Friction Grip in Wellheads: An Innovative Approach to Load Support & Sealing

Transcription

1 Friction Grip in Wellheads: An Innovative Approach to Load Support & Sealing Brent Harrald Principal Engineer Plexus Ocean Systems Ltd. December 2009 Page 1

2 Table of Contents Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 2

3 Introduction to Plexus Ocean Systems Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 3

4 Who is Plexus? Plexus Ocean Systems Limited rents and sells wellhead products and associated equipment to a number of major oil & gas operators. Plexus products utilize patented POS- GRIP technology to grip tubular components. Page 4

5 Plexus Today Offices in Aberdeen, London, & Malaysia Publicly traded on London AIM 70+ worldwide employees In year ending 30 June 2009: 14% increase in turnover to 15.1m Profit before tax of 1.8m Less than 2% of global wellhead market share Page 5

6 Introduction to Conventional Wellhead Technology Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 6

7 The Wellhead Industry The wellhead industry is mature, large, and regulated Global market f/ wellhead equipment is over 1 billion / annum Major wellhead suppliers include Cameron, Dril-Quip, FMC, GE Oil & Gas (Vetco), Wood Group. Standard wellhead design regulated by API 6A & API 17D Page 7

8 What is a Wellhead? A wellhead is the pressurecontaining end connection of a well which: Provides a connection point for the Blowout Preventer (BOP) equipment while drilling a well Provides a connection point for the X-mas Tree equipment while producing a well Seals the annulus between casing strings Suspends multiple casing strings Page 8

9 Conventional Wellhead Hanger Support Technology Mandrel Wellhead Casing supported by hanger landed on shoulder Fixed landing point Casing hanger can be run through BOP stack Enables use of high-grade metal-to-metal seals Slip & Seal Wellhead Casing support through slips Adjustable landing point Requires BOP stack to be lifted to cut casing Resilient seals only Page 9

10 Wellhead Location This presentation will focus on surface wellheads Exploration well OR Production well Surface wellhead OR Subsea wellhead Page 10

11 Drilling from Jack-up Rigs w/ Mudline Suspension BOP Surface Wellhead: Supports little casing weight Seals annulus Provides BOP interface Fixed distance means spaceout is required Mudline Suspension: Supports most casing weight Page 11

12 Development of POS-GRIP Exploration Wellheads Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 12

13 Initial Concept The idea: an adjustable surface wellhead for use above mudline suspension systems on jack-up drilling rigs Page 13

14 Existing Adjustable Wellheads Slip & Seal Wellhead Adjustable Shoulder Wellhead Adjustable Casing Sleeve Page 14

15 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 15

16 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 16

17 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 17

18 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 18

19 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 19

20 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 20

21 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 21

22 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 22

23 POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 23

24 POS-GRIP Wellhead Technology POS-GRIP is a method of supporting oil field tubulars with an externally activated radial friction grip. In wellheads, POS-GRIP replaces the conventional casing slips or landing shoulders. Contact Stress at interface: Q Coefficient of friction at interface: m Contact Area at interface: A Load Capacity = Q x m x A Page 24

25 Materials in a POS-GRIP System Wellhead Housing Body Requirements Low Young s Modulus Corrosion resistance & NACE compliance Compression Ring Requirements High Young s Modulus & high strength Compression Collar Requirements Little distortion when split Hanger Requirements High Young s Modulus & high strength Corrosion resistance & NACE compliance General Requirements Cost, availability, etc. Page 25

26 Assessment of Friction Profiles Consider load-supporting friction interface Need as high a static coefficient of friction as possible WH bore or POS-GRIP element surface kept smooth Hanger OD should be rough to maximize friction: many potential options exist Page 26

27 Small-scale friction testing Which rough hanger surface to use? Test & assess several profiles in small-scale testing Test multiple samples of each potential profile Measure load capacity & bite Shear Load Normal Load Measure block travel Page 27

28 Hanger Design: Friction Profile Selected Design hanger outer diameter: Biased tooth profile selected as standard Incorporate flutes through the toothed area so fluid returns can flow past hanger when it is being run Annulus seal profile above gripping section Friction profile Annulus seal profile High capacity Low capacity Page 28

29 Grip Coefficient Rough profile bites into smooth profile: Grip coefficient (F); not coefficient of friction (m) Frictional load support & shear strength combined Values must be determined empirically Local plastic deformation in WH / POS-GRIP element bore Page 29

30 Load Capacity Calculation Method Load Capacity = Grip Coefficient x Contact Stress x Contact Area Contact stress determined by various engineering methods External pressure at friction interface decreases contact stress Page 30

31 Load Capacity Calculation Method Load Capacity = Grip Coefficient x Contact Stress x Contact Area Contact stress determined by various engineering methods Internal pressure at friction interface increases contact stress Page 31

32 Tolerance Study 3 critical interfaces, over 6 critical dimensions in load path Strong dependence of load capacity on tolerance stack-up Must over-design to have sufficient capacity in worst-case tolerance stack-up Compression ring / collar interface Compression collar / WH body interface WH body / hanger interface ACT-SUM: Experimental Spread of POS-GRIP Activation Curves Indicating Hanger Clearance Regimes Tensioner Load (pounds) Minimum Load (Loose Clearance) Maximum Load (Tight Clearance) Mean Load Flange Gap (mils) Page 32

33 POS-GRIP Activation Activation applied via hydraulic stud tensioners Load control could eliminate tolerance stack-up, but Distance control is operationally far easier Distance control with feedback? Page 33

34 Physical Test w/ FEA Correlation Verify 6 million pound load capacity of 18-3/4 system Test in several different configurations, under several different loadings Compare strain gauge data to 3D FEA results FEA Correlation Plot: Von Mises Stresses in Housing ID, Case "A" NH007: No Hanger: Squeeze 0.99" (To 0.32" Flange Gap) September 12, 2001: 11:49 AM - 11:53 AM Von Mises FEA 1 Von Mises FEA Von Mises Stresses (psi) Von Mises Actual (1 mean Von Mises Actual (2 mean Von Mises Actual (1 min Von Mises Actual (1 max Von Mises Actual (2 min Von Mises Actual (2 max FEA Correlation Plot: 13-3/8" Hanger ID, Case "D" L13H006: 13-3/8" Loose Clearance Hanger: Hanger Load (1.6 million #) September 20,2001: 3:34 PM - 3:41 PM Axial FEA Distance along Line 1 (inches) Axial FEA 4 Axial FEA 5 Hoop FEA 3 Stress (psi) Hoop FEA Hoop FEA Axial Actual (mean) Hoop Actual (mean) Location along line 1 (inches) Axial Actual (min) Axial Actual (max) Hoop Actual (min) Hoop Actual (max) Page 34

35 13-5/8 & 18-3/4 POS-GRIP Adjustable Wellheads Designed f/ up to 15 ksi exploration wells (short-term, high-pressure) Between 45 & 72 hours saved compared to conventional equipment f/ 18-3/4 size (up to 2 BOP lifts eliminated) First installed 1998 Through end of 2009: Over /8 10K systems installed Over /4 15K systems installed Page 35

36 Development of HG Production Wellhead Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 36

37 New Market: Long-Term Use in Production Wells The aim: Re-engineer the existing systems for use on production wells 1997: POS-GRIP patented in UK 1998: First 13-5/8 10 ksi WH installed 2000: Design exercise f/ 18-3/4 15 ksi WH s initiated 2004: First 18-3/4 15 ksi WH s installed in North Sea Page 37

38 New Materials Long-term production life makes the requirement for corrosion resistant alloys (CRA s) common Hanger body materials most affected Most common CRA, Alloy 718, is: Slower to machine Requires plasma ion nitriding instead of gas nitriding Reduced grip coefficient Page 38

39 New Tooth Profile Biased teeth limit lockdown capability; Therefore change to symmetrical tooth profile Test grip coefficient to verify capacity of new profile High capacity Low capacity Avg. capacity Avg. capacity Page 39

40 Fatigue Study Fatigue testing in conjunction w/ the University of Aberdeen Study fatigue performance of unbiased tooth profile: 2 samples each at 2 separate contact stresses Cycled between 40% & 80% of static failure load 1 million cycles at 3Hz frequency 1 test sample in each contact stress taken to static failure after cycles F max =80% of static load capacity Shear Load F min =40% of static load capacity Time Page 40

41 Fatigue Study Results No degradation of applied load / movement profile over cycles Static failure test after fatigue tests produces grip coefficient result no less than result achieved in static conditions. 100 Start-up ,000 cycles Percentage of static failure load Percentage of static failure load Shear displacement (um) Shear displacement (um) Percentage of static failure load ,000 cycles Percentage of static failure load million cycles Shear displacement (um) Shear displacement (um) Page 41

42 POS-GRIP HG Sealing Takes advantage of already-present high-contact stress, forcedconcentric bore, & rigid lockdown Built into outer diameter of hanger, so a seal is only needed at one interface (instead of two) Conventional annulus seal HG seal Page 42

43 HG Seal Qualification Test program designed to simulate temperature (250 deg. F) / pressure (15 ksi) cycles expected over field life Standard API 6A Appendix F test cycle+ 10 temperature cycles + another API 6A Appendix F test cycle Page 43

44 HG Production WH Designed for up to 15 ksi production wells (long-term) Available in 13-5/8 & 18-3/4 sizes Utilizes 15 ksi-rated metal-to-metal HG seals First installed 2005 Nine installed through 2009 Page 44

45 Development of 18-3/4 20 ksi Wellhead Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 45

46 Increasing Pressure: 20 ksi Production WH The aim: Take the proven 18-3/4 15 ksi production system & adapt it for use in a 20 ksi environment 1997: POS-GRIP patented in UK 1998: First 13-5/8 10 ksi WH installed 2000: Design exercise f/ 18-3/4 15 ksi WH s initiated 2004: First 18-3/4 15 ksi WH s installed in North Sea 2005: 15 ksi HG seal qualification testing complete 2005: First HG wellhead installed in North Sea Page 46

47 Extended Seal Qualification HG seal to be requalified to 20,000 psi, deg F Extended field-life service, similar to 15,000 psi qualification New test arrangement allows heating & cooling of test fixture internally, to best simulate real-world conditions Heat In Returns Out Heating / Cooling Unit Page 47

48 Additional FEA High-Pressure Concerns Confirmed static component stresses & contact stresses in new design Planned consideration of dynamic aspects of loading by performing: Limit load FEA Elastic shakedown Fracture mechanics FEA Page 48

49 States of stress in a POS-GRIP wellhead are fundamentally different to those in a conventional wellhead von Mises equivalent stress States of Stress: No Internal Pressure von Mises equivalent stress Compression rings in Tension 0 psi 0 psi WH Body in Compression Pressure in WH bore = 0 psi Pressure in WH bore = 0 psi Mandrel Wellhead POS-GRIP Wellhead Page 49

50 States of Stress: Internal Pressure States of stress in a POS-GRIP wellhead are fundamentally different to those in a conventional wellhead von Mises equivalent stress von Mises equivalent stress Large Change in State of Stress, 0 psi WH in tension 0 psi Little Change in State of Stress WH Body remains in Compression Pressure in WH bore > 0 psi Mandrel Wellhead Pressure in WH bore > 0 psi POS-GRIP Wellhead Page 50

51 Plexus 20 ksi rated Surface Production Wellhead Designed f/ 20 ksi production wells (long-term, high-pressure) Initial design / proof of concept complete 20 ksi HG metal-to-metal seal qualification in progress Page 51

52 Future POS-GRIP Applications Introduction Plexus Ocean Systems Conventional wellhead technology POS-GRIP: Development of a New Product From initial idea to first commercial implementation (13-5/8 & 18-3/4 exploration wellheads) From short-term use to long-term use (HG production wellheads) Increasing pressure (18-3/4 20 ksi POS-GRIP wellheads) The Future (POS-GRIP subsea & connectors) Page 52

53 The Future The Aim: Extend POS-GRIP s use into still more challenging environments 1997: POS-GRIP patented in UK 1998: First 13-5/8 10 ksi WH installed 2000: Design exercise f/ 18-3/4 15 ksi WH s initiated 2004: First 18-3/4 15 ksi WH s installed in North Sea 2005: 15 ksi HG seal qualification testing complete 2005: First HG wellhead installed in North Sea 2008: Contract awarded f/ design of 20 ksi WH Page 53

54 The Future: M2S Subsea Conversion First use of POS-GRIP subsea First system installed in 2008 With full metal-to-metal production casing string sealing, converted mudline suspension to 13-5/8 5 ksi subsea wellhead Page 54

55 The Future: HPHT Subsea TB Subsea connector to allow tieback to pre-drilled HPHT well Metal-to-metal HG seals Joint-industry partnership kicking off in 2010 Page 55

56 Any Questions? Thanks for your time Brent Harrald Page 56