Offshore Oil Formation

The formation of oil takes a tremendously long time.  Millions of years ago plants and animals of the oceans died & settled on the ocean floor.  While large organisms contributed to the oil it was often the mass of small and microscopic organisms that contributed the bulk of the carbon for OIL.

Over many thousands of years bacterial action and extreme pressure from layers of sediment converted the organic matter to oil & gas.  The extreme pressure came form the continuous build up of sediment.  The pressure created tremendous amounts of heat which helped the process along.

The oil moved within the soil and oil reserves formed when non-porous rock lay above porous rock. Oil seeps up through the porous rock & is trapped by the non-porous rock.

Sedimentary Basins of Canada

1. Western Canada Sedimentary Basin (our primary source of oil)

2. Hudson Bay Basin 3. Mackenzie and Banks Basins

4. Canadian Arctic Basin 5. Baffin Bay

6. Labrador Sea Shelves 7. Scotian Shelf 8. Grand Banks

9. Anticosti 10. Maritimes Basins.

Atlantic Sedimentary Basins

Oil (light-green lines and blobs) and gas (red lines) in the Hibernia Formation (yellow) in the Carson Basin, mainly in stratigraphic traps. The brick colour underlying the oil and gas stream lines represents the Egret type source rock.

Hibernia Cross Section

Oil and Gas Traps

All oil and gas traps have

1. a nonporous rock cap and

2. a porous rock source. 

The porous rock allows the oil to seep into the cavity and the nonporous rock prevents the oil from leaving.

Oil Reserves

Fold Trap: the up fold or anticline in the layers of the

earth's crust form the reservoir.

Oil Reserves

Fault Trap: the vertical movement of the earth's crust forms a v-shaped reservoir.

Oil Reserves

Salt Dome Trap: The salt dome forms an up-fold in the earth's crust not unlike the anticline caused by tectonic forces.

Oil Reserves

Stratigraphic trap: has a former limestone reef as its porous rock feeding the

reservoir.

Submersible Oil Rig Supported primarily on large pontoon-like structures

submerged below the surface. The operating decks are elevated 100 or more feet [30 m] above the pontoons on large steel columns.

Once on the desired location, this type of structure is slowly flooded until it rests on the seafloor. After the well is completed, the water is pumped out of the buoyancy tanks, the vessel refloated and towed to the next location.

Submersible rigs are normally limited to ocean depths of 20 m.

Semi Submersible Float on the ocean This floating drilling unit has pontoons and

columns that, when flooded with seawater, cause the pontoons to submerge to a predetermined depth. Although it is moved by wave action, it sits low with a large part of its structure under water. This, combined with eight huge mooring anchors, make it a very stable installation

200 m for anchored and 2000 m for dynamically positioned

Ocean Ranger (semi submersible) Valentine's Day, 1982: a terrible storm rages off the

coast of Newfoundland. On the Grand Banks, the Ocean Ranger, the world's mightiest drilling rig, is pounded by waves more than 20 metres high. At the height of the storm, the "indestructible" rig begins to tip over, then capsizes. All 84 men on board — 56 of them from Newfoundland — perish.

http://archives.cbc.ca/environment/extreme_weather/topics/349/

http://archives.cbc.ca/environment/extreme_weather/topics/349-1874/

http://www.thecanadianencyclopedia.com/index.cfm?PgNm=TCE&Params=A1ARTA0005876

Jack-up Oil Rig

Instead of floating over its drilling location the Jackup has long leg structures, which it lowers to and into the sea bed raising the rig out of the water. (100 m)

Gravity Based Oil Rigs

The Hibernia GBS sits on the ocean floor approximately 200 metres in depth with its topsides extending approximately 50 metres out of the water. The platform acts as a small concrete island with serrated outer edges designed to counter ice bergs.

http://www.hibernia.ca http://www.thecanadianencyclopedia.com/

index.cfm?PgNm=TCE&Params=M1ARTM0011173

FPSO

A Floating Production, Storage and Offloading Vessel

Once the field is depleted, the FPSO can be moved to a new location. In areas of the world subject to cyclones (NW Australia) or icebergs (Canada), some FPSOs are able to release their mooring/riser turret and steam away to safety in an emergency.