session 5: casing drilling ® hydraulics. hydraulic issues system comparison annular flow &...
TRANSCRIPT
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