Drilling Torque & Drag

Torque & Drag CASING

Objectives At the end of this module you will be able to: 

Explain and define Side Forces

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Explain and define Friction Factor

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Understand causes of Torque Torque and Drag

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Build a Broomstick Plot

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Understand the mechanisms to reduce Torque and Drag

Torque and Drag Uses 

Define rig equipment requirements

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Determine Dete rmine drillability drillability of the well

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Optimize the trajectory and BHA / drill string /bit design

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Simulate drilling and completion (casing) runs

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Identify problem areas

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Determine circumstances for sticking events

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Establish mud program needs

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Evaluate the effectiveness of hole cleaning actions

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Determini Dete rmining ng reaming, reaming, backrea backreaming ming and short short trip requirements

Torque and Drag Modeling To understand computer modeling two key points must be understood: Model (Representation) – noun(C): a representation of something, either as a physical object which is usually smaller than the real object, or as a simple description of the object which might be used in calculations.

Garbage In = Garbage Out

Torque & Drag CASING SideForce’s & Friction

The Weight Component of Side Force

incl

weight

Sidewall Forces – Tension and DLS Building Section tensile

tensile

resultant

tensile load weight weight

Dropping Section

tensile

resultant

weight

tensile load

tensile load

Sidewall Forces – Tension and DLS*

Wall force with pipe tension and DLS:

SF  =

DL

× π  × L ×

18 × 10 3

Sidewall Forces – Tension and DLS Wall force with pipe tension and DLS: Wear => Casing, Drill string components DE

Sideforce Components Wn : side weight = linear weight x sin( inclination ) Wn

Wn

FB

FB

T W C

FC

FB FB : bending side force (zero in soft string model)

curvature side force

FC = T x string curvature

T Total Side Force = -Wn + FC + FB

FB

Side Forces - Worst Case Scenario???

DE

Exercise Example: Calculate the wall force across a 30’ section of 5°/100’ DLS considering a tension of 100,000 lbs below the DL. SF  =

Exercise:

5 × π  × 30 ×100000 18 ×103

=

2617.91lbf  / 30 ft 

KOP of 1500' and a build up to 30 inclination. Our TD is 10,000'. The drillstring tension at 1500' when we are drilling at TD could be around 180,000 lbs. If the average length of a joint of drillpipe is 31' and if we want to limit our side force to 2,000 lbs per joint of drillpipe what is the maximum DLS can be used? °

 DLS  =

18 ×103 × SF  π  × L × T 

=

18 ×103 × 2000 π  × 31×180000

=

2.050 / 100 ft 

The Stiffness Component of Side Force

When does stiffness start to become a factor? 5” drill pipe 16 deg/100ft 3 1/2” drill pipe 22 deg/100ft

Stiffness – BHA as a Hollow Cylinder Stiffness Coefficient = E xI where: E = Young’s Modulus (lb/in2) I = Moment of Inertia in4 Moment of Inertia I = p (OD4 - ID4) ÷ 64 OD = outside diameter ID = inside diameter DE

Stiffness – BHA as a Hollow Cylinder Which one is more stiff?

Drill Collar?

DE

Drill Pipe? Casing? Liner?

The Buckling Component of SideForce Fb Fb

String is in compression

Fb

Sinusoidal & Helical Buckling

DE

DE

Buckling - Worst Case Scenario???

DE

Dawson-Pasley Buckling Criteria

F CR

=

2×

 E × I  × K B × W  × sin θ  r 

CR

DE

θ 

= Inclination

 E 

= Young' s Modulus

K  B

= Buoyancy factor (unitless)

 I 

= Moment of  inertia

of  the hole at the point of  interest (deg)

4

(inch )

W

= Unit

r

= Radial clearance between pipe

weight in air (lbs/in) tool joint and hole (in)

Guidelines for Analyzing Buckling Problems Sinusoidal buckling is an indication of the onset of fatigue wear. Classical Sinusoidal buckling is defined by Dawson & Pasley ‘82 (SPE 11167) with references to Lubinski in ‘62. Modified Sinusoidal buckling defined by Schuh in ‘91 (SPE 21942) and is used in Drilling Office. Helical buckling generally results in side force loads. Helical buckling defined by Mitchell (SPE 15470) and Kwon (SPE 14729) in ‘86. Generally Helical buckling should be considered at compressional loads √2 times those calculated for Sinusoidal buckling 

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Summary Four Components of Side Force Weight

always a consideration, light drill pipe in Horizontal wells

Tensile

more pronounced with high tension and high dog legs

Stiffness

negligible effect with dog legs less than 15 deg/100ft

Buckling

high compressional loads with neutral point significantly above the bit (near surface)

Stiff vs. Soft String Model Soft String 

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Drill string always in contact with the borehole Contact area, curvature

Stiff String 



overestimated 

Drill string curvature can be different than wellbore Contact areas are , side forces More accurate torque loss calculation in a low inclination wellbore

Borehole/Drill string contact LOWTOR LOW TORTU TUOSIT OSITY Y WELLS ELLS (loc (local DLS DLS > well well curva rvature) re)

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Wn

Wn

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StiffStiff- and soft-string soft-string models models give the same result for an unto un tortu rtuou ous s plan plan

T

SOFTSTR FTSTRING/ NG/ BOREHOLEC OLECONTACT

Wn

Wn

T STIFFST FFSTRING/ RING/ BOREHOLECO LE CONTACT

T

T : axial load, Wn : component of drillstring drillstring weight perpend perpendicu icular lar to borehol borehole e axis axis

T

Something Additional!! Tort To rtuo uosi sity ty in Plan Planne ned d Trajec Trajecto tori ries es Why Why add add to tortu rtuosi osity ty to pla plans? ns?  

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Account for more than “Ideal” T&D numbers Allows more consistent results between different eng neers Account for drilling system used

Recommended Values (no offset data)   

DE

Vertical, tangent sections 0.75/100ftperiod 0.75/100ftperiod Build, drop sections 1.5/100ft period Turn only sections 1.0/100ft period

Friction It is the resistance to motion that exists when a solid object is moved tangentially with respect to another which it touches.

Friction

Motion W

Coefficient Of Friction and Critical angle

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The frictional drag force is proportional to the normal force. The coefficient of friction is independent of the apparent area of contact

When does the Pipe Stop Moving?

Tan -1 (1/FF) = Inclination

Effect of Friction (no doglegs)

Effect of Friction (no doglegs) (a) Lowering: Friction opposes motion, so ∆T = W cos I − Ff  ∆T = W cos I −

W sin I

(b) Raising: Friction still opposes motion ∆T = W cos I + Ff  ∆T =

W cos I +  µ W sin I

Exercise 1 What is the maximum hole angle (inclination angle) that can be logged without the aid of drillpipe, coiled tubing, other tubulars or sinker bars? (assume FF = 0.4)

Friction Factors In reality, Friction Factor (FF) used in modeling is not a true sliding coefficient of friction. It acts as a correlation coefficient that lumps together the friction forces caused by various effects, including friction. Typically the FF will depend on a combination of effects including: Formation Mud type Roughness of Support Tortuosity Borehole Condition     

Friction Factors - Rotation Rotating

Sliding

Backreaming Friction Vector

RPM Vector Drilling Friction Vector Backreaming friction factor from weight loss/overpull while drill string is rotating 0