminum pellets) is pumped down the well and out the perforations. The pressure from this fluid makes small fractures in the sandstone that allow oil to flow into the well, while the proppants hold these fractures open. Once the oil is flowing, the oil rig is removed from the site and production equipment is set up to extract the oil from the well.

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3. Directional Drilling

Directional drilling is a subsection of drilling which involves deviating a well bore along a planned course to a subsurface target whose location is a given lateral distance and direction from the vertical.

3.1 Applications of Directional Drilling

3.1.1 Sidetracking: Side-tracking was the original directional drilling technique.

Initially, sidetracks were “blind”. The objective was simply to get past a fish in vertical hole. Oriented sidetracks are performed to hit a specific target. It may be necessary due to an unsuccessful fishing job in a deviated well. Oriented sidetracks are most widely used. They are performed when, for example, there are unexpected changes in geological configuration (Figure 1-1).

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3.1.2 Inaccessible Locations: Targets located beneath a city, a river or in

environmentally sensitive areas make it necessary to locate the drilling rig some distance away. A directional well is drilled to reach the target (Figure 1-2).

Figure 1-2 Inaccessible locations

3.1.3 Salt Dome Drilling: Salt domes have been found to be natural traps of oil

accumulating in strata beneath the overhanging hard cap. There are severe drilling problems associated with drilling a well through salt formations. These can be somewhat alleviated by using a salt-saturated mud. Another solution is to drill a directional well to reach the reservoir (Figure 1-3), thus avoiding the problem of drilling through the salt.

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Figure 1-3 Salt dome drilling

3.1.4 Offshore Multiwell Drilling: Directional drilling from a multiwell offshore

platform is the most economic way to develop offshore oil fields (Figure 1-4). Onshore, a similar method is used where there are space restrictions e.g. jungle, swamp. Here, the rig is skidded on a pad and the wells are drilled in “clusters".

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3.2 Types of Directional Wells

A carefully conceived directional drilling program based on geological information, knowledge of mud and casing program, target area etc., is used to select a hole pattern suitable for the operation. However, experience has shown that most deflected holes will fit one of the following types.

Directional Patterns

 L profile well (Build And Hold)

 S profile well (Build and Drop)

 J profile well (Deep Kick-Off and Build)

 Horizontal well (can be a sub category of J profile well) – Single

– Extended reach drilling (ERD) – Multilateral

3.2.1 “L” profile (Build and Hold)

The well is drilled at shallow depth and the inclination is locked in until the target zone is penetrated.

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3.2.2 “S” Type Well

The well is deflected at a shallow depth until the maximum required inclination is achieved. The well path is then locked in and, finally, the inclination is reduced to a lower value or, in some cases, the well is returned back to vertical by gradually dropping off the angle.

3.2.3 “J” Type Well

The well is deflected at a much deeper position and after achieving the desired inclination the well is locked in until the target zone is penetrated.

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3.2.4 Horizontal Well

The well is deflected at a deeper depth and the angle of inclination achieved is 90 degree.

3.3 Geometry of a Directional Well

A directional well is drilled from the surface to reach a target area along the shortest possible path. Owing to changing rock properties, the hole path rarely follows a single plane but, instead, changes its inclination and direction continuously. Thus, the deviated well should be viewed in three dimensions, such that hole inclination and hole direction are specified at each position. Terms that are commonly used in directional drilling are defined below.

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Fig: S profile showing different parts.

A simple build/hold/drop well profile, known as an "S" well, is shown in Figure above.

The kickoff point (KOP) is the beginning of the build section. A build section is frequently designed at a constant buildup rate (BUR) until the desired hole angle or end-of-build (EOB) target location is achieved.

Hole angle, or inclination, is always expressed in terms of the angle of the wellbore from vertical.

The direction or azimuth of the well is expressed with respect to some reference plane, usually true north. The location of a point in the well is generally

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expressed in Cartesian coordinates with the wellhead or the rig's rotary kelly bushing (RKB) usually as the reference location.

True vertical depth (TVD) is expressed as the vertical distance below RKB.

Measured depth (MD) The distance measured along the actual course of the bore hole from the surface reference point to the survey point.

Departure / drift is the distance between two survey points as projected onto the

horizontal plane.

The EOB specification also contains another important requirement, which is the angle and direction of the well at that point. The correct angle and direction are critical in allowing the next target to be achieved; also, it may be necessary to penetrate the pay zone at some optimum angle for production purposes.

A tangent/hold section is shown after the build section. The purpose of the tangent is to maintain angle and direction until the next target is reached.

In the example well, a drop section is shown at the end of the tangent. The purpose of a drop is usually to place the wellbore in the reservoir in the optimum orientation with respect to formation permeability or in-situ formation stress; alternatively, a horizontal extension may be the preferred orientation in the case of a pay zone that contains multiple vertical fractures or that has potential for gas or water coning.

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4. DRILLING OF DIRECTIONAL WELL

Directional wells are drilled with specialized equipments which are placed in the Bottom Hole Assembly. There are many specialized equipments which are used to drill directional wells. Some of the combinations of the specialized directional equipments are:

1. Steerable Downhole Mud Motor (SDMM) & Measurement While Drilling (MWD).

2. Whipstock & MWD. 3. Jetting & MWD.

In all these combinations the former refers to directional equipment which actually deviates the well from the vertical. The latter refers to a measurement system which detects the change in orientation of the well caused due to the former. Earlier a magnetic single shot or multiple shot was used to determine the direction and orientation of the well. However a MWD system has completely replaced the magnetic single or multiple shot as it gives readings in real time. Largely, a combination of SDMM and MWD system is used in the drilling industry.

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4.1 Bottom Hole Assembly

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BIT

MUD

MOTOR

FLOAT

SUB

UBHO

NMDC (x 2)

DRILL

COLLAR

HWDP

DRILL PIPE

SAMPLE BHA

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The bottom hole assembly is connected to the rig through a series of drill pipes.

4.2 SIZES OF BHA COMPONENT

Sizes of BHA components for different hole section

Hole section

CASING

SIZE SDMM TUBULARS MULESHOE

THREAD CONNECTIONS 26” 20” 9 5/8” 8” 5” 7 5/8” R 7 5/8” R 17 ½ “ 13 3/8“ 9 5/8” 8” 5” 6 5/8” R 7 5/8” R 12 ¼” 9 5/8”” 8” 8” 5” 6 5/8” R 6 5/8” R 8 ½” 7” 6 ¾” 6 ¾” 3 ½” 4 ½” R 4” IF 6“ 5” 4 ¾” 4 ¾” 2 7/8” 3 ½” R 3 ½” IF

All sizes in inches

4.3 PARTS OF A BHA

4.3.1 Drill bit

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Every bit has an IADC (International Association of Drilling Contractors) nomenclature e.g. A tricone bit might have an IADC number as 117 where the 1st digit refers to the formation, 2nd to the teeth, 3rd to the bearing. A few examples of bits are Poly Crystalline Diamond Cutter bit (PDC), Tricone Roller Bit (TCR), coring bit.

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4.3.2 Steerable Downhole Mud Motor

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Steerable Downhole Mud Motor

The above figure shows a steerable downhole mud motor connected to a bit.

Motor Selection

• These are the three common motor configurations which provide a broad range of bit speeds and torque outputs required satisfying a multitude of drilling applications.

• High Speed / Low Torque - 1:2 Lobe

• Medium Speed / Medium Torque – 4:5 Lobe • Low Speed / High Torque – 7:8 Lobe

High Speed / Low Torque (1:2) motor typically used when:

• Drilling with diamond bits.

• Drilling with tri-cone bits in soft formations. • Directional drilling using single shot orientations.

• Medium Speed / Medium Torque (4:5) motor typically used for: • Conventional and directional drilling

• Diamond bit and coring applications • Sidetracking wells

Low Speed / High Torque (7:8) motor typically used for:

• Most directional and horizontal wells. • Medium to hard formation drilling. • PDC bit drilling applications

Components of PDM Motors

• Dump Sub Assembly • Power Section

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• Drive Assembly • Adjustable Assembly • Sealed Bearing Section

Dump Sub Assembly

• Hydraulically actuated valve located at the top of the drilling motor • Allows the drill string to fill when running in hole.

• Drain when tripping out of hole

• When the pumps are engaged, the valve automatically closes and directs all drilling fluid flow through the motor.

Power Section

• Converts hydraulic power from the drilling fluid into mechanical power to drive the bit

• Stator – steel tube containing a bonded elastomer insert with a lobed, helical pattern bore through the center.

• Rotor – lobed, helical steel rod

• When drilling fluid is forced through the power section, the pressure drop across the cavities will cause the rotor to turn inside the stator.

• Pattern of the lobes and the length of the helix dictate the output characteristics • Stator always has one more lobe than the rotor.

Dump Sub

• Allows Drill String Filling and Draining • Operation

- Pump Off - Open - Pump On - Closed • Discharge Plugs • Connections

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• With more stages, the power section is capable of greater differential pressure, which in turn provides more torque to the rotor.

The stator elastomer can be made of different materials, such as NBR, HNBR, EPDM etc. The elastomer is chosen considering the type of operation involved. For higher temperature and pressure conditions, where oil based mud is used; better elastomers such as HNBR is used.

Drive Assembly

• Converts Eccentric Rotor Rotation into Concentric Rotation– Universal Joint

Adjustable Assembly

• Can be set from zero to three degrees

• Field adjustable in varying increments to the maximum bend angle

• Provides a wide range of potential build rates in directional and horizontal wells

Sealed Bearing Section Drive

Assembly Sealed Bearing Section

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• Transmits axial and radial loads from the bit to the drillstring

• Thrust Bearing • Radial Bearing

• Oil Reservoir • Balanced Piston

• High Pressure Seal •Bit Box Connection

Operation modes

Rotating mode- In this mode the entire drill string is rotated with the help of rotary table. The drill bit is rotating due to the combined action of mud motor and the rotary table speed.

Sliding mode- In this mode the entire drill string is not rotated. The drill bit is only rotating due to the mud motor. The bend of the mud motor is made to face in a specified direction or angle. Drilling carried out in this way is called sliding.

4.3.3 Float Sub

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Float sub houses the float valve which acts as a non return valve and prevents the backflow of mud into our tool during a sudden pressure shoot up.

4.3.4 UBHO (Universal Bore Hole Orienting subs)

Fig. UBHO

UBHO‟s are also called mule shoe subs as they house the mule shoe. The muleshoe is inserted for the alignment of the MWD string. At the bottom of the MWD tool is a cut with mates with the landing key in the muleshoe. The key helps in orienting the MWD string with the bent in the mud motor.

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4.3.5 NMDC (Non Magnetic Drill Collar)

Fig. NMDC

NMDCs house the MWD tool. Usually 2 non magnetic drill collars are used in the BHA in order to reduce the magnetic interference between the earths magnetic field and the magnetic field from the other magnetic components in the drill.string. NMDC‟s are made up of stainless steel.

4.3.6 Heavy Weight Drill Pipes

Fig. A stand of HWDP comprising 3 HWDPs

As the name suggests the HWDP‟s are heavier than normal drill pipes and impart weight to the BHA. But we must be careful as to how many weights are used as the weight given to the bit will be difficult to control

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4.3.7 Drill Collars

Drill Collars also contribute weight to the BHA which in turn provides the pressure to the bit required for drilling. Drill collars are larger than normal drill pipes.

There are a few more important components in the BHA that have not been shown in the schematic diagram

4.3.8 Stabilizers

Stabilizers provide stiffness to the BHA and they are of the same size of the hole being drilled or 1/8”, ¼”, ½” underguaged. The placement of stabilizers is extremely critical in a BHA as it would help in the building, holding and dropping sections of a well.

There are majorly two types of stabilizers:

1) Near bit stabilizers: They are screw on stabilizers and are screwed on the bearing assembly of the mud motor.

2) String stabilizers: As the name suggests the string stabilizers are present in the string or the BHA usually at 30 or 60 feet from the bit.

Stabilizers can also be classi0fied by the nature of the blades.

1) Integral blades: Stabilizers which are manufactured along with the blades 2) Welded blades: Such stabilizers have welded blades.

Note: The blades can be spiral or straight.

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Integral Blades Welded Blades

Fig. String stabilizer

Reasons for Using Stabilizers

• Placement / Gauge of stabilizers control directional • Stabilizers help concentrate weight on bit

• Stabilizers minimize bending and vibrations

• Stabilizers reduce drilling torque less collar contact

• Stabilizers help prevent differential sticking and key seating.

4.3.9 Crossovers

Drill pipe, drill collar and other specialized drill string items do not have standardized threads. In order to assemble two drill string elements having different connections a cross over is used.

Types of cross overs: A) Box by box B) Box by pin C) Pin by pin

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5. Measurement

5.1 INCLINATION/ AZIMUTH/ MEASURED DEPTH

Any form of measuring instrument has to measure the values of azimuth, inclination and measured depth to know the location of the well bore that has been drilled by the directional driller. These values let a directional driller know whether he is in the right path or not

 Hole Direction/ Azimuth is the angle, measured in degrees, of the

horizontal component of the borehole or survey instrument axis from a known north reference. This reference is true north and is measured clockwise by convention. Hole direction is measured in degrees and expressed in either azimuth form (0° to 360°) or quadrant form (NE, SE,

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 Inclination is the angle, measured in degrees, by which the wellbore or

survey instrument axis varies from a true vertical line.

 Measured depth refers to the actual length of hole drilled from the surface

location (drill floor) to any point along the wellbore.

5.2 True North and Magnetic North

Geographic North or True North is one end of the line drawn through the center of the earth‟s rotational axis. Magnetic North is one end of the line drawn through the center of the earth‟s magnetic field. The lines lie near each other but they are not aligned. They diverge and provide two different points of reference.

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5.3 Earth’s Magnetic Field

The outer core of the earth contains iron, nickel and cobalt and is ferromagnetic so the earth can be imagined as having a large bar magnet at its center, lying (almost) along the north-south spin axis. The magnetic field lines emerging from the magnetic North are parallel to the surface of the Earth at the equator and point steeply at the poles.

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• B = Total field strength of the local magnetic field • Bv = Vertical component of the local magnetic field. • Bh = Horizontal component of the local magnetic field.

Magnetic Dip Angle/ Magnetic Inclination Angle

Lines of magnetic force radiate from earth‟s core. The angles at which magnetic force lines penetrate the earth surface determine the strength of magnetic field.

Magnetic Declination

It is the difference in degrees between magnetic north and true north at a given location.An uncorrected azimuth called the raw reading is first corrected for magnetic declination and then for others.

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6. Measurement While Drilling

6.1 Introduction

As we know most of the wells today are deviated wells. Thus while drilling such wells it is important to know the exact orientation and location of the wells. A Measurement While Drilling system provides the orientation of the well in real time.

6.2 What Is MWD?

Measurement While Drilling (MWD) systems measure formation properties (natural gamma rays), wellbore geometry (inclination, azimuth), drilling system orientation (toolface), and mechanical properties of the drilling process. Traditionally MWD has fulfilled the role of providing wellbore inclination and azimuth in order to maintain directional control in real time.

6.3 Mud Pulse Telemetry

The MWD tool is normally placed in the bottom hole assembly of the drillstring, as close to the drill bit as possible. The MWD tool is an electromechanical device which makes the measurements described above, and then transmits data to surface by creating pressure waves within the mud stream inside the drillpipe. These pressure waves or pulses are detected at the surface by very sensitive devices (standpipe pressure transducers with pre-amplifiers) which continuously monitor the pressure of the drilling mud. These data are passed on to sophisticated decoding computers which deconvolute the encoded data from downhole. This whole process is virtually instantaneous, thus, enabling key decisions to be made as the wellbore is being drilled. Other, more exotic transmission systems do exist e.g. drillpipe acoustic, electromagnetic and hardwire telemetry. But the vast majority of all commercial systems utilize mud pulse telemetry by generating either a pulse or a modulated carrier wave which is

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4000-5000 ft./sec or 1200-1500 m/sec). Mud pulse telemetry MWD tools use positive pulse, negative pulse or carrier wave (mud siren) schemes to transmit measured parameters from downhole to surface in realtime to aid in formation evaluation, directional control, drilling efficiency and drilling safety. Downhole information is registered by the MWD sensors and then passed on to the MWD tool microprocessor. The microprocessor then routes this information to the surface by activating the tool transmission system. Mud pulse telemetry involves the modulation of the flow of mud through the drillstring by means of a mechanical valve or rotary valve mounted within the MWD tool. At the surface, the data are decoded and depth correlated. The data are then output to hard copy and graphical display, much like a wireline logging system. The true value of MWD can thus be appreciated by its provision of real time dynamics and directional drilling data augmented by real time formation evaluation measurements, which are considered equivalent and often times superior to sophisticated wireline logs.

As MWD tools and measurements have become more reliable and cost effective, the practice of replacing both standard (e.g. gamma ray, resistivity) logs and triple combo (which also include neutron porosity and formation density measurements) wireline logs has become common place.

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6.4 MWD Principles

Three Basic Telemetry Types:

6.4.1 Positive Mud Pulse Telemetry

Positive mud pulse telemetry (MPT) uses a hydraulic poppet valve to momentarily restrict the flow of mud through an orifice in the tool to generate an increase in pressure in the form of a positive pulse or pressure wave which travels back to the surface and is detected at the standpipe.

6.4.2 Negative Mud Pulse Telemetry

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 pressure in the form of a negative pulse or pressure wave which travels back to the surface and is detected at the standpipe.

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6.4.3 Continuous Wave Telemetry

Continuous wave telemetry uses a rotary valve or “mud siren” with a slotted rotor and stator which restricts the mud flow in such a way as to generate a modulating positive pressure wave which travels to the surface and is detected

at the standpipe.

6.4.4 Electromagnetic Telemetry

The electromagnetic telemetry (EMT) system uses the drill string as a dipole electrode, superimposing data words on a low frequency (2 - 10 Hz) carrier signal. A receiver electrode antenna must be placed in the ground at the surface (approximately 100 meters away from the rig) to receive the EM signal. Offshore, the receiver electrode must be placed on the sea floor. Currently, besides a hardwire to the surface, EMT is the only commercial means for MWD data transmission in compressible fluid environments common in underbalanced drilling applications. While the EM transmitter has no moving parts, the most

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common application in compressible fluids generally leads to increased downhole vibration. Communication and transmission can be two-way i.e.

a) downhole to uphole: Mud telemetry

b) uphole to downhole. The EM signal is attenuated with increasing well depth and with increasing formation conductivity.

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6.5 MWD TOOL Components

6.5.1 Dummy Switch

It is the up hole end component of the MWD tool. It helps in lowering

down the tool and retrieving the tool when a stuck up takes place.

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Centralizer has the function of keeping the MWD tool centered inside the Monel. It prevents excessive lateral vibrations and also provides electrical connections between battery, electronics and pulsar driver.

6.5.3 Electronics Module

The electronics module can be easily identified as it is the longest component in the MWD string. Electronics module is also known as the Direction and Inclination (DnI) module and it is the brain of the string. It is majorly composed of a circuit with three important sensors temperature, accelerometers and magnetometers being at 1.6 feet away from the downhole end of the DnI module.

Sensors

A) Temperature

Our tool works efficiently within the range 0- 150 degree Celsius hence it is important that the DnI module houses a temperature sensor. The temperature sensor is activated earlier than the accelerometers and magnetometers are.

B) Accelerometer

Accelerometers are used to measure the earth‟s local gravitational field. Each accelerometer consists of a magnetic mass (pendulum) suspended in an electromagnetic field. Gravity deflects the mass from its null position. Sufficient

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current is applied to the sensor to return the mass to the null position. This current is directly proportional to the gravitational force acting on the mass. The gravitational readings are used to calculate the hole inclination, toolface, and the vertical reference used to determine dip angle.

There are 3 accelerometers aligned in the 3 axis directions to read the gravity field individually in the X, Y, Z direction and then the effective gravity field is calculated.

C) Magnetometer

Magnetometers are used to measure the earth‟s local magnetic field. Each magnetometer is a device consisting of two identical cores with a primary winding around each core but in opposite directions. A secondary winding twists around both cores and the primary winding. The primary current (excitation current) produces a magnetic field in each core. These fields are of equal intensity, but opposite orientation, and therefore cancel each other out such that no voltage is induced in the secondary winding. When the magnetometer is placed in an external magnetic field which is aligned with the sensitive axis of the magnetometer (core axis), an unbalance in the core saturation occurs and a voltage directly proportional to the external field is produced in the secondary winding. The measure of voltage induced by the external field will provide precise determination of the direction and magnitude of the local magnetic field relative to the magnetometer‟s orientation in the borehole.

There are 3 magnetometers aligned in the 3 axis directions to read the magnetic field individually in the X, Y, Z direction and then the effective magnetic field is calculated.

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6.5.4 Gamma Tool

The tool consists simply of a highly sensitive gamma ray detector in the form of a scintillation counter. The scintillation counter is composed of a thalium activated single sodium iodide crystal backed by a photomultiplier. When a gamma ray strikes the crystal a small flash of light is produced. This flash is too small to be measured using conventional electronics. Instead, it is amplified by a photomultiplier, which consists of a photocathode and a series of anodes held at progressively higher electrical potentials, all of which are arranged serially in a high vacuum.

The Gamma tool can be easily identified in the string as it is the shortest component of the string.

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6.5.5 Battery

• Lithium thynoil chloride battery. • Rated voltage 28.8 V & 26 amp-hour • Thresh hold voltage is 21.5 v

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6.5.6 Pulsar Driver System

The Pulsar driver can be identified easily in the MWD string as it has screen housing at the down hole end. The pulsar driver system possessed by Jindal has a BL 3 phase DC motor which is controlled by the Electronic module through the electrical pin connections present in the various MWD tool components. The up hole connections of pulsar driver system have 6 pin male connection. The down hole end is connected to the stringer assembly.

The pulsar driver is divided into 3 major sections

A) Snubber assembly- mainly consists of the electric circuit

B) Oil fill housing- mainly houses the 3 phase BL DC motor and capacitor bank. C) Screen housing- consists mainly of the bellow, servo shaft, servo poppet.

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6.5.7 STRINGER ASSEMBLY

The different components used to assemble the stringer assembly are shown in the diagram below.

The components of the stringer assembly are 4, 5, 6, 7, 8, 6, 10, polypack and servo orifice.

The piston shaft is hollow and on top of the shaft is fixed lower piston cap, poly pack, upper piston cap and servo orifice in sequence. This assembly is then placed inside the helix/stinger. This combination is then screwed in the planum/stringer barrel which has a spring inside. A poppet is now attached to the end of the stringer shaft. Our stringer assembly is now prepared. The stringer assembly is attached to the downhole end of the pulsar driver.

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6.6 MWD STRING

6.6.1 Gamma Job

D/I Module – Centralizer – Battery Module – Centralizer – Gamma Module – Centralizer – Pulsar Driver – Stringer Assembly

6.6.2 Non-Gamma Job

Battery 2 – Centralizer – D/I Module – Centralizer – Battery 1 – Centralizer – Pulsar Driver – Stringer Assembly

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Fig. showing

the

placement of

MWD

1. Above the SDMM, a

Universal Bent Housing

Orienting (UBHO) sub is

torqued. A mule shoe is

oriented inside the UBHO in

such a way that the

landing key is in line with the

bend of the mud motor.

This process is called

scribing.

2. The mule shoe is then

fixed inside the UBHO with

the help of 2 set screws.

3. Non Magnetic Drill

Collars are torqued above

the UBHO.

4. The programmed

MWD tool with the helix facing

down hole are lifted from the

spear point of dummy switch

and lowered into the

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landing key of mule shoe (in the UBHO).

5. Further one more NMDC is torque, if required, followed by Drill collars and Heavy weight drill pipe.

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6.9 Working of MWD tool



When the pumps are switched on the single axised accelerometer in the snobber assembly of the Pulser Driver senses the vibrations and sends the same message to the DnI through pin 7.



The DnI awaits for a few seconds known as the transmit delay time before it activates the pulsing action in the Pulsar Driver through pin 6.



The to and fro motion of the servo poppet produces the pressure waves which contains the data from the DnI module. The amplitude of these pressure waves are very low and are required to be amplified in order to be transmitted to the transducer at the surface.

1

2

3

5

6

7

8

1

2

4

9

10

PIN 1 GROUND 0 V PIN 2 BATTERY-1 28.8V PIN 3 BATTERY-2 28.8V PIN 4 B- BUS 27.9V PIN 5 Q-BUS 0-2.5V PIN 6 PULSE 05V PIN 7 FLOW 05V PIN 8 GAMMA 05V PIN 9 MOD-1 ---- PIN 10 MOD-2 ----

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

The amplification of the pressure amplitude is done by the stringer assembly. When the tool is placed in the muleshoe, the servo poppet as well as the stringer poppet are in the closed position.



When mud flows through the NMDC housing the MWD tool, there is a pressure difference because of which the stringer poppet retracts and compresses the spring in the plenum. The stringer poppet is now in the open position.



The 3- phase DC motor controls the movement of the servo poppet. The servo poppet when is in the open position provides a free path to the mud to enter the plenum. Hence the pressure inside and outside are balanced.



The spring will now try to reach its least energy position as all forces are balanced except for the spring force. Hence the spring now expands pushing the poppet back to its closed position. This causes an increase in pressure & cause the pulse magnitude to increase.



The servo poppet closes and the process is repeated.



The servo orifice on the upper piston cap allows the mud to bleed during the compression and expansion of the spring.



The magnified pulse now travels through the mud in the drill string and is read by the pressure transducer.

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6.10 MWD Tool Retrieval Equipment

The outer diameter of our tool is 1.88” hence in the case of a stuck up it is possible for us to retrieve the MWD string with the help of equipments above.

 There are two types of assembly for tool retrieval depending upon the angle of the well. Well the angle of inclination is less than 45 degrees we use a overshot, sinker bar and cross over.

 For angles more than 45 degrees we use a spring jar which provides flexibility to the assembly.

 The selection of overshot bell is integral and the difefernt sizes of overshot bells are 1.75”, 2” and 2.25”

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 The assembly is run along with the CCL (casing collar locator) tool of the wireline unit.

 Go down with the wireline unit while monitoring tension and depth.

 One it has reached the bottom, rather found the tool, move up and down while monitoring the tension.

6.11 TOOLFACE

The angle at which the steering tool is pointed is termed as the toolface.

Fig. Toolface

Toolfaces are used to change the hole direction. The low angles the accelerometers are not as accurate as the magnetometers so low angle toolface are based on magnetic readings. Using magnetic toolfaces means pointing the steering tool in the direction of the target.

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Once the direction/azimuth is achieved the toolface changes from magnetic toolface to gravity toolface. The well bore has achieved direction and can be moved left or right of the original direction.

6.12 Fluidic Vortex

The fluidic pulser generates a vortex within a chamber by momentarily restricting the mud flow, thus creating a turbulent flow regime. The resulting change in pressure loss can be switched on and off rapidly, circa 1millisecond, and the resultant pressure wave created can be of high amplitude (145 psi). MWD directional survey instrument is used to monitor the direction (magnetic) and inclination (the angle of the tool's long axis from vertical) of the borehole.

In the MWD drilling environment, there are many sources of magnetic interference that can cause inaccurate directional measurements. A ferromagnetic steel object that is placed in a magnetic field will become magnetized. The amount of induced magnetism is a function of the external field strength and magnetic permeability of the object. In order to prevent magnetic interference, the directional survey instrument is housed in a nonmagnetic stainless steel collar. The MWD tool is usually arranged in a section of the bottom-hole assembly (BHA) which is made up of a series of non-magnetic collars to reduce the impact of the drilling assembly's steel components on the magnetic field at the location of the survey sensor.

It is possible to optimize the position of the survey instrument by estimating the pole strength for various BHA configurations, based upon

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spacing is used, there could still be other sources of magnetic interference which will cause erroneous directional readings. These include “hot spots” in the non-magnetic steel or areas of mechanical damage caused by rethreading/welding or manufacturing impurities. A continual quality assurance procedure ensures that such anomalies are not present in MWD collars and stabilizers. More significantly, other BHA components may be made of magnetic material and/or already has magnetic anomalies that affect azimuth readings. Other sources of

magnetic interference may be caused by proximity to iron and steel magnetic materials from previous drilling or production operations, magnetic properties of the formation, and concentrations of magnetic minerals (iron pyrites, etc) in excess of six percent.

6.13 Azimuth Correction Technique

It is often advantageous to reduce the number of non-magnetic drill collars so that the directional and formation evaluation sensors can be located closer to the bit. (This also eliminates the extra cost of using monel collars.) This will assist

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in real-time decision making by allowing readings to be made as soon as possible following formation penetration. To address this problem, a number of methods have been devised for making corrections to magnetic surveys. The following correction techniques are designed to reduce the influence of spurious magnetic fields associated with the BHA:

Magnetic Azimuth Correction Algorithm

This is a proprietary method by which magnetic azimuth can be calculated in the event that the z-axis magnetometer reading is corrupted by a spurious longitudinal field resulting from an insufficient length of nonmagnetic BHA components. The tool senses such a spurious field as a bias on the z-magnetometer measurement. The method requires the operator to specify expected values for total magnetic field and dip angle, and it then computes the azimuth angle which is consistent with a magnetic field vector as close as possible to the expected value. Accuracy of this azimuth angle is dependent on the accuracy of the input nominal values for the earth's magnetic field and gravity field. The corrected magnetic azimuth accuracy is dependent on the surface location of the well and the direction and inclination that is being drilled. At higher latitudes and higher inclinations and the farther the direction is from north or south, the accuracy of the corrected azimuth will degrade. The operator will have to decide whether to use the corrected azimuth or the uncorrected azimuth based on concerns for azimuth accuracy.

Rotation Algorithm

This is a refinement to the Magnetic Azimuth Correction Algorithm above, which makes use of downhole tool rotation to reduce errors caused by bias in x-axis and y-x-axis magnetometers, in addition to the z-x-axis magnetometer bias. Also, accelerometer bias errors on the x-axis and y-axis can be reduced with this procedure. Such biases may be caused not only by calibration drift, but also by

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the collar. This method requires a minimum of three surveys at different tool face angles, to define a circle centered at a point which represents the transverse biases. This method can reduce errors caused by magnetic anomalies which rotate as the survey tool is rotated. It does not reduce errors which do not rotate, such as interference from an adjacent casing string.

6.14 Basic Hydraulics

6.14.1 System Pressure

System pressure is the pressure felt throughout the system. While drilling, the cuttings must be removed either with the help of water, weighted mud, foam, steam or air. The column of water or mud in the hole is called the drilling fluid and they exert a hydraulic pressure against the formation. This is known as the hydrostatic head or hydrostatic pressue. It is usually measured in pounds per square inch

Bernoulli‟s

principle

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The diagram illustrates 3 different pressure regions. The pressure in or after the restriction is higher. In the area of restriction the pressure is relatively low. After the restricted area the pressure returns to normal.

6.14.2 Annular Velocity

It is the velocity the fluid is flowing with in closed pressure system such as the annulus. Erosion on the metal surfaces of the MWD tool as well as around areas where restriction occurs are directly related to annular velocity and the amount od solids in the mud. There are two flow regimes Turbulent and Laminar. Turbulent flow oocurs when the velocity reaches a critical point known as the critical velocity. Below the critical velocity we have a laminar flow of mud.

Fig. Example of turbulent and laminar flow

A more turbulent flow gives better hole cleaning. But turbulent flows can cause washout of the hole.

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6.14.3 Pressure Pulses

Most tools today use bernoulli‟s principle to communicate between tool and the surface computer. The data from the tool is encoded as pressure pulses and decoded at the surface. The high pressure pulses are formed due to the restriction in the hydraulic system. A sensor at the surface converts the mechanical pressure into electrical signals. The electrical signal is send to signal converter and to a computer. The surface computer decodes the data and displays it on the screen.

6.14.4 Drilling Fluid

In the oil and gas industry the drilling fluid is referred to mud exceptions being foam and air. The fluid column (mud) acts as part of the communication system also known as the qbus.

The mud system controls the quality of the mud and is critical for successfully transmitting MWD data. Thick or more viscous mud affect pulses by creating less sharp peaks. Sometimes when gas or mud enters the mud it gives symptoms that look like pulse failure.

6.15 Factors Affecting the Mud Pulse

There are a number of sources of interference in the MWD drilling environment, although the main ones are as follows:

6.15.1 Mud Pump Noise

Excessive noise, either from the mud pumps or high torque mud motors can, in rare instances, create unacceptable signal to noise ratios. In order to prevent this, some MWD companies deploy surface measurement of pump strobes in order to characterize a mud pump signature. This is then used in the

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surface decoder as a pump subtraction filter. In many cases, the pump subtraction filter can be used to detect premature pump damage before any other physical signs are available.

6.15.2 Rig and Drill string Noise

Drill string vibration will, typically, generate high frequency noise which can lead to a dramatic deterioration of the transmitted signal. Very often, by simply making adjustments to the WOB and RPM, it is possible to avoid damaging critical torsional and lateral resonance. A number of vibration prediction programs are available which can estimate critical RPM for a given drilling assembly. It is also possible to use high frequency surface measurement devices, such as the Baker Hughes INTEQ ADAMS and DynaByte technology provided by the Drilling Dynamics Group. (The Drilling Dynamics Group within Baker Hughes INTEQ uses EXLOG (now part of Baker Hughes INTEQ), ARCO and ELF patented surface measurement technologies).

6.16 Reliability

Reliability is the probability of a product performing without failure, a specified function under given conditions for a given period of time. A unit of measure is Mean Time Between Failure (MTBF). In this respect, the reliability standard is expressed as follows:

Reliability = MTBF = Operating Hours (Perfect Hours)

Failure

Factors Affecting Reliability: • Shock and Vibration • Telemetry System

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• Downhole Temperature • Drilling Practices

• Complexity of Tool

• Service Company Quality Assurance (TQM) • Competition

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7. TENSOR MWD BATTERY MANUAL

GE Power Systems supplies this manual for information and insight to our clients on safe handling and transportation of Lithium battery products. This manual contains information supplied by battery and battery pack manufacturers and suppliers. The information contained within is easily obtained via the Internet or by contacting the Battery Suppliers listed in the front of the manual.

http://www.spectrumbatteries.com/supp2.htm

http://www.spectrumbatteries.com/Prod_in/chart.htm http://www.batteryeng.com/safety.htm

http://www.spectrumbatteries.com/Prod_in/passivation_information.htm http://www.batteryeng.com/func_perf.htm

PLEASE NOTE AND READ – THE ABOVE HYPERLINKS.

These hyperlinks can be used to access more detailed data about battery manufacturers and battery pack assembly companies..

SAFE STORAGE AND HANDLING

In most cases, improper handling and storage, resulting in such problems as overheating and short-circuiting cause damage to batteries. The common safety practices have been outlined below; safety precautions to take with regard to all aspects of battery storage and handling.

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Approved By

Director

Document & Revision No.

JIN-DD-MWD-INDUCTION.MANUAL-01

Reviewed By Date of issue

1. Shelf

Batteries should be stored in their original shipping boxes, if possible, to keep them isolated from each other, preventing external short circuits. Do not store batteries loosely, and do not place batteries on metal surfaces.

2. Temperatures and Environment

Batteries should be stored in a cool, dry, well-ventilated area with an optimal storage temperature range of 0-25_C. If prolonged storage is anticipated, batteries should be protected against excessive humidity. This will prevent moisture from forming an electrical pathway between the feed-through terminal and battery cover, which can lead to severe galvanic corrosion of the feed-through pin, thus compromising the hermeticity of the battery.

3. Hazard Consideration

Lithium battery storage areas should be clearly marked and provided with “Lith-X” fire extinguishing material. Batteries might burst if subjected to excessive heating. In case of fire, only “Lith-X” fire extinguisher should be used, as water will cause exposed lithium to ignite. Signs should clearly state – WATER IS NOT TO BE USED IN CASE OF FIRE.

LITHIUM BATTERY SAFETY MANUAL

The following paragraphs will discuss the safe handling of Lithium Thionyl Chloride (LTC) batteries under the abnormal hazardous conditions of:

1. Leaking or venting batteries, 2. Hot batteries,

3. Exploding batteries, 4. Lithium fires.

Mwd Manual

DIRECTIONAL DRILLING

INDUCTION MANUAL

DIRECTIONAL DRILLING

INDUCTION MANUAL-01

Issue/Revision : JIN-DD-MWD.IND.MANUAL-01

Table of Contents

1. INTRODUCTION

PERSONAL PROTECTIVE EQUIPMENT

TAKE PRIDE IN YOUR WORK AND WHERE YOU WORK!

Work Smart – Work Safe

MWD ENGINEER RESPONSIBILITIES

2. Oil exploration & Drilling

2.1 Forming oil

2.2 Locating Oil

2.3 Oil Drilling Preparation

2.4

Oil Rig Systems

2.5 Testing For Oil

3. Directional Drilling

3.1 Applications of Directional Drilling

3.2 Types of Directional Wells

3.3 Geometry of a Directional Well

4. DRILLING OF DIRECTIONAL WELL

4.1 Bottom Hole Assembly

BIT

MUD

MOTOR

FLOAT

SUB

UBHO

NMDC (x 2)

DRILL

COLLAR

HWDP

DRILL PIPE

4.2 SIZES OF BHA COMPONENT

4.3 PARTS OF A BHA

5. Measurement

5.1 INCLINATION/ AZIMUTH/ MEASURED DEPTH

5.2 True North and Magnetic North

5.3 Earth’s Magnetic Field

6. Measurement While Drilling

6.1 Introduction

6.2 What Is MWD?

6.3 Mud Pulse Telemetry

6.4 MWD Principles

6.5 MWD TOOL Components

It is the up hole end component of the MWD tool. It helps in lowering

down the tool and retrieving the tool when a stuck up takes place.

6.6 MWD STRING

Fig. showing

the

placement of

MWD

6.9 Working of MWD tool







1

2

3

5

6

7

8

1

2

4

9

10















6.10 MWD Tool Retrieval Equipment

6.11 TOOLFACE