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Lecture 11

 

Crude Oil Production Methods (Fig. 1)

•         Primary (~ 50 %)

–        Free flow

–        Pumping

•         Secondary (~ 20 %)

–        Water pressure

–        Gas pressure (CO2)

•         Tertiary (~ 10 %)

–        Steam

–        Detergent

 

Oil distribution is very uneven on a global scale.  Most oil reservoirs are concentrated in the area around the Persian Gulf, in member states of OPEC (Organization of Petroleum Exporting Countries) (see Fig. 5.46) The oil production in many countries, including the USA, has passed a maximum in the last decades (Fig. 2).

 

The oil price reflects major political events in the recent past (Fig. 3). 

 

In 1973, M. King Hubbert of USGS made a remarkable prediction for the development of  oil production in the USA.  His prediction is very close to the actual decline in oil production over the last 30 years (Fig. 4).

 

Because of the widening gap between production and consumption of oil in the USA, the demand for imports has grown considerably in the past and will continue to increase in the near future (Fig. 5).

 

Synfuels and unconventional hydrocarbons

 

Synfuel: Conversion of naturally occurring carbonaceous raw material to fuels resembling petroleum and natural gas.  These materials have H/C ratios lower than gas and gasoline and typically contain more S and N (Fig. 6)

 

Approaches: Increase of H in fuel and/or decrease in S and N content.

 

Options

•         Unconventional Hydrocarbons

–        Oil Shale

–        Tar Sands

–        Gas Hydrates

–        Coal-bed methane

à Problems: extraction and removal of S and N

•         Conversion of coal

–        Gasification

•         Above ground

•         In-situ

–        Liquefaction

à Problems: low H/C ratio and high S and N content

 

Gas hydrates

 

•         Gas hydrate is a compound formed by water ice which has entrapped gas molecules (Fig. 7)

•         The entrapped gas consists mainly of methane, but can also contain higher hydrocarbons or CO2

•         Hydrates are stable at low temperature, high pressure conditions (Fig. 8)

•         Other names: Methane hydrates; Clathrates

•         Gas hydrates are found along continental margins in sediments of the continental slop, in very deep lakes and in permafrost locations (Fig. 9)

 

Gas hydrates - potential

 

•         Very large reservoir of natural gas (methane)

•         Mainly in water depths > 1000m

•         Gas hydrates are solid

•         Extraction possibilities

–        Mining

–        Heating

–        Depressuring

–        Gas exchange

•         No current extraction underway

 

 

Oil Shale

•         Carbonaceous rock that produces oil when heated to pyrolysis T (420oCà538oC)

•         Hydrocarbons formed in similar way as oil, but remained in source formation

–        à content of organic material < 25 %

•         Typically depleted in lighter components

à high viscosity

à    high sulfur content

 

Large deposits, but hardly used at this time (Fig. 10).  The main US oil shale deposits are in the Green River Basin, in the upper Colorado Watershed (see Fig. 5.55)

 

Oil Shale – overview

 

•         Large, but low-grade deposits

•         Large-scale surface mining necessary

•         Retorting needs large amounts of water

–        ~ 3 to 4 barrels of water per barrel of oil

•         US oil shale deposits are in regions with scarce water resources

–        Difficult restoration after mining

–        Competition between oil shale retorting and agriculture