PTRT 1321 OilField Hydraulics Chapter 5 Blowout Prevention

PTRT 1321 Oil-Field Hydraulics Chapter 5 Blowout Prevention Equipment Oil and Gas Technology Program

BOP’s Generally reliable Must be properly operated and maintained Designed to close in the well when a kick occurs Most can be quickly opened and closed hydraulically • Hydraulic energy stored in accumulator • Two types usually included in a stack • • – Annular preventers (at least one) – Ram preventers (at least two usually three or more) • Spools included to create vertical space for connecting lines Oil and Gas Technology Program

Stack Configurations • API RP-53, Blowout Prevention Equipment Systems – – – A – annular blowout preventer G – rotating head R – single ram preventer (blind or pipe rams) Rd – double ram preventer Rt – triple ram preventer S – spool with side outlet connections for choke and kill lines • M stands for 1000 psi plus the bore size is usually indicated as well • Each well must be considered on an individual basis Oil and Gas Technology Program

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Annular Preventers • Also called bag or spherical preventers • Versatile pressure-control devices – Kelly – Drill collars – Drill pipe – Work string – Tubing – Wireline – Open hole (in an emergency) • Can act as a lubricating head when stripping (moving) pipe under pressure Oil and Gas Technology Program

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Packing Elements • Many sizes and pressure ratings • High-tensile rubber (Buna-N, neoprene) (Viton is an high-temperature resistant rubber) backed by steel fingers molded into the rubber • Manufacturer recommendations for rubber selection • Resistance against corrosion, sour gas and/or extreme cold Oil and Gas Technology Program

Abuse or Misuse of Packing Elements • Improperating pressure – Max pressure typically 1500 psi – Moving pipe at this pressure can cause damage • Closing pressure reduced to about 800 psi • Small fluid leak appears which helps lubricate the pipe as it’s moved • Do not close annular preventer on open hole or wireline unless absolutely necessary (excess stretch can permanently deform and/or abrade the element) • Pre-split elements are helpful when stripping pipe Oil and Gas Technology Program

Operations • More hydraulic fluid is needed to close annular preventer than ram preventer • More pressure doesn’t speed up the close • Larger lines, fittings and regulators (more fluid volume) can help • Improved operations – Store in cool dry place away from ozone (motors) – Never use higher pressure than necessary – Always test the packer when installed in the preventer – Check manufacturer’s manual for operating data Oil and Gas Technology Program

Annular BOP Maintenance • Inspection – missing rubber between or missing fingers – scratches or burrs (can be removed with fine grit sandpaper) • Wiper seals in good condition (especially check top seal) • Store rubber parts in cool, dry, dark place • H 2 S environment requires rubber to be trimmed to avoid stress-corrosion cracking • Be sure ringed grooves are clean and free of grease • Ensure that the preventer returns to its full open position after being closed • Replace all rubber elements at least annually Oil and Gas Technology Program

Ram Preventers • Two basic types – Pipe rams – seal around pipe – Blind (blank) rams – seal open hole • Steel blocks with elastomer sealing elements • Installed on opposite sides of preventer housing • Available in many sizes and pressures and as multiple unit to save vertical space Oil and Gas Technology Program

Pipe Rams • Standard pipe rams designed to close around a specific pipe size • They will not close around a tool joint Oil and Gas Technology Program

Blind Ram • Large packing elements seal on themselves • Seal open hole • Do not seal around pipe Oil and Gas Technology Program

Blind Shear Ram • Blade can shear pipe • Packer elements still close open hole and seal • Saves space in the BOP stack Oil and Gas Technology Program

Variable Bore Ram • Can seal on a range of pipe sizes • Steel reinforcing elements similar to annular preventer (rotate inward to support rubber in contact with the pipe • Sizes shown in Table 5. 1 Oil and Gas Technology Program

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RAM Maintenance • Inspect and replace damaged or missing rubber elements • Replace bonnet seal whenever opened • Piston rods free from burrs, scratches, etc • Clean and refinish ram cavity • Check weep hole packing and replace as needed Oil and Gas Technology Program

Installation • Writing on housings should be right side up • Clean ring grooves and mating surfaces • Clean and defect-free flanges and sealing rings • Tight flange nuts on flanges • Center the BOP stack over the wellbore – Easy to say not always easy to accomplish – Can cause long-term damage to stack bore and/or ram faces and well bore • Pressure testing Oil and Gas Technology Program

BOP Operating Units • Accumulator system • Operate rapidly and reliably when a kick occurs • Most operate at 3000 psig • Hydraulic fluid (or chemical and water mixture) in reservoir and in precharged (1000 psi) bottles • Flexible bladder separates the nitrogen gas from the fluid – WHY? ? Oil and Gas Technology Program

Pressure Basics Oil and Gas Technology Program

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Useable Fluid Volume Sufficient fluid plus reserve (80 gal cylinder) Working pressure limits 1500 – 1200 psi Nitrogen pre-charge 1000 psi Fluid pressure to 3000 psi 13 gal raises pressure to 1200 psi 40 additional gal to raise pressure to 3000 psi Pressure-reducing-and-regulating valve to maintain output pressure at 1500 psi • Useable fluid volume that which raises pressure above 1200 psi • • Oil and Gas Technology Program

Determining Volume Requirements • Gal required to close all the annular and ram BOP’s • Multiply this volume by factor of 3 to obtain the useable volume required • This includes a safety factor of 50% • Once you know what you need then determine the useable volume stored in the accumulator Oil and Gas Technology Program

39. 84/80 = 0. 5 26. 48/80 = 0. 333 10/80 = 0. 125 Oil and Gas Technology Program

• Charging Fluids – Non-corrosive, non-foaming hydraulic oil – Add fresh water/water soluble oil mixture (w/glycol if needed for freeze protection) • Nitrogen precharge – Check periodically as nitrogen can leak away – Leak rate varies with each bottle – Manufacturer’s or operator’s procedure Oil and Gas Technology Program

Maintenance • Every 30 days or each time system is rigged up (whichever is sooner) • Clean, inspect, repair, lubricate • Steps listed on page 5 -10 • Guidance only each system has specific requirements – check manufacturer for details Oil and Gas Technology Program

Choke Manifolds • Provide flow path for circulating fluid out of the BOP stack under controlled pressure • Manifold provides multiple paths for flow so choke can be replaced or repaired • RP 53 describes choke manifolds and give planning and installation guidelines • See list on page 5 -15. Oil and Gas Technology Program

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Chokes • Controls flow rate in a line • Restriction or orifice • Small choke provides more decrease than large choke but more back pressure • Well control chokes are designed to handle abrasive fluids • Manual chokes are available but most well control applications use remotely adjustable chokes • Choke and kill lines should be: – Inspected frequently – Short nipples with correct strength (Sch. 40, 80, etc) – Avoid low pressure hoses (bursting and bends) Oil and Gas Technology Program

Chokes Fixed (positive) choke Oil and Gas Technology Program Manually adjustable choke (VG-series)

Remotely Adjustable Cameron 5, 000 – 15, 000 psi operating ranges Trimmed for H 2 S service Most common has 2” opening Oil and Gas Technology Program Swaco 10, 000 – 15, 000 psi operating ranges Normal or trimmed for H 2 S service Seals fully closed and can replace a valve Both hydraulically actuated

Gas-Handling Equipment • Vital part of any well control system • Removal of the gas from the fluid coming from the well allows for proper fluid handling downstream • Gas handling must include likelihood of gases that are explosive mixtures – Gas separators – Degassers Oil and Gas Technology Program

Gas Separator • Installed to the end of the manifold or choke line • Break out the free gas before the fluid enters the return pit • Not typically sufficient for viscous fluids Oil and Gas Technology Program

Degasser • Not used for large gas volumes • Centrifugal pump sprayer also common Oil and Gas Technology Program Vacuum pump

Safety Valves, Floats, Inside BOP’s • Basic requirement for well control is a method of closing off the work string – Safety valves – Floats – Inside Blowout Preventers • Usually handled by the floor crew • Safety valves – Upper kelly cocks – Safety valves Oil and Gas Technology Program

Safety Valves • Upper kelly cock is a safety valve installed between the kelly and the swivel • Simple ball, flapper, or plug valve that can be closed with a special operating wrench Oil and Gas Technology Program

Safety Valves • TIW™ valve (Texas Iron Works) • Full opening ball or plug valve • Lower kelly cock – Backs up the upper kelly cock – Fluid saver • Advantages – Operated each time a joint is made up • Crew training • Wrench always nearby – Can also be used as a stabbing valve Oil and Gas Technology Program

Inside BOP’s (Back-pressure valves) • Gray™ valve • Check valve • Used when you must run pipe into the hole under pressure • Not full opening so it restricts ID • Install above a closed safety valve unless a special release tool is available Oil and Gas Technology Program

Back-pressure Valves (Inside BOP’s) Oil and Gas Technology Program

Mud Return Indicator • Measures flow rate of returning fluid (paddle) • Establish trend during normal operations • Deviation (increase) from normal flow rate may indicate a kick • Check for properation by cycling flow and observe change in pump strokes Oil and Gas Technology Program

Fluid Volume Measurement Basic kick warning instrument Combines flow sensor and a pump stroke counter Integrates the two to determine the volume Can also use a trip tank to directly measure the fluid displaced by one or more strings of pipe • Pit volume indicators use floats to determine the fluid level in each pit and integrate them to determine the total fluid volume • Gas detectors • • Oil and Gas Technology Program

Pit-volume Indicator Hole Fill-up Device Oil and Gas Technology Program Trip Tank Arrangement