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

Confidential to DGD JIP 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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

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

Static Pressures in a Conventional Wellbore 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 PRESSURE, psi 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures in a Conventional Wellbore (alternate view) MW = 15 lb/gal Gradient = 0.780 psi/ft 7,800 PRESSURE, psi Top of Drillpipe Bottom of Hole Top of Annulus Drillstring Annulus 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures in a Conventional Wellbore SPP = ? 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 PRESSURE, psi BHP = ? 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures in a Conventional Wellbore SPP = 2,200 psi ( 800 + 1,200 + 200 = 2,200 ) 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 7,800 8,000 9,200 psi PRESSURE, psi 3. Wellbore Pressures Confidential to DGD JIP

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 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Static Pressures - DGD PRESSURE DEPTH Seawater Hydrostatic DGD Mud Hydrostatic BOP 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures Conventional vs. DGD DEPTH Seawater Hydrostatic DGD Mud Hydrostatic Conventional Hydrostatic BOP 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD No DSV DEPTH DGD Mud: Drillstring and Annulus Return Line Seawater Drillstring Hydrostatic BOP 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP U-tubing BOP Circulating Static STATIC FLUID LEVEL 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP What is Delta MW (DMW)? = Mud hydrostatic - Seawater hydrostatic in the water column PRESSURE DEPTH 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 = 3,328 psi Note that the U-Tube driving pressure is, typically, DMW - 50 psi 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures in an DGD Wellbore SW Density = 8.6 lb/gal Mud Weight = 16 lb/gal DEPTH, ft 10,000 What is the BHP ? 20,000 PRESSURE, psi 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Example #3 - Solution At ML, 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 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (No DSV) DEPTH DGD Mud: Drillstring and Annulus Return Line BOP Drillstring Hydrostatic 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures in DGD Wellbore No DSV (alternate view) Drillstring Annulus BHP Static Pressure across the Mudlift Pump Static Fluid Level in DP PRESSURE, psi Bottom of the Hole 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (w / DSV) Static Pressure across the Mudlift Pump PRESSURE DEPTH Annulus Return Line Drillstring DSV BOP 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures - DGD w / DSV DEPTH Annulus Return Line MLP Drillstring Bit + DSV BOP 3. Wellbore Pressures Confidential to DGD JIP

Circ. Pressures in a Conventional Wellbore (alternate view) Drillstring MW = 15 lb/gal Bit AFP 7,800 PRESSURE, psi Annulus Static 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Circ. Pressures in an DGD Wellbore (alternate view) Drillstring MW = 15 lb/gal MW = 15 lb/gal Bit AFP 7,800 PRESSURE, psi Annulus Static Conventional MLP Drillstring Annulus 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Effect of Hydrostatics on Wellbore Pressure Profile Depth, ft Gas @ 1 lb/gal Cement @ 16 lb/gal Mud @ 12 lb/gal Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? Water @ 8.6 lb/gal 10,000 520 4,472 6,240 8,320 Pressure, psi 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 520 Gas @ 1 lb/gal 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? Drillstring Annulus 10,000 20,000 Distance from Standpipe, ft 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP “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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

~SEAWATER HYDROSTATIC PRESSURE Confidential to DGD JIP Subsea Mudlift Drilling System FLOATER Surface Pump: Constant Rate Mudlift Pump: Const. Inlet Press. ~SEAWATER HYDROSTATIC PRESSURE 10,000’ SEAFLOOR BOP MUDLIFT 30,000’ KICK What next?? 3. Wellbore Pressures Confidential to DGD JIP 27

Confidential to DGD JIP Kick Detection and Control 3. Wellbore Pressures Confidential to DGD JIP 28

Confidential to DGD JIP Kick Detection and Control Influx has stopped and pressures have stabilized ATM 3. Wellbore Pressures Confidential to DGD JIP 28

Confidential to DGD JIP Kick Detection and Control ATM 3. Wellbore Pressures Confidential to DGD JIP 28

Confidential to DGD JIP Dynamic Underbalance Dynamic Underbalance = required increase in BHP to stop influx while circulating Total Underbalance = (conventional) SIDP = Dynamic Underbalance + AFP AFP = Annular Friction Pressure Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Pressure Profile in Wellbore During a Connection (w/DSV) Circulating - before connection During Connection - Rig Pump Stopped - Annular Friction Pressure (AFP) is lost - Annular Friction Pressure (AFP) is applied at the MLP inlet Circulating - after connection Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures Before Connection DEPTH BOP Return Line - Circulating Annulus - Circulating 3. Wellbore Pressures Confidential to DGD JIP

Static and Circulating Pressures in DGD DEPTH BOP Return Line - Circulating Static Return Line Friction Annulus - Circulating Annulus - Static AFP 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures in DGD After Rig Pump is Stopped for Connection DEPTH BOP Static Return Line Friction Annulus - Static AFP 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Static Pressures in DGD After Rig Pump is Stopped. AFP Applied at MLP to Avoid Chance of Kick PRESSURE DEPTH BOP Static Return Line Friction New Annulus - Static Old Annulus - Static AFP 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures in DGD. Rig Pump is Restarted. AFP is Removed DEPTH BOP Return Line - Circulating Static Return Line Friction New Annulus - Circulating Old Annulus - Static AFP 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP 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 Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Static and Circulating Pressures in DGD - no Kick DEPTH BOP Return Line - Circulating Static MLP Return Line Friction Annulus - Circulating Annulus - Static AFP 3. Wellbore Pressures Confidential to DGD JIP

Circulating Pressures in DGD - Kick in Progress - no Action MLP Speeds Up - Automatically PRESSURE DEPTH BOP Return Line - w/Kick Return Line - Before Kick Extra Return Line Friction Annulus - Before Kick Annulus - w/Kick Kick, 2.5 ppg 3. Wellbore Pressures Confidential to DGD JIP

Slow Down MLP to Stop Influx - Kick Still Near Bottom Kick at Bottom - 2.5 lb/gal kick fluid PRESSURE DEPTH Annulus Return Line BOP Hydrostatic Effect of Large Kick at Bottom Kick 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Intensity Wellbore Pressure Profile - Small Kick Kick Intensity = 0.5 lb/gal = 0.052 * 0.5 * 10,000 = 260 psi PRESSURE DEPTH Annulus Return Line BOP 8,000 Effect of Kick Intensity - Small Kick 18,000 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Size and Intensity on Wellbore Pressures Profile Kick still near Bottom - 2.5 lb/gal kick fluid BOP Return Line Effect of Kick Intensity and Size DEPTH Annulus PRESSURE Kick 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Size and Intensity on Wellbore Pressures Profile Kick Halfway up Annulus - 2.2 lb/gal kick fluid PRESSURE DEPTH Annulus Return Line BOP Effect of Kick Intensity and Large Kick Kick 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Size and Intensity on Wellbore Pressures Profile Top of Kick at Mudline PRESSURE DEPTH Annulus Return Line BOP Kick ~ 1.8 lb/gal Effect of Kick Intensity 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Size and Intensity on Wellbore Pressures Profile Bottom of Kick at Mudline PRESSURE DEPTH Annulus Return Line BOP Kick - 2.1 lb/gal Effect of Kick Intensity 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kick Size and Intensity on Wellbore Pressures Profile Kick is Out of Hole PRESSURE DEPTH Annulus Return Line Effect of Kick Intensity BOP 3. Wellbore Pressures Confidential to DGD JIP

Effect of Kill Mud on Wellbore Pressures Profile Kill Mud Totally Fills Hole PRESSURE DEPTH Annulus Return Line - Before Kick Effect of Kill Mud BOP 3. Wellbore Pressures Confidential to DGD JIP

Effect of Very Large Kick on Wellbore Pressures Profile DEPTH Annulus Return Line Annulus Filled with Gas May need Surface Choke BOP 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Pressure Profile in Wellbore During SIDP Measurement w/DSV Static Conditions DSV Set at Exact Balance DSV Set ONE or TWO lb/gal above balance Pressure Profile when DSV opens How to interpret the results and determine SIDP and Kick Intensity Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (w / DSV) Exact Balance - no Kick DEPTH Annulus Return Line Drillstring DSV BOP 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (w / DSV) - No Kick 0.052 * 1 * 10,000 = 520 psi 0.052 * 2 * 10,000 = 1,040 psi PRESSURE DEPTH BOP Drillstring DSV in Balance DSV + 1 lb/gal DSV + 2 lb/gal Return Line 10,000 Annulus DSV 30,000 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (w / DSV) 0.5 lb/gal Kick 0.052 * 0.5 * 20,000 = 520 psi PRESSURE DEPTH Drillstring DSV in Balance w/0.5 lb/gal kick BOP Return Line 10,000 Annulus DSV 30,000 3. Wellbore Pressures Confidential to DGD JIP

Static Pressures - DGD (w / DSV) 0.5 lb/gal Kick 0.052 * 1 * 10,000 = 520 psi 0.052 * 0.6 * 20,000 = 624 psi PRESSURE DEPTH BOP Drillstring DSV in Balance DSV @ 1 lb/gal + 0.6 lb/gal kick Return Line 10,000 Annulus DSV 30,000 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Measuring SIDP w/DSV In the last example above, after a total shut-in, it takes 1,144 psi to open the DSV The DSV is set for 1 lb/gal above balance This accounts for 520 psi The remaining 624 psi corresponds to a kick intensity of 0.6 lb/gal Conclusion: SIDP = 1,144 - 520 = 624 psi Kick Intensity = 0.6 lb/gal Increase mud weight by 0.6 lb/gal 0.052 * 1 * 10,000 = 520 psi 0.052 * 0.6 * 20,000 = 624 psi Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Factors Affecting Pressure Profile in Wellbore Hydrostatics (mud weight) (Drillstring & Ann.) Friction (circulation rate) (Drillstring & Ann.) Changed MLP Inlet Pressure (Drillstring & Ann.) Kick (Kick Intensity) (Drillstring & Ann. Kick (Hydrostatics) (Annulus) Area Change (e.g., nozzles) (Drillstring) DSV Setting (Drillstring) Similar to conventional -- brief description of key elements in a good balanced cement plug operation U-tube effects -- need to show how/where the calculations are impacted by U-tube considerations (link to a calculation display?) Need to link to graphic of the cement U-tube? Does our existing graphic work or do we need something different? 3. Wellbore Pressures Confidential to DGD JIP

SUMMARY of Wellbore Pressures - DGD (w / DSV) Static BOP Circulating Return Line Drillstring DEPTH Annulus PRESSURE DSV 3. Wellbore Pressures Confidential to DGD JIP

Wellbore Pressures - Summary Drillstring Annulus Return Line Circulating Conventional Circulating - DGD - No DSV Pressure Static - DGD Static - Conventional ML ML Distance from Standpipe 3. Wellbore Pressures Confidential to DGD JIP

Confidential to DGD JIP Questions? Static Pressures Circulating Pressures Kick Hydrostatic Kick Intensity Friction Delta MW (DMW) = ? Dynamic Underbalance? 3. Wellbore Pressures Confidential to DGD JIP

by Hans C. Juvkam-Wold November 2000 The End Subsea Mudlift Drilling Basic Technology by Hans C. Juvkam-Wold November 2000 The End 3. Wellbore Pressures 3. Wellbore Pressures Confidential to DGD JIP