SEATOOLS B.V. (J. v.d. Heydenstraat 11, NE Numansdorp, NL-3281, NL)
| CLAIMS 1. Well head cover tool having an upright orientation and comprising a top, side wall means forming a first open interior chamber and a second open interior chamber and having a downwardly directed open end at the bottom of said tool, wherein the first open interior chamber is suited for covering a well head, wherein the first chamber is closable, e.g. by the tool comprising a first operable valve connected to the first chamber, and wherein the second chamber is connectable to a pump for reducing pressure in the second chamber with respect to an outside pressure when the tool is placed on or in a seabed, for pressing the tool against the seabed by the resultant pressure difference between the interior pressure of the second chamber and the outside pressure. 2. Well head cover tool of claim 1, wherein at least a portion of the side wall means are configured for cutting into the seabed. 3. Well head cover tool of any preceding claim, wherein the tool when placed upright on the seabed, is configured to provide a downward force larger than a predetermined value. 4. Well head cover tool of any preceding claim, wherein the second chamber has a surface area perpendicular to the direction of upright orientation, wherein the second chamber is configured to withstand a second pressure difference between the interior pressure of the second chamber and an outside pressure, wherein said surface area is chosen such that the second pressure difference multiplied by the second surface area exceeds a predetermined value. 5. Well head cover tool of any preceding claim, wherein the first chamber is connectable to at least one of a pump and a container. 6. Well head cover tool of any preceding claim, wherein the second chamber is arranged around the first chamber, in particular first and second chambers being coaxially arranged. 7. Method of covering a well head, comprising the steps of: forming a first open interior chamber around at least a portion of the well head to cover at least the portion of the well head, leaving the interior volume of the first chamber in fluid communication with the outside environment; fixing the first open interior chamber to the well head, leaving the interior volume of the first chamber in fluid communication with the outside environment; closing the first open interior chamber to cover at least the portion of the well head. 8. Method of covering a well head, comprising the steps of: arranging first side wall means around the well head on or in a seabed, for forming a first open interior chamber to cover the well head, and arranging adjacent the well head and on or in the seabed a second open interior chamber comprising a closed top, side wall means forming the second open interior chamber and being connected to the first side wall means and having a downwardly directed open end; reducing pressure in the second chamber with respect to an outside pressure; and once a predetermined pressure difference between the interior pressure of the second chamber and an outside pressure has been achieved, closing the top of the first open interior chamber to cover the well head. 9. Method of claim 7 or 8, comprising the further steps of providing a well head cover tool comprising a top, side wall means forming a first open interior chamber and a second open interior chamber and having a downwardly directed open end at the bottom of said tool, wherein the first open interior chamber is arranged for covering the well head, wherein the tool comprises a first operable valve connected to the first chamber, and wherein the second chamber is connectable to a pump for reducing pressure in the second chamber with respect to an outside pressure when the tool is placed on or in a seabed, for pressing the tool against the seabed by the resultant pressure difference between the interior pressure of the second chamber and the outside pressure; and the steps of: opening the first valve; arranging the tool over the well head onto or in the seabed such that the first chamber covers the well head and the open end is substantially closed by the seabed, and reducing pressure in the second chamber to a predetermined pressure difference between the interior pressure difference of the second chamber and an outside pressure; and at least one step of closing the first valve, connecting a container to the first valve and connecting a pump to the first valve. 10. Method of claim 7, 8 or 9, comprising the further steps of: determining a predetermined pressure to be achieved in the first chamber once enclosed; determining an upward pressure to be established within the first chamber and an outside downward pressure exerted by the environment, in particular sea water, on the seabed at least near the location of the well head to be covered; forming the second chamber such that it is configured to withstand a predetermined second pressure difference between the interior pressure of the second chamber and the outside downward pressure, and that the second chamber has a second surface area such that the second pressure difference multiplied by the second surface area exceeds a predetermined pressure a predetermined value. 11. Method of claim 7, 8, 9 or 10, comprising arranging the second chamber around the first chamber. |
TECHNICAL FIELD
The present disclosure relates to covering well heads, in particular submerged wells for hydrocarbon harvesting and more in particular to covering well heads suffering from
blowout.
BACKGROUND
Easily accessible oil and gas reserves are becoming scarce nowadays, forcing to deep sea oil and gas drilling. In drilled wells the hydrocarbons may exert very high pressures to the drilling conduits and the well heads, posing risks to damaging the conduit and/or well head. Safety measures such as blowout preventers are therefore required on a well head.
Damaged and/or malfunction equipment and may lead to
environmental pollution, as exemplified by the "Deep Water
Horizon" disaster in the Gulf of Mexico, Spring 2010.
Up to the filing date of the present disclosure, the leaking well head in that disaster could not be closed
satisfactorily.
It is an object to provide a well head cover tool and a method to provide safer well heads. A further object is to provide a well head cover tool and a method for covering a well head to prevent or contain a blowout. SUMMARY
A well head cover tool is provided having an upright orientation and comprising a top, side wall means forming a first open interior chamber and a second open interior chamber and having a downwardly directed open end at the bottom of said tool. The first open interior chamber is suited for covering a well head. The first chamber is closable, e.g. by the tool comprising a first operable valve connected to the first
chamber. The second chamber is connectable to a pump for
reducing pressure in the second chamber with respect to an outside pressure when the tool is placed on a seabed, for pressing the tool against the seabed by the resultant pressure difference between the interior pressure of the second chamber and the outside pressure.
The tool may thus be held in place assisted by the force of the outside pressure, in particular a water column pressing down on the tool.
Advantageously, at least a portion of the side wall means are configured for cutting into the seabed, so as increase the holding force of the tool against upward pressure.
The tool when placed upright on the seabed, may be configured to provide a downward force larger than a
predetermined value, so as to resist a predetermined upward force and to more clearly characterise the behaviour of the tool.
The second chamber may have a surface area
perpendicular to the direction of upright orientation, and the second chamber may be configured to withstand a second pressure difference between the interior pressure of the second chamber and an outside pressure. The said surface area may then be chosen such that the second pressure difference multiplied by the second surface area exceeds a predetermined value.
Such cover tool facilitates determining forces to be exerted by the tool.
The first chamber may be connectable to at least one of a pump and a container, in particular via the optional first valve, so that contents of the first container may be drawn off in a controlled fashion and/or be reclaimed.
In another aspect a method of covering a well head is provided comprising the steps of:
forming a first open interior chamber around at least a portion of the well head to cover at least the portion of the well head, leaving the interior volume of the first chamber in fluid communication with an outside volume;
fixing the first open interior chamber to the well head, leaving the interior volume of the first chamber in fluid communication with an outside volume; closing the first open interior chamber to cover the portion of the well head.
The portion may comprise an entire well head portion protruding from a seabed. By covering the well head, fluid communication between the interior volume of the first chamber and the outside environment is restricted or restrictable to a controllable flow from the first chamber or to cutting off fluid communication between the interior volume of the chamber and an outside volume, in particular the outside environment,
altogether. The first chamber may be part of a well head cover tool to be fixed to the well head. The first chamber and/or such well head cover tool may partly or totally be manufactured or assembled on site. The first chamber may comprise a valve for controllably maintaining the interior volume in fluid
communication with the outside volume, e.g. the outside
environment, and controllably closing the first chamber. E.g. with the valve, venting and/or exploiting the well head may be achieved. Thus, fixation of the first chamber to the well head may be done with little or no interference to the fixation method by pressure exerted by and/or material flowing from the well head. Hence, controlled closure of the well head is possible, also in case of a blowout and continuous flow of well products, e.g. hydrocarbons. This prevents the first chamber, which may be part of a cover tool, being "blown" from the well head.
The fixation of the first chamber to the well head may be in any known manner, e.g. screwing, welding etc, and may be done directly or indirectly to any part of the well head and/or associated portions such as a blowout preventer.
In an particularly efficient method, the first chamber is fixed to the well head indirectly by fixing the first chamber to a seabed to which the well head is fixed in turn, e.g. with anchoring means such as piles or suction anchors.
In another aspect, a method of covering a well head is provided, which comprises the steps of: arranging first side wall means around the well head on or in a seabed, for forming a first open interior chamber to cover the well head, and
arranging adjacent the well head and on or in the seabed a second open interior chamber comprising a closed top, side wall means forming the second open interior chamber and being connected to the first side wall means and having a downwardly directed open end;
reducing pressure in the second chamber with respect to an outside pressure; and
once a predetermined pressure difference between the interior pressure of the second chamber and an outside pressure has been achieved, closing the top of the first open interior chamber to cover the well head.
Here, the first chamber is fixed to the seabed by the second chamber. By first providing a pressure difference in the second chamber the tool is forced on or in the seabed, without having to counteract an upward force exerted by pressure of and/or material being emitted from the well head.
The steps of arranging the first and second side wall means may be consecutive steps in any particular order, e.g. by placing two tubular or caisson-like objects adjacent or around each other on or in the seabed.
Efficiently, the method comprises the further steps of providing a well head cover tool comprising a top, side wall means forming a first open interior chamber and a second open interior chamber and having a downwardly directed open end at the bottom of said tool, wherein the first open interior chamber is arranged for covering the well head, wherein the tool
comprises a first operable valve connected to the first chamber, and wherein the second chamber is connectable to a pump for reducing pressure in the second chamber with respect to an outside pressure when the tool is placed on or in a seabed, for pressing the tool against the seabed by the resultant pressure difference between the interior pressure of the second chamber and the outside pressure;
and the steps of: opening the first valve;
arranging the tool over the well head onto or in the seabed such that the first chamber covers the well head and the open end is substantially closed by the seabed, and
reducing pressure in the second chamber to a predetermined pressure difference between the interior pressure difference of the second chamber and an outside pressure;
and at least one step of
the step of closing the first valve,
the step of connecting a container to the first valve and
the step of connecting a pump to the first valve.
In such method, the first and second chambers are integrated in one tool facilitating correct placement and correct operation of the tool.
For improving operational predictability and reliability, the method may comprise the further steps of:
determining a predetermined pressure to be achieved in the first chamber once closed off;
determining an upward pressure to be established within the first chamber and an outside downward pressure exerted by the environment, in particular sea water, on the seabed at least near the location of the well head to be covered;
forming the second chamber such that it is configured to withstand a predetermined second pressure difference between the interior pressure of the second chamber and the outside downward pressure, and such that the second chamber has a second surface area, such that the second pressure difference
multiplied by the second surface area exceeds a predetermined pressure a predetermined value.
For instance to prevent asymmetric forces, and/or for protection of the first chamber, the second chamber may be arranged around the first chamber. In a particular embodiment, the first and second chambers are coaxially arranged. This also holds for well head cover tools fixed directly to the well head or associated portions and/or objects such as a blowout
preventer, as well as for well head cover tools fixed to the seabed by anchoring and/or under the force of one or more pressure differences.
Within this text "seabed" should be understood to mean the bottom of any type of a body of a flowable medium, in particular water, be it a lake, a sea, an ocean, an estuary or a river etc, but the cover tool and/or the method may also be applied in a flowable granular medium such as loose desert soil e.g. sand and dust. Other objects than a well head may also be covered.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1A is a side view of an embodiment of a well head cover tool over a well head;
Fig. 2 is a cross section view of the well head cover tool of Fig. 1 from plane B-B in Fig. 1 ;
Fig. 3 is a cross section view of the well head cover tool of Fig. 1 in plane A-A in Fig. 1;
Figs. 4 and 5 are view similar to Fig. 3 of different stages in a method of covering the well head with the tool of Fig. 1;
Fig. 6 is a cross section view of the well head cover tool of Fig. 1 from plane K-K in Fig. 3;
Fig. 7 is detail J of Fig. 3.
DETAILED DESCRIPTION OF EMODIMENTS
The above-described aspects will hereafter be more explained with further details and benefits with reference to the drawings showing an embodiment of the invention by way of example .
It is noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms "upward", "downward", "below", "above", and the like relate to the embodiments as oriented in the drawings, unless otherwise specified. Further, elements that are at least
substantially identical or that perform an at least substantially identical function are denoted by the same
numeral .
The Figs show a well head cover tool 1 having an upright orientation and comprising a top 3, side wall means 5, 7 forming a first open interior chamber 9 and a second open interior chamber 11 and having a downwardly directed open end 13 at the bottom 15 of said tool 1. The first open interior chamber 9 is suited for covering a well head 17 in a seabed 18. In case the well head 17 comprises a blowout preventer and/or (portions of) further systems (not shown) , the first chamber 9 should cover these too, preferably. In the shown embodiment, the second chamber 11 is formed in-between first side wall means 5 and second side wall means 7, thereby surrounding the first chamber 9 coaxially. The first and second side wall means 5, 7 are interconnected by supporting wall portions 19 fortifying the tool 1. The supporting wall portions 19 comprise apertures 21 so that different portions of the second chamber 11 separated by supporting wall portions 19 are in fluid communication with each other .
The top 3 of the tool 1 provides closed top wall means
23, 25 to the first and second chambers 9, 11.
The tool 1 comprises a first operable valve 27 connected to the first chamber 9. A pump assembly 28 is shown connected to the second chamber 11 via a connector 29. The shown pump assembly 28 is connected to an electromotor 30. The first valve 27 is also suited to connect to a pump (not shown) , possibly via one or more conduits (not shown) . The second chamber 11 and/or the connector 29 may be provided with a second operable valve (not shown) .
On the outside of the tool 1 hoisting means, here hooks and/or eyes 31 are provided for operation.
The presently disclosed method of covering the well head 17 is best understood from comparing Figs. 3-5.
First, the tool 1 arranged above the well head 17 to be covered, with the open end 15 facing the well head and the seabed (Fig. 3) . Next, the tool 1 is arranged with the first chamber surrounding and covering the well head 17 (Fig. 4 ) . During this, the valve 27 is open, so that the interior volume of the first chamber 9 is in fluid communication with the outside
environment, such as the sea water. Thus, pressure build-up inside the first chamber 9 is prevented. The bottom end 15 of the tool 1 is made to contact the surface of the seabed 18 and preferably at dig into the surface of the seabed for some distance so as to substantially close off the bottom at least the second chamber 11 .
Next, suction is applied to the chamber 11 , here via the pump assembly 2 8 . Thus, an underpressure is provided in the second chamber 1 1 . Due to the pressure difference between the pressure inside second chamber 11 and the pressure outside the tool 1 due to the water column above the tool 1 , the tool 1 is forced into the seabed 18 , with seabed material entering the second chamber 11 and possibly the first chamber 9 (Fig. 5 ) . This is similar to the proven technology of suction anchors which have served for mooring numerous vessels and oil rigs in very deep oceans.
The holding force, or the force required to separate (unearth) the tool 1 from the seabed F ho i d is determined by the pressure difference ΔΡ between the pressure inside the second chamber P 2 and the outside downward pressure exerted by the environment P do wr here a water column up to the water surface, times the surface area of the second chamber A 2 , plus the friction force F F of the material of the seabed 18 onto the embedded portions of the tool 1 , here portions of the various walls 5 , 7 , 19 , that are cut into the seabed 18 . This should be more than the upward force F up of the pressure P WH that the
(material of the) well head 17 can exert onto the tool 1 via the upward surface area Ai of the first chamber 9 . In formula:
Fh o id = ( ( P d own - P 2 ) x A 2 + F F ) > P WH X Ai = F up The value of the first (pressure-based) component of the force F ho i d can thus be determined by determining the
dimensions of the second chamber. If the well head pressure P WH is known, the required dimensions of the tool can be readily determined, whereby the friction force F F can be taken as an additional safety margin.
Once the tool 1 is in place, the first valve 27 can be closed and (further) leakage of the well head 17 can be
prevented. The underpressure in the second chamber 11 can be increased or maintained, or if the friction force F F is
sufficient, the underpressure may be reduced or the second chamber 11 may even be flooded.
The tool 1 may be anchored so tightly into the seabed 18 that the valve 27 or any further connector instead of the valve 27 may be used for harvesting material from the well head 17 and/or pumping on the well head 17, in fact replacing previously existing well head connectors.
For removing the tool 1, the first and/or second chambers 9, 11 may be put on an overpressure with respect to the surrounding pressure Pdown so that the tool 1 is blown out of and off the seabed 18.
The invention is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims.
For instance a second chamber may be arranged next to the first chamber, not surrounding it.
The first and second chambers, also when arranged coaxially, may be assembled on-site, since underwater welding is a proven technique, in particular mounting top wall means on the first chamber. Such later-fitted top wall means may be closable with other means than a valve, however a valve is preferred since this allows manipulating the pressure inside the first chamber .
The cover means may comprise more than two chambers, e.g. in a variant to the shown embodiment being separated by closed walls 19 and/or comprise double walls. The holding force is then determined by the sum of all pressure differences times the respective effective surface areas of the chambers
concerned. Such embodiments may provide improved security against leakage and/or collapse under pressure, which may be particularly relevant when the closing-off functionality of the tool is dependent on the pressure difference.
The cross-sectional shape of the tool need not be substantially circular or annular, but may be polygonal. The tool may comprise further anchoring means and/or weighing down means such as fins, screw thread portions etc. and at least a portion of the tool and/or wall portions may be applied on or in the seabed by driving means.
The bottom of an embodiment of a well head cover tool may comprise connecting means, e.g. one or more screw thread portions, eyes, hooks, welding segments etc. for fixation to a well head and/or to other associated objects, so as to fix (at least the first chamber of) the tool to the well head. Such cover tool may also be used to cover (an exit or leak of) a well head having a sideways (i.e. not vertically upright) exit or leak .
One or more valves may be provided to any chamber.
The pressure in any chamber may be monitored, for this monitoring means such as pressure sensors or connections to which pressure sensors can be mounted may be provided.
The operating principle of the tool and the method shown in the exemplary embodiment may also be described as follows: the operating principle is based on the principle of suction anchors. The tool comprises a large cylinder which has an inner wall which forms a pressure vessel and an outer wall forming a vacuum vessel around the pressure vessel. The pressure vessel has on the top side a large valve. The under side of both the pressure vessel and the vacuum vessel is open.
The diameter of the pressure vessel should be chosen such that that it can accommodate and cover the well head and associated blowout preventer and that the cylinder can rest on the seabed. The tool is placed over the well head with the valve on the pressure vessel open such that no pressure can build up and oil leaking from the well head can flow off freely.
After placement of the tool, using an (underwater) pump the vacuum vessel is evacuated such that the tool is sucked into the seabed. When the tool is fixed strongly enough to the well head, here: dug in deep enough, the valve may be closed and the well head is effectively closed.
A conduit and/or manifold may be connected to the valve to further operate and exploit the well.
The diameter of the outer wall needs to be chosen such that the effective pressure force of the water column is larger than the pressure of the well inside the pressure vessel.
The construction and the materials should be strong enough to withstand the various forces to be encountered, such as the forces acting on the tool, the well head, the seabed etc.
The construction of the proposed tool may be quite simple and straightforward, preventing complications during design, calculations and manufacturing and allowing rapid manufacturing in case of emergency.
Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise .