Offshore Engineering Flashcards
What are the characters of drilling structures?
- limited structure motions,
- good station-keeping,
- accommodate variable deck loads
What are the characteristics of storage structures?
- store the crude oil temporarily before transporting
- floating and karge conrete GBSs
Export system types?
-transporting produced oil to shore
- underwater pipeline: site close to shore
- shuttle tankers: remote offshore locations: SPM or SBM to moor tankers
What are the fixed bottom supported structures?+ examples
When their lowest frequency of motion is ABOVE the highest frequency of significant wave excitation. Behave as rigid.
-minimal platforms
-jacket structures
- gravity base structures
-Jack-ups
What are the compliant bottom supported structures? +examples
Their lowest frequency of motion is BELOW the energy of waves. They are not fixed but magnitude of movement is reduced. Used for deeper parts of seafloor.
- compliant tower
- articulated platforms
What are minimal platforms?
used for marginal filed development
what are jacket structures?
- used for drilling production
-tubular members form 3D space frame - 2-3 decks of superstructure
-limited to 150-180m
What are gravity base structures?
placed on seafloor and held down by their weight
What are jack-ups?
-typically three-legged structure with a buoyant deck
- used for exploratory drilling operation - can move from site to site
What is a compliant tower?
- steel tubular jacket used for support surface facilities (alike)
- flexes with forces of waves and current (less steel)(unalike)
What are articulated platforms?
-upright tower that oscillates around a cordon joined hinged at seafloor
- used as single-point mooring system (SPM)
What are the neutrally buoyant floating offshore structures?
- spars
- semi-submersible
-FPSs - ship+shaped FOSOs
-drillships
What are the positively buoyant floating offshore structures?
-TLPs
-TLWPs
-buoyant towers
What is the floating production system (FPS)?
consists of a semi-submersible unit equipped with drilling production equipment
What is the floating production!storage and offloading system (FPSO)?
consists of large tanker type vessel moored to the seafloor
What is a semi-submersible platform?
multi-legged floating structures with a large deck. legs connected with pontoons at the bottom
what are SPAR platforms?
-consists of a large diameter single vertical cylinder supporting the deck
-surface deck with drilling/production equipment, three risers. hull moored to seabed
- used in 3 000 feet, up yo 7500 feet
What are the type of spars? describe them
- classic spar: outer layered with hard tanks for buoyancy, middle section empty, lowers section with soft tanks for horizontal floating during installation
- truss spar: middle section with truss to reduce current drag, horizontal plates between the truss bays to minimize heave motions
- cell spar: hull consists of ring-stiffened tubes (cells), tubes connected by vertical and horizontal plates (cheaper)
What is a tension leg platform (TLP)?
- consists of a floating structure held on place by tensioned tendons connected to the seabed by templates
-tensioned tendons provide for the use of TLP in a broad water dept - larger ones were deployed to up to 4000 feet
what are the mini-TLPs?
- has a relatively low cost developed for production of smaller deepwater reserves which would be uneconomic to produce using more conventional production systems
- can be used as a utility, satellite or early production platform for larger deepwater discoveries
What are the installation methods for subsea pipelines?
- J-lay with an inclined tower,
-J -lay with a vertical tower, - S-lay,
- Reel method,
-piggyback,
-multiple lay
What are the two wave energy converters?
Oceanlinx,
Wave Dragon
Describe oceanlinx
technology for extracting energy from ocean waves, converting to air flow and using it to turn on turbines for electricity production.
describe wave dragon
An overtopping type of converter, consists of two wave reflectors focusing waves to a ramp, a reservoir for collecting overtopping water and a number of hydro turbines for converting pressure head into power
What are the three possibilities for offshore renewable energy?
-Wind turbine
-wave energy converter
-tidal tubrine
What does the power output of a wind turbine depends on?
- wind speed
- rotor diameter
- aerofoil of the blade
-chord length of the blade
what is the purpose of
-rotor hub
-rotor blade
-nacelle
-tower
in a wind turbine?
- connect generator and blade
-harvests wind power
-where generator is installed
-support top side structure
What are the three types of wave energy converters?
-oscillating water column
-oscillating body
-overtopping
describe oscillating water column
-wave surface oscillation induces air flow inside the chamber
-air flow derives turbine
describe oscillating body (bottom mounted flap)
-base fixed to the seabed
-flap rotates around the hinge due to wave load
-the rotation drives the generator to produce power
describe oscillating body (heaving buoy)
-base fixed or floating
-floater moves up and down during to wave load
-oscillation drives generator to produce power
describe overtopping
-base is fixed or floating
-floater moves up and down due to wave load
-oscillation drives generator to produce power
describe a tidal turbine
-much smaller than wind turbines (due to higher water density)
-challenges: reducing cost of installation, maintenance and hence making energy price competitive
what are the two types of tidal turbines, describe them?
sea bed devises: -out of range waves,
-expensive to install and maintain,
-reduced current near bed,
floating tidal turbines:
-subject to wave loading
-easy to install and maintain
What does choosing a concept in offshore depends on?
- highest net present value (NPV),
- construct ability and install ability issues
- site conditions
- contracting constrains
What are the main factors that the offshore development depend on?
- production volume,
- environment,
- water depth,
- distance to shore,
- drilling centres,
- cost,
What does well completion involve, whats the difference, between surface and seabed completion?
it involves adding the bottom hole equipment to make the well commercially viable
- surface - dry tree
- seabed - wet tree
What platforms are considered for deepwater operations?
- TLPs
- FPSO
-SPAR
-semi submersibles - subsea tieback
what are the main features of TLPs?
- custom designed
- surface completed wells,
- integral drilling
- no oil storage
What are the main features of SPARs?
-custom designed for site specific applications,
- single drilling centre completed wells or
- remote completed wells by specialist vessel
- integral oil storage or no storage
what are the main features of FPSOs?
-new build or tankers conversion
- remote wells, normally completed subsea
-drilling/work over requires specialist vessel,
- integral oil storage and offloading,
-flexible risers
short development
What are the main features of semi submersibles?
- new build or conversion,
- remote subsea wells with work over by specialist vessel
-wells below integral drilling - no oil storage
- flexible risers
What are the main features of subsea tie back to shallow water?
(connection between new and existing oil and gas facility)
- improving the economics of marginal fields
- decreases the overall capital expenditure
- custom design
- multiple drilling centres
- remote subsea wells,
- no oil storage, oil exported from host platform
-short development
riser systems provide link between platforms and?
- oil/gas wells,
-subsea satellite wells, - other platforms,
- export facilities( pipeline to shore)
what can risers handle?
- drilling and production,
- import and export,
- water or gas injection,
- gas lift,
- hydraulic and electrical lines,
-Hydraulic work-over (HWU): repair wells onshore and offshore
what are the classifications of risers?
- rigid ( nominally vertical)
- manufactured from steel pipe,
-used for: oil well drilling from the platform, if large amount of access needed (straight entry into the well, where water depth does not permit a flexible risers) - flexible (catenaries):
may be manufactured from polymer (moderate depth) or steel (deeper water) or titanium
- can cope better with platforms
What are the functional requirements for risers?
- carrying corrosive fluid,
- withstanding environmental loads,
-proving capacity, - economical,
-safe, minimize fire hazard, - arranged in a limited working space,
- allowing for monitoring and ROV intervention
what is riser’s purpose?
- drilling (rigid)
- completion/workover
-production/injection
-export
what are the types of risers?
- low/high pressure drilling risers,
- completion/ workover risers,
- bundled risers,
-TTR,SCR,
-flexible/hybrid risers
What are the types of mooring systems?
-buoy turret loading (BTL)
- ship integrated turret (SIT)
- external turret production(ETP)
- spread mooring
Describe the upstream offshore oil and gas value chain
applies to the operation of exploration, drilling, hydrocarbon production and transmission via truck,rail, ship or pipeline to the refinery intake value,
Describe the downstream offshore oil and gas value chain
includes all work done at refinery, distillation, cracking, reforming , blending storage, mixing and shipping
what are the 3 main offshore operations?
drilling, production, installation/recovery
describe the drilling aspect of offshore engineering (project management, equipment, operational components)
- project management and engineering - drilling installation, well design, contracting, cementing, drilling fluids
- equipment and systems: drilling platforms ( a factory or a manufacturing plant used to drill oil/natural gas wells); types( jackup, drillship, semi-submersible)
-operational components : weather (marine forecast, operational limits), wind, waves, heave, pitch , roll conditions
describe the production aspects of offshore engineering (equipment and systems)
- surface facilities - platforms, etc. (storage, processing, offloading)
- subsurface facilities: mooring systems,
- export facilities: risers, subsea pipelines, shuttle tanker
describe the installation/recovery aspects of offshore engineering
- fixed structure,
-floating structure,
-topside installation,
-pipeline - lay operation, - launching/recovery of ROV
what are the 3 main points of pipe laying?
- trenching - cutting a trench or ditch in the seabed
- laying the pipe,
- back filling the trench and burying the pipe
what are the two methods for pipelay?
J -lay method
S-lay method
