SPE DISTINGUISHED LECTURER SERIES is funded principally through a grant of the

SPE FOUNDATION The Society gratefully acknowledges those companies that support the program by allowing their professionals to participate as Lecturers. And special p thanks to The American Institute of Mining, g Metallurgical, g and Petroleum Engineers (AIME) for their contribution to the program.

BP EXPLORATION Wellbore Quality Characterization for Drilling and Casing Running R nning in Challenging Wells Dr. Colin Mason Senior Drilling Specialist Sunbury-on-Thames United Kingdom Telephone: +44 1932 739518 Email: [email protected]

Lecture Overview Introduction ¾ Definition ¾ Measuring wellbore quality ¾ Managing M i wellbore llb quality lit ¾ Field case studies ¾ Conclusions ¾

Introduction ¾ ¾ ¾ ¾ ¾ ¾ ¾

"Wellbore quality" common oilfield concept Often associated with directional drilling g Often linked with performance improvements Diverse interpretations p for each discipline p No unique definition exists No proven method of measurement exist Context: Drilling and Completions

Wellbore Quality Parameters Attribute Tortuosity Wellbore spiralling p g Cuttings bed Ledging Lost circulation Wellbore breakout Formation damage Target hole size Measurable

Influenced by y Directional driller Directional drilling g BHA Drilling practices Drilling practices / environment Drilling practices / environment Mud weight / exposure time Mud type / mud properties Planning / Learning Chosen methodology

Definition – Quality Wellbore ¾ ¾ ¾ ¾ ¾ ¾

Straight wellbore – minimal tortuosity and minimal hole spiralling (micro(micro-tortuosity) Round gauge hole – minimal wellbore breakbreak-out, no washwash-outs and hole not undergauge Smooth wellbore – minimal ledging Clean hole – minimal residual cuttings bed Integrity – no leakage, no formation damage Fit for purpose – casing or logs will run to depth

Benefits – Quality Wellbore ¾ ¾ ¾ ¾ ¾ ¾ ¾

Improved weight transfer – better ROP Good hole cleaning g–g gauge g hole Lower vibration – constant drilling parameters Trouble--free trips Trouble p & casing g runs – g gauge g hole Better log quality – gauge, non non--spiralled hole Competent cement bond – gauge hole Reduced torque and drag – low tortuosity

Influences: Subsurface Environment Geology influences wellbore quality ¾ ¾ ¾ ¾ ¾ ¾ ¾

Pore Pressure / Fracture Gradient Geothermal Gradient Formation Types Rock Strength Stress Orientation Fractures / Faulting Life of field issues – depletion

Influences: Wellbore Placement Wellpath selection ¾ Tortuosity (planned versus actual) ¾

0

M16

M11

M14

M09

M15 M05 M

M03M02 M

M18

M M06 M15z M

M01 F21

F19 M12 M M08 F20 M07 M

M17 M10 F18

TVD D BRT (ft)

M04

M13

5,000

10 000 10,000 0

5,000

10,000

15,000

20,000

25,000

Equivalent Departure (ft)

30,000

35,000

40,000

Influences: Mud System

In this application an OBM is needed to stabilise a shale

Influences: Directional Drilling Tools Rotary Steerable Tool

Long gauge PDC bit

Steerable Motor Tricone Bit

Hole Spiralling – Introduction ¾ ¾ ¾ ¾ ¾ ¾

Hole spiralling exists in most wells Pitch, amplitude, drift, gauge – key parameters Negatively impacts drilling and completion operations Usually can be detected from logs Eff t more pronounced Effects d in i horizontal h i t l / ERD wells ll Long gauge bits – tend to help reduce spiralling

Hole Spiralling – Imaging

Hole Spiralling – Image Log

Image Log shows Spiral Hole from PDM and d RSS (Cannot be seen in Survey)

Limitation of MWD Survey Tools

MWD survey tool crosses the trough or valley of a spiral hole. Inclination and direction of the drift is being measured. This effect is called “micro-tortuosity”

Problems associated with a Spiralled Hole Reduced Drift Higher friction forces, forces higher T&D Lower ROP, poor weight transfer Casing g hangs g up Ambiguous log response

Unstable bit Cuttings Bed Traps

Higher vibration

Poor hole cleaning

More tool failures

Backreaming and short trips

Shortened bit life

Stuck pipe

More trips

Poor cement job

Spiralling results from Unstable Bit Confined by high-side high side troughs

Confined by low-side p peaks

How Spiralling is Created

Measuring Wellbore Quality ¾

Explicit methods – physical measurements – individual measures possible – difficult to interpret in terms of wellbore quality – specific examples illustrated

¾

Implicit methods – indirect measurements – measure responses to wellbore quality – Illustrated by analogy and applications

Measuring Wellbore Quality Explicit Methods ¾ ¾ ¾ ¾ ¾

Drift – caliper logs Surface finish – inferred from image logs Micro--tortuosity / spiralling – pitch, Micro pitch amplitude Tortuosity / doglegs – statistical analysis Pseudo measure – directional difficulty index

Caliper Logs – Drilling vs vs. Trip-Out 12 Colville HRZ 11.5

Kuparuk Kuparuk C

Miluveach

Kingak

Colville

11

Diamete er (ins.)

10.5 10 95 9.5 9 8.5 8

Caliper during Drilling Caliper during Trip-Out

7.5 7 16,000

16,500

17,000

17,500

Measured Depth (ft)

18,000

18,500

19,000

Measuring Wellbore Quality Implicit Methods ¾ ¾ ¾ ¾ ¾

Require a methodology / philosophy Identify appropriate response variable Information to characterize responses Analysis and interpretation Scoring / ranking process

Head Trauma Injury Assessment Scenario ¾ ¾ ¾ ¾ ¾ ¾

Patient arrives at Emergency Room Apparent Head Injury Immediate assessment of brain function needed No immediate visual assessment possible p – no useful explicit measure How does the physician carry out the evaluation? Responses to stimuli are carried out – implicit measures

Head Trauma Injury Assessment

Three responses determine overall severity of head trauma

GCS ≥ 13 Mild Brain Injury 9 ≤ GCS ≤ 12 Moderate Brain Injury GCS = Glasgow Coma Scale

3 ≤ GCS ≤ 8 Severe Brain Injury

The Wellbore Quality Scorecard (WQS) Methodology ¾ ¾

¾ ¾ ¾ ¾

Technique based on head trauma assessment Wellbore quality inferred from response variables – drilling, trippingtripping-out and casing running Primary response variables are T&D parameters Surface logging data used to characterize responses Trend analysis principal evaluation tool Extent and intensity of data variations evaluated

Example – Torque Trend Data 35 30

Torque e (kft.lb)

25

Narrow bandwidth

Very low open hole friction factor indicative of good drilling practices also OBM used so good lubricity hole quality considered excellent

20 15 FF = 0.17/0.11 Surface Torque

10

Bitt Torque o que

5 0 1,000

2,000

3,000

4,000

5,000

6,000

Measured Depth (m)

7,000

8,000

9,000

Wellbore Quality Scorecard – Guidelines Drilling Response (5 points)

Score

Severe drilling S d illi problems bl - stuck pipe - near stuck pipe incident

0 1

Transient drilling problems - poor hole cleaning with high cuttings bed - severe pack-off - severe loss circulation - erratic torque and drag response

2 2 2 3

Torque and drag response - all parameters follow smooth trend - lower than expected torque and drag

4 5

Final Trip-out Response (7 points) St k pipe Stuck i Residual cuttings bed / differential sticking - section length with overpulls > 100 klbs - section length with overpulls > 50 klbs Ledges - isolated overpulls > 100 klbs - isolated overpulls > 50 klbs

Score 0 1 2

3 4

Casing Running Response (8 points)

Score

Severe casing g running gp problems - stuck casing - casing pulled due to downhole problems

0 0

Differential sticking environment - static friction > 100 klbs on connections - static friction > 50 klbs on connections

1 2

Intervention needed during casing run - unplanned rotation needed - unplanned circulation needed - joints j i t wiped i d tto reduce d d drag

3 4 5

Casing run without significant problems - elevated but smooth drag levels - achieved expected drag levels - better than expected drag levels

6 7 8

Transient tripping-out problems - loss circulation - unplanned circulation - unplanned reaming and back back-reaming reaming

5 5 5

Drag response - smooth drag levels measured throughout - better than expected drag levels recorded

6 7

Wellbore Quality Scores – Interpretation ¾

WQS is recorded as a response mnemonic – D4T5C5 (Drilling 4; TrippingTripping-out 5; Casing Running 5)

¾

WQS = sum of each response score 0 < WQS ≤ 2

stuck pipe or stuck casing

2 < WQS ≤ 6

low quality wellbore

6 < WQS ≤ 10

medium wellbore quality

10 < WQS ≤ 14

high wellbore quality

14 < WQS < 20

excellent wellbore quality

WQS = 20

“The Perfect Wellbore!”

Case Study – Horizontal Well Norway 26” conductor @ 486m

13-3/8” shoe @ 1,521m

Size ins ins.

Weight ppf

Grade

Connection Type

Top TVD RKB

Bottom TVD RKB

Bottom MD RKB

26"

267

X-65

XLC XLC--S

Surface

478 m

478 m

13--3/8" 13

72

P-110

Dino Vam

Surface

1443 m

1521 m

9-5/8 5/8"

53 5 53.5

P-110

New Vam

Surface

2654 m

3200 m

5½"

32.6

Q-125

Vam Top

2554 m MD

2516 m

5398 m

5½” TOL @ 2,554m

Drill 2,198m 8½” horizontal section Run 2,844m 5½” 5½ thick wall liner

9-5/8" shoe @ 3,200m

5½” shoe @ 5,398m

Case Study – Drilling Response (D3) 50

1,000

Erratic Torque Response 45

800

35

700

30

600

25

500

20

400

15

300

10

200

5

100

0 3,100

3,300

3,500

3,700

3,900

4,100

4,300

4,500

Measured Depth (m)

4,700

4,900

5,100

5,300

0 5,500

String R RPM

Surface Torque (kNm)

40

900

Vibration problems in chalk reservoir

BHA 8: RSS + PDC Bit BHA 9: RSS + PDC Bit FF=0.20/0.15 String RPM

Case Study – Tripping-out Response (T2) 300

9-5/8" Shoe @ 3,200m

Hooklo oad (tonnes) / Surface Torqu ue (kNm)

BHA 9: Hookload 250

TD @ 5,398m

BHA 9: Surface Torque Pick-Up: FF=0.15/0.20

200

Elevated Drag 4,400-4,600m

Elevated Drag 5,200-5,400m

Mud Type: OBM Weight = 1.50 SG PV = 36 cP YP = 21 lbf/100ft²

150

100 Reaming/Back-reaming Reaming/Back reaming needed to reduce drag 50

0 0

500

1,000

1,500

2,000

2,500

3,000

Measured Depth (m)

3,500

4,000

4,500

5,000

5,500

Case Study – Liner Running Response (C3) 250

9-5/8" Shoe @ 3,200m 67m 453m 2,252m 69m 2,557m

Ho ookload (tonne es) / Torque (k kNm)

200

8¼" ¼ Reamer Shoe S 5" 18.0# Q125 H-125 Liner 5" 26.7# Q125 Vam Top HT 5½" 32.6# Q125 Vam Top HT 7" 32.0# P110 Vam Top HT 5½" 26.4# DP 5½" FH

Severe Slip stick effect when running liner

Liner Shoe @ 5,398m

Mud Type: OBM Weight = 1.50 SG PV = 35 cP YP = 19 lbf/100ft²

Surface Torque Hookload Slack-Off: FF=0.12/0.45

150

100

50 8¼" solid centraliser on 5" casing 8" solid centraliser on 5½" casing 8¼" solid centraliser on 7" casing 0 0

500

1,000

1,500

2,000

2,500

3,000

Measured Depth (m)

3,500

4,000

4,500

5,000

5,500

Completed Wellbore Quality Scorecard Horizontal Well Offshore Norway

WQS

Drilling Response (max 5 points) Persistent erratic torque response observed. Observation is indicative of vibration problems typically seen in the chalk reservoir. Vibrations are considered a transient problem and should not significantly g y impact p overall wellbore q quality. y Average rotary friction factors of 0.20/0.15 are typical of fieldfield-wide torque behaviour.

3

Final Trip Trip--out Of Hole Response (max 7 points) Elevated drag levels in excess of 50klbs are observed from 4,300 to 4,600m and from 5,200 to 5,400m , indicating g a possible p hole cleaning gp problem. Overpulls p also occur at chalk / shale transition zones. A form of slipslip-stick axial drag is also present when trippingtripping-out through the open hole section. Average pickpick-up friction factors of 0.15/0.20 are typical of field field--wide experience.

2

Liner Running Response (max 8 points) Liner running in open hole is far from smooth; significant axial slipslip-stick events observed which increase in intensity with depth. String has to be worked significantly over last 600m. String also had to be torqued to overcome tight spots / ledges. Slack--off friction factors of 0.12/0.45 are in line with field Slack field--wide experience.

3

WQS (D3T2C3) A score of 8 corresponds to a medium quality wellbore.

8

Cost vs vs. Wellbore Quality Relationship Field data suggests

Optimum WQS ⇒ lowest D&C costs

Well C Cost

Too high WQS ⇒ higher D&C costs

THE PERFE ECT WELLBORE E!

Low WQS ⇒ very high D&C costs

Train Wreck 0

2

Low Quality 4

Medium Quality 6

8

High Quality 10 WQS

12

Excellent Quality 14

16

18

20

Wellbore Quality Scorecard Learnings ¾ ¾ ¾ ¾ ¾ ¾

A low WQS does not always equate to poor performance A low l WQS can b be d due tto d degree off diffi difficulty lt off drilling d illi and casing running in that field Poorlyy designed g casing g run can result in failure Implications of scoring wellbore quality need to be understood by operators / service companies Wellbore Quality has to be managed at field level Need to understand Cost vs. Wellbore Quality relationship

Managing Wellbore Quality Drilling Practices ¾ ¾ ¾ ¾ ¾ ¾ ¾

Operating Parameters (WOB, RPM, Flow Rate) Connection practices Hole cleaning practices Mud weight management Managing packpack-offs Vibration management ECD management

Managing Wellbore Quality Tripping / Casing Running Practices ¾

Surge and Swab Pressure Cycles – can result in rock fatigue

¾

Managing g g Downhole Problems – cuttings bed, ledging, pack pack--offs, overpulls

¾

Circulation Losses – especially during casing running

Enhancing Wellbore Quality Emerging Technologies ¾

Continuous Circulation System – reduces swab and surge cycles in well

¾

ECD Reduction – reduces downhole annular pressures

¾

Fracture Gradient Enhancement – strengthens wellbore by forming stress cage

Wellbore Quality Characterization Conclusions ¾ ¾ ¾ ¾ ¾ ¾ ¾ ¾

Characterization important concept Can reflect degree of difficulty Most value for horizontal and ERD wells Industry standard definition needed Measurement protocol biggest challenge Wellbore quality scorecard promising technique Software needed: efficiency, clarity & consistency Wellbore quality enhancing technology exists

Additional Slides

Hole Spiralling – Inferred from Logs

Log Evidence: Caliper vs. Neutron Porosity vs. Sonic DT

Image Log – 8½ 8½” Section

Image Logs – 6-1/8 6-1/8” Hole Spiralling

Image Logs – 6-1/8 6-1/8” Hole Spiralling

Wellbore Quality vs. vs Tubing Life ¾ ¾ ¾ ¾

Slant drilling g Canada Heavy Oil Reservoir Pad Drilling 600m TVD

Canada – High DLS Slant Well

Tubing Wear vs. DLS/hole angle for high-DLS well Well on production for 2½ months before failure

Canada – Low DLS Slant Well

Tubing Wear vs. DLS/hole angle for low-DLS well Well on production for 21 months before failure

Drilling 12¼” 12¼ Section – Azerbaijan Well 45

900 Surface Torque - BHA 7

40

S f Surface T Torque - BHA 6 On-Bottom: FF=0.25/0.30

30

Off-Bottom: FF=0.25/0.30

800

700

Surface RPM WOB = 20 klb klbs Bit Torque = 5 kft.lb Flow Rate = 1,000 GPM

600

25

500

20

400

15

300

10

200

5

100

0 1,000

1,500

2,000

2,500

3,000 Measured Depth (m)

3,500

4,000

4,500

0 5,000

String R RPM

Surface To orque (kft.lb)

35

Mud Type: SOBM Weight = 1.60 1 60 SG PV = 40 cP YP = 29 lbf/100ft²

Tripping-out 12¼ 12¼” Hole – Azerbaijan Well 500 450 Hookload Pick-Up: FF=0.20/0.20

400

Hooklo oad (klbs)

350 300 250 200 150 100 50 0 0

500

1,000

1,500

2,000

2,500

3,000

Measured Depth (m)

3,500

4,000

4,500

5,000

Running 9-5/8” 9-5/8 Casing – Azerbaijan Well 800

13-3/8" Shoe @ 1,560m

12-1/4" TD @ 4,415m

700

7 Hookload Static Up Drag Static Down Drag Pick-Up Trend Sl k Off Trend Slack-Off T d Slack-Off: FF=0.20/0.30 Block Velocity

600

500

400

6

5

4

Mud Type: yp SOBM Weight = 1.60 SG PV = 37 cP YP = 26 lbf/100ft²

300

3

200

2

100

1

0

0 5,000

0

500

1,000

1,500

2,000

2,500

3,000

Measured Depth (m)

3,500

4,000

4,500

Block Veloc city (m/s)

Hooklo oad (klbs)

8

WQS – Azerbaijan Well

WQS: Wytch Farm ERD Wells 0

M16

M11

M14

M15 M05

M09

2 M03M02

8 M18

M06 M15z

M01 F21

F19 M12 M08 F20 M07

M17 M10 F18

TVD BRT (ftt)

M04

M13

5,000

10,000 0

5,000 ,

10,000 ,

15,000 ,

20,000 ,

25,000 ,

Equivalent Departure (ft)

30,000 ,

35,000 ,

40,000 ,

Wytch Farm – Torques 12¼” 12¼ Section 40

35

M05 M09 M11 M14 M16

Surface To orque (kft.lb)

30

25

20

15

10

5

0 0

1,000

2,000

3,000

4,000

5,000

Measured Depth (m)

6,000

7,000

8,000

9,000

Wytch Farm – 9-5/8 9-5/8” Casing Runs 60

M09

40

M11 M14

String We eight (klbs)

20

M16

0

-20

-40

60 -60

-80

-100 0

1,000

2,000

3,000

4,000

5,000

6,000

Measured Depth (m)

7,000

8,000

9,000

10,000

Wytch Farm ERD Wells – WQS Summary

C Comments t on hi high h WQS ¾

Good learning curve

¾

Continuous ERD drilling program