Offshore Engineering

Question 1

What are the characteristics of storage structures?

Answer 1

• store the crude oil temporarily before transporting
• floating and karge conrete GBSs

Question 2

Export system types?

Answer 2

-transporting produced oil to shore
- underwater pipeline: site close to shore
- shuttle tankers: remote offshore locations: SPM or SBM to moor tankers

Question 3

What are the fixed bottom supported structures?+ examples

Answer 3

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

Question 4

What are the compliant bottom supported structures? +examples

Answer 4

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

Question 5

what are jacket structures?

Answer 5

• used for drilling production
  -tubular members form 3D space frame
• 2-3 decks of superstructure
  -limited to 150-180m

Question 6

What are gravity base structures?

Answer 6

placed on seafloor and held down by their weight

Question 7

What are jack-ups?

Answer 7

-typically three-legged structure with a buoyant deck
- used for exploratory drilling operation - can move from site to site

Question 8

What is a compliant tower?

Answer 8

• steel tubular jacket used for support surface facilities (alike)
• flexes with forces of waves and current (less steel)(unalike)

Question 9

What are articulated platforms?

Answer 9

-upright tower that oscillates around a cordon joined hinged at seafloor
- used as single-point mooring system (SPM)

Question 10

What are the neutrally buoyant floating offshore structures?

Answer 10

• spars
• semi-submersible
  -FPSs
• ship+shaped FOSOs
  -drillships

Question 11

What are the positively buoyant floating offshore structures?

Answer 11

-TLPs
-TLWPs
-buoyant towers

Question 12

What is the floating production system (FPS)?

Answer 12

consists of a semi-submersible unit equipped with drilling production equipment

Question 13

What is the floating production!storage and offloading system (FPSO)?

Answer 13

consists of large tanker type vessel moored to the seafloor

Question 14

What is a semi-submersible platform?

Answer 14

multi-legged floating structures with a large deck. legs connected with pontoons at the bottom

Question 15

what are SPAR platforms?

Answer 15

-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

Question 16

What are the type of spars? describe them

Answer 16

• 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)

Question 17

What is a tension leg platform (TLP)?

Answer 17

• 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

Question 18

What are the two wave energy converters?

Answer 18

Oceanlinx,
Wave Dragon

Question 19

Describe oceanlinx

Answer 19

technology for extracting energy from ocean waves, converting to air flow and using it to turn on turbines for electricity production.

Question 20

describe wave dragon

Answer 20

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

Question 21

What are the three possibilities for offshore renewable energy?

Answer 21

-Wind turbine
-wave energy converter
-tidal tubrine

Question 22

What does the power output of a wind turbine depends on?

Answer 22

• wind speed
• rotor diameter
• aerofoil of the blade
  -chord length of the blade

Question 23

What are the three types of wave energy converters?

Answer 23

-oscillating water column
-oscillating body
-overtopping

Question 24

describe oscillating water column

Answer 24

-wave surface oscillation induces air flow inside the chamber
-air flow derives turbine

Question 25

describe oscillating body (bottom mounted flap)

Answer 25

-base fixed to the seabed -flap rotates around the hinge due to wave load -the rotation drives the generator to produce power

Question 26

describe oscillating body (heaving buoy)

Answer 26

-base fixed or floating -floater moves up and down during to wave load -oscillation drives generator to produce power

Question 27

describe overtopping

Answer 27

-base is fixed or floating -floater moves up and down due to wave load -oscillation drives generator to produce power

Question 28

describe a tidal turbine

Answer 28

-much smaller than wind turbines (due to higher water density) -challenges: reducing cost of installation, maintenance and hence making energy price competitive

Question 29

what are the two types of tidal turbines, describe them?

Answer 29

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

Question 30

What are the main factors that the offshore development depend on?

Answer 30

- production volume, - environment, - water depth, - distance to shore, - drilling centres, - cost,

Question 31

What platforms are considered for deepwater operations?

Answer 31

- TLPs - FPSO -SPAR -semi submersibles - subsea tieback

Question 32

riser systems provide link between platforms and?

Answer 32

- oil/gas wells, -subsea satellite wells, - other platforms, - export facilities( pipeline to shore)

Question 33

what can risers handle?

Answer 33

- drilling and production, - import and export, - water or gas injection, - gas lift, - hydraulic and electrical lines,

Question 34

what is riser’s purpose?

Answer 34

- drilling (rigid) - completion/workover -production/injection -export

Question 35

What are the types of mooring systems?

Answer 35

-buoy turret loading (BTL) - ship integrated turret (SIT) - external turret production(ETP) - spread mooring

Question 36

what are the 3 main offshore operations?

Answer 36

drilling, production, installation/recovery

Question 37

what are the 3 main points of pipe laying?

Answer 37

1. trenching - cutting a trench or ditch in the seabed 2. laying the pipe, 3. back filling the trench and burying the pipe

Question 38

what are the two methods for pipelay?

Answer 38

J -lay method S-lay method