14.3.7 ABANDONED WELLS
If Wells are Abandoned as Dry or When they have Completed their Useful Life, What Happens to the Well Lining? (Answer given by a senior oil industry geologist.)
If a well fails to penetrate a productive hydrocarbon zone or has finished its productive life, it will be abandoned. Zones which have not be cased off and/or zones which have been opened up to the reservoir are sealed with cement. Several further cement plugs will be set within the cased intervals with a final plug near to the surface. After checking for leaks and the integrity of the cement and casings, the wellhead will be cut off and the site restored. Depending upon the age and quality of the casing strings used, some may be partially recovered before final sealing and abandonment of the well.
14.4 THE NATIONAL IMPORTANCE OF OIL IN NIGERIA
Oil is very important to the Nigerian economy. Oil revenues provide about 25% of GDP, 90% of foreign exchange earnings and 70% of budgetary expenditure. The government can expect revenues in the order of US$ 20 million a day, even at the depressed prices of the mid 1990s.
Moreover oil will continue to be important to Nigeria in the foreseeable future because other sectors of the economy are unlikely to develop and because the country has enormous reserves. At the end of 1997 Nigeria was reckoned to have proven oil reserves of 15.5 billion barrels (2.11 billion tonnes). Currently the country produces just over 2 million barrels a day (270,000 tonnes) which is about 735 million barrels or 100 million tonnes a year.
Intensive exploration in the Niger Delta and also in the Lake Chad Basin and in Bauchi State is expected to push the reserves up to about 25 billion barrels (3.40 billion tons).
14.5 INTERNATIONAL IMPORTANCE OF NIGERIAN OIL
Nigeria is a very important oil producing country both because of its reserves and because of its current production capacity. In 1996 Nigeria accounted for 3.2% of the world's oil production, being the world's thirteenth largest producer (equal with Kuwait). However Nigeria accounts for about 10% of the world's Light crude oil. Light crudes are valued above other heavier crudes for two reasons: first, they yield larger amounts of light oil products such as benzene, kerosene and propane; and second they contain much lower levels of sulphur, one of major contributors to polluting acid rain. Nigerian Lights consistently out-price other crudes. Thus:
| Source:- US$/Barrel |
Dubai (Middle East) | Brent (North Sea) | Nigeria Light |
| Year | |||
| 1992 | 17.61 | 19.27 | 19.92 |
