Hydraulic and earth engineering – Fluid control – treatment – or containment – Floatable matter containment
Patent
1981-07-01
1983-11-22
Taylor, Dennis L.
Hydraulic and earth engineering
Fluid control, treatment, or containment
Floatable matter containment
210922, 405210, E02B 1504
Patent
active
044165650
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method by collection and separation of oil, gas and water from an oil/gas well and a column for usage by the same.
During the last years many attempts have been made to control oil and gas streaming out of blowing oil/gas wells on the sea bed. Such attempts are undertaken to avoid pollution of the surrounding sea and sea-shores, highly being a danger for damaging marine life and pollutioning large sea-shore areas. Additionally high waste economic losses follow flowing of such wells.
Existing equipment of to-day, such as booms, skimmers, sombreros etc. have proved to be insufficient under prevailing weather conditions. Therefore, new ways had to be developed to collect and separate gas and oil blowing uncontrolled from wells at the sea bed.
Means therefore are required, which can collect and commercially utilize gas and oil from such wells during the period of time in which other means are working to control the blow out, e.g. drilling relief wells.
Means in the shape of sombreros, e.g. according to U.S. Pat. No. 3,664,136, have been put into action to avoid pollution of the sea water and the surroundings. The intention of such sombreros has been to collect the oil-gas mixture blowing out of the subsea oil well. Principal reasons for failure of such sombreros have been escape of oil and gas below the edge of the sombrero and the attempt to transfer the oil-gas mixture, usually from the top of the sombrero to the sea surface. Caused by the proportional expansion of the gas escaping from the oil-gas mixture, such attempt has serious problems during the significant expansion of the gas volume by transportation of the oil-gas mixture in risers up to the sea surface.
One criterion by controlling a blowing well using a structure arranged on the well is to separate oil from gas and to control the two components individually. Furthermore, the pressure increasing within the structure caused by the flowing gas-oil mixture has to be controlled and limited to a pressure which does not exceed the strength of the bearing soil. Otherwise damage to soil layer and oil/water piping will occur.
Separation of the gas from the oil, as gas and oil have quite different behaviours as to pressure drops and expansion, large pressure fluctuations caused by gas bubbles in transportation risers from the sea bed to the sea surface as well as cavitation problems in the pumps, will be required to avoid such problems.
For the requirements it should be demanded of structures as follows: Insignificant or no soil failure, limitation of pressure fluctuations, insignificant or no damage to flowlines on or near the sea bed, operational independency of water depths, easy and ready installation, reliability and mobility. Furthermore, demands to economical construction and maintainance as always will be important.
The problem of soil failure will arise when the structure covering the well head and having an open lower end placed on the sea bed, is filled with the oil-gas mixture from the well, causing pressure differences inside/outside the structure. If the pressure difference outside and inside the structure near the sea bed exceeds 3-5 m H.sub.2 O, a breakdown of the soil normally will be expected. Such breakdowns normally will cause leakage at the sea bed surface or in the soil. Pressure fluctuations at the sea bed, e.g. at 300 m water depth, vary a lot more than the soil limit of 5 m H.sub.2 O. This low pressure difference limit of approximately 5 m H.sub.2 O makes it necessary to be able to minimize the fluctuations in oil/gas pressure within any structure placed open to the sea bed.
While the pressure at the bottom of a structure will be equal to the height of the liquid in the structure times the specific gravity of the liquid plus the atmospheric pressure, the gas pressure within such a structure will be the same in all directions.
If gas and oil are transferred together through a riser where the pressure in the riser sections is depending upon the vertical position of the sections, the bottom pressure continuou
REFERENCES:
patent: 3653215 (1972-04-01), Crucet
patent: 3745773 (1973-07-01), Cunningham
patent: 3762548 (1973-10-01), McCabe
patent: 4318442 (1982-03-01), Lunde et al.
patent: 4358218 (1982-11-01), Graham
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