Grayce P. Storey
The third type of recovery is tertiary or enhanced. This “can sometimes be achieved if the viscosity of the oil is lowered so that it flows more easily, either by heating the oil (by injecting steam, for example) or by injecting chemicals into the reservoir.”
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Secondary and tertiary methods have increased recovery in the U.S. from about 25 percent to 32 percent.
Enhanced recovery can be subdivided into three categories: miscible, chemical and thermal.
The miscible processes involve the displacing of fluids mixed with oil in a way so that there is no sharp interface between the injected and displaced fluid. This causes the capillary trapping capacity to be reduced and therefore more oil can be mobilized. The miscibility of a fluid is expressed in two types: direct miscibility where by fluids are mixed in all proportions and developed miscibility where components exchange between two fluids.
The five miscible drive fluids are hydrocarbon, solvents, nitrogen, carbon dioxide, enriched hydrocarbon gas and high-pressure hydrocarbon gas.
In chemical processes “chemicals are added to the displacing fluid to change its physico-chemical properties and those of the oil.”
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The aim is to increase the viscosity of the displacing fluid in order that more oil can be recovered. Caustic chemicals are used in this process.
The aim of the thermal processes is to inject or generate heat. This process is the most widely used of all the enhanced recovery techniques.
“Two principal methods are used to generate and transport heat for thermal recovery-surface generation and underground in situ combustion.”
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The most common is surface heat generation. This procedure involves water to transfer heat to the surface reservoir.
Water is cheap and an excellent heat carrier. The water can be converted to steam and carries three times more heat.
REFINING OF OIL (see Appendix 6)
The process of refining oil is first distillation. This means to boil oil until it turns to vapor and travel up the column where condensation causes it to turn back into liquid. Gases travel to the top of a column and at different points various liquids are drawn off. From oil we get gas, gasoline, Kerosene and diesel fuel. The heavier the liquids the less it rises in the tower. Residual fraction can be used as fuel oil or it can go into another tower (the vacuum distillation column) to be separated into still different fractions. Except for the USSR, Eastern Europe and China the primary world refining capacity continued to decline in 1983. Western Europe and Japan had the largest cutbacks. The primary capacity was 0.9 million barrels a day and 0.6 million barrels a day down in 1982. In the Middle East countries a new refining capacity was introduced in 1983. The primary capacity increased by 0.4 million barrels a day. The Indonesia refining capacity also increased.
“The refining industry in many areas of the world has been living with considerable excess primary capacity for several years although substantial reductions have taken place in the United States and Western Europe.”
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The results have no upgrading facilities. Low demands in 1983 brought about low usage rates.
TRANSPORTATION OF OIL (see Appendix 7)
Since oil is found hundreds or thousands of miles from where it is needed means of transportation is of necessity. In the early days oil was moved in barrels on a horse drawn wagons. After which it was taken by rail, barge or ship to the various destinations.
Today the large amount of oil is moved by pipelines from the well to the refinery or port. The sea-going tankers move it from country to country. When the output is small or the country is less-developed the road and rail tankers or barges are used.
The most economical way to move large amounts of oil over land is by way of the pipeline. They may be beneath the ground several feet or supported above the ground. Pumping stations along the line assist in the flow. The climate determine the necessity of insulation for the pipes. Sometimes heating stations are built along the line, again to aide in the flow.
When oil has to be shipped a tanker is used. This is a ship used especially to transport oil. The ship is divided into many small tanks. The object being to prevent the slopping about of cargo and if the ship were hold the result would be small leaks.
By the “end of 1983 the world tankers and combination carrier fleet comprised 3482 ships of 10,000 deadweight tons (dwt) and over totalling 329.3 million dwt. This consisted of 3138 tankers (289.2 million dwt) and 344 combination (40.1 million dwt.)”
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