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Earth's physical resources: petroleum
The discovery of of the world's first major underground oilfield in Pennsylvania, USA...
The discovery of of the world's first major underground oilfield in Pennsylvania, USA in 1859 sparked the continuing era of the world's reliance on cheap energy from oil and gas. This unit begins by examining the geological characteristics of petroleum and the key ingredients necessary to form oil and gas accumulations. Then there is a brief description of industrial operations during the life cycle of an oilfield, starting with subsurface analysis and exploration drilling. The unit also highlights the role of safety and environmental management as an integral part of the petroleum business and concludes with a short review of global resources and non-conventional petroleum.
When you have completed this unit, you should be able to explain in your own words, and use correctly, all the bold terms printed in the text. You should also be able, among other things, to do the following:
- Interpret graphs and evaluate tables of data relating to different aspects of petroleum.
- Given basic geological information for a petroleum play, recognise the main ‘ingredients’ (petroleum charge, reservoirs, seals and traps) that contribute to its potential.
- Understand the roles played by different means of exploration in contributing to defining a petroleum play, and its evaluation.
- Describe the various options for petroleum production in different settings.
- Discuss the various hazards to operators and the environment that are presented by exploiting petroleum reserves.
- Understand the criteria used in assessing petroleum reserves globally and in the UK.
- Discuss the conditions under which unconventional petroleum resources form, and the requirements for their future exploitation.
- Learning outcomes
- 1 The chemistry of petroleum – what is petroleum?
- 2 Key ingredients for petroleum accumulation
- 3 Exploring for oil and gas
- 4 Petroleum production
- 5 Safety and the environment
- 6 Oil and gas reserves
- 7 Non-conventional sources of petroleum
- 8 Unit summary
- 9 Glossary
6.3 The global picture
The global occurrence of petroleum is very patchy and there are sound geological reasons for this. The most significant is the distribution of continental and oceanic crust, because source rocks, the prerequisite for any petroleum system, are confined to continental crust, including continental shelves. Elsewhere, and mainly concealed beneath the world's great oceans, vast areas of oceanic crust have no source rocks and therefore no petroleum potential. Similarly, igneous and most metamorphic rocks cannot source and rarely host petroleum, so areas where they predominate, such as Scandinavia and the Canadian Shield, are poor in petroleum resources.
In contrast, petroleum-rich countries generally have one of the following two features:
Particularly prolific petroleum basins within their borders. The top five countries in terms of their share of proved world oil reserves (as at end 2004) are: Saudi Arabia 22.1%, Iran 11.1%, Iraq 9.7%, Kuwait 8.3% and the United Arab Emirates 8.2%.
Large continental or continental shelf areas, which are statistically more likely to contain sedimentary basins with the key ingredients for petroleum. For example, the five largest countries in the world (by area) contain the following share of total proven world oil reserves (as at end 2004): Russian Federation 6.1%, Canada 1.4%, China 1.4%, United States 2.5% and Brazil 0.9%.
There are specific features of the geology of the Middle East that make it so richly endowed with petroleum. The region contains several world-class source rocks ranging in age from Palaeozoic to Tertiary, with very thick reservoirs and seals above them, in enormous, low-relief anticlines. In addition, most of its reserves were easily discovered because of the simplicity and sheer size of the traps.
This is an extract from an Open University course which is no longer available to new students. If you found this interesting you could explore more free Environmental Science course units or view the range of currently available OU Environmental Science courses.