Mineral oils: processes and products – Refining – Water removal
Patent
1990-02-16
1991-10-08
Davis, Curtis R.
Mineral oils: processes and products
Refining
Water removal
208187, 585 15, 585867, C10G 3304
Patent
active
050551787
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for extracting the water mixed with a liquid fluid by formation of gas hydrates by means of at least one gas.
This gas which forms hydrates with water may be, for example, methane, ethane, ethylene, propane, propene, n-butane, i-butane, H.sub.2 S, or CO.sub.2 and may come from natural deposits such as deposits of natural hydrocarbon gas, petroleum gas, or other gases.
These hydrates form when the water is in the presence of the gas, whether it is in the free state or in the dissolved state in a liquid fluid such as a liquid hydrocarbon, and when the temperature reached by the mixture, particularly of water, gas, and possibly liquid fluid such as oil or a condensate, becomes lower than the thermodynamic temperature at which the hydrates form, said temperature being determined for a known gas composition and when the gas pressure is fixed. The thermodynamic temperature increases in proportion to the pressure of the gas or gases, so that the higher the pressure, the less the gas and water have to be cooled to form hydrates.
The invention is particularly useful for transporting petroleum and gas products when the conditions required for hydrate formation are reached.
Indeed, natural gas or petroleum produced by a deposit usually contains water which, under certain thermodynamic conditions such as the climatic conditions of the North Sea or winter or polar conditions, reacts with the gas or gases to form hydrates which clog pipes and generate substantial financial losses.
According to the invention, hydrates are formed in the dispersed form, possibly with an additive, in order (easily) to separate the water contained in the hydrate from the liquid fluid with which it is mixed.
Advantageously, this formation of hydrate in the dispersed form may be accomplished before or during transportation of fluids attaining the conditions of hydrate formation.
These conditions obtain naturally when a pipeline is under the sea where the temperature of the water may be 3.degree. or 4.degree. C., for example.
Thus, on the one hand, formation of hydrates which occurs naturally, either completely or only partially, prevents any or some consumption of the hydration energy essential for extraction of the water, in addition to which dispersion of the hydrates prevents them from coalescing and blocking the pipes.
The possibility of forming hydrates that disperse within a liquid was discovered when it was found that certain surfactants which hitherto were not used for this purpose, have an excellent ability to change the mechanism by which hydrates are formed.
Instead of finding that hydrates clump together forming very solid blocks and plugs, or deposits in the systems in which the hydrate-generating fluid flows, it has been observed, over a very broad temperature range, that these surfactants disperse these hydrates in this fluid and thus prevent their clumping.
When a mixture of given gases, fluids, and surfactants is subjected to a temperature significantly lower than the temperature at which hydrates start to form, the fluid thickens without blocks or plugs forming, this thickening increasing with decreasing temperature.
These additives are very advantageous on the one hand because of their effectiveness:
very low concentration (generally less than 2% or even 0.5% by weight with respect to the water),
and because of their moderate cost.
The invention provides a process for extracting the water mixed with a liquid fluid that is substantially insoluble in said water, characterized in particular by carrying out the following steps: being formed from water and gas in a sufficient quantity, the gas being suitable for forming hydrates; possibly being with a remaining part of the fluid, and and water.
Before or during the formation of hydrates, an additive suitable for producing hydrates in the dispersed form may be used.
The liquid fluid may include hydrocarbons.
Advantageously, the additive, the water, and said fluid will be able to permit dispersion of the fluid in the water.
The additive may includ
REFERENCES:
patent: 3124926 (1965-03-01), Walker et al.
patent: 3126334 (1964-03-01), Harlow
Bourgmayer Paul
Rojey Alexandre
Sugier Andre
Davis Curtis R.
Diemler William C.
Institut Francais du Pe'trole
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