Session 5: CASING DRILLING® Hydraulics

HYDRAULIC ISSUES System comparison Annular flow & ECD Hydraulic lift Hole cleaning Underreamer activation Mud selection

ENGINEERING TOPICS FOR REVIEW

MECHANICAL ISSUES Torque and Drag Casing protection

• Buckling• Fatigue• Wear

Vibration

Wireline Operations

DIRECTIONAL DRILLING Motor selection Directional performance

Our industry has a long history of developing “best practices” for conventional drilling.

Natural tendency is to transfer conventional “best practices” to CASING DRILLING®.

Often conventional “best practices” need to be adjusted for unique conditions of CASING DRILLING®.

The following sessions are aimed at helping sort through these issues.

CHANGING PARADIGMS:CONVENTIONAL PRACTICE TO CASING DRILLING®

Tesco CDE Software is Main Engineering Calculation Tool

Functions of the Hydraulic System

Transport drilled cuttings out of hole. Control near wellbore fluid. Support wellbore wall. Lubricate bit and drillstring. Power downhole motor (if used).

While avoiding: Erosion of borehole wall. Fracturing the formation. Damage to production zone.

Comparison of Casing to Drillpipe & Collars

EXAMPLE

Hole Size = 8.75”Bit depth = 8,000 ft9-5/8” set at 500 ft

Flow rate = 450 gpm

Bit Jets = 14, 14, 14, 14

11.8 PPG MUDPV = 14Yp = 11

8,000 ft of 7” 23# Casing

COMPARED TO

540 ft 6.25 x 2.812 drill collars7460 ft of 4” Drill Pipe

7” Casing DP & Collars

Annular Velocity for Casing is High, but Constant

0

1000

2000

3000

4000

5000

6000

7000

8000

100 200 300 400 500

Annular velocity, ft/min

Dep

th, f

t

Casing

DP & Col

7” Casing DP & Collars

Re = 2584

Re = 3268

Re = 3947

All sections in turbulent flow

0

1000

2000

3000

4000

5000

6000

7000

8000

0 500 1000 1500 2000 2500

Pressure, psi

Dep

th, f

t

Casing

DP & Col

Inverted Pressure Profile (450 GPM)

7” Casing DP & Collars1438 psi 2181 psi

Pbit=487 psiECD = 13.5 ppg ECD = 12.0 ppg

0

1000

2000

3000

4000

5000

6000

7000

8000

100 200 300 400

Annular velocity, ft/min

Dep

th,

ft Casing

DP & Col

0 1000 2000 3000

Pressure, psi

Casing

DP & Col

Re-designed Hydraulics for CASING DRILLING®

(DECREASE FLOW TO 300 GPM, MUD WT TO 10.8 PPG & BIT JETS TO 11-11-11-11)

7” CasingECD = 11.9 ppg

1042 psi 2181 psi

300 GPM

450 GPM

Re = 1919

PUMP HORSEPOWER

ConventionalFlow Rate = 450 gpmDelta P = 2,181 psiHHP = 572 hp

HHP = P * Q / 1714 HHP = Hydraulic horsepower P = pump pressure ,psi Q = flow rate, gpm

CASING DRILLING®

Flow Rate = 300 gpmDelta P = 1,042 psiHHP = 182 hp

Diesel => 145,000 BTU/galAssume 40% efficiencyDiesel cost => $4.00/gal

Savings: 390 hp $1300/day

40% fuel savings observed on TESCO CASING DRILLING® rigs.

Flow Rate

EC

D

Friction Cuttings load

Minimum ECD

Optimum

Increased flow rate reduces cuttings load in annulus. Increased flow rate increases friction in annulus.

9

9.5

10

10.5

11

11.5

100 300 500

Flow Rate, gpm

EC

D. p

pg

Conv, ROP = 200 ft/hr

Conv, ROP = 400 ft/hr

Conv, ROP = 600 ft/hr

CD, ROP = 200 ft/hr

CD, ROP = 400 ft/hr

Drilling with 7” CasingDrilling with 6 1/8” DC and 4” DP

Depth = 3,200 ft Mud Wt = 8.9

Conventional operating rangeCasing Drilling operating range

Lower Flow Rate is Optimal

Cuttings Transport

From Applied Drilling Engineering pp175

0

0.2

0.4

0.6

0.8

1

0 0.02 0.04 0.06 0.08 0.1

Inverse Annular velocity, min/ft

Cut

ting

s T

rans

port

rat

io

50 25 12.516.7 10

Lower limit set bySand in water

Typical muds and cuttings

Annular velocity, ft/min

Typical Casing Drilling range

Is High Annular Velocity Detrimental?• Borehole erosion may be associated with turbulent flow.

• Turbulence typically begins at a Reynolds Number of 2100 – 2500.

Re = 928 * * Vel * de / = mud density, ppgVel = fluid velocity, ft/sec = fluid viscosity, cpde = equivalent hydraulic diameter

Dhole

2 - ODpipe2

Best Estimate: de = Dhole2 + ODpipe

2 –

Ln(Dhole / Odpipe)Approximation: de = 0.816 * (Dhole - Odpipe)

0

1000

2000

3000

4000

5000

0 100 200 300 400

Annular Velocity, Ft/Min

Rey

no

lds

Nu

mb

er

7" casing

4-1/2" Drill Pipe

Higher Transition Velocity for Narrow Annuli

8.75 “ hole, 10 ppg mud, Pv = 10, YP = 5

Turbulent

Is high annular velocity a concern?

Observations:

Annular velocity is often higher for CASING DRILLING® than around drill pipe for conventional drilling.

It is not unusual for the flow regime to be turbulent for CASING DRILLING® applications.

No detrimental effect of turbulent flow has been observed while drilling with casing (even at 475 ft/min with water).

Some publications indicate borehole wall damage once thought to be from turbulent flow is actually caused by drillstring vibration.

• Designing flow rate based on ECD and hole cleaning will take care of concerns about hole erosion.

Eccentric Casing in Borehole Results in Reduced ECD

30% reduction

AnnularPressure

Drag Force

End Force

Fluid Flow

Hydraulic Lift Flow in annulus lifts casing to reduce WOB

Also occurs with drill pipe, but is much less

Is a good monitor of hole cleaning

Better indicator in vertical wells.

Hydraulic Lift=

Fluid Drag+

Annular DP times end area+

DP from cuttings times end area

Drag Force +End Force HL = /4 * [Dh*Dc*Dpa + + 0.052*Dc

2* (e - m ) ]Cuttings Force

HL = Hydraulic lift, lbDh = borehole diameter, inDc = casing OD, inDpa = annular pressure loss, psim = clean mud density, ppge = effective mud density including cuttings, ppg

Hydraulic Lift Calculations

0

100

200

300

5 10 15 20 25 30 35 40 45 50

RPM

GPM

VAQUILLAS A1 198 Pump-Off Observed at 2074 ft

0

500

1000

1500

Pump Pressure

Time, seconds

Fill Pipe

32,000 lb Pump-Off

Note: Blocks were stationary

30000

40000

50000

60000

70000

HookLoad

Balling on casing Pack off on borehole wall

Balled Shale from shaker after working casing.

Hydraulic Lift Helps Monitor Condition of Hole

Procedure to Monitor Hydraulic Lift

Record hookload with bit off bottom, pumps off, and casing rotating slowly.

Engage mud pump(s) and bring flow rate up to drilling speed and record hookload.

Difference in hookload between having pumps on and off is hydraulic lift.

Zero WOB

Begin drilling

In fast drilling formations, if ROP decreases while drilling joint down, pick up an re-zero WOB to zero out cuttings loading effect.

Back-Reaming May Help Clean the Hole

0

5000

10000

15000

20000

25000

30000

1200 2200 3200 4200 5200 6200

Measured Depth, ft

Hyd

raul

ic L

ift, l

b.

Pump-Off

Predicted

Backreamed each connection

ANB Cattle Co

Trip

Trip

Typical Lobo Hydraulic Lift(without Back Reaming)

0

5,000

10,000

15,000

20,000

25,000

30,000

500 2500 4500 6500 8500

Measured depth, ft

Hyd

rau

lic

lift

, lb Measured

Predicted*

* Predicted before drilling, constant 320 gpm

Walter Despain

0

5000

10000

15000

20000

25000

30000

Measured Pump-Off

Calculated Pump-off

5

10

15

20

500 1500 2500 3500 4500 5500 6500 7500 8500

Depth, ft

ECD from Pump-Off, ppg

200

300

400

GPM

Hydraulic Lift Warns of Lost Circulation

Lost Circulation

Vaquillas A1 198

0

100

200

300

400

3 6 9 12 15

RPM ROP

1250

1300

1350

1400

1450Pressure

Example 1585 ftTime, minutes

0

5,000

10,000

15,000 WOBWOB St PtTorque

BMT 179

Annular Pressure May Change as Joint is Drilled

1200

1300

1400

1500Pressure

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

WOBWSPTorque"True" WOB

Example 2518 ftTime, minutes

0

50

100

150

200

250

300

350

2 7 12 17 22 27

Block Position

ROP

BMT 179 high speed data

WOB Zero

Annular Pressure Changes While Drilling

Soft formationHarder

formation

1. Start rotary (breaks gels).

2. Bring up mud pump.

3. After pressure stabilizes, zero WOB.

4. Set bit on bottom.

5. Adjust RPM & WOB.

Must be done each time flow rate is changed.

Hydraulic Lift Affects Proper Bit Start After Connection

1. One-time change in WOB due to casing length change.

2. Permanent change in hydraulic lift.

Must pick up off bottom to change flow rate and re-zero WOB.

What Happens if flow Rate is Changed with Bit on Bottom?

Thin Mud is Better than Reduced Flow Rate

Mud A – 9.25 ppg, 18 cp, 12lb/100 ft2

Mud B – 8.9 ppg, 12 cp, 5lb/100 ft2

0

5,000

10,000

15,000

20,000

1000 3000 5000Measured depth, ft

0

Hyd

rau

lic

Lif

t, lb

Mud A - 300 gpm

Mud A - 250 gpm

Mud B - 300 gpm

CASING DRILLING® Mud Selection

Conventional mud design uses chemistry and commercial mud products to develop fluid loss control.

Rheology designed for cuttings carrying capacity at low velocities.

Drilled solids and “Plastering Effect” with CASING DRILLING® provides superior fluid loss control.

Operator often wants to provide “Cadillac” mud on initial use of CASING DRILLING®.

Thin muds with slightly lower density are much superior for CASING DRILLING®.

CASING DRILLING® Pilot Bit Selection

Best bit for conventional drilling may not be best bit for drilling with casing.

Pilot bit is smaller. Flow rate is less. Nozzle size may be dictated by LCM.

Typically use fewer blades on PDC bit to better accommodate flow rate and limited nozzle size.

May use less aggressive bit than underreamer.

Matrix bit is best to control erosion Flow may be high for bit size. Erosion control on steel bit is less effective.

Erosion

P1

Pa

P2

P3

d1

Internal Jet

Bit Jets

d3

d2

Type 5 Underreamer

Underreamer Activation Pressure

SpringForce

Activation Size Pressure 4-1/2” 220 psi 5-1/2” 110 psi 7” 180 psi 9-5/8” 120 psi10-3/4” 140 psi13-3/8” 125 psi

Required activation pressure depends on piston area, rod area, spring design. Required activation pressure independent of

mud properties and flow rate. Delivered activation pressure depends on flow

rate, mud weight, bit nozzles, and internal nozzle.

Underreamer pressures cannot be determined accurately by surface flow test

due to cavitation at low back pressure.

Hydraulic Balancing

Mud Motor

Underreamer

MWD

RSS

BitAnnulus

Hydraulics Balancing (The Annulus)

Is the flow rate enough to clean the hole? 150 ft/min

Is the flow rate low enough that it will not break down the formation? (2 ppg leakoff, 9.2 ppg mud)

What is the hydraulic lift?

180 GPM 400 GPM

Hydraulics Balancing (MWD / RSS)

CASING DRILLING™ typically required less flow than a conventional application for the size of directional tools used.

What flow kits are available in the

Is there a pressure drop requirement for the RSS

180 GPM 400 GPM

300 GPM 600 GPM

Hydraulics Balancing (The Mud Motor) What are the options for a low flow motor.

- 7/8 power sections- What is the rev/gal. Does this limit the upper flow range?

180 GPM 400 GPM

300 GPM 600 GPM

300 GPM 550 GPM

Hydraulics Balancing (The Underreamer)

Does the flow rate provide enough differential pressure to open the Underreamer?

This is only an issue at very low flow rates

180 GPM 400 GPM

300 GPM 600 GPM

300 GPM 550 GPM

210 GPM

Hydraulics Balancing (The Bit)

What is the HHP? (>2.0)

How small can you run the jets? (what is the LCM program?)

What’s the minimum pressure drop for RSS to operate.

180 GPM 400 GPM

300 GPM 600 GPM

300 GPM 550 GPM

210 GPM

310 GPM (4 x 12)

Operating Flow Range for CASING DRILLING™

180 GPM 400 GPM

300 GPM 600 GPM

300 GPM 550 GPM

210 GPM

310 GPM (4 x 12)

Hydraulics Balancing (The Sum of the Parts)

Minimum 310 GPM Maximum 400 GPM

Higher AV is usually not a problem.

Higher ECD is manageable.

Fluid loss improved by mechanical plastering.

Hydraulic lift provides means of monitoring hole conditions.

Thin mud should be used as much as possible.

Pipe rotation increases pressure only slightly.

Discharge coefficient for bit nozzle should be 1.03.

CASING DRILLING® requires less horsepower resulting in fuel savings

Circulating pressures can be calculated adequately with conventional flow models.

Hydraulics Summary