1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and devices and, more particularly, to mechanisms and techniques for recharging a device that generates a subsea force.
2. Discussion of the Background
During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel.
The existing technologies for extracting the fossil fuel from offshore fields may use a system 10 as shown in
However, during normal drilling operation, unexpected events may occur that could damage the well and/or the equipment used for drilling. One such event is the uncontrolled flow of gas, oil or other well fluids from an underground formation into the well. Such event is sometimes referred to as a “kick” or a “blowout” and may occur when formation pressure exceeds the pressure of the column of drilling fluid. This event is unforeseeable and if no measures are taken to prevent it, the well and/or the associated equipment may be damaged.
Thus, a pressure controlling device, for example, a blowout preventer (BOP), might be installed on top of the well to seal the well in case that the integrity of the well is affected. The BOP is conventionally implemented as a valve to prevent the release of pressure either in the annular space between the casing and the drill pipe or in the open hole (i.e., hole with no drill pipe) during drilling or completion operations.
As understood by those of ordinary skill in the art, in deep-sea drilling, in order to overcome the high hydrostatic pressures generated by the seawater at the depth of operation of the BOPs, the accumulator 30 has to be initially charged to a pressure above the ambient subsea pressure. Typical accumulators are charged with nitrogen but as precharge pressures increase, the efficiency of nitrogen decreases which adds additional cost and weight because more accumulators are required subsea to perform the same operation on the surface. For example, a 60-liter (L) accumulator on the surface may have a useable volume of 24 L on the surface but at 3000 m of water depth the usable volume is less than 4 L. To provide that additional pressure deep undersea is expensive, the equipment for providing the high pressure is bulky, as the size of the canisters that are part of the accumulator 30 is large, and the range of operation of the BOPs is limited by the initial pressure difference between the charge pressure and the hydrostatic pressure at the depth of operation.
In this regard,
As discussed above with regard to
As disclosed in U.S. patent application Ser. No. 12/338,652, attorney docket no. 236466/0340-005, filed on Dec. 18, 2008, entitled “Subsea Force Generating Device and Method” to R. Gustafson, the entire disclosure of which is incorporated herein, a novel arrangement, as shown in
The pressure in both chambers 40 and 42 may be the same, i.e., the sea pressure (ambient pressure). The ambient pressure in both chambers 40 and 42 may be achieved by allowing the sea water to freely enter these chambers via corresponding valves (not shown). Thus, as there is no pressure difference on either side of the piston 38, the piston 38 is at rest and no force F is generated.
When a force is necessary to be supplied for activating a piece of equipment, the rod 44 associated with the piston 38 has to be moved. This may be achieved by generating a pressure imbalance on two sides of the piston 38.
Although the arrangement shown in
As shown in
One feature of the device shown in
According to an exemplary embodiment and as shown in
The low pressure recipient 60 may include a movable piston 74 that defines a low pressure gas chamber 76. This low pressure gas (or vacuum) chamber 76 is the chamber that is filled with gas (air for example) at atmospheric pressure and provides the low pressure to the opening chamber 42 of the BOP. The low pressure recipient 60 may include a port 78, which may be a hydraulic return port to the BOP.
A piston assembly 80 penetrates into the low pressure recipient 60. The piston assembly 80 is provided in the reset recipient 70. The piston assembly 80 includes a piston 82 and a first extension element 84. The piston 82 is configured to move inside the reset recipient 70 while the first extension element 84 is configured to enter the low pressure recipient 60 to apply a force to the piston 74. The piston 82 divides the reset recipient 70 into a reset opening retract chamber 86 and a reset closing extend chamber 88. The reset opening retract chamber 86 is configured to communicate via a port 90 with a pressure source (not shown). The reset closing extend chamber 88 is configured to communicate via a port 92 to the pressure source or another pressure source. The release of the pressure from the pressure source to the reset recipient 70 may be controlled by valves 94 and 96. A solid wall 98 may be formed between the low pressure recipient 60 and the reset recipient 70 to separate the two recipients. A second extension element 100 of the piston 82 may be used to lock the piston 82. The piston 82 may be locked in a desired position by a locking mechanism 102. Mechanisms for locking a piston are know in the art, for example, Hydril Multiple Position Locking (MPL) clutch, from Hydril Company LP, Houston, Tex. or other locking device such as a collet locking device or a ball grip locking device.
However, it would be desirable to provide other systems and methods for recharging the low pressure recipient.
According to one exemplary embodiment, there is a recharging mechanism for resetting a pressure in a low pressure recipient connected to a subsea pressure control device. The recharging mechanism includes the low pressure recipient configured to have first and second chambers, the first chamber being configured to receive a hydraulic liquid at a high pressure and the second chamber being configured to include a gas at a low pressure; a valve fluidly connected to a first port of the first chamber of the low pressure recipient; a pumping device fluidly connected to a second port of the first chamber of the low pressure recipient; and a blowout preventer (BOP) section fluidly connected to the valve and configured to close or open a ram block. The pumping device is configured to evacuate the hydraulic fluid from the first chamber of the low pressure recipient when the valve closes a fluid communication between the first port of the first chamber and the BOP section.
According to another exemplary embodiment, there is a pumping device configured to reestablish a low pressure in a low pressure recipient connected to a subsea pressure control device. The pumping device includes first and second enclosures connected to each other by a passage; a piston provided in the first enclosure to split the first enclosure in first and second chambers; a first port connected to the first chamber and configured to fluidly communicate with a source of high pressure; a second port connected to the second chamber and configured to fluidly communicate with the source of high pressure; and a rod connected to the piston and configured to extend through the first enclosure, the passage and the second enclosure in such a way that a fluid from the second enclosure is prevented to enter the first enclosure.
According to still another exemplary embodiment, there is a method for reestablishing a low pressure in a low pressure recipient with a pumping device. The method includes a step of connecting first and second enclosures of the pumping device to each other by a passage; a step of providing a piston in the first enclosure that splits the first enclosure in first and second chambers; a step of connecting a first port to the first chamber to fluidly communicate with a source of high pressure; a step of connecting a second port to the second chamber to fluidly communicate with the source of high pressure; and a step of connecting a rod to the piston to extend through the first enclosure, the passage and the second enclosure in such a way that a fluid from the second enclosure is prevented to enter the first enclosure.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of BOP systems. However, the embodiments to be discussed next are not limited to these systems, but may be applied to other systems that require the repeated supply of force when the ambient pressure is high such as in a subsea environment, as for example a subsea pressure control device.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to an exemplary embodiment, a novel way to recharge a low pressure recipient is discussed next. According to this embodiment, a pump may be connected to the low pressure recipient to remove the seawater or other fluid and reestablish a low pressure of a gas inside the low pressure recipient. The pump may be configured to vent into the sea the seawater from the low pressure recipient or to recirculate the seawater. The pump may be configured to handle one or more low pressure recipients. The pump may be placed undersea, next to the low pressure recipient or on a ship above the well.
According to an exemplary embodiment illustrated in
Valve 150 is configured to place in fluid communication the low pressure recipient 60 with an opening chamber 142 the BOP section 140 and also to allow a pressure source 170 to provide pressure to the BOP section 140, as will be discussed later. Another pressure source may be connected to a closing chamber 144 of the BOP section 140 and this pressure source may include another low pressure recipient 180, one or more accumulators 182, and/or a pipe 184 connected to a ship (not shown) at the sea level. All these power sources are connected to a port 186 of the BOP section 140. Pipe 184 may be connected to a pump provided on the ship. BOP section 140 is part of a BOP and includes the closing and opening mechanism for a ram block 146 that is connected via a rod 148 to a piston 149. The pressure differences on the piston 149, pressures created in the closing chamber 144 and the opening chamber 142, determine the movement direction of the ram block 146.
According to an exemplary embodiment illustrated in
Pumping device 120 may include a pump or a similar device that is capable of moving a fluid. According to an exemplary embodiment, the pumping device 120 includes a first enclosure 126 and a second enclosure 128 connected to each other via a passage 130. The first enclosure 126 has a larger cross-sectional area A1 than a cross-sectional area A2 of the second enclosure 128. The cross-sectional areas A1 and A2 represent the area of each of the enclosures taken substantially perpendicular on axis X along which a piston 132 moves inside the first enclosure 126. Piston 132 is connected to a rod 134 that extends in the first enclosure 126, the passage 130, and the second enclosure 128. A cross-sectional area A3 of the rod 134 may be smaller than area A2. Optionally, a piston 136 having area A3 may be connected to the rod 134. Areas A1 to A3 may be chosen to amplify the effect on the pump. By providing an appropriate pressure at ports 122 and/or 124, the piston 132 is forced to move along axis X. Thus, rod 134 moves inside the second chamber 128 to absorb fluid from chamber 77 and to discharge the absorbed fluid outside the pumping device 120.
A movement of the rod 134 along a direction opposite to X absorbs the seawater from chamber 77 of the low pressure recipient 60. A movement of the rod 134 along X forces the seawater absorbed from chamber 77 along pipe 137. Valves 190 and 192 (directional valves configured to allow a flow only in one direction) prevent the seawater from entering back into chamber 77 or absorbing the seawater along pipe 137. Pipe 137 may be configured to release the seawater in the ambient or may send the seawater along pipe 194 and 174 to the pressure source 170. Piston 132 may have a seal 138 for reducing fluid communication between the chambers 126a and 126b of the first enclosure 126.
Chamber 77 of the low pressure recipient 60 also communicates with valve 150. Valve 150 may be a conventional sub plate mounted (SPM) valve or other known valve. An SPM valve is actuated between the various positions by a pilot valve 152. The pilot valve 152 may be a solenoid valve (electrically activated valve). The pilot valve 152 is connected to the SPM valve 150 as shown in the figure.
In one application, both the SPM valve 150 and the pilot valve 152 are provided in the MUX POD (not shown) device. The MUX POD may be located on the lower marine riser package (LMRP) while the BOP section 140 is located on the BOP stack. In this regard,
Returning to
After this operation is performed, the SPM valve 150 moves in the position shown in
Pressure source 170 may be used to provide the necessary high pressure for closing the ram block in the BOP section 140. The pressure source 170 may include, for example, an enclosure 172. The enclosure 172 may be configured to hold a fluid under pressure. The enclosure 172 may also be configured to directly communicate via a pipe 174 with the ship 210 for receiving more pressure under given conditions. Alternatively, the enclosure 172 may be connected to the pumping device 120, via pipe 194, to boost its pressure.
According to an exemplary embodiment, at least a pressure sensor may be provided in chamber 76 of the low pressure recipient 60 to monitor the low pressure in this chamber. Further, according to another exemplary embodiment, position detection sensors as described in U.S. Provisional Patent Application Ser. No. 61/138,005, Attorney Docket No. 236460/0340-004, filed on Dec. 16, 2008, to R. Judge, the entire disclosure of which is incorporated herein by reference, may be provided (i) in the pumping device 120 to detect the position of piston 132, (ii) in the low pressure recipient 60 to detect the position of piston 74, and/or (iii) in the BOP section 140 to detect the position of piston 149. Knowing some or all of the positions of the pistons 74, 132, and/or 149, may allow a controller (not shown) to control the release of high pressure from power source 170 to port 152c and also to control valve 152 and the pumping device 120.
According to an exemplary embodiment illustrated in
The disclosed exemplary embodiments provide a device and a method for repeatedly recharging a low pressure recipient. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.