World oil consumption = 74 MBPD

= 27 BBO/yr

USA oil consumption = 19 MBPD

= 7 BBO/yr (BBO = billion barrels oil)

USA uses about ¼ of the oil used by the world. Generally, energy-wise, the USA uses ¼ of the world’s use.

All oil deposits contain natural gas, but not all natural gas deposits contain oil.

Until 1978, essentially all natural gas produced in the USA was a byproduct of oil drilling. The price of natural gas was regulated (thus, there was diminished incentive to explore and drill just for it), whereas the price of oil was not regulated.

Carbon to hydrogen ratio of oil:

By mass: C/H = 7/1.

By atoms (since the atomic weight of C = 12 and that of H = 1): C/H = 1/1.7.

Thus, our chemical formula for oil is C_nH_1.7n. All is a mixture of many many individual hydrocarbon compounds.

Use of oil:

Transportation > industry > commercial+residential > electrical generation.

Note very little oil is used to generate electricity in the USA. (Thus, the argument that we need ANWR oil to overcome the electricity crisis in California does not appear to "hold water" – or oil.)

Study Figure 7.8. Note the use of the term "gas oil" for the mid range fractions.

For the USA, on average, about 45% of the refinery output is gasoline, and about 10% is chemical feedstock.

Oil is the result of decay (and geological heating and pressurization) of tiny marine creatures and plant materials. See Bodansky, Ch 9 for more info.

Oil is found in porous rock. The analogy is a wet sponge. The oil deposit is capped by impermeable rock – see Figure 7.9. It depicts an "anticline".

Drilling of oil reservoirs:

Primary recovery: Initially as the reservoir is tapped, the natural pressure of the deposit causes the oil to flow to the surface. A pump placed at the wellhead, as depicted in Figure 7.10, helps by sucking the oil to the surface.

Secondary recovery: Water is pumped into the deposit to force the oil to the surface.

Generally in the USA, primary + secondary recovery remove about 30% of the oil from the deposit. The average for the world is about 25% recovery (see Bodansky, Ch 10).

Tertiary or enhanced recovery: Steam is injected into the deposit to help loosen the oil and induce it to flow to the surface. This is successfully used to recovery heavy oil from fields in central California. Sometimes CO₂ or N₂ (recovered from the natural gas associated with the oil) are injected to provide pressure in the deposit to force the oil to the surface.

Generally, primary + secondary + tertiary methods bring the recovery to 40-50%, though in some cases larger recoveries are obtained.

Message: about 50-75% of oil remains in the ground after drilling.

USA:

More drilled wells per sq mile than any other country. Average depth of USA wells now 8000 ft. 30% success rate on drilling for oil. If one continues to drill deeper and deeper (and to add energy-intensive extraction methods), eventually the point is reached where the energy of the oil extracted = the energy used in extraction.

New oil in the USA comes mainly from offshore wells and from deep wells. Offshore oil drilling has been restricted by environmental concerns. Offshore drilling is 10x as expensive per foot drilled as onshore drilling. Some offshore drilling is done in water a mile deep. The USA average is drilling in 2000 ft of water.

North Slope Oil:

Purdhoe Bay deposit: 10-20 bbo of economically recoverable oil. Yearly production rate is about 0.45 bbo/yr – about 20% of USA production and about 6% of USA consumption.