W3- O&G Infrastructure & Drilling

Question 1

Offshore platforms

Answer 1

Gravity-based structure (GBS): modular concrete base

Steel jacket fixed platform: most common, pile driven in seabed

Compliant towers: narrow & flexible tower, attached to seabed

Tension leg platforms: steel/wire legs tethered to seabed & resist vertical loads

Semi-submersibles: moored or DP, i.e. floatel

FPSO: large ship, moored or DP - good for deep water

Spar: floating hollow cylinder, mooring lines to seadbed

BLP: provides process, drilling facilities (PUQs)

Launch installed jacket: jacket built horizontally, slid off barge

Question 2

Loading types

Answer 2

Live: loading considered temporarily imposed to structure

Dead: permanent loading caused by structure

Environmental: caused by environment, i.e. wave

Construction: associated with structure construction/installation

Accidental: unexpected events such as impact

Question 3

Factors influencing cost of drilling

Answer 3

Daily drilling rate (DDR)
Duration of drilling
Remoteness
Extra services required

Question 4

Use of power on platform

Answer 4

Power generation
Diesel gen
Flare
Evacuation boats
Waste management
Start-up operations
Separation systems

Question 5

Use of water on platform

Answer 5

Drainage system
Fresh water
Sewage
Firewater
Sea water system

Question 6

Drilling process & most common drill used

Answer 6

Rotary drill

1) Power swivel transmits drilling mud through drill string to provide power to drill bit at bottom of string
2) Drill bit grinds up rock, creating drill cuttings
3) Drilling mud transports cuttings to surface to allow constant drilling.
4) Mud is filtered using shale shakers to remove cuttings

Question 7

Drill bit Types

Answer 7

Small chisel shapes protrude from roller to break rock

Fixed cutter: more common as high durability, so less bit changeouts. Better for hard formation, i.e. shale

Tri-cone: better for soft formations, i.e. clay

Question 8

Drill pipe

Answer 8

Transmit drilling mud to provide power for drill bit;
Protects the bit and bottom hole from build up of hot cuttings

Question 9

Pipe casing

Answer 9

Larger than drill pipe- supports borehole, provides isolation of zones in well and supports well bore from blow out

Question 10

Oil well lifecycle & general types (by source)

Answer 10

Planning, drilling, completion, production, abandonment

Types: oil only, O&G, gas only)

Question 11

Oil well types (by purpose)

Answer 11

Wildcat: no known data of area
Exploration: test area for O&G accumulation
Appraisal: drilling wells to test flows and volumes of HC
Production
Injection: water/gas injection to increase recovery
Disposal: dispose water, gas and waste that is not done overboard
Satellite: drilled and connected to subsea manifold that produce back to original production platform

Question 12

NG use & advantages

Answer 12

NG used for power for electricity & heating as abundant, low price and cleaner burning fuel

Question 13

Drilling mud purpose

Answer 13

Water, bentonite, barite

Maintain hydrostatic pressure on reservoir to prevent formation of pressure -> blowout while drilling;
Supports wellbore and prevents collapse

Secondary: circulates cuttings out wellbore, cooling and lubrication of drill bit & provide hydraulic power to drill bit

Question 14

Types of drilling mud

Answer 14

Water based mud

Oil-based mud (more expensive and harmful to environment, but better for HT HP reservoirs)

Question 15

Properties affecting drilling mud

Answer 15

Mud weight
Viscosity
Gel strength
Mud chemistry

Question 16

Fluid pumping

Answer 16

Critical as mud must be delivered to drill bit

If pumping stops, drilling also stopped as drill cuttings not removed

Question 17

What do surface shale shakers do?

Answer 17

Separate cuttings from mud via vibration

Mud must be recycled as expensive

Question 18

Directional drilling

Answer 18

Obtains info, hits targets and stimulates reservoirs that vertical drilling cannot.
Provide drilling relief well to prevent blowout

Slower and more expensive

Question 19

Kicks

Answer 19

Well control problem where pressure in drilled rock is higher than mud hydrostatic pressure acting on borehole

Greater formation pressure forces formation fluids into wellbore (kick)

If not controlled via mud circulation adjustments, kick can develop into blowout

(signs: flow increase, mud pit volume increase)

Question 20

Blowout

Answer 20

Uncontrolled release of HC after pressure control systems failed (kick-> blowout)

Spark during blowout -> fire

Question 21

Blowout preventers (BOPs) & types

Answer 21

Isolate well while the hydrostatic balance is regained

BOP ram types: blind, pipe, shear rams

Question 22

Completions

Answer 22

Provides redundant barrier to leaks via acids and fracturing fluids pumped into well to fracture, clean, prepare and stimulate reservoir

Question 23

Wellhead

Answer 23

Top of well to provide structural and pressure interface and easy access to well

Question 24

Christmas tree

Answer 24

Set of valves to regulate pressure, control flows from well and allow access to wellbore

Question 25

Manifolds

Answer 25

Assembly of pipes, valves and fittings where fluids selectively directed to varous process streams

Connects wells to export pipelines and risers

Question 26

Subsea production and pipelines

Answer 26

Production: petroleum extracted from seabed and tied-back to pre-existing facility

Pipelines: can have concrete coating for protection;
Vertical pipelines = risers

Question 27

Flowlines and gathering lines

Answer 27

Short distances;
O&G to processing facility

Question 28

Feeder lines

Answer 28

O&G to transmission lines

Question 29

Transmission line

Answer 29

Long distances;
Crude to refinery/storage

Question 30

Product lines

Answer 30

Refined petroleum from refinery to distribution centre

Question 31

distribution lines

Answer 31

Local distribution from transmission lines

Question 32

Tankers

Answer 32

Crude tankers- carry unrefined oil from platform to refinery

Product tankers- carry refined oil from refinery to distribution

Question 33

Pipelines

Answer 33

Smaller process area;
Can transport at higher P, but difficult to maintain

Question 34

Decommissioning

Answer 34

All wells plugged using kill mud and cement to ensure no seepage after abandonment

Drill cuttings disposed of; pipelines sealed; topsides and jackets up to 60m below surface removed