API RP 90:2006(2012) pdf download

API RP 90:2006(2012) pdf download.Annular Casing Pressure Management for Offshore Wells.
The production riser section is abose the tie-back connector. Most of the production riser section is made up of special lied casing tub4llars and connections. Special joints such as stress joints. keel joints, or transition jornLs may also be included in the production riser design.
a coinbinatkin of methods, sir by the pbeform deck stricture. The surface welihead installed at the upper end olthe production riser provides a hang-off point for the production riser and tubing strings and pros ides the structural and pressure-containing conneclion point for the surface production tree.
7.1.3 PotentIal Leak Paths into the A” annulus
The potential leak paths into the ‘A” annulus include the following:
7.1.3.1 From the top of the highest production packer to the subsea welihead (or mudline packoff if used)
• A cement seal integrity failure in the “H” annulus combined with a casing leak in the production casing.
• Uncemcnted section in the ‘it” annulus combined with a casing leak in the production casing.
• Pmduclion tubing connection leak..
• Hole in production tubing sir parting of the production string.
• Production packer leak.
• Leak in components such as control lines and mandrels
7.1.3.2 From the top of the subsea welihead (or mudline packoft it used) to the surface welihead (single or dual production riser)
• Connection leak in the prikluctiiin riser.
• I-bk in production riser, allowing seawater to flow into production riser.
• Inner production riser leak into the outer production riser.
• Production siring connection leak above mudhne packofi’s.
• Hole in production tubing or parting of production tubing (above rnudl inc p.ackolfs).
• Leak in components such as control lines and mandrels abuse niudline packofts.
• Mudline pockotT leaks.
• Area decribesl in 7.1.3,1 leaks below the mudline lii mudline packoffs not used,
7.1.3.3 Subsea wellhead and production riser tie-back components
• Production casing seal leak,
• ‘flc-hack connector IcalL
7.1.3.4 Surface wellhead and tree
• Tubing hanger (or seal) leak.
• Control line or injection line leak.
• Gai. lift string leak.
7.2 DESIGN CONSiDERATiONS
72.1 Casing Strings
When first brought on production. all new wells with liquid packed annuli will normally exhibit a pressure increase because of heating and the subsequent thermal expansion of the fluids. This annular pressure buildup is rekrrcd to as thermal casing pressure. Since all ol the casing strings with the exception of liners or the prsxluction casing ola dual bore production riser system tied back from a liner will be sealed in the subsea wellhcad. design of the casing should consider the possibility of trapped annuli and the thermal effects associated with producing the well. When practical, the casing strings should he designed to withstand all potential thermal pressure. or incorporate thermal pressure mitigation systems. Typical mitigation systems include the fillowing:
an open casing shoe (uncemented) below the affected annulus, nitrogen blankets, syntactic foam material applied to the outside of the affected casing string, pressure rupture disks or a relief valve. Annular pressure mitigation should be analyzed during the design process.
When practical. the production casing string should be designed to withstand the calculated thermal pressures in “A’ annulus. or the design should allow the thermal pressure to be bled off or incorporate a pressure buffer such as a nitrogen cap. However, if the potential exists for casing collapse, then bleeding off the thermal casing pressure should be carefully evaluated. If pressure is left on the casing, ii should be monitored for changes and to ensure that it is not masking SCP.
7.2.2 Production String
The production string is the primary conduit for produced (or injected) fluids and it should be designed in withstand the maximum anticipated pressures, temperatures and composition of fluids that it is expected to handle. The production string is normally considered to be the primary well barrier preventing uncontrolled flow from the producing formation. In many wells, (he production string consists primarily of the production tubing. In 04her wells, the produchon siring is more elaborate, with multiple potential leak paths such as control lines and mandrels, The production string is often the sOUft’C of SCP in the “A” annulus because of connection leaks, erosion and corrosion of the connection or pipe body, or pipe body failure, such as collapse.
Additional considerations fur the design of the production tubing within the production riser section include the following items:
• Dynamic loading caused by the motions of the surface facility and the production riscr system should be taken into account during the design phase to ensure adequate fatigue life.
• Centralization of the tubing to prevent buckling between the constraints of the surttce tubing hanger and the tubing hanger.t packoff deployed below the mudline, if used.
• Adequate protection of the control lines for critical functions such as the SCSSV and chemical injection lines.