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 sppggecial thanks to The American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) for their contribution to the program. BP EXPLORATION Wellbore Quality Characterization for Drilling and Casing R unning in Challenging Wells Dr. Colin Mason Senior Drilling Specialist Sunbury-on-Thames United Kingdom Telephone: +44 1932 739518 Email: masoncj@bp.com Lecture Overview

¾ Introduction ¾ Definition ¾ Measuring wellbore quality ¾ Manag ing we llbore qua lity ¾ Field case studies ¾ Conclusions Introduction

¾ "Wellbore quality" common oilfield concept ¾ Often associated with directional drilling ¾ Often linked with performance improvements ¾ Diverse interpppretations for each discipline ¾ No unique definition exists ¾ No proven method of measurement exist ¾ Context: Drilling and Completions Wellbore Quality Parameters

Attribute Influenced by Tortuosity Directional driller Wellbore sppgiralling Directional drilling BHA Cuttings bed Drilling practices Ledging Drilling practices / environment Lost circulation Drilling practices / environment Wellbore breakout Mud weight / exposure time Formation damage Mud type / mud properties Target hole size Planning / Learning Measurable Chosen methodology Definition – Quality Wellbore

¾ Straight wellbore – minimal tortuosity and minimal hole spiralling (micro(micro--tortuosity)tortuosity) ¾ Round gauge hole – minimal wellbore break-break-out,out, no wash-wash-outsouts and hole not undergauge ¾ Smooth wellbore – minimal ledging ¾ Clean hole – minimal residual cuttings bed ¾ Integrity – no leakage, no formation damage ¾ Fit for purpose – casing or logs will run to depth Benefits – Quality Wellbore

¾ Improved weight transfer – better ROP ¾ Good hole cleaning – gggauge hole ¾ Lower vibration – constant drilling parameters ¾ TroubleTrouble--freefree trippgs & casing runs – gggauge hole ¾ Better log quality – gauge, nonnon--spiralledspiralled hole ¾ Competent cement bond – gauge hole ¾ Reduced torque and drag – low tortuosity Influences: Subsurface Environment

Geology influences wellbore quality ¾ Pore Pressure / Fracture Gradient ¾ Geothermal Gradient ¾ Formation Types ¾ Rock Strength ¾ Stress Orientation ¾ Fractures / Faulting ¾ Life of field issues – depletion Influences: Wellbore Placement

¾ Wellpath selection ¾ Tortuosity (planned versus actual)

0 M13 M04

5,000 M M M M BRT (ft) BRT M M M11 M15 F21 M16 M01 F18 07 F19 08 M09 05 M10 M17 15z 06 03 M12 DD F20 M14 M18 M02 TV

10, 000 0 5,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 Equivalent Departure (ft) 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 Hole spiralling exists in most wells ¾ Pitch, amplitude, drift, gauge – key parameters ¾ Negatively impacts drilling and completion operations ¾ Usually can be detected from logs ¾ Effect s more pronounced i n h ori zon tal / ERD we lls ¾ Long gauge bits – tend to help reduce spiralling Hole Spiralling – Imaging Hole Spiralling – Image Log

Image Log shows Spiral Hole from PDM and 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 , higher T&D Lower ROP, poor weight transfer Casinggg hangs 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 troughs

Confined by low-side 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 Drift – caliper logs ¾ Surface finish – inferred from image logs ¾ Micro-tortuosity / spiralling – pitch, amplitude ¾ Tortuosity / doglegs – statistical analysis ¾ Pseudo measure – directional difficulty index Caliper Logs – Drilling vs. Trip-Out

12 Colville HRZ Kuparuk Kuparuk C Miluveach Kingak

11.5 Colville

11

10.5

10 r (ins.)

ee 959.5

9 Diamet

8.5

8 Caliper during Drilling Caliper during Trip-Out 7.5

7 16,000 16,500 17,000 17,500 18,000 18,500 19,000 Measured Depth (ft) Measuring Wellbore Quality

Implicit Methods ¾ Require a methodology / philosophy ¾ Identify appropriate response variable ¾ Information to characterize responses ¾ Analysis and interpretation ¾ Scoring / ranking process Head Trauma Injury Assessment

Scenario ¾ Patient arrives at Emergency Room ¾ Apparent Head Injury ¾ Immediate assessment of brain function needed ¾ No immediate visual assessment possible – no useful explicit measure ¾ How does the physician carry out the evaluation? ¾ 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 3 ≤ GCS ≤ 8 Severe Brain Injury GCS = Glasgow Coma Scale The Wellbore Quality Scorecard (WQS)

Methodology ¾ Technique based on head trauma assessment ¾ Wellbore quality inferred from response variables – drilling, tripping-tripping-outout and casing running ¾ Primary response variables are T&D parameters ¾ Surface logging data used to characterize responses ¾ Trend analysis principal evaluation tool ¾ Extent and intensity of data variations evaluated Example – Torque Trend Data

35 Narrow Very low open hole friction factor bandwidth 30 indicative of good drilling practices also OBM used so good lubricity hole quality considered excellent 25

20 (kft.lb) ee 15

Torqu FF = 0.17/0.11 Surface Torque 10 Bit T orque

5

0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Measured Depth (m) Wellbore Quality Scorecard – Guidelines

Casing Running Response (8 points) Score Drilling Response (5 points) Score Severe casingggp running problems Severe d r illing probl ems - stuck casing 0 - stuck pipe 0 - casing pulled due to downhole problems 0 - near stuck pipe incident 1 Differential sticking environment Transient drilling problems - static friction > 100 klbs on connections 1 - poor hole cleaning with high cuttings bed 2 - static friction > 50 klbs on connections 2 - severe pack-off 2 - severe loss circulation 2 Intervention needed during casing run - erratic torque and drag response 3 - unplanned rotation needed 3 - unplanned circulation needed 4 Torque and drag response - jitjoints w ipe dtd to re duce drag 5 - all parameters follow smooth trend 4 - lower than expected torque and drag 5 Casing run without significant problems - elevated but smooth drag levels 6 Final Trip-out Response (7 points) Score - achieved expected drag levels 7 Stuck pi pe 0 - better than expected drag levels 8 Residual cuttings bed / differential sticking Transient tripping-out problems - section length with overpulls > 100 klbs 1 - loss circulation 5 - section length with overpulls > 50 klbs 2 - unplanned circulation 5 - unplanned reaming and back-reaming 5 Ledges Drag response - isolated overpulls > 100 klbs 3 - smooth drag levels measured throughout 6 - isolated overpulls > 50 klbs 4 - better than expected drag levels recorded 7 Wellbore Quality Scores – Interpretation

¾ WQS is recorded as a response mnemonic – D4T5C5 (Drilling 4; Tripping-Tripping-outout 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 Size Weight Grade Connection Top Bottom Bottom @ 486m ins. ppf Type TVD RKB TVD RKB MD RKB 26" 267 XX--6565 XLCXLC--SSSurface 478 m 478 m 1313--3/8"3/8"72 PP--110110 Dino Vam Surface 1443 m 1521 m 13-3/8” shoe 9-5/8" 53. 5 P-110 New Vam Surface 2654 m 3200 m @ 1,521m 5½" 32.6 QQ--125125Vam Top 2554 m MD 2516 m 5398 m

5½” TOL Drill 2,198m 8½” horizontal section @ 2,554m Run 2,844m 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 45 900 BHA 8: RSS + PDC Bit Vibration problems in chalk reservoir BHA 9: RSS + PDC Bit 40 800 FF=0.20/0.15 String RPM 35 700

30 600 String

25 500 R orque (kNm) orque PM

20 400 Surface T Surface 15 300

10 200

5 100

0 0 3,100 3,300 3,500 3,700 3,900 4,100 4,300 4,500 4,700 4,900 5,100 5,300 5,500 Measured Depth (m) Case Study – Tripping-out Response (T2)

300

9-5/8" Shoe TD @ BHA 9: Hookload @ 3,200m 5,398m 250 BHA 9: Surface Torque Pick-Up: FF=0.15/0.20 Elevated Drag Elevated Drag 4,400-4,600m 5,200-5,400m e (kNm) uu 200 Mud Type: OBM Weight = 1.50 SG PV = 36 cP YP = 21 lbf/100ft²

Surface Torq Surface 150

100 ad (tonnes) / / (tonnes) ad

oo Reaming/Back- reaming needed to reduce drag

Hookl 50

0 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 5,500 Measured Depth (m) Case Study – Liner Running Response (C3)

250 9-5/8" Shoe Liner Shoe @ 3,200m @ 5,398m 8¼S¼" Reamer Shoe Severe Slip stick effect 67m 5" 18.0# Q125 H-125 Liner when running liner 453m 5" 26.7# Q125 Vam Top HT 200 2,252m 5½" 32.6# Q125 Vam Top HT Mud Type: OBM 69m 7" 32.0# P110 Vam Top HT Weight = 1.50 SG 2,557m 5½" 26.4# DP 5½" FH PV = 35 cP Nm) kk YP = 19 lbf/100ft²

150 Surface Torque Hookload Slack-Off: FF=0.12/0.45 s) / Torque( ee

100 okload (tonn oo H 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 3,500 4,000 4,500 5,000 5,500 Measured Depth (m) Completed Wellbore Quality Scorecard

Horizontal Well Offshore Norway WQS

Drilling Response (max 5 points) 3 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 siggypnificantly impact overall wellbore qyquality. Average rotary friction factors of 0.20/0.15 are typical of fieldfield--widewide torque behaviour. Final TripTrip--outout Of Hole Response (max 7 points) 2 Elevated drag levels in excess of 50klbs are observed from 4,300 to 4,600m and from 5,200 to 5,,gpgpp400m indicating a possible hole cleaning problem. Overpulls also occur at chalk / shale transition zones. A form of slipslip--stickstick axial drag is also present when tripping-tripping-outout through the open hole section. Average pick-pick-upup friction factors of 0.15/0.20 are typical of fieldfield--widewide experience. Liner Running Response (max 8 points) 3 Liner running in open hole is far from smooth; significant axial slip-slip-stickstick 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. SlackSlack--offoff friction factors of 0.12/0.45 are in line with fieldfield--widewide experience. WQS (D3T2C3) 8 A score of 8 corresponds to a medium quality wellbore. Cost vs. Wellbore Quality Relationship

Field data suggests Low WQS ⇒ ! very high D&C costs EE ost CT WELLBOR CT EE ToohighWQSToo high WQS ⇒ CC higher D&C costs Well THE PERF

Optimum WQS ⇒

Train Low Medium High Excellent lowest D&C costs Wreck Quality Quality Quality Quality

0 2 4 6 8 101214161820 WQS Wellbore Quality Scorecard

Learnings ¾ A low WQS does not always equate to poor performance ¾ A low WQS can be due to degree o f difficult y of d rilli ng and casing running in that field ¾ Poorlyyg designed casin g run can result in failure ¾ Implications of scoring wellbore quality need to be understood by operators / service companies ¾ Wellbore Quality has to be managed at field level ¾ Need to understand Cost vs. Wellbore Quality relationship Managing Wellbore Quality

Drilling Practices ¾ Operating Parameters (WOB, RPM, Flow Rate) ¾ Connection practices ¾ Hole cleaning practices ¾ Mud weight management ¾ Managing packpack--offsoffs ¾ Vibration management ¾ ECD management Managing Wellbore Quality

Tripping / Casing Running Practices ¾ Surge and Swab Pressure Cycles – can result in rock fatigue ¾ Managgging Downhole Problems – cuttings bed, ledging, packpack--offs,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 Characterization important concept ¾ Can reflect degree of difficulty ¾ Most value for horizontal and ERD wells ¾ Industry standard definition needed ¾ Measurement protocol biggest challenge ¾ Wellbore quality scorecard promising technique ¾ Software needed: efficiency, clarity & consistency ¾ Wellbore quality enhancing technology exists Additional Slides Hole Spiralling – Inferred from Logs

Log Evidence: Caliper vs. Neutron Porosity vs. Sonic DT Image Log – 8½” Section Image Logs – 6-1/8” Hole Spiralling Image Logs – 6-1/8” Hole Spiralling Wellbore Quality vs . Tubing Life

¾ Slant drilling Canada ¾ Heavy Oil Reservoir ¾ Pad Drilling ¾ 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” Section – Azerbaijan Well

45 900

Surface Torque - BHA 7 Mud Type: SOBM 40 SfSurface Torque - BHA BHA6 6 Weight = 1 .60 SG 800 On-Bottom: FF=0.25/0.30 PV = 40 cP YP = 29 lbf/100ft² Off-Bottom: FF=0.25/0.30 35 700 Surface RPM

WOB = 20 klbs 30 600 Bit Torque = 5 kft.lb Flow Rate = 1,000 GPM String 25 500 rque (kft.lb) R oo PM 20 400

Surface T 15 300

10 200

5 100

0 0 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 Measured Depth (m) Tripping-out 12¼ ” Hole – Azerbaijan Well

500

450 Hookload Pick-Up: FF=0.20/0.20 400

350

300

ad (klbs) 250 oo

200 Hookl

150

100

50

0 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 Measured Depth (m) Running 9-5/8” Casing – Azerbaijan Well

800 8 13-3/8" Shoe 12-1/4" TD @ 1,560m @ 4,415m 700 7 Hookload Static Up Drag 600 Static Down Drag 6 Pick-Up Trend Slack - Off T rend Slack-Off: FF=0.20/0.30 VeloBlock 500 Block Velocity 5

ad (klbs) 400 4 Mud Type: SOBM c oo Weight = 1.60 SG (m/s) ity PV = 37 cP

Hookl 300 YP = 26 lbf/100ft² 3

200 2

100 1

0 0 0 500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000 Measured Depth (m) WQS – Azerbaijan Well WQS: Wytch Farm ERD Wells

0 M13 M04 ) tt

5,000 M07 M08 M15z M05 M06 M03 M15 M11 F21 M16 M01 F18 M09 F19 M10 M17 M12 F20 M14 M1 M0 TVD BRT (f 8 2

10,000 05,000 10,000 15,000 20,000 25,000 30,000 35,000 40,000 Equivalent Departure (ft) Wytch Farm – Torques 12¼” Section

40

35

M05 30 M09 M11 M14 25 M16

rque (kft.lb) rque 20 oo

15 Surface T Surface

10

5

0 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 Measured Depth (m) Wytch Farm – 9-5/8” Casing Runs

60

40 M09 M11 M14 20 M16

0

ight (klbs) -20 ee

-40 String W String

-60

-80

-100 0 1,000 2,000 3,000 4,000 5,000 6,000 7,000 8,000 9,000 10,000 Measured Depth (m) Wytch Farm ERD Wells – WQS Summary

CthihWQSComments on high WQS ¾ Good learning curve ¾ Continuous ERD drilling program