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Lesson 3

Lesson 3. Dual Gradient Drilling Basic Technology. by Hans C. Juvkam-Wold. Wellbore Pressures. Contents. Static Pressures in a conventional wellbore Circulating Press. in a conventional wellbore Static Pressures in an DGD wellbore

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Lesson 3

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  1. Lesson 3 Dual Gradient DrillingBasic Technology by Hans C. Juvkam-Wold Wellbore Pressures Confidential to DGD JIP

  2. Contents • Static Pressures in a conventional wellbore • Circulating Press. in a conventional wellbore • Static Pressures in an DGD wellbore • Circulating Pressures in DGD wellbores, with and without Drillstring Valve (DSV) • Pressure Profiles During a Connection • Pressure Profiles when a Kick Occurs Confidential to DGD JIP

  3. Static Pressures in a Conventional Wellbore 0 Mud Weight = 15 lb/gal Gradient = 0.780 psi/ft DEPTH, ft Same inside and outside the wellbore 10,000 7,800 0 PRESSURE, psi Confidential to DGD JIP

  4. Static Pressures in a Conventional Wellbore 0 Depth Pressure ft psi 0 0 1 0.78 2 1.56 3 2.34 10 7.8 100 78 1,000 780 2,000 1,560 3,000 2,340 5,000 3,900 10,000 7,800 Mud Weight = 15 lb/gal Gradient = 0.780 psi/ft DEPTH, ft Same inside and outside the wellbore 10,000 7,800 0 PRESSURE, psi Confidential to DGD JIP

  5. Static Pressures in a Conventional Wellbore (alternate view) MW = 15 lb/gal Gradient = 0.780 psi/ft 7,800 PRESSURE, psi Top of Drillpipe Top of Annulus Bottom of Hole Annulus Drillstring 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  6. Circulating Pressures in a Conventional Wellbore SPP = ? 0 Drillstring Friction = 800 psi Pressure Across bit = 1,200 psi Annular Friction = 200 psi Mud Weight = 15 lb/gal Drillstring & Annulus Static DEPTH, ft Drillstring Circulating Annulus Circulating 10,000 Bit 0 BHP = ? PRESSURE, psi Confidential to DGD JIP

  7. Circulating Pressures in a Conventional Wellbore SPP = 2,200 psi ( 800 + 1,200 + 200 = 2,200 ) 0 Drillstring Friction = 800 psi Pressure Across bit = 1,200 psi Annular Friction (AFP) = 200 psi Mud Weight = 15 lb/gal Static, DS & Annulus DEPTH, ft Drillstring Annulus 10,000 Circ. BHP = DPHYDRO + AFP = 7,800 + 200 = 8,000 psi 9,200 psi 8,000 7,800 0 PRESSURE, psi Confidential to DGD JIP

  8. Circulating Pressures in a Conventional Wellbore (alt. view) MW = 15 lb/gal 9,200 psi Bit Circ. BHP = 8,000 psi 7,800 PRESSURE, psi Static 2,200 Annulus Drillstring 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  9. Seawater Hydrostatic BOP DEPTH DGD Mud Hydrostatic PRESSURE Static Pressures - DGD Confidential to DGD JIP

  10. Seawater Hydrostatic BOP DGD Mud Hydrostatic DEPTH Conventional Hydrostatic PRESSURE Static Pressures Conventional vs. DGD Confidential to DGD JIP

  11. Return Line Seawater Drillstring Hydrostatic BOP DGD Mud: Drillstring and Annulus DEPTH PRESSURE Static Pressures - DGDNo DSV Confidential to DGD JIP

  12. Static Circulating STATICFLUIDLEVEL BOP U-tubing Confidential to DGD JIP

  13. DEPTH PRESSURE What is Delta MW (DMW)?= Mud hydrostatic - Seawater hydrostatic in the water column Seawater Hydrostatic = 0.052 * 8.6 * 10,000 = 4,472 psi Mud Hydrostatic in the water column = 0.052 * 15 * 10,000 = 7,800 psi DMW = Difference in Hydrostatic = 7,800 - 4,472 = 3,328 psi 4,472 psi DMW Note that the U-Tube driving pressure is, typically, DMW - 50 psi = 3,328 psi Confidential to DGD JIP

  14. Static Pressures in an DGD Wellbore 0 SW Density = 8.6 lb/gal Mud Weight = 16 lb/gal DEPTH, ft 10,000 What is the BHP ? 20,000 0 PRESSURE, psi Confidential to DGD JIP

  15. Example - Calculation • Seawater hydrostatic = 0.052 * 8.6 * 10,000 = 4,472 psi • Mud Hydrostatic = 0.052 * 16 * 10,000 = 8,320 psi • BHP = 4,472 + 8,320 BHP = 12,792 psi Confidential to DGD JIP

  16. Example #2 If the 20,000-ft well discussed in the previous example were to be drilled conventionally, what mud weight would you use in order to achieve the same BHP? Hint: Use the same mud weight from top to bottom. p = 12,792 psi Confidential to DGD JIP

  17. Example #2 - Solution BHP, p = 0.052 * MW * Depth 12,792 = 0.052 * MW * 20,000 MW = 12,792 / (0.052 * 20,000) MW = 12.30 lb/gal { Note that (8.6 + 16.0) /2 = 12.30 …} any comments? p = 12,792 psi Confidential to DGD JIP

  18. Example #3 A new well is to be drilled using DGD. Water depth is 8,000 ft. Depth BML is 19,000 ft. BHP is expected to be 20,000 psi. What DGD Mud weight will be required? 8,000’ ML 19,000’ p = 20,000 psi Confidential to DGD JIP

  19. Example #3 - Solution AtML, p1 = 0.052 * Density * Depth p1 = 0.052 * 8.6 * 8,000 = 3,578 psi Hydrostatic Pressure below the ML, p2 = 20,000 - 3,578 = 16,422 psi MW = 16,422 / (0.052 * 19,000) MW = 16.62 lb/gal 8,000’ ML 19,000’ p = 20,000 psi Confidential to DGD JIP

  20. Return Line Drillstring Hydrostatic BOP DGD Mud: Drillstring and Annulus DEPTH PRESSURE Static Pressures - DGD (No DSV) Confidential to DGD JIP

  21. Static Pressures in DGD Wellbore No DSV (alternate view) Annulus Drillstring BHP Static Pressure across the Mudlift Pump Static Fluid Level in DP PRESSURE, psi Bottom of the Hole 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  22. Static Pressure across the Mudlift Pump Return Line Drillstring BOP DEPTH Annulus PRESSURE DSV Static Pressures - DGD (w / DSV) Confidential to DGD JIP

  23. Return Line Drillstring BOP MLP DEPTH Annulus Bit + DSV PRESSURE Circulating Pressures - DGD w / DSV Confidential to DGD JIP

  24. Circ. Pressures in a Conventional Wellbore (alternate view) MW = 15 lb/gal Drillstring Bit AFP 7,800 PRESSURE, psi Annulus Static 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  25. Circ. Pressures in an DGD Wellbore (alternate view) MW = 15 lb/gal MW = 15 lb/gal Drillstring Bit AFP 7,800 PRESSURE, psi Annulus Static Conventional MLP Annulus Drillstring 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  26. Factors Affecting Pressure Profile in Wellbore • Hydrostatics (mud, water, gas, cement slurry) • Friction • Drillpipe • Annulus • Area Change (nozzle, tool joint, MWD Sub, etc.) • Kick • Hydrostatics (kick density lower than mud density) • Kick Intensity Confidential to DGD JIP

  27. Effect of Hydrostatics on Wellbore Pressure Profile 0 Depth, ft Cement @ 16 lb/gal Gas @ 1 lb/gal Mud @ 12 lb/gal Water @ 8.6 lb/gal 10,000 0 520 6,240 4,472 8,320 Pressure, psi Confidential to DGD JIP

  28. Effect of Hydrostatics on Wellbore Pressure Profile Drillstring Annulus 8,320 Mud @ 12 lb/gal Cement @ 16 lb/gal 6,240 PRESSURE, psi 4,472 Water @ 8.6 lb/gal 520 Gas @ 1 lb/gal 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  29. Effect of Friction on Pressure Profile in Conventional Wellbore Bit MW = 15 lb/gal High Circ. Rate Higher circulation Rate means Higher Friction Loss Medium Circ. Rate PRESSURE, psi Static Drillstring Annulus 0 0 10,000 20,000 Distance from Standpipe, ft Confidential to DGD JIP

  30. “Dynamic Shut-in” of Kick(Stop Influx while Circulating) • When well kicks, MLP speeds up (pump is controlled by constant pump inlet pressure) • Change pump from pressure control to rate control. Slow down MLP to pre-kick rate • As a result the wellbore pressure increases until the influx stops (PWELLBORE = PFORMATION) • The kick is now under control • SIDP can now be determined Confidential to DGD JIP

  31. Subsea Mudlift Drilling System FLOATER Surface Pump: Constant Rate Mudlift Pump: Const. Inlet Press. ~SEAWATER HYDROSTATIC PRESSURE 10,000’ SEAFLOOR BOP MUDLIFT 30,000’ What next?? KICK Confidential to DGD JIP

  32. Kick Detection and Control Confidential to DGD JIP

  33. Kick Detection and Control Influx has stopped and pressures have stabilized ATM Confidential to DGD JIP

  34. Kick Detection and Control ATM Confidential to DGD JIP

  35. Dynamic Underbalance Dynamic Underbalance = required increase in BHP to stop influx while circulating Total Underbalance = (conventional) SIDP = Dynamic Underbalance + AFP AFP = Annular Friction Pressure Confidential to DGD JIP

  36. Pressure Profile in WellboreDuring a Connection (w/DSV) • Circulating - before connection • During Connection - Rig Pump Stopped - Annular Friction Pressure (AFP) is lost • During Connection - Rig Pump Stopped - Annular Friction Pressure (AFP) is applied at the MLP inlet • Circulating - after connection Confidential to DGD JIP

  37. BOP DEPTH PRESSURE Circulating Pressures Before Connection Return Line - Circulating Annulus - Circulating Confidential to DGD JIP

  38. BOP DEPTH PRESSURE Static and Circulating Pressures in DGD Return Line - Circulating Static Return Line Friction Annulus - Circulating Annulus - Static AFP Confidential to DGD JIP

  39. BOP DEPTH PRESSURE Static Pressures in DGD After Rig Pump is Stopped for Connection Static Return Line Friction Annulus - Static AFP Confidential to DGD JIP

  40. BOP DEPTH PRESSURE Static Pressures in DGD After Rig Pump is Stopped. AFP Applied at MLP to Avoid Chance of Kick Static Return Line Friction New Annulus - Static Old Annulus - Static AFP Confidential to DGD JIP

  41. BOP DEPTH PRESSURE Circulating Pressures in DGD. Rig Pump is Restarted. AFP is Removed Return Line - Circulating Static Return Line Friction New Annulus - Circulating Old Annulus - Static AFP Confidential to DGD JIP

  42. Pressure Profile in Wellbore- Changes when a Kick Occurs • Drilling - before kick begins • Kick in progress - no action taken yet • Influx is stopped - kick is still near bottom • Kick moves up the hole • Top of kick is at mudline • Bottom of kick is at mudline • Kill mud is filling annulus • Kill mud all the way Confidential to DGD JIP

  43. BOP DEPTH PRESSURE Static and Circulating Pressures in DGD - no Kick Return Line - Circulating Static MLP Return Line Friction Annulus - Circulating Annulus - Static AFP Confidential to DGD JIP

  44. BOP DEPTH PRESSURE Circulating Pressures in DGD - Kick in Progress - no Action MLP Speeds Up - Automatically Return Line - w/Kick Return Line - Before Kick Extra Return Line Friction Annulus - Before Kick Annulus - w/Kick Kick, 2.5 ppg Confidential to DGD JIP

  45. Return Line BOP Hydrostatic Effect of Large Kick at Bottom DEPTH Annulus PRESSURE Slow Down MLP to Stop Influx- Kick Still Near Bottom Kick at Bottom - 2.5 lb/gal kick fluid Kick Confidential to DGD JIP

  46. Return Line BOP Effect of Kick Intensity - Small Kick DEPTH Annulus PRESSURE Effect of Kick Intensity Wellbore Pressure Profile - Small Kick Kick Intensity = 0.5 lb/gal = 0.052 * 0.5 * 10,000 = 260 psi 8,000 18,000 Confidential to DGD JIP

  47. BOP Effect of Kick Size and Intensity on Wellbore Pressures Profile Kick still near Bottom - 2.5 lb/gal kick fluid Return Line Effect of Kick Intensity and Size DEPTH Annulus Kick PRESSURE Confidential to DGD JIP

  48. Return Line BOP DEPTH Annulus PRESSURE Effect of Kick Size and Intensity on Wellbore Pressures Profile Kick Halfway up Annulus - 2.2 lb/gal kick fluid Effect of Kick Intensity and Large Kick Kick Confidential to DGD JIP

  49. Return Line BOP DEPTH Annulus PRESSURE Effect of Kick Size and Intensity on Wellbore Pressures Profile Top of Kick at Mudline Kick ~ 1.8 lb/gal Effect of Kick Intensity Confidential to DGD JIP

  50. Return Line BOP DEPTH Annulus PRESSURE Effect of Kick Size and Intensity on Wellbore Pressures Profile Bottom of Kick at Mudline Kick - 2.1 lb/gal Effect of Kick Intensity Confidential to DGD JIP

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