Friction Grip in Wellheads: An Innovative Approach to Load Support & Sealing Brent Harrald Principal Engineer Plexus Ocean Systems Ltd. December 2009 Page 1
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
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
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
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
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
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
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
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
Wellhead Location This presentation will focus on surface wellheads Exploration well OR Production well Surface wellhead OR Subsea wellhead Page 10
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
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
Initial Concept The idea: an adjustable surface wellhead for use above mudline suspension systems on jack-up drilling rigs 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Page 13
Existing Adjustable Wellheads Slip & Seal Wellhead Adjustable Shoulder Wellhead Adjustable Casing Sleeve Page 14
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 15
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 16
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 17
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 18
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 19
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 20
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 21
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 22
POS-GRIP Friction-grip Wellhead Concept Type 1 Type 2 Page 23
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
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
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
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
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
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
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
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
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 2200000 ACT-SUM: Experimental Spread of POS-GRIP Activation Curves Indicating Hanger Clearance Regimes 2000000 1800000 Tensioner Load (pounds) 1600000 1400000 1200000 1000000 800000 Minimum Load (Loose Clearance) Maximum Load (Tight Clearance) Mean Load 600000 400000 200000 0 0 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 Flange Gap (mils) Page 32
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
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 80000 70000 Von Mises FEA 1 Von Mises FEA 2 60000 Von Mises Stresses (psi) 50000 40000 30000 20000 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 30000 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 3 10000 0 12.0 17.0 22.0 27.0 32.0 37.0 42.0 47.0 Distance along Line 1 (inches) 20000 10000 Axial FEA 4 Axial FEA 5 Hoop FEA 3 Stress (psi) Hoop FEA 4 0 17.0 22.0 27.0 32.0 37.0 42.0 47.0 Hoop FEA 5-10000 Axial Actual (mean) Hoop Actual -20000 (mean) -30000-40000 -50000 Location along line 1 (inches) Axial Actual (min) Axial Actual (max) Hoop Actual (min) Hoop Actual (max) Page 34
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 70 13-5/8 10K systems installed Over 25 18-3/4 15K systems installed Page 35
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
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 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Page 37
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
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
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
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 100 480,000 cycles Percentage of static failure load 80 60 40 20 75 70 105 Percentage of static failure load 80 60 40 20 71 113 0 0 20 40 60 80 100 120 Shear displacement (um) 0 0 20 40 60 80 100 120 Shear displacement (um) Percentage of static failure load 100 80 60 40 20 750,000 cycles 71 114 Percentage of static failure load 100 80 60 40 20 1 million cycles 69 113 0 0 20 40 60 80 100 120 Shear displacement (um) 0 0 20 40 60 80 100 120 Shear displacement (um) Page 41
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
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
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
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
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 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Page 46
Extended Seal Qualification HG seal to be requalified to 20,000 psi, 0 350 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
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
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
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
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
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
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 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 Page 53
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
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
Any Questions? Thanks for your time Brent Harrald beh@posgrip.com 01224-774-222 Page 56