Priority is hereby claimed to FR 10 59976 filed on Dec. 1, 2010, the entire disclosure of which is hereby incorporated by reference herein.
The present invention relates to a capture and storage installation for hydrocarbons escaping an underwater well.
The invention applies to hydrocarbon recovery on an uncontrolled oil and gas eruption site.
A recent accident in the Gulf of Mexico revealed the difficulty of controlling and stopping an erupting underwater oil well, when a confinement system cannot contain the pressure from the well. Furthermore, in such a situation, capturing and bringing up the fluid is pointless without adequate support on the surface, while the surface means necessary to treat an oil effluent are difficult to mobilize quickly on-site.
U.S. Pat. No. 7,448,404 describes an underwater hydrocarbon storage installation including a plurality of tanks. However, this installation is not adapted for intervening on an accidental hydrocarbon leak. In fact, it involves a heavy rigid structure, difficult to deploy quickly and requiring dedicated vessels, which are generally not available on the site of an offshore oil accident. Furthermore, all of the tanks are connected in parallel to a supply pipe by bleeds provided with valves, and said bleeds risk becoming plugged quickly due to the formation of hydrates resulting from cooling of the oil-gas-water mixture coming from the erupting well.
An object of the present invention provides an installation making it possible to capture and store, at the bottom of the sea at a great depth, erupting fluid for a period of several days to several weeks, or more, while waiting to be able to process it on the surface, the installation being relatively inexpensive and being able to be deployed easily and quickly by an vessel of opportunity, of the towboat type, generally able to be mobilized in one or two days.
The present invention provides an installation for capturing and storing hydrocarbons escaping from an underwater well, characterized in that it comprises a plurality of tanks each including a filling opening and adapted to be arranged on the sea bottom around the well and a device for capturing and distributing hydrocarbons escaping the well. The device includes a bell, means for positioning the bell above the well and transfer means for selectively connecting the apex of the bell to the filling opening of any one of the tanks in a fluid manner so as to transfer the fluid into that opening.
According to other features of this installation, the installation may include one or more of the following features:
One embodiment of the invention will now be described in light of the appended drawings, in which:
The storage device shown in
The bladder 1 has a very large length and is made up of three juxtaposed strings 2 of compartments 3. All of the compartments 3 communicate with each other, so that the bladder can be completely inflated from a filling opening 4 provided at one of its ends, visible in
Each compartment 3 is connected by welding and/or sewing to the adjacent compartments by flat strips 5, at certain points of which communication passages or tunnels 6 with large diameters are provided.
As is well known, offshore eruptions are generally made up of a mixture of oil, gas and water at a high pressure (around 100 to 300 bars) and high temperature (around 50 to 80° C.). Upon cooling in contact with the sea water and due to the relaxation, the viscosity of the oil increases and it can even congeal; the gas, in the presence of water, can form hydrate crystals (similar to ice crystals) that tend to plug the channels or channel constrictions. As a result, the diameter of the passages 6 is chosen to be large enough to prevent any risk of plugging by the hydrates.
As an example of dimensions:
Thus, the storage capacity of a bladder 1 is in the vicinity of 100,000 barrels (15,900 m3).
The bladder is completed by valve bridges 7 arranged under the two longitudinal strips 5 at a rate of two valve bridges per compartment 3. The valve bridges 7 are formed by strips made of the same flexible material as the bladder and welded/sewed thereto by their ends. A cable 8 is slipped into each series of valve bridges and protrudes at each end of the bladder, where it is provided with a connecting tip 108 (
The bladder is also completed by a small number of connectors 9 arranged on the upper surface of compartments 3 neighboring the ends of the bladder.
The total mass of such a bladder and its two cables is in the vicinity of 135 tons.
To store the bladder and place it on standby, the two side strings 213 thereof are folded on the middle string 2A (
The drum 12 supporting the bladder 1 is placed onboard a towboat 14 or another easily available vessel. The onboard mass is in the vicinity of 170 tons, which makes it possible to load it with handling means commonly available in an oil port.
A mooring 15 is arranged at a suitable location on the bottom 13, said mooring being connected to one end of two parallel initiation cables 16 each provided with connecting tip 116.
The bladder 1 is lowered, under the effect of its own weight, to the mooring 15, and each of its cables 8 is connected to the free end of the corresponding cable 16 by a ROV (Remote Operated Vehicle) using the tips 108 and 116.
Then (
To dam an uncontrolled eruption of an offshore wellhead 19 (
To that end, when a bladder 1 has been completely unwound from the drum 12 temporarily motorized to power on and ensure the reversibility of the lowering operation; the following bladder is attached thereto using the tips 108 of four cables (
Then (
The bell 22 is kept in position using a positioner which may include several moorings 27 arranged in a circle around the wellhead and each connected to the periphery of the bell by a towing chain 28. The bell can float or be weighed down, and in that case placed on a stabilizing structure (legs+cushion).
In use, the orifice 26 is arranged under the funnel 104 of a first bladder 1 by a ROV. The oil-gas-water mixture leaving the wellhead at high pressure and high temperature is confined by the bell 22 and oriented into the gooseneck 23. It emerges therefrom via the orifice 26 and thereby penetrates the bladder. The latter starts to inflate and deploy flat owing to the rupture of the connections. This inflation spreads from compartment 3 to compartment 3 as long as the captured mixture is not congealed.
When the bladder is completely filled or stops filling, the ROV makes the gooseneck 23 pivot until the orifice 26 is located below the funnel 104 of the following bladder.
For a leak of 100,000 barrels per day, one sees that each bladder can collect substantially one day of leakage, because when such a substantial flow rate, the cooling of the mixture is relatively slow. As a result, with fourteen bladders, it is possible to collect two weeks of fluid, which leaves the same amount of time to cover the well.
If the flow rate is lower, each petal fills more slowly, and possibly incompletely due to the faster cooling of the fluid.
To that end, each petal containing cold oil can be towed at a shallow depth in the “off-bottom tow” configuration. One of the difficulties in the recovery lies in the fact when that the oil is brought to a shallow depth, the gas relaxes, and part of the gas dissolved in the liquids leaves the liquid phase and takes up a more significant space. Thus, the passage from 1,000 m deep to 500 m deep results in a doubling of the gas volume. From 1,000 m to 100 m deep, the volume of gas is multiplied by 10, but from 1,000 m to the surface, it is multiplied by 100.
That is why it is preferable to tow the bladders above the bottom 30 without returning them to the surface.
To that end, a compensating balloon 31, forming an attached bladder, is fastened on a connector 9 of the bladder situated close to the top point thereof. Chains 32 are fixed to the cables 8 in place of at least one portion of the moorings 15 and 17, the assembly having an equivalent weight. The recovered mixture being lighter than water, the bladder stays at a small distance above the bottom 13, as shown in
A towing chain 33 is then hooked to the bladder 1, which is pulled by the vessel 14 while rising to the bottom 30. During that movement, the spacing of the bladder above the bottom prevents any deterioration, and the gas that is freed and relaxes gradually fills the balloon 31, facilitating the rise of the bladder.
When the bottom 30 is reached, the bladder is stabilized using moorings 34, and the vessel 29, provided with oil treatment equipment 35 and a riser for the oil product 36, is anchored nearby. The riser 36 is connected on a clip 37 situated at one end or in several locations of the petal to allow the light oil to rise naturally. A pumping system can also be lowered into the riser to activate the fluid.
As will be understood, if the hydrocarbon leak is not controlled when all of the bladders are filled, it is possible to continue the recovery operation by moving the bladders away from each other in the manner indicated above and depositing new, empty bladders on the bottom 13.
Number | Date | Country | Kind |
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10 59976 | Dec 2010 | FR | national |
Number | Name | Date | Kind |
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3113699 | Crawford et al. | Dec 1963 | A |
3503443 | Trageser et al. | Mar 1970 | A |
3724662 | Ortiz | Apr 1973 | A |
4320991 | Rogers | Mar 1982 | A |
4358218 | Graham | Nov 1982 | A |
5820300 | Sonoda et al. | Oct 1998 | A |
6739274 | Eagles et al. | May 2004 | B2 |
7448404 | Samuelsen et al. | Nov 2008 | B2 |
7882794 | Baylot et al. | Feb 2011 | B2 |
Number | Date | Country |
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2 852 917 | Oct 2004 | FR |
2 242 220 | Sep 1991 | GB |
Number | Date | Country | |
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20120141206 A1 | Jun 2012 | US |