PART FIVE 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 11.2PG. 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 MexicoNorth Sea West Africa

Patterns of Offshore Oil Production FIGURE 11.3PG. 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.