Wells – Processes – Separating material entering well
Patent
1995-07-28
1998-01-27
Dang, Hoang C.
Wells
Processes
Separating material entering well
166243, 210170, 2105122, 210788, E21B 4340
Patent
active
057113742
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a method for cyclone separation of oil and water in a production flow from a hydrocarbon reservoir.
DESCRIPTION OF THE RELATED ART
The invention also relates to an apparatus for separation of oil and water in a production flow from a hydrocarbon reservoir, said apparatus comprising one cyclone or a plurality of cyclones.
The production flow from a hydrocarbon reservoir contains large amounts of water, as well as other impurities. At some point the production flow must therefore be processed, a process during which oil and water are separated. Through this separation the so-called "produced water" appears. Separating the water at an early stage offers the advantage of freeing the production system from the encumbrance of the separated water component.
All the way up through the production pipe, to the wellhead and beyond, a loss of pressure occurs in the production flow, resulting in gas generation. In the cyclone separation of the production flow, this gas will be a very disruptive and undesirable element.
Liquid/liquid cyclone separation is a very favorable process, but requires, as indicated, that large amounts of gas be avoided. It is known that a separation under high pressure, for example at 400 bar, means, in practice, that no gas is present during the process. In addition, at this point the liquid has hardly been affected by shearing forces and will therefore contain few emulsions or components which are difficult to separate.
OBJECTS AND SUMMARY OF THE INVENTION
This recognition is the basis of the invention, which consists in making a cyclone separation of oil and water in a production flow under favorably high pressures, as they exist downhole.
In a well this method requires the use of cyclones which have a small diameter, so that one obtains small units in terms of volume and achieves good separation by means of high g forces.
By carrying out the separation of oil/water in the reservoir one will, because of the high pressure, avoid the generation of gas components resulting from the inevitable drop of pressure above the separation cyclone, a circumstance which otherwise would cause problems in the liquid/liquid separation.
This early separation of water and oil in the production flow will provide great benefits in connection with the further transport and treatment of the oil. Today water/oil mixtures are separated after/above the wellhead. According to the invention, one intentionally descends into the well to exploit the special, favorable conditions there, namely the high pressure and the low degree of emulsion. High pressure means that one may, in practice, proceed as if there were only one phase (liquid phase). At the high pressure existing downhole there will be practically only one phase, i.e., only a small amount of gas. The separated water may be returned to the reservoir. This means that the oil content of the water is not lost, but returns to the reservoir. The produced water may, for example, also be reinjected into a so-called "waste zone" higher up in the well, above the oil reservoir. Such a waste zone will therefore be a zone having less pressure, making it possible to direct the produced water up between the well casing and the production pipe, in several cases without pumping.
According to the invention a method is thus proposed for cyclone separation of oil and water in a production flow from a hydrocarbon reservoir, characterized in that the production flow is subjected to cyclone separation downhole in the reservoir.
According to the invention, this cyclone separation may advantageously be carried out in several stages.
It is especially advantageous according to the invention that the water produced by the cyclone separation be passed back to the reservoir.
The water produced by the cyclone separation may also be directed to a zone in the well outside the reservoir or to an injection point. The water produced by the cyclone separation may, for example, also be passed to a well zone in a higher layer having less pressure.
REFERENCES:
patent: 4296810 (1981-10-01), Price
patent: 4688650 (1987-08-01), Hayatdavoudi et al.
patent: 4738779 (1988-04-01), Carroll et al.
patent: 4805697 (1989-02-01), Fouillout et al.
patent: 5296153 (1994-03-01), Peachey
patent: 5456837 (1995-10-01), Peachey
Dang Hoang C.
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