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SUBSEA WELL CONTROL

SUBSEA WELL CONTROL. SUBSEA STACK DIFFERENCES. Choke and kill line connected directly to stack Choke and Kill lines are Manifolded so that either can be used for circulation and returns during a kill operation Use of blind/shear rams are used in place of ordinary blind rams

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SUBSEA WELL CONTROL

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  1. SUBSEA WELL CONTROL

  2. SUBSEA STACK DIFFERENCES • Choke and kill line connected directly to stack • Choke and Kill lines are Manifolded so that either can be used for circulation and returns during a kill operation • Use of blind/shear rams are used in place of ordinary blind rams • Rams are equipped with integral or remotely operated locking systems

  3. SUBSEA BOP ARRANGEMENT

  4. SUBSEA BOP ARRANGEMENT

  5. SUBSEA BOP ARRANGEMENT

  6. SUBSEA BOP ARRANGEMENT

  7. SUBSEA STACK AND CHOKE MANIFOLD ARRANGEMENT

  8. Subsea BOP Controls

  9. SUBSEA CONTROL SYSTEM

  10. SUBSEA CONTROL SYSTEM

  11. SUBSEA CONTROL SYSTEM TYPICAL HYDRAULIC HOSE BUNDLE 1. 1” I.D. Supply Hose 2. 3/16” I.D. Pilot Hose 3. Outer Protective Jacket

  12. SUBSEA CONTROL SYSTEM

  13. Shuttle Valve Power Fluid port isolated from Blue Pod The shuttle valves isolate the control fluid system between the selected pod and the redundant pod. The power fluid from the selected pod will shift the shuttle valve. Power Fluid to Bop’s Functions Power Fluid from Yellow Pod

  14. SUBSEA CONTROL SYSTEM

  15. Closing Sequences - Close BOP,s from remote panel. - Activate solenoid valve. - Shift 3 position 4 way valve. - Send pilot signal to the close SPM valve on both pod with 3000 psi. - Close SPM valve shift on the selected blue pod. - Power fluid from Subsea bottles is able to flow and close function on BOP. - The fluid from opening chamber is vented to the sea through the open SPM valve. - Accumulator pumps pressure up all accumulator and BOP’s bottles to 3000 psi.

  16. Opening Sequences - Open BOP,s from remote panel. - Activate solenoid valve. - Shift 3 position 4 way valve. - Send pilot signal to the open SPM valve on both pod with 3000 psi. - Open SPM valve shift on selected blue pod. - Power fluid from Subsea bottles is able to flow and open function on BOP. - The fluid from closing chamber is vented to the sea through the close SPM valve. - Accumulator pumps pressure up all accumulator and BOP’s bottles to 3000 psi.

  17. Block Sequences - Block BOP,s from remote panel. - Activate solenoid valves. - Shift 3 position 4 way valve in block. - Release pressure on pilot lines, pilot fluid is vented back to the reservoir. - SPM valve on selected blue pod shift to close position. - Allowing the pressure from BOP’s function to be released, the power fluid is vented to the sea through the SPM valve.

  18. Changing Pod Sequences - Select yellow pod from remote panel. - Activate solenoid valve. - Shift 3 position 4 way valve on yellow pod. - Close BOP,s from remote panel. - Activate solenoid valve. - Shift 3 position 4 way valve. - Send pilot signal to the close SPM valve on both pod with 3000 psi. - Close SPM valve on selected yellow pod shift. - The power fluid from Subsea bottles can flow and the shuttle valve can shift allowing the power fluid to pressure up the close function on BOP. - Accumulator pumps pressure up all accumulator and BOP’s bottles to 3000 psi.

  19. Subsea Animation

  20. Subsea Accumulator Bottles The subsea accumulator bottles capacity calculations should compensate the hydrostatic pressure gradient at the rate of .445psi/ft of water depth.

  21. Precharge pressure with water depth

  22. BOP Response Time Response time between activation and complete operation of a function is based on BOP closure and seal off. SURFACE SUBSEA 18 3/4” 30 sec. 18 3/4” 45 sec. 60 sec. 30 sec. 45 sec. Time to unlatch the lower marine riser package should not exceed 45 seconds Remote valves should not exceed the minimum observed ram BOP

  23. Hydril GL Secondary Chamber This allows to balance the opening force on the piston created by the drilling fluid H. P. in the marine riser Requires lowest hydraulic closing pressure OPENING PRESSURE

  24. Vetco H-4 Connector 0 to 2o Drilling 2o to 4o Stand by & Prepare to disconnect 4o to 6o Disconnection

  25. - Choke LineFriction

  26. Choke Line Friction Losses If SICP is held constant until kill rate is achieved, BHP will be increased by an amount equal to CLFL. To accomplish constant BHP, a method must be used while bringing the mud pump to kill rate Choke Line Friction Losses: There are four recognized methods of recording choke line friction losses at slow circulating rates of 1- 5 bbls / min

  27. First Method 500 RECORD THE PRESSURE REQUIRED TO CIRCULATE THE WELL THROUGH THE MARINE RISER WITH THE BOP OPEN 500 PSI IN THIS CASE

  28. First Method 700 RECORD THE PRESSURE REQUIRED TO CIRCULATE THROUGH A FULL OPEN CHOKE: 700 PSI IN THIS CASE CHOKE LINE FRICTION LOSSES = 700 - 500 = 200 PSI

  29. Second Method CIRCULATE THE WELL THROUGH A FULL OPEN CHOKE WITH THE BOP CLOSED AND RECORDING THE PRESSURE ON THE (STATIC) KILL LINE. THE KILL LINE PRESSURE WILL REFLECT THE CHOKE LINE PRESSURE LOSS. 200 PSI IN THIS CASE 200

  30. Third Method CIRCULATE DOWN THE CHOKE LINE AND UP THE MARINE RISER WITH THE BOP OPEN. THE PRESSURE REQUIRED FOR CIRCULATION IS A DIRECT REFLECTION OF THE CHOKE LINE FRICTION LOSS. 200 PSI IN THIS CASE 200

  31. Fourth Method CIRCULATE DOWN THE KILL LINE TAKING RETURNS THROUGH A FULL OPEN CHOKE WITH THE WELL BORE AND RISER ISOLATED BY CLOSING THE BOP’s. PRESSURE OBSERVED IS DOUBLE THE CLFL: IN THIS CASE 400 PSI / 2 CLFL = 200 PSI 400

  32. Bringing Pump to Kill Rate Speed 1200 500 If CLFL is not accounted for, casing pressure varies from SICP at pump start up to SICP + CLFL with the pump at kill rate. This results in BHP increasing by an amount equal to CLFL. 700 700 200 Increase to 5200 psi BHP : 5000 psi

  33. SPM Pressure 0 700 10 630 20 560 30 500 Bringing Pump to Kill Rate Speed: First Method 1000 500 Reduced Choke Pressure = SICP - CLFL = 700 - 200 = 500 psi Create a chart where CLFL and pump rates are divided by 3: 500 700 200 BHP : 5000 psi

  34. Bringing Pump to Kill Rate Speed: Second Method keeping the Kill Line gauge constant while bringing the pump up to speed eliminates the effect of CLFL. No pre calculated CLFL information is required. It would be advisable to rig a remote kill pressure gauge which could be seen by the choke operator. 700

  35. Riser Loss/Riser Margin Riser Collapse Overburden Pressure

  36. Riser Loss/Riser margin In case of a riser loss (emergency drive off, anchor chain breaks, ship drift), there will be a reduction in hydrostatic pressure.

  37. Riser Loss • This drop in hydrostatic pressure on the well bore: • is equal to the hydrostatic differential between fluid in the riser and sea water • The hydrostatic from the air gap is lost

  38. Riser Loss/Riser Margin Example: Calculate the reduction in BHP is the riser is torn off: 1- hydrostatic from air gap is lost: 65 x 12.9 x . 052 = 43.6 psi 2- hydrostatic differential in riser: 2,150 x (12.9 - 8.6) x .052 = 480.7 psi 3- reduction in BHP: 43.6 + 480.7 = 524.3 psi 65’ 4,450’ 2,150’ MW: 12.9 ppg SW: 8.6 ppg 2,950’

  39. Riser Loss/Riser Margin Example: To calculate the riser margin: Riser margin= HP reduction/ (TVD-Riser length)X0.052 524.3/(7400-2215)x0.052 = 1.94 ppg MW plus riser margin 12.9ppg+1.94ppg =14.84 65’ 4,450’ 2,150’ MW: 12.9 ppg SW: 8.6 ppg 2,950’

  40. Riser collapse In deep water, the potential for riser collapse exists if the level of drilling fluid in the riser drops due to gas unloading the riser or in case of heavy losses.

  41. Riser collapse Assuming the worst case to be during an emergency or accidental line disconnection, thepressure at the bottom of the riser would equal the seawater hydrostatic. The fluid level in the riser would fall until the equilibrium is reached.

  42. Riser collapse (vacuuminside ) Example: If a riser has a collapse pressure of 500 psi, how far could the mud level fall before sea water collapses the riser? 500 / .445 = 1123’ 1123 + 60 = 1183 feet A riser fill up valve should be used if the collapse pressure could exceed the collapse pressure rating of the riser. 60’ 2,150 ‘ SW: .445 psi/ft

  43. Riser collapse (gas inside riser ) Example: If a riser has a collapse pressure of 500 psi,and is filled with 0.1psi/ft of gas how far could the mud level fall before sea water collapses the riser? 60’ Riser collapse =water depth x SW gradient-(Airgap+water depth)x riser fluid gradient 500=yx0.445-(60+y)x0.1 500=0.445y-(6+0.1y) 500=0.445y-6-0.1y 506=0.345y Y=1466ft Level drop to collapse point=1466+60=1526ft 2,150 ‘ SW: .445 psi/ft

  44. Riser collapse (gas inside riser ) Example: If a riser has a collapse pressure of 500 psi,and is filled with 0.1psi/ft of gas how far could the mud level fall before sea water collapses the riser? 60’ Level drop from sea level before riser collapses Collapse press + Air gap x Riser fluid grad SW gradient –Riser fluid Gradient 2,150 ‘ =1466 ft Add Airgap 60 ft ?= 1466 +60= 1526 SW: .445 psi/ft

  45. Overburden Pressure Overburden Pressure is the pressure exerted at any given depth by the weight of the sediments, or rocks, and the weight of the fluids that fill pore spaces in the rock. Generally considered to be 1 psi / ft on land while offshore part of this overburden is replaced by about .65 psi/ft.

  46. Maximum press at the shoe Example: Calculate the MAMW: 1- calculate formation depth: 600 - 220 - 80 = 300 ft 2- calculate overburden pressure: 300 x .65 = 195 psi 3- calculate SW pressure: 220 x .455 = 100 psi 4- calculate the pressure at shoe: 195 + 100 = 295 psi 5- convert this pressure to a MW: 295 / ( 600x .052) = 9.4 ppg 80’ 220’ 600’ SW: .455 psi/ft Overburden: .65 psi/ft

  47. Dynamic MAASP • Dynamic MAASP is the MAASP while killing a well on a subsea stack • Dynamic MAASP =Static MAASP -CLF

  48. Shut- in Procedure: HARD SHUT-IN • Stop rotation • Pick up the drill string to hang off position • Stop the pump • Flow check • If the well flows • Close BOP • Open remote control choke line valves (Fail safe valves) • Notify Tool Pusher and OIM • Record time, SIDPP, SICP and pit gain • Check Space out • Hang off and lock pipe rams

  49. Shut- in Procedure:SOFT SHUT-IN • Pick up the drill string to hang off position • Stop rotation • Stop the pump • Flow check • If the well flows • Open remote control choke line valves (Fail safe valves) • Close BOP • Close choke • Notify Tool Pusher and OIM • Record time, SIDPP, SICP and pit gain • Check Space out • Hang off and lock pipe rams

  50. Subsea kill sheet (differences with surface) • Inclusion of choke line friction calculations • Casing set depth vs length of casing in the hole • Inclusion of Riser displacement volumes • Dynamic Casing Pressure

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