UNIT FIVE

Chapter 11

Off-shore Oil Formation and Reserves

How Oil Is Formed • Millions of years

ago plants and animals of the oceans died & settled on the ocean floor.

Bacterial action and

extreme pressure

from layers of

sediment converted

the organic matter

to oil & gas.

Oil reserves form

when non-porous rock

lies above porous

rock. Oil seeps up

through the porous

rock & is trapped by

the non-porous rock.

Oil Reserves Pg. 183

• 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.

Techniques Used to Locate Reserves

Before 1900’s

• The search for oil was limited. Had to look along

fault lines for oil seeping to the surface (EX: Jed

& Granny Clampett and the “Beverly Hillbillies”).

After early 1900’s

• Geologists knew to drill in gentle anticlines or

faulted sedimentary rock where reservoirs of oil

might occur. (Not always successful).

Techniques Used to Locate Reserves

• ships tow sound emitters and hydrophones to send sound towards earth’s crust.

• different rock layers

reflect sound differently.

• computers convert the sound data into 3D pictures of the ocean’s rock layers.

Modern oil exploration on the seas

Techniques Used to Locate Reserves

• “Wild cat” wells are drilled to test for oil:

– if they strike oil then delineating wells are drilled to

determine the size of the reservoir.

– If they miss oil then the core samples are examined

for evidence of oil.

Patterns of Offshore Oil Production

FIGURE 11.2 PG. 184

• Most oil regions of the world are on land.

• Oil regions under the ocean floor are concentrated in the North sea around the UK and in the Gulf of Mexico.

Gulf of Mexico North Sea West Africa

Patterns of Offshore Oil Production

• FIGURE 11.3 PG. 185

• It also reveals that offshore oil production is increasing faster than land production of oil.

• West Africa, especially around the Ivory Coast, seems to have high oil reserves and is increasing in oil production.