S07 Directional Drilling: Optimised Drilling Practices Course

OPTIMISED DRILLING PRACTICES COURSE

S07 Directional Drilling

SECTION OBJECTIVE To understand the importance of directional drilling in today’s wells

Without advanced directional drilling technology, it would not be economical to produce from most offshore and onshore fields

Why Drill Directionally?

Offshore Development

Environmental Sensitivity

Production Enhancement

GREATER ARIAL DRAINAGE MEANS FEWER PLATFORMS/LOCATIONS AND CAN ALSO MEAN FEWER WELLS AND ENHANCED PRODUCTION

ENVIRONMENTAL SENSITIVITY

WYTCH FARM EXTENDED REACH DRILLING

WYTCH FARM EXTENDED REACH WELLS 10 km

8 km 6 km

Poole Harbour

M11

M05 M02

TD Locators Well Sites

M03 M09

TVD, m

Lateral Displacement, KM 0 1000 2000

1 2 13-3/8”

3

4

5

6

7

8 9-5/8”

9

10 7”

EXTENDED REACH DRILLING

PRODUCTION ENHANCEMENT

2005: LCD Phase 1 wells Objective: Rejuvenate oil production- extending field life

Original Gas Cap

Accessing 1-2mmbbl

OGOC LCD well Redundant Production well

Oil Rim Objective: Rejuvenate oil production- extending field life

LCD well 6-7mmGBP 2 year life

10-20m thick

Encroaching Aquifer

Post-4D

PRODUCTION IMPROVEMENTS

Horizontal Wells

SO ! HOW DO WE DO THIS?

WHAT’S IMPORTANT???

THE FIRST THING IS – WHERE’S THE TARGET WRT THE RIG?

Reference Systems and Coordinates Inclination – Angle in degrees between vertical and the wellbore axis

α

Reference Systems and Coordinates Azimuth – Magnetic North – True (Geographic) North – Grid North

Quadrants

Reference Systems and Coordinates

UTM = Universal Transverse Mercator

Greenwhich = 0 deg Meridian

Grid Sector 31U = SNS

GLOBAL MAGNETIC EFFECTS

Dog Leg Severity (DLS) 

DLS is a measure of a combination of angle and azimuth change over a given distance. Either deg/100ft or deg/30m depending on units of measure used.



Great care needs to be exercised in the initial well planning as excessive DLS can result in:-



Additional drilling torque and drag



Excessive and localised casing wear especially if DLS is shallow and well will be deep



Problems running specialist tools in to the well that have large OD 

For deep wells with shallow kick offs DLS is normally restricted to an average of 2.5 – 3 .0 deg. For shallow wells is can be up to 5 deg.

CONE (ELLIPSE) OF UNCERTAINTY 

With all survey methods there is always some built in error. The better quality the survey the better accuracy.



As the well gets deeper the directional company plot the cumulative error. In a vertical hole this is usually a cone. In a directional well it is normally an ellipse.

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It is important to track both for collision issues with other wells and to know uncertainty in the even of a relief well being required.



In some cases on critical wells a gyro survey may be run before entering critical zones.

Ellipse of Uncertainty The tool systems for surveying directional wells have limited accuracy.  The survey may also be subject to errors resulting from downhole changes in the magnetic field, or magnetic interference.  The ellipse represents the variation in position of a given well survey point based on the maximum possible error. 

Directional Drilling Introduction; 

Direction

Depth (TVD)

Directional Drilling is the science of deviating a well bore along a planned course to a subsurface target whose location is a given lateral distance, depth and direction from the surface.

Lateral Distance

33

History and Development

34

Reasons for Directional Wells •

Sidetracking

•

Inaccessible locations

•

Salt domes

35

Reasons for Directional Wells

Fault Controlling Multiple wellbores from one well

Onshore drilling to an offshore location

36

Reasons for Directional Wells Multilateral Wells

Short – Medium and Long Radius Wells

37

Directional Well Types Vertical

Slant (J)

“S”

Horizontal

38

Directional Well Terminology

39

Features of a Directional Drill Profile •

True vertical depth

•

Measured depth

•

Turn rate

•

Build up rate

•

Azimuth

•

Dog Leg Severity (DLS) 40

Features of a Directional Drill Profile

41

Jet Bits

Open Hole Whipstocks Whipstock is held in place by a string stabiliser and bit in the BHA. Some were run on a bolt that was sheared when whipstock sat on bottom. The whole assembly is run in hole, pointed in the correct direction using a gyro and spudded into the bottom of the well. The well is kicked off from the whipstock using a small bit and a pilot hole is drilled. On POOH with the BHA the whipstock is also recovered. A larger bit and a “Bullnose” are then run and the small hole is redrilled using the bullnose to guide the new bit into the old hole.

PDM with Bent Sub Advantages: 

They drill smooth curves.



Dog leg severity is more predictable.



They can be used in most formations.



Compatible with steering tools and mud pulse guidance systems.

Disadvantages: 

Reactive torque makes is difficult to guide especially when using a PDC bit



Rotating the drill string is limited due to large bit offset with a bent sub. Motor housing can be damaged



Poor hole cleaning when sliding



Difficult to drive a PDC bit due to torque stalling the motor



Hard to hold a tool face due to reactive torque with a PDC bit

Steering Tools / Side Entry Sub

49

UBHO (Universal Bottom Hole Orientation) Sub

50

Basic Surveying Tools

Totco



Only measures inclination

Gives two holes as a “check”



Usually dropped down the string and fished, or retrieved on a trip



Anderdrift Vertical Inclination Indicator  



 

Run as part of the BHA; working parts inside a “drill collar”. The tool resets whenever the pump stops. The weighted bob latches into one of the grooves, depending on the inclination. When the pumps start, the inner parts move down causing a number of pressure pulses visible to the Driller on his standpipe gauge. Gives a “free” survey; takes no extra time. Eliminates the risk of fishing a Totco in a vertical well. Only normally used on top hole from floating rigs as a cheap alternative to give inclination only for well head verticality

Magnetic Single Shot  





The magnetic single shot records the magnetic direction (Azimuth) and its inclination from vertical (Inclination) of the openhole part of the wellbore. It can also be used to determine the toolface of a deflection device when deviating the well. The instruments consist of five basic units: – Battery Power Pack – Light bulb timing device or sensor – Camera unit – Compass and Inclinometer unit – Camera Tool Reliability is affected by – Pressure limitations – Temperature limitations (Normally Film limited) – Shock loading

Single shot survey disc

Magnetic Multishot

Camera 

The camera has three main components: – the film seat (the film is disc shaped) – a camera lens – a light bulb

The lens assembly is pre-focused and there are no adjustable parts.  A single shot camera unit has no shutter mechanism. Exposure of the film is controlled by varying the duration of a light bulb.  The biggest factor of error on a single shot tool is the films resolution and how well it is developed. 

Electronic Multi Shot (EMS) 

The EMS instrument provides the same information as the magnetic multi-shot.



It uses a system of magnetometers and accelerometers very similar to the steering tool but is battery operated.

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The tool is programmed on surface, shots are taken at programmed time intervals and stored in memory, data are dumped from the memory and processed when the tool is back on surface after the run.

ROTARY BHA’S

DIRECTIONAL CONTROL WITH ROTARY SYSTEMS

Depends on: 1. Gauge and stabiliser placement 2. Diameter and length of drill collars 3. Weight on bit 4. Rotary speed 5. Bit Type 6. Formation properties – dip, hardness etc 7. Flowrates used 8. ROP

GAUGE & PLACEMENT OF STABILISERS There are three fundamental principles :• FULCRUM PRINCIPLE • STABILISATION PRINCIPLE • PENDULUM PRINCIPLE

WEIG HT

FULCRUM - BUILD FULCRUM PRINCIPLE

PIVOT POINT FULCRUM

SIDE FORCE AT BIT RESULTANT FORCE AT BIT

FULL GAUGE NEAR BIT STABILISER SIDE FORCE AT STABILISER

PACKED – Vertical and Tangent DRILL COLLAR FULL GAUGE STRING STABILISER

STABILISATION PRINCIPLE

FULL GAUGE NB STABILISER

C

B B A

DRILL COLLAR FULL GAUGE STRING STABILISER

B

SHORT DRILL COLLAR

BIT

A A

PACKED ASSEMBLY FORCES BIT TO DRILL A REASONABLY STRAIGHT HOLE

PENDULUM - DROP PENDULUM PRINCIPLE FULL GAUGE STRING STABILISER DRILL COLLAR FULL GAUGE STRING STABILISER DRILL COLLAR

BIT WOB

WEIGH T EXCESSIVE WOB MAY CAUSE BUILD

VARIABLE GAUGE STABILISERS These tools enable a rotary assembly to behave in a manner dependent on the stabiliser gauge status i.e. whether full or under gauge.

PLACEMENT WILL DEPEND ON REQUIREMENTS

DRILL COLLARS FACTORS THAT WILL INFLUENCE DIRECTION CHANGE: • OUTSIDE DIAMETER • WEIGHT • LENGTH BETWEEN STABILISERS

Drill Bits and Their Effect on Rotary Assemblies Roller Cone Bits: 

Tendency to walk right.



Long tooth bits in soft to medium formation have greater walk



Short tooth in hard formation have less walk.



Higher rotary speed needed, less life on bearings of bit.

68

Drill Bits and Their Effect on Rotary Assemblies PDC Bits:  Almost no walk Tendency.  Long gauge PDCs hold inclination and hole direction.  Short gauge PDCs sometimes can build better than cone bits. Also used on the pendulum assemblies.  Higher rotary speed and low WOB could affect build rate.  Creates high rotary surface torque. 69

FORMATION ANISOTROPY DIP ANGLE =

UNEQUAL CHIP VOLUMES

< 45o up dip > 45o down dip

Fd 500 Up0 dip 250 0 Fd Deviation 0 force (N) 250 Down0 dip 500

1 5

3 0

4 5

6 0

7 0

100 0 500 0 Fd Deviation 500force (lbs) 100 0

BIT WALK TENDENCIES Direction required is right of down dip direction.

Direction required is left of down dip direction.

Bit tends to walk left

Direction required is left of up dip direction.

Direction required is right of up dip direction.

Bit tends to walk right

Greater than 45o down dip

Less than 45o up Bit tends to walk Bit tends to walk right left dip

MOTORS

DOWNHOLE MOTORS POSITIVE DISPLACEMENT MOTORS (PDM’s) ADVANTAGES :• • • • • •

Elimination of lateral vibration String and casing wear reduced Lower torque in string, especially in deviated holes Reduced fatigue loads on drill pipe Can be run with light weight at continuous speeds The ability to orient and drill ahead.

DOWNHOLE MOTORS DISADVANTAGES :• • • • • •

Can deliver large localised dog legs Can under cut hole in soft formations if reaming done Can lead to an unplanned side track if reaming in soft formation with no rotation Leads to poor hole cleaning in long slide sections Can hang up with wall friction in long deviated holes making it difficult to slide With the wrong motor it can stall out when using aggressive PDC bits due to torque generation

POSITIVE DISPLACEMENT MOTORS

STATOR

By varying the number of lobes on the rotor/stator the motor can deliver high speed/low torque or low speed/high torque

This needs to be matched to bit and formations to be drilled

ROTOR

Steerable Mud Motors

77

1980’S - STEERABLE MOTORS

• Bend closer to the bit reduces bit offset. • After kick-off, drill tangents, adjust trajectory without POOH.

DRILLING WITH A STEERABLE MOTOR

Mud Motor Bent Housing Stabilizer Bit

OPERATION OF A STEERABLE MOTOR Sliding

Changing Trajectory (Sliding) • Drill-string Rotation Stopped • Bit pointed in desired direction • Interval drilled without drill-string rotation

Tangent Sections (Rotating) • Drill-string rotated continuously • Stabilization may provide inclination control • Rotary speed has to be reduced as motor angle increases or can lead to fatigue failure of motor housing

Rotating

BIT TILT

MOTOR ASSEMBLY

BENT SUB

ADJUSTABLE BENT HOUSING

TILT AXIS

MOTOR ASSEMBLY

TILT AXIS

ROTARY STEERABLE SYSTEM (RSS)

1. 2. 3. 4. 5. 6. 7.

Continuous drillstring rotation No reduction in ROP while sliding Better hole cleaning Fewer wiper trips Optimized drilling parameters Optimized bit cutting structure Higher overall ROP

RSS Borehole Quality Smooth profile Increased drilling radius Good gauge No spiraling Reduced cuttings beds

Improved drilling efficiency 98 m/day with PDM 193 m/day with RSS U and W shaped wells, up to 144° inc

With a Mud Motor - Micro doglegs in excess of 14 °/100’ With a RSS  - Micro doglegs Typically less than 2 °/100’

87

ROTARY STEERABLE SYSTEM 1. Technology leap via Rotary Closed Loop Drilling Systems 2. Improved reservoir development = fewer wells / platforms 3. Can boost production while delivering significant cost savings in field development

Schlumberger Powerdrive

Pad out

Pad in

Push the bit technology 89

Schlumberger Powerdrive

90

Powerdrive Video

91

HALLIBURTON GEOPILOT

Point the bit technology

Applied side force – BHI-AutoTrak A non rotating sleeve is used to reference and to position pads. Side force is used to move bit from its center line. Point the Bit

93

Baker Hughes “Autotrak” tool and path drilled

94

Geosteering Assemblies

96

BIG BENEFITS 1. Ensure optimal entry into the reservoir 2. Navigate within the bounds of the reservoir 3. Predict exit from the reservoir

EXAMPLE OF GEOSTEERING

Directional Resitivity

Resistivity

Gamma

Poor quality reservoir Planned 7” Shoe

Actual Poor quality reservoir

TD

98

LWD Tool

100

Sonic Tool LWD

101

MWD/LWD Mud Pulse Telemetry Pressure spikes sent through liquid drilling fluids. Positive Pulse Negative Pulse Continuous wave tools - The information is contained in the phase variation of this wave, and not the amplitude. May have to restrict ROP to accommodate data rate Sends surveys/data on command – pumps off/still pipe Slow Data Transfer rate Does not work well with Heavy Viscous muds Does not work well with UBD Drilling Fluids Sometimes hard to downlink data to RSS/MWD/LWD 102

Schlumberger War Room Onshore real time monitoring

103

Schlumberger War Room

104

SHOCK AWARENESS • With all this new technology down hole shock are the biggest cause of failures. With MWD/LWD tools shocks can be monitored at surface and acted on by the Directional Driller to prevent premature tool failure.

Bit Bounce

Whirl

Stick Slip

Axial Vibration

Lateral Vibration

Torsional Vibration 105

106

VIBRATIONS • Vibration is defined as “movement to and fro” • Some vibration while drilling is inevitable • Vibration is worse when systems are excited at their natural frequency (which is governed by mass and stiffness) • Vibration at the natural frequency of a system can often lead to resonance which can have catastrophic effects……

107

Excessive vibration can cause… 

Catastrophic drill string failure e.g. twist off



MWD / motor / rotary steerable damage or failure



Hole enlargement



Premature bit wear and failure



Reduce rate of penetration



Increased overall cost of well

…………Basically inefficient drilling. Any energy going into vibration is not going into drilling! 

108

EXAMPLE VIBRATION LOG •

3 hours showing repeated occurrence of increasing vibration levels

•

Rig crew reducing SWOB to address problem

•

Need to reduce the duration and number of occurrences of excessive vibration

109

SCHLUMBERGER VIBRATION MONITORING Non-IWOB (Integrated Weight on Bit) Collar • Measurements: • Peak to peak MWD RPM • Shock (Two available settings) 1. cps: (counts per sec) = number of shocks >50 G per sec 2. Peak: In this mode, tool sends up largest shock and “shock risk” (from level 0 to 3) IWOB Collar • Measurements: As per non-IWOB collar, plus… • Torsional vibration MVC (Multi Vibration Cartridge) • Measurements: • Axial shocks • Lateral shocks

110

Gyro While Drilling Gyro While Drilling (GWD) has now been available for some time. This allows top hole drilling of multi wells with out the need to keep stopping to take wireline gyro surveys. It is still expensive so its value needs to be evaluated per application

111

Current Directional Drilling Technology Limits 

Al Shaheen Field Offshore Qatar for Maersk Oil – April 2008 Longest Extended Reach well 40,320 ft (12,289m md). Lateral reach 35,770 ft (10,902m). Longest 8 ½” Section and Open Hole section - 35,449ft (10,804m)



Deepest MWD/LWD downlink 40,320ft (12,289m) kept wellbore within a 3ft sweet spot of the 10ft thick reservoir for 95% of the open hole section.



Shortest measured length from vertical to horizontal 35 feet TVD. (SPE 35244-PA)

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So, what have we learnt?

DISCUSSION TIME