Workshop on Directional Drilling in Rocky Mountain Region
64
University of Colorado Law School University of Colorado Law School Colorado Law Scholarly Commons Colorado Law Scholarly Commons Workshop on Directional Drilling in the Rocky Mountain Region (November 13) 2003 11-13-2003 SLIDES: Directional Drilling: The Promise and the Peril SLIDES: Directional Drilling: The Promise and the Peril Alfred W. Eustes III Follow this and additional works at: https://scholar.law.colorado.edu/workshop-on-directional-drilling- rocky-mountain-region Part of the Energy and Utilities Law Commons, Energy Policy Commons, Environmental Health and Protection Commons, Environmental Law Commons, Environmental Policy Commons, Hydraulic Engineering Commons, Natural Resource Economics Commons, Natural Resources Law Commons, Natural Resources Management and Policy Commons, Oil, Gas, and Mineral Law Commons, Property Law and Real Estate Commons, Science and Technology Law Commons, and the State and Local Government Law Commons Citation Information Citation Information Eustes III, Alfred W., "SLIDES: Directional Drilling: The Promise and the Peril" (2003). Workshop on Directional Drilling in the Rocky Mountain Region (November 13). https://scholar.law.colorado.edu/workshop-on-directional-drilling-rocky-mountain-region/2 Reproduced with permission of the Getches-Wilkinson Center for Natural Resources, Energy, and the Environment (formerly the Natural Resources Law Center) at the University of Colorado Law School.
Transcript of Workshop on Directional Drilling in Rocky Mountain Region
University of Colorado Law School University of Colorado Law School
Colorado Law Scholarly Commons Colorado Law Scholarly Commons
Workshop on Directional Drilling in the Rocky Mountain Region (November 13) 2003
11-13-2003
SLIDES: Directional Drilling: The Promise and the Peril SLIDES: Directional Drilling: The Promise and the Peril
Alfred W. Eustes III
Follow this and additional works at: https://scholar.law.colorado.edu/workshop-on-directional-drilling-
rocky-mountain-region
Part of the Energy and Utilities Law Commons, Energy Policy Commons, Environmental Health and
Protection Commons, Environmental Law Commons, Environmental Policy Commons, Hydraulic
Engineering Commons, Natural Resource Economics Commons, Natural Resources Law Commons,
Natural Resources Management and Policy Commons, Oil, Gas, and Mineral Law Commons, Property Law
and Real Estate Commons, Science and Technology Law Commons, and the State and Local Government
Law Commons
Citation Information Citation Information Eustes III, Alfred W., "SLIDES: Directional Drilling: The Promise and the Peril" (2003). Workshop on Directional Drilling in the Rocky Mountain Region (November 13). https://scholar.law.colorado.edu/workshop-on-directional-drilling-rocky-mountain-region/2
Reproduced with permission of the Getches-Wilkinson Center for Natural Resources, Energy, and the Environment (formerly the Natural Resources Law Center) at the University of Colorado Law School.
Directional DrillingThe Promise and the Peril
Alfred W. Eustes III, Ph.D., P.E.Department of Petroleum Engineering
Colorado School of MinesGolden, Colorado
Some of the material presented in this course is courtesy of the following:
Colorado School of MinesSchlumberger AnadrillBaker Hughes Inteq
Weatherford InternationalParker Drilling
Will Fleckenstein, Ph.D.
All copyrights reserved by individual copyright owners and are not to be copied without written consent of individual copyright holders.
3
Directional Drilling
• The art and science of drilling a wellbore along a predetermined trajectory.
• The tools and techniques used are determined by the complexity of the well path and the desired precision of the attempt to follow that trajectory.
4
Relief wells
Presenter
Presentation Notes
Directional techniques are used to drill relief wells in order to “kill” blowout wells. The relief well is deviated to pass as close as possible to the uncontrolled well in the reservoir. Heavy mud is pumped into the reservoir to overcome the pressure and bring the wild well under control.
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Controlling vertical wells
Original Well PathCorrected Well Path
Presenter
Presentation Notes
Directional techniques are used to “straighten crooked holes”. In other words, when deviation occurs in a well which is supposed to be vertical, various techniques are used to bring the well back to vertical. This was one of the earliest applications of directional drilling.
6
Sidetracking
Original Well PathCorrected Well Path
Original Well Path
Original Well PathSidetrack
Sidetrack
Presenter
Presentation Notes
Sidetracking out of an existing wellbore is another application of directional drilling. This sidetracking may be done to bypass an obstruction ( a “fish”) in the original wellbore or to explore the extent of the producing zone in a certain sector of a field.
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Inaccessible locations
Presenter
Presentation Notes
Directional wells are often drilled because the surface location directly above the reservoir is inaccessible, either because of natural or man-made obstacles. Examples include reservoirs under cities, mountains and, lakes.
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Fault drilling
Presenter
Presentation Notes
Directional drilling is also applicable in fault drilling. It is sometimes difficult to drill a vertical well in an inclined fault plane. Often, the bit will deflect when passing through the fault plane, and sometimes the bit will follow the fault plane. To avoid this problem, the well can be drilled on the “up dip” or “down dip” side of the fault and deflected into the producing formation.
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Re-entry/Multi-lateral wells
Presenter
Presentation Notes
Re-entry and Multi-lateral drilling employs the full range of directional drilling tools and techniques. Including planning, wellbore engineering, and careful consideration of the numerous aspects of drilling straight and deviated holes. Well configurations can include dual stacked, dual opposing, dual opposing stacked, spokes, lateral tie-back, and herringbone.
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Short radius drains 61¹4 in. – 4 1¹4 in.
Original wellMedium radiusrequires completionin shale 7- or 5-in. line
Reentering Existing Wells
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Designer Wells
12
Reference Systems and Coordinates
• Depth Reference– True Vertical Depth
(TVD)• Pressure calculations
– Measured Depth (MD)• Volume calculations• Geolograph
• Reference Points– Ground level (GL)– Rotary kelly bushing
(RKB)– Rotary table (RT)– Rig floor (RF)
True Vertical Depth Measured Depth
Along Hole Path
Presenter
Presentation Notes
Measured Depth (MD) or “Along Hole Path” is the distance measured along the actual course of the wellbore from the surface reference point to the survey point. This depth is always measured in some way, e.g., pipe tally or wireline depth counter. True Vertical Depth (TVD) is the vertical distance from the depth reference level to a point on the borehole course. In most drilling operations the rotary table (RT) elevation is used as the working depth reference (BRT or RKB). This is also referred to as derrick floor elevation. For floating drilling rigs the rotary table elevation is not fixed; hence, a mean rotary table elevation has to be used.
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Inclination
• Inclination (Drift) – The angle (in degrees)
between the local vertical (local gravity vector as indicated by a plumb bob) and the tangent to the well bore axis at a particular point.
– By oilfield convention, 0°is vertical and 90° is horizontal.
Drift - Degrees from Vertical to High Side(Vertical Plane)
3030°
3° 10°
Presenter
Presentation Notes
The inclination of a borehole at a point is the angle between the borehole axis and vertical. Pendulums and accelerometers can be used to measure the earth’s local gravitational direction. Pendulum technology is found in the mature product offerings (single- and multi-shots). This technology is limited in accuracy and resolution. Advanced survey systems take advantage of accelerometers to measure the earth’s gravitational pull. Each accelerometer consists of a magnetic mass (similar to a pendulum) suspended in an electromagnetic field. Gravity deflects the mass from its null position. Sufficient 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.
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Azimuth
• Azimuth (hole direction)– The azimuth of a borehole
at a point is the direction of the borehole on the horizontal plane, measured as a clockwise angle (0°- 360°) from the North reference.
– All magnetic tools give readings referenced to magnetic north; however, the final calculated coordinates are referenced to either true north or grid north.
Azimuth - Degrees from North to High Side (Horizontal Plane)
N
S AzimuthW E
Presenter
Presentation Notes
The azimuth of a borehole at a point is the direction of the borehole on the horizontal plane, measured as a clockwise angle (0°- 360°) from the North reference. Azimuth is calculated from measurements of the earth’s local magnetic field. Compasses and magnetometers can be used to measure the earth’s local magnetic field. Compasses are low in accuracy and resolution, and not well suited to a drilling environment. Magnetometers offer enhanced accuracy in areas free of magnetic interference, and are robust enough for drilling operations. Each magnetometer device consists 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 therefor cancel each other 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 imbalance 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 a precise determination of the direction and magnitude of the local magnetic field relative to the magnetometer’s orientation in the borehole.
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Target Area
Target
Driller: relative to borehole directionGeological: relative to geology
Bigger is easier to hit
Presenter
Presentation Notes
The target is specified by the Geologist, who will not merely define a certain point as the target but also specify the acceptable tolerance, e.g., a circle of radius 100 feet having the exact target as its center. A target zone should be selected as large as possible to achieve the objective. If multiple zones are to be penetrated, the multiple targets should be selected so that the planned pattern is reasonable and can be achieved without causing excessive drilling problems.
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Radius Definitions
300 - 3000 ft
1500 - 4000 ft2000 - 6000 ft
40 - 70°/100 ft140 - 82 ft radii
3000 - 1000 ft radii
LongRadius
MediumRadius
IntermediateRadius(Flex Motors)
2° - 6° /100 ft
1000 - 140 ft radii6° - 40° /100 ft
300 - 1000 ft
70 - 150°/100 ft82 - 40 ft radiiShort Radius
(ArticulatedMotors)
Presenter
Presentation Notes
This slide shows how the new term INTERMEDIATE radius is pulled from a segmentation of the traditional short radius into rotatable and slide only segments and by reaching up in radius to the tight (low) side of medium radius. The basic break point between short and intermediate radius is 82 feet, which also corresponds to the extreme low side of radius which is curently considered to be rotable with special management of pipe fatigue damage. Radius less than 82 feet is still considered the realm of short radius articulated motors and slide drill only. Consequently, lateral length of short radius is less than intermediate radius and ranges from 500 to 1500 feet depending upon sliding friction limits in the hole.
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Build and Hold (Slant)
Kick off Point (KOP)
Build Section
Top of Slant Slant
Target
Presenter
Presentation Notes
Features: - Shallow kick-off point (KOP) - Build-up section (may have more than one build up rate) - Tangent section Applications: - Deep wells with large horizontal displacements - Moderately deep wells with moderate horizontal displacement where intermediate� casing is not required
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“S” Type Well (Build and Drop)
Kick off Point (KOP)Build Section
Top of SlantSlant (Tangent)
Target
Top of Drop
Drop Section
Hang
Slant Angle
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Horizontal (Single)
Kick off Point (KOP)
Build Section
Target
Reach
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Wall Force
• Force of tool joint against borehole wall• According to A. Lubinski,
– Keep WF less than 2,000 lbf in water based muds– Keep WF less than 3,000 lbf in non-aqueous based
muds• Problems from wall contact
– Casing wear– Drill pipe wear– Fatigue failure– Keyseating
2 sin2
length of joint
j
j
LWF T DLS
L
=
=
21
Survey Techniques
• Find inclination and azimuth at various points along the wellbore
• Usually get– Inclination (from vertical)– Azimuth (from north)– Measured depth (from RKB, GL, etc.)
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Surveying Data Gathering Techniques
• Simple drift • Photographic film
– disks / strip
• Memory modules– multi-shot / MWD
• Wireline– surface readout
• Mud pulse telemetry– MWD
Presenter
Presentation Notes
Photographic film is similar to that used in your regular camera. Once the image has been taken down hole, the tool has to be retrieved, and the image processed such that it can be manually interpreted. Memory modules allow for data to be stored in the tool. This information has to be associated to time/depth, such that when it is downloaded at the surface it can be correlated to the wellbore path and orientation. It can be used in a multi-shot service or as a backup (in some cases with higher data density) to MWD data. Wireline systems allow surface readout of the tool’s parameters during the drilling/orientation process. Obvious drawbacks are that you cannot rotate the drillstring, and it is not the preferred situation for well control (BOP operation, split bushings, ability to circulate), but the main advantage is an instantaneous look at the BHA’s position and orientation. Mud Pulse Telemetry provides real time data during the drilling/orientation process. It is only available for magnetic, dynamic, and formation evaluation sensors (no gyro). This system overcomes the limitations of wireline.
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Simple Drift
• Every rig has a simple drift• Only measures inclination
– No azimuth information
• Sometimes dropped right before a trip• Sometimes run on slick line• Operates on a pendulum
– Timer– Punches paper disk (twice at 180° separation)
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Magnetic Single-Shot
• Function– Provides photographic
record of inclination, direction and toolface orientation at a single point in the open hole section of the well
• Limitations– Requires non-magnetic
drill collars– Temperature– Must re-run to confirm
changes in toolface
Presenter
Presentation Notes
Magnetic survey instruments use a magnetic compass to measure the direction of a wellbore in relation to magnetic north. Magnetic instruments determine both direction and inclination using a plumb bob or drift arc that is designed to seek the low side of the hole. To measure inclination and direction, the instrument camera photographs the attitude of the plumb bob in reference to a calibrated angle indicator and in reference to a compass. These parameters and the measured depth of the survey station are used to calculate the well’s position. Single-Shot surveys, which photograph the instrument at a single position, are often used by the directional driller to track the bit’s progress while drilling is underway. The compass unit of a magnetic survey instrument is placed in a non-magnetic drill collar (NMDC) to isolate the compass from the drillstring’s magnetic interference. Placement of the instrument within the NMDC varies with the wellbore attitude, latitude, and the bottomhole assembly. Magnetic survey directional readings also must be adjusted for the difference between local magnetic North and True North or Grid North. The amount of correction varies geographically and with time. Baker Hughes INTEQ offering == SS (Single-Shot)
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Electronic Multi-Shot
• Function– Records inclination,
direction and toolface– Records raw magnetic
and gravity field data– All data electronically
measured and recorded
• Limitations– Needs non-magnetic drill
collars– Temperature
Presenter
Presentation Notes
The electronic multi-shot makes use of some of the latest technology in downhole magnetic surveying, achieving new standards of magnetic survey accuracy using tri-axial accelerometers and magnetometers to measure a variety of downhole parameters. In addition to hole inclination and direction, it also calculates the magnetic dip angle and field strength at each survey station. These values are used to determine downhole magnetic interference, providing a good measure of survey validity. In addition, the probe measures downhole temperature and is modeled for a range from 32° to 302°F (0° to 150°C). The system is armed at the surface, then run like a standard multi-shot. The tool can be programmed for either the single-shot, multi-shot or core orientation mode, with variable delay times and station intervals set at the surface. Survey data for as many as 1023 data points can be stored. Surface equipment includes a system printer and a rugged portable computer which processes results. Following the survey, the tool is reconnected to the system computer, which processes the data and generates a survey report at rigsite. Because it uses an electronic memory to store survey data, the system eliminates many of the error sources associated with camera-based systems, such as data entry error, or misinterpretation of data. Baker Hughes INTEQ offering == EMS (Electronic Magnetic Surveyor)
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MWD/LWD Measurements
• Inclination aka: drift, slant, angle• Azimuth aka: direction, compass heading
– Gravitational and magnetic field sensitivity– Magnetic dip angle
• Drilling operating parameters– Torque– Weight on Bit (WOB)– Pressure
• Tool face orientation (which way is the bit pointed)• Sensor temperature• Formation evaluation measurements
– Gamma Ray, resistivity, density, neutron, sonic, pressure
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Geosteering
• A technique used to direct a wellbore path– in terms of geologic
features– not in terms of simple
geometric constraints
• Requires close cooperation of geologist and drilling engineer
• Use of LWD and MWD helps determine a path through a formation while drilling
• To apply, need to have:– Knowledge of log
response of formation(s)– Experienced personnel– Good MWD and LWD
equipment
• Useful in– Reservoirs that are thin
and/or complex– Medium to short radius
horizontal wells
28
Survey Errors
• Two types– Systemic – regularly
occurring and are not compensating
– Random – irregularly occurring
• Reading errors• Mechanical malfunctions• Calibration errors• Instrument alignment• Drillstring measurement• Inherent math
approximations• Natural magnetic interference• Hot spots• Numerical calculations and
data recording• Gyroscopes
– Drift– Precession– Orientation
29
Station Errors
No
rth
Horizontal View
TV
D
Section View
MeasuredDepth
Probability distributions
2-sigma ellipsoid
30
Ellipsoid of Uncertainty
East
South
Dep
th
Wellbore Path
1
2Ellipse of
uncertaintyaround each
survey station
Expanding coneof uncertainty
31
Target vs Ellipse of Uncertainty
Target
Ellipse ofUncertainty
WellboreTrajectory
32
Continuous Inclination & Azimuth
33
Spider Plot (Platform Hogan)
About 5,000’
34
Anti-collision
• Major versus minor risk– Major – significant risk to people and environment– Minor – negligible risk
• Wellbore may have multiple risks• Separation based on company rules (10 m)• Anti-collision diagram
– Traveling cylinder plot with tolerance lines– Preplanned trajectory
• Used in the field– Don’t cross the tolerance line
35
Drive Sub(Bit Box)
BearingAssembly
DeflectionDevice
Stator
Drive Sub Universal Joint Assembly
Rotor
1 Stage a) Mono Lobeb) Multi Lobe
Positive Displacement Motor
Presenter
Presentation Notes
The positive displacement (PDM) downhole motor is powered by the circulating fluid to provide rotation and torque to the bit without the need for rotation of the drill string. It is a simple and rugged drilling tool. The PDM consists of four basic components: * By-Pass Valve * Power module (rotor and stator) * Universal joint assembly/deflection device (transmission element) * Bearing assembly with drive sub PDMs operate effectively with all types of drilling mediums, at any mud weight, including water, salt water, oil-base, oil emulsion, fluids with high viscosity or which contain lost circulation material and compressible fluids. The motor design is modular in construction. Depending on the required application the various modular assemblies (PDM systems differ mainly in the power module) can be modified or replaced enabling motor geometry to be constructed for specific applications.
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Stator(Elastomer)
Rotor
Fluid Flow
Direction Of Rotation
Universal Joint
PDM - Fluid Flow Path
Presenter
Presentation Notes
A PDM power module consists of an elastomer molded stator with a spiral shaped chamber and a helicoidal profile steel rotor coated with a special hardfacing to reduce wear and avoid corrosion. A continuous seal is formed between the elastomer of the stator and the coated surface of the rotor. As the drilling fluid is pumped through the motor, it fills the cavities between the dissimilar shapes of the rotor and stator, displacing the rotor. The resulting motion is transferred through the bearing assembly to the drive sub, delivering rotation and torque at the bit. The rotational SPEED (angular velocity) of the rotor is proportional to the drilling fluid FLOW rate through the motor cavities. The TORQUE generated is proportional to the drilling fluid PRESSURE DROP across the power module, and is typically a function of the weight on bit (WOB). Increasing weight on bit will create more torque and thereby increase differential pressure across the power module until the motor stalls, so an increase in WOB usually causes an increase in pump pressure. By adjusting the bit speed and torque to changing downhole conditions, the driller can enhance bit life and optimize penetration rates.
37
Short Radius: Drilling the Curve
Flexible Fixed Bend Motor Articulated Motor
38
Rotary Steerable Systems
Direct Side Forcei.e. Push the Bit
Bit Tilt without Side Forcei.e. Point the Bit
39
Whipstock
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Technology Overview
Long ShortMedium
Build Rate (deg./100’, deg/30m)
Curvature
Tool Type
Pipe Rotation
Completions
MWD Type
M1XL Motors
M1X MotorsArticulated Motors
Collar
Conventional
Slide Drill - No Rotation
Composites
Conventional - No Restrictions
Special
M1XI Motors
Project Specific
Intermediate6 40 72
1000300
14043
8025
Radius (ft.)Radius (m)
Probe(Primary Application)
Flexible (Primary Application)(Secondary Application)
Premium - Limited Rotation
150
4012
Presenter
Presentation Notes
This slide shows the four main areas of a horizontal drilling project design that are affected by borehole curvature. The blended areas represent the curvatures at which technologies overlap. Tool Type Conventional Rotary, Steerable motors up to 6º/100’ Fixed bend, adjustable , and specialized flexible tools up to 40º/100’ Articulated (Short Radius) motors up to 150º/100’ MWD Type Collar type tools up to 12º/100’ Probe based tools up to 30º/100’ Flexible articulated tools up to 150º/100’ Pipe Rotation Conventional tubulars, unlimited rotation up to 26º/100’ Premium tubulars, limited rotation up to 70º/100’ Slide drill only to 150º/100’ (rotation of composites under consideration) Completions Use of conventional equipment up to 30º/100’ Special design considerations up to 80º/100’ Project specific design up to 150º/100’
41
Technology Overview
Long ShortMedium
Build Rate (deg./100’, deg/30m)
Curvature
Tool Type
Pipe Rotation
Completions
MWD Type
M1XL Motors
M1X MotorsArticulated Motors
Collar
Conventional
Slide Drill - No Rotation
Composites
Conventional - No Restrictions
Special
M1XI Motors
Project Specific
Intermediate6 40 72
1000300
14043
8025
Radius (ft.)Radius (m)
Probe(Primary Application)
Flexible (Primary Application)(Secondary Application)
Premium - Limited Rotation
150
4012
$ $$$
Presenter
Presentation Notes
This slide shows the four main areas of a horizontal drilling project design that are affected by borehole curvature. The blended areas represent the curvatures at which technologies overlap. Tool Type Conventional Rotary, Steerable motors up to 6º/100’ Fixed bend, adjustable , and specialized flexible tools up to 40º/100’ Articulated (Short Radius) motors up to 150º/100’ MWD Type Collar type tools up to 12º/100’ Probe based tools up to 30º/100’ Flexible articulated tools up to 150º/100’ Pipe Rotation Conventional tubulars, unlimited rotation up to 26º/100’ Premium tubulars, limited rotation up to 70º/100’ Slide drill only to 150º/100’ (rotation of composites under consideration) Completions Use of conventional equipment up to 30º/100’ Special design considerations up to 80º/100’ Project specific design up to 150º/100’
42
Side Force and Tilt Angle
Bit Tilt Angle
Side Force at Bit
Hole Gauge
Resultant Force at Bit
Hole Axis
Side Force at Stabilizer
Formation Anisotropy
43
Dip Angle and Deviation Force
30°
35° 35° 35°
35°
Hole Inclination = 30°
Real Dip Angle = 35°
Effective Dip Angle = 30°+35°=65°
There will be a down-dip deviation force
Hole Inclination = 0°
Effective Dip Angle = 35°
There will be a up-dip deviation force
Hole Inclination = 35°
Real Dip Angle = 35°
Effective Dip Angle = 0°
There will be no deviation force
Asymmetric rock failure still deviates borehole.
Presenter
Presentation Notes
There are a few points concerning the effect of rock hardness on directional behavior which should be mentioned. In very soft formations, the formation may be eroded by the drilling fluid exiting from the bit nozzles creating an overgauge hole. This can make it difficult to build angle, even with a strong build assembly. If this problem is anticipated, then fairly large nozzels should be fitted in the bit. If it occurs while drilling, then the pump rate should be reduced and prior to making each connection, increase the flow rate to clean the hole with the bit one joint off bottom. Hole washing or enlargement in soft formations may also cause packed assemblies to give a dropping tendency at high inclinations. This may be counteracted by increasing WOB and reducing flow rate. BHAs tend to respond more closely to their theoretical behavior in harder formations. This is mainly because the hole is more likely to be correct gauge. In medium to hard formations, building assemblies are more responsive as maximum bit weight may be applied to produce the required build. The main directional problem encountered in hard formations is getting a pendulum assembly to drop angle. Generally speaking the harder the formation, the longer it takes a dropping assembly to respond. There may also be a conflict between the need to reduce WOB to get the dropping trend established and the need for high WOB to maintain an acceptable ROP.
44
Oriented Mode (Slide)
Wellbore Trajectory
– Controlled curvature
– Controlled direction
– No drill string rotation
Presenter
Presentation Notes
When operated in the oriented mode, steerable motors drill a well path with controlled curvature and direction. Steerable motors when oriented initiate or propagate wellpath deflection due to the effect of the u-joint housing/AKO tilt on the bit attitude.
45
Rotary Mode
Wellpath
– Behavior same as arotary drilling assembly
– Hole slightly over size
Presenter
Presentation Notes
When steerable motors are operated in the rotary mode, the motor drills with the behavior of a rotary drilling assembly. Steerable motors are made to drill a straight course by rotation of the drill string, which negates the bit tilt or bit side force. Extended rotation of steerable motors is made possible by concentric stabilization of the bearing housing and motor top-end locations, as well as the relatively low tilt angle. Two additional BHA design considerations will have significant effect on steerable motor dogleg development. By reducing the diameter of the motor top-end string stabilizer, the build rate capability of the motor can be enhanced and an angle-build tendency in the rotary mode can be developed. Similarly, movement of the motor top-end stabilizer to a higher position will generally reduce dogleg capabilities, although this tendency will eventually be offset by drilling assembly deflection between bearing housing and motor top-end stabilization. The normal mode of operation through intervals of significant angle change is an alternation of oriented and rotary footage. After establishing actual dogleg development performance, the course length of oriented “sets” is controlled such that oriented drilling is minimized. Typically, course lengths for oriented sets are 15-90 ft (4.6-27.7#m), depending on required DLS and formation characteristics.
46
Influences on Direction
(a) (c)(b)
Stabilizer
(d)
47
Torque and Drag
• Higher with– Any directional
change– Undulations (mini-
doglegs)– Thick mud cake– Ledges– Non-lubricating mud– Cuttings beds– Swelling formations
• Affects– Available WOB– Available TOB– Margin of overpull
• Changes with– Running in the hole– Pulling out of the
hole– Sliding
• Axial drag• Lock up
– Rotation
48
Torque and Drag Example
49
Buckling
• Load starts bending the pipe• When load reaches critical point, buckling
starts• Starts as sinusoidal shape laying on bottom of
borehole• More load starts the pipe snaking up the sides
of the borehole• Eventually, pipe winds into a helical shape
(spring shaped)• Lock up occurs
50
Mud Weights for Directional Drilling
Mud Weight Increasing >
Dev
iatio
n In
crea
sing
>
Hole Collapse Fracturing
Unstable
51
Cuttings Beds
52
Drill Pipe Stress
53
Cementing Issues
• Annular settling– Free water on highside
• Centralization– Difficult to achieve
• Reciprocation– May not be possible
54
Directional Drilling Planning
• Surface coordinates– Latitude and longitude– Local grid coordinates
• Target– TVD– Boundaries
• Limitations– Lease lines– Other wellbores
• Hole and casing sizes• Casing points• KOP• Maximum build and drop
rates
• Geology• Mud weights and type• Offset information
– Directional performance of BHA
– Dips• Geological sequence• Rig information
– Drill string– Mud Pumps– Mast strength
• Well profile• Offset histories
55
Wellbore Profile
• S-profile more difficult than slant profile– More hole to be
drilled– Drop off restricts
WOB and rate of penetration (ROP)
– Not as responsive to directional control
– More drag
• S-profile used when:– Intermediate targets– Wellbore must be
vertical in reservoir
56
Horizontal Drilling
• Any 90° hole• Technology has
caught up with idea• Continuous
improvements– Directional control– Reduced costs
• Utilizes– Geosteering– MWD and LWD– Underbalanced
drilling
• Reservoir analysis techniques are starting to catch up with drilling technology
57
Requirements for Horizontal Boreholes
• Hit the target• Smooth turns and builds for long reach• Gauge borehole for problem-free drilling• Minimal formation damage• Reasonable cost
58
Approaches to Horizontal Drilling
59
Multilateral Drilling
• Multilateral wells– Single trunk– Multiple laterals (sometimes called branches or drainholes)– Can be vertical, horizontal, or deviated
• Able to reach multiple targets in same formation• Laterals can be completed separately• Large drainage area for small environmental footprint• Difficult to operate
– Operations– Stimulation– Production
• Potentially expensive
60
Extended Reach Drilling
1 Mile Deep
61
Extended Reach Drilling
• Long near-horizontal borehole
• Useful for environmentally sensitive areas– BP at UK Wytch Farm
field– Up to 10 kilometers
(6.2 miles)• Only one location
– Minimizes rig footprints
• Issues– Torque limitations– Hole instabilities– Cuttings transport– Not horizontal– Cannot slide– Equivalent circulating
density (ECD) high– Casing running
• Floated?
– Swab and surge
62
Directional Drilling Costs
• Additional costs for directional drilling equipment– Mud motor, MWD, people, etc. $10,000/day
• Rig may need to be larger making for a larger location– Larger mud pumps, need more flow
• Casing and tubing design– Ovality and bending stress
• Additional mud cost and solids control equipment– Mud weight is usually higher– Cuttings bed development
• Additional borehole risk– Tectonic stress directions
• Slower ROP, more time on location• Torque and drag higher
Thank you.
Any Questions?
