METHODS OF DEFLECTING A WELLBORE con't 3

Downhole Motor

• Turbodrills have been around for many years but are seldom used for directional drilling 

• Turbodrills have very high rotary speeds (500 to 1200 rpm)  

• Because of the high rpm, bit life is limited
• Diamond and PDC bits are more applicable to turbodrills
• Turbodrills have low starting torque
• If the motor is in a bind, it is hard to get the motor started
• Turbodrills are used in directional drilling where the temperature exceeds the limit of a positive displacement motor

Positive displacement motors were introduced in the 1960’s

Rotor/stator configuration

Speed (RPM) / Torque (Ft-Lbs.)

• For best performance, the power section should be matched to the bit and formation being drilled.  The speed and torque of a power section is directly linked to the number of lobes on the rotor and stator.  The higher the number of lobes, the higher the torque and the lower the RPM.

 

Dump sub

•         Not often used
•   Allows string to fill or drain when tripping
•   Allows low volume circulation in stuck bit situations

 

Power pack section

Rotor is hard

Stator is flexible

Stator housing is thin

PDM is not a drill collar

 

 

•  Reverse application of the Moineau pump principle
•  Elastomer lined - steel tube stator
•  Chrome  coated steel rotor
•  Converts Hydraulic HP (flow & pressure) to Mechanical HP (rpm & torque) There are three main producers of motor  power sections in the world:

 

Typical PDM power curve

 

•  Rotor is coupled to transmission
•  Transmission shaft is coupled to the bearing pack
•  The adjustable bent housing enables the bend to be changed at the wellsite
•  The housing can be adjusted 0.26 to 3.0 degrees depending upon motor size

  

Bearing function

•   On bottom thrust bearings carry force from the bit    (WOB)
•   Off bottom thrust bearings carry the hydraulic load  of the mud and weight of the rotor
•   Radial bearings carry side loads
•   Flow restrictor diverts a portion of the mud for    lubrication

METHODS OF DEFLECTING A WELLBORE

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METHODS OF DEFLECTING A WELLBORE con't 2

METHODS OF DEFLECTING A WELLBORE con't 4

Advanced Reservoir Engineering

Advanced
Reservoir
Engineering

Tarek Ahmed
Senior Staff Advisor
Anadarko Petroleum Corporation
Paul D. McKinney
V.P. Reservoir Engineering
Anadarko Canada Corporation

Dedication

This book is dedicated to our wonderful and understanding wives, Shanna Ahmed and Teresa McKinney, (without whom this
book would have been finished a year ago), and to our beautiful children (NINE of them, wow), Jennifer (the 16 year old
nightmare), Justin, Brittany and Carsen Ahmed, and Allison, Sophie, Garretson, Noah and Isabelle McKinney.

The primary focus of this book is to present the basic
physics of reservoir engineering using the simplest and
most straightforward of mathematical techniques. It is only
through having a complete understanding of physics of
reservoir engineering that the engineer can hope to solve
complex reservoir problems in a practical manner. The book
is arranged so that it can be used as a textbook for senior
and graduate students or as a reference book for practicing
engineers.
Chapter 1 describes the theory and practice of well testing
and pressure analysis techniques, which is probably one
of the most important subjects in reservoir engineering.
Chapter 2 discusses various water-influx models along with
detailed descriptions of the computational steps involved in
applying these models. Chapter 3 presents the mathematical
treatment of unconventional gas reservoirs that include
abnormally-pressured reservoirs, coalbed methane, tight
gas, gas hydrates, and shallow gas reservoirs. Chapter 4
covers the basic principle oil recovery mechanisms and the
various forms of the material balance equation. Chapter 5
focuses on illustrating the practical application of the MBE
in predicting the oil reservoir performance under different
scenarios of driving mechanisms. Fundamentals of oil field
economics are discussed in Chapter 6.  

click here to download

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Well Engineering & Construction

Well Engineering & Construction

hussain rabia

Chapter 1 : Pore Pressure 1
Chapter 2 : Formation Integrity Tests 49
Chapter 3 : Kick Tolerance 71
Chapter 4 : Casing Properties 99
Chapter 5 : Casing Design Principles 143
Chapter 6 : Cementing 201
Chapter 7 : Drilling Fluids 265
Chapter 8 : Practical Rig Hydraulics 305
Chapter 9 : Drill Bits 339
Chapter 10 : Drillstring Design 383
Chapter 11 : Directional Drilling 439
Chapter 12 : Wellbore Stability 525
Chapter 13 : Hole Problems 569
Chapter 14 : Horizontal & Multilateral Wells 625
Chapter 15 : High Pressure & High Temperature Wells 675
Chapter 16 : Rig Components 711
Chapter 17 : Well Costing743

to download click here

METHODS OF DEFLECTING A WELLBORE con't 2

Rotary BHA

• The rotary BHA consists of a bit, drill collars, stabilizers, reamers, subs and other special tools run below the drill pipe
• Motors were used to put the wellbore on course and rotary BHA’s were used to drill the majority of the well
• Even though rotary assemblies are used only occasionally, we will still look at them
• Steerable motor assemblies in the rotating mode are still rotary BHA’s subject to the same influences as the rotary BHA
• A slick assembly is simply a bit and drill collars

 

• The deviation tendency is caused by the bending of the drill collars
• The point at which the collars touch the wall of the hole is the tangency point
• The resultant force applied to the formation is not in the direction of the hole axis but in the direction of the drill collar axis

• The resultant force can be broken up into its components FB and FP

 

• FB is the side force caused by the bending of the collars or building force
• FP is the force due to gravity or pendulum force
• Ideally, if

1.        FP > FB, the hole inclination will drop
2.        FP < FB, the hole inclination will increase
3.       FP = FB, the hole inclination will remain constant

• The building force can be increased by increasing bit weight, which drives the tangency point down
• The building force is also affected by the stiffness of the collars
• Stiffer collars will bend less
• As the diameter of the collar increases, the stiffness of the collar increases

• The pendulum force can be increased by reducing bit weight and using larger diameter collars
• ØSome inclination is required to have a pendulum force
• ØFor a slick assembly, the building and pendulum force will balance at relatively low inclinations; therefore, they are not expected to build much inclination

• So why does the inclination exceed 1 to 2o in some areas while it does not in other areas?
• If the bed dip is relatively flat, we seldom have any deviation problems
• When bed dip is encountered, we can experience deviation problems in harder rock

• Deviation problems are associated with formation dip
• The anisotropy of the formation causes deviation

 

• If the formation deviation tendency can be defined as a force FF, the resultant force at the bit would be
  -FB + FP + FF   
•  The wellbore will continue to build angle until the sum of the forces is equal to zero 
•  Unfortunately it is difficult to define FF and it changes with depth     

Rule of thumb

• If the bed dip is less than 45 degrees, the bit will have a tendency to deviate perpendicular to the bed dip (up dip)   
• If bed dip is above 65 degrees, the bit will have a tendency to deviate along the bed dip 
• Between 45 and 65 degrees, the bit can do either
• In directional drilling, it is the difference between the bit angle and the formation dip 
• The formation may want the bit to drop inclination when the wellbore is at an inclination greater than bed dip 
• The two forces associated with a rotary assembly are the building force (FB) and the dropping force (FP) 
• If we want to make a building assembly, the building force must be maximized 
  Stabilizers are used as fulcrums in order to increase the side force at the bit
   

Building assembly

A building assembly is constructed by placing a stabilizer near the bit
Bending of the drill collars above the stabilizer causes the building force at the bit to increase substantially

• At low inclinations, the drill collars are bent by increasing bit weight

• At higher inclinations, gravity will bend the collars and the build tendency is less affected by bit weight   
• In order to make a dropping assembly, the pendulum force is maximized by placing a stabilizer at least 30 to 90 feet above the bit

 

•     If the collars touch the wall of the hole between the stabilizer and the bit, the tangency point becomes the place where the collars first touch the wall of the hole
•     If the stabilizer is too far above the bit, the collars will touch the wall and the pendulum force will be reduced  

-A holding assembly is constructed by placing stabilizers closer together so that the collars are more rigid
-Bit side force is minimized

• Holding inclination is the most difficult with a rotary assembly

• Analysis by Amoco indicated that

1. -Assembly A proved to be the most successful even though it maintained inclination only 60 percent of the time
2. -Assembly B maintained inclination less than 50 percent of the time
3. -Assembly C held inclination less than 50% of the time 

To better understand the forces on a rotary BHA, lets look at a single stabilizer assembly with the stabilizer positioned at various distances from the bit

• Rotary BHA’s were not very efficient as it was difficult to predict the actual performance of any rotary BHA
• Frequent trips were required to change stabilizer placement and size

• The build, hold or drop tendency of the rotary BHA could be adjusted but the walk tendency could not be changed substantially

• A pure rotary assembly is used only occasionally today
• Derivatives of the rotary assembly are used frequently
• Steerable motor assembly 
• Rotary steerable assembly

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METHODS OF DEFLECTING A WELLBORE

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Jetting

Jetting was used as an alternative to whipstocks 

• Jetting was only effective in softer rocks since formations have to be eroded to change the trajectory of the wellbore 
• A bit with a larger diameter nozzle facing the side of the hole was used to erode the formation to one side of the bit                       

• The larger nozzle was oriented in the desired direction
• The formation was washed as the assembly was lowered into the hole 

•  If the rocks were too soft, the entire bottom of the hole may wash out without substantially altering the hole trajectory
• In harder formations, the bit often had to be turned slightly left and right to erode the side of the hole 
• Penetration rate while jetting, was very slow 
• Once a portion of the hole had been jetted and the bit worked to bottom, the assembly was rotated to continue drilling ahead   
• Jetting created a high dogleg severity in a short interval even though surveys may not indicate it   

• The jet deflection bit was actually the first steerable assembly 

1.   While jetting, the drill string was not rotated in order to effect a trajectory change (slide drilling) 
2.   After jetting, the drill string was rotated to drill ahead

 

METHODS OF DEFLECTING A WELLBORE

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METHODS OF DEFLECTING A WELLBORE con't 4

METHODS OF DEFLECTING A WELLBORE

Any number of directional tools can be used to deflect a wellbore or make the wellbore go where we want it to go

Methods of Deflection

• Whipstocks
• Jetting
• Rotary BHA
•  Rotary BHA with adjustable stabilizer
• Motor
•       Steerable motor
• Rotary steerable assembly

• Over time, the tools we have used to deviate a wellbore in the desired direction have changed

• Newer and more efficient tools have been developed and will be developed in the future

Significant advances in directional drilling technology

 Whipstock

•      One of the earliest tools used in the industry was the whipstock
•  The whipstock is a metal wedge placed in the wellbore that causes the bit to deviate
•     In the early years of the petroleum industry, they were used to sidetrack wells if a portion of the drill string became stuck
•      As directional drilling started in the 1930’s, whipstocks were oriented and used to change the inclination and azimuth of the wellbore Whipstocks were not very efficient
•      In order to use a whipstock, the drill string was pulled from the hole and a whipstock was run into the well
•      On a retrievable whipstock, a pin was sheared and the bit drilled off the whipstock
•  

  Retrievable whipstock

•      Because the bit had to be run in with the whipstock, it was a smaller diameter than the hole
•      A second trip was made to open the hole to full gage 
•   In harder rock, a reaming trip may have been required
•   Using the whipstock required a minimum of three trips, which was not cost effective
•   Permanent whipstocks were no better even though a full sized bit could be used to drill off it
•      Today, whipstocks are used frequently to sidetrack out of casing
•      The majority of casing sidetracks are now performed with a whipstock 

 

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Directional drilling

Directional drilling is the art and science involving the intentional deflection of a wellbore in a specific direction in order to reach a predetermined objective below the surface of the earth

• At one time it was thought that all wells were vertical
• Methods to measure deviation were developed in the 1920’s (initially acid bottle)
• Directional drilling developed after 1929 when new survey instruments were available (inclination and direction)
• The first controlled directionally drilled well was drilled in the Huntington Beach Field in 1930 to tap offshore reserves from land locations
• Directional drilling became more widely accepted after a relief well was drilled near Conroe, Texas in 1934

• Today, directional drilling is an integral part of the petroleum industry
• It enables oil companies to produce reserves that would not be possible without directional drilling
• One of the primary uses of directional drilling was to sidetrack a well even if it was to go around a stuck BHA

 

• Sometimes multiple sidetracks are used to better understand geology or to place the wellbore in a more favorable portion of the reservoir
• Straight hole drilling is a special application of directional drilling

1. To keep from crossing lease lines
2. To stay within the specifications of a drilling contract
3. To stay within the well spacing requirements of a developed field

 

• Drilling multiple wells from a single structure or pad
• Most offshore development would not be possible without directional drilling
• Inaccessible surface location
• Drilling in towns, from land to offshore and under production facilities

• Drilling around salt domes
• Salt can cause significant drilling problems and directional drilling can be used to drill under the overhanging cap
• Steeply dipping sands can be drilled with a single wellbore
• Fault drilling
• In hard rock, deviation can be a problem
• Sometimes the bit can track a fault
• Drilling at a higher incident angle minimizes the potential for deflection of the bit
•  Relief well drilling
• Directional drilling into the blowout when the surface location is no longer accessible
• Very small target and takes specialized equipment
•  Horizontal drilling
• Increasing exposure of the reservoir to increase productivity
•  Multilateral drilling
• Drilling more than one wellbore from a single parent wellbore

•        Extended reach drilling wells are characterized by high inclinations and large departures in the horizontal plane

• Extended reach wells are wellbores where the horizontal departure is significantly higher than the true vertical depth of the well, which is the horizontal departure – TVD ratio (HD/TVD)
• Extended reach wells have been drilled with HD/TVD ratios greater the 6/1.
  BP drilled a well at Wytch Farm with a measured depth of 34,967’ (10,658 m), a TVD of 5,266’ (1,605 m) and horizontal departure of 33,181’ (10,114 m) 
  
  

  
  

  
  

  
  

  •    There are four basic hole patterns
  •      Not all wells conform to the basic hole patterns and may be a combination of patterns
  •     For simplicity, the basic hole patterns are defined as:
  • 
  •