Patent Application
20120285362
This application claims the benefit of Provisional Application titled: A Method For Containing an Underwater Oil Leak and Protecting the Environment, filed on May 12, 2010 by Richard M. Evans.
This invention is not the result of any federally sponsored research or development. Not applicable.
1. Field of the Invention
This invention is an improved suction anchor. Suction anchors are used by various offshore industries as moorings for various offshore structures or vessels. The offshore petroleum industry is a primary user of such anchors. This background information frequently mentions use by the petroleum industry. However, the use of suction anchors is not limited to the petroleum industry. For example, wind turbines can be anchored at sea using suction anchors.
Subsea suction anchors are commonly used in the offshore petroleum industry to moor or anchor offshore structures. These suction anchors may also be known as suction piles or suction caissons. Often, but not always, these suction anchors are essentially a cylindrical tube with one end closed by a top plate and one end open. Cylindrical anchors are circular in cross section, but other anchors may be rectangular, oval, hexagonal, or any number of other closed shapes in cross section. A pump is used to depressurize or pressurize the interior so the anchor moves into or out of the sea floor soil. What is essential is that they must not collapse when the required stresses are placed on them, and that they must remain anchored to the sea floor when stresses are applied. A commonly used method for installing suction anchors involves lowering them to a point near the sea floor. In preparation for dropping the anchor, valves are opened to allow water to evacuate the interior of the anchor. Tension on the attached cables is greatly reduced, and the anchor is allowed to fall in a controlled drop to the sea floor. The weight and momentum of the heavy anchor drives it partially into the subsurface soil.
When the anchor is dropped, even open valves resist the downward motion somewhat. This resistance reduces the speed of the dropping anchor and therefore reduces the depth of self weight penetration. This self weight penetration is usually only partial, and additional means are needed to force the anchor to fully imbed into the soil. In the case of suction anchors, suction penetration is used. A pump is attached to the suction anchor. Water is pumped out of the interior of the anchor. This causes a differential water pressure on the interior and exterior of the suction anchor. The desired result is that this differential pressure forces the suction anchor deeper and deeper into the sea floor until a desired depth is attained. Problems are known which hinder or stop the anchor from achieving the desired penetration depth. Instead of further imbedding the anchor, suction may cause soil to be pulled upward into the tube of the anchor. This problem is known as piping or plugging. Certain subsea soil conditions increase the chance of piping or plugging. A top layer of silt, among other soil problems, may increase the likelihood of this problem, and cause the anchor to fail to fully penetrate the soil. A partially installed anchor could not be relied upon, and could pull out of the subsurface with dangerous results. A submersible remotely operated vehicle, ROV, might suction away undesirable subsea soil inside the anchor with a pump if it could access its interior. Current suction anchors have no way for an ROV to gain such access to the interior of the installed or partially installed suction anchor. Alternately, a surface vessel could lower a clamshell shovel or other device to remove undesirable soil from the interior of a suction anchor. However, current suction anchors provide no means to access the interior of the anchor to do so. Also, an ROV or surface vessel might replace undesirable contents with desirable contents inside the anchor if it could access the interior of the suction anchor. Again, current suction anchors provide no means to enter the anchor to do so.
Another requirement of the petroleum industry is perfect alignment. For example, in the early stages of drilling a well, conductor pipe is installed below the subsea surface. This conductor pipe has a large diameter. This pipe must be perfectly aligned before it is installed. The next section of conductor pipe must be perfectly aligned with the first before it can be installed, and so forth. In later stages of drilling, blowout preventers, drilling pipe and casing pipe must also be perfectly aligned in order to be installed or used. Unfortunately all of these objects have different diameters. The blowout preventer is very large. Drilling pipe has a small diameter. A suction anchor at the wellhead might have an access port of the correct diameter to help align conductor pipe. But this port could not also align a blowout preventer, or permit it to be lowered beyond the level of the port. Such a port would also be the incorrect diameter for aligning a drill pipe string or casing pipe string. Hydraulic arms on an ROV might be useful for aligning a blowout preventer for installation. However, hydraulic arms or jacks must have something to press against or to attach to. Although it would be useful for an ROV to enter the interior of a suction pile, current technology does not provide a means for it to do so.
A pipe, drill bit, or other tool might become damaged below the subsea surface. To replace such damaged equipment is a lengthy process. A pipe string would be hoisted upward to the surface structure. One by one, each pipe in the pipe string would have to be disassembled. Then the next pipe would be raised and disassembled until the faulty piece of equipment finally was brought to the surface. It would be replaced and then the process would be reversed. Pipe after pipe would be attached and lowered step by step to the seafloor level and below. If an ROV could replace damaged equipment at the sea floor level it could provide a great savings in time and money. For example, a subsea wellhead might be 1 mile below the sea surface. If an ROV could replace a piece of damaged equipment at the sea floor level, raising and lowering the pipe string one mile in each direction could be avoided. Lateral or vertical motion of the pipe string would hinder such an operation. An ROV might hold a pipe string in alignment for such an operation, or a port in the top of a suction anchor might hold the pipe string in alignment. A strong suction anchor might temporarily hold the weight of the pipe string to avoid vertical movement. In any case, the ROV would need to access the damaged part above the blowout preventer and below the top of the suction anchor. No means for such access is available in current technology.
Pressurizing or depressurizing a doored suction anchor would raise or lower the anchor. This up/down motion would have great force. It could be used to drive a pile or a string of conductor pipe into the sub soil.
The interior of a suction anchor could be used for storage. A wide range of equipment might be stored inside. Such storage would be useless without access to the interior. No access is currently available.
Another problem that can occur in the offshore industry is surface accidents. A surface accident can cause heavy objects or debris to fall to the sea floor. If such an accident occurred on an offshore structure, it would likely occur directly above a subsea wellhead. Falling debris could fall near or directly onto critical components, such as a subsea blowout preventer or other critical equipment. It is desirable to protect critical equipment. But it is also desirable to have access to subsea components to inspect them, to check gauges or instruments, to remove and replace faulty parts, and so forth. A remotely operated vehicle, ROV, could be used for all of these purposes. A blowout preventer or other equipment placed inside a typical suction anchor would be protected, but not accessible. A blowout preventer not surrounded by a suction anchor would be accessible, but less protected.
An advantage of suction anchors is that they are reusable. When they are no longer needed at a location, they can be extracted from the soil and moved to a new location. To extract the anchor, a pump is typically used. It is attached to the suction anchor. For removal of the anchor, water is pumped into the interior of the anchor. The pressure differential forces the anchor upward and out of the sea floor soil. It can then be moved to a new location and reused.
2. Prior Art
U.S. Pat. No. 6,910,831 B2 Jun. 28, 2005 lists very many publications related to suction anchors in its “OTHER PUBLICATIONS” section. The same patent lists several U.S. patents and two foreign patents. These are in its “References Cited” section. These patents are listed here:
U.S. Patent Application No. U.S. 2008/0292409 A1, dated Nov. 27, 2008 refers to two other patents in its paragraphs 0002 and 0003. These are listed here:
U.S. Pat. No. 4,432,671 cites the following patents in its “CITATIONS” section:
U.S. Pat. 4,432,671 also lists many patents that it is referenced by. Many of these may be relevant to this patent.
U.S. Pat. 4,575,282 is also a type of suction anchor.
The Wikipedia “Caisson” article shows a caisson which is entered by people. However, the caisson does not use pumping means to lower more than 30% of an anchor body into a sea floor soil or to raise more than 30% of an anchor body out of the sea floor. Also, it uses an air lock rather than a door. Also it is meant to be used in very shallow water where people can survive. It uses a pressure differential to keep water out of the interior. It is not a suction anchor It has a different purpose and use than the invention described here.
This is an improved reusable suction anchor, method of using this suction anchor, and method of manufacturing this suction anchor. It provides access to the interior of the anchor, by ROV or crane operated shovel for example, using doors and gaskets. It provides a simple way to eliminate piping or plugging. It provides a simplified way to install or maintain a blowout preventer or to replace damaged parts at the sea floor rather than at the sea surface. It also provides a simplified way to align various diameters of pipe and to install conductor pipe. It also provides storage and protection from falling objects. It provides a method to contain an uncontrolled underwater oil leak, as a backup to a non-functioning blowout preventer, especially if it is installed before the uncontrolled oil leak occurs.
None of the illustrations are meant to limit the size, location, number, or type of doors, latches, latch catches, opening and closing mechanisms, attachment points, holes, throughput ports, valves, or mud fins illustrated. They are also not meant to limit the shape or size of the body of the anchor. The illustrations only show possible embodiments of the invention.
An interior hung door might be used as follows: In order to reuse a suction anchor, it must be pulled out of the sea floor and moved to a new location. The interior door of
Interior doors might also be unhinged, but these are not illustrated.
Referring initially to
In
The invention is an improved suction anchor which has a door or doors. The door or doors provide access to the interior of the suction anchor. The door or doors also provide improvements in the ability to avoid plugging or piping, alignment ability, conductor pipe installation, pile driving, use of walls as a base for pressing against or pulling on, replacing parts at the sea level rather than at the surface, protection of critical components, storage, and the ability to control an uncontrolled oil leak as a backup to a non-functioning blowout preventer (BOP). All of these are explained below.
Conventional suction anchors are well known. They consist of a body or skirt member which has a permanently attached top plate. The anchor is typically dropped and its weight and momentum drive the lower portion of the body partially into the subsea soil. A pump is attached and pumps water out of the interior of the anchor body. This creates a differential pressure on the inside and outside of the suction anchor. The greater pressure above presses the anchor deeper into the soil.
In the present invention a door or doors are provided in the suction anchor. The top plate itself may or may not be replaced by a door. A portion of the top plate may or may not be cut away and replaced by a door. A portion of the body may or may not be cut away and replaced by a door. A door or doors might be hinged or unhinged.
It is desirable to retain the ability to hold a differential pressure. In order to do so, a seal is provided. The seal would be placed where a door or doors meet the body or top plate of the suction anchor. The seal would likely be a gasket or gaskets. The gasket or gaskets would be placed at the location where a door meets the body or top plate of the suction anchor. Gaskets could be attached to the body, door, or top plate portion of the anchor. Gaskets might be placed at all or some of these locations.
Door opening and closing means may be an integral part of the anchor. If so, the means would likely be a hydraulic or electric motor attached to the suction anchor body, top plate, or door. A submersible remotely operated vehicle (ROV) could attach a pump to operate a hydraulic motor to open or close the door or doors. An ROV could attach electric cables or wires to operate an electric motor to open or close doors. Alternately, the opening and closing means might be an ROV. The ROV could attach to the door or latch and open or close the door. The whole ROV, while attached, might be raised or lowered by a winch on a surface vessel, attached to the ROV by an elongate member such as a cable or chain, in order to open or close doors. The ROV, while attached, might use its own propeller power to open or close a door or doors. The ROV could attach an elongate member to the door or latch. The top end of the elongate member could be winched up or down from the winch on a surface vessel to open or close the door or doors. Any combination of opening and closing means might be used to open or close multiple doors.
The door or doors might have valves, throughput ports, holes, screens, attachment points, or flanges attached or as an integral part of the door or doors. A door or doors might have a single valve, throughput port, hole, attachment point, screen or flange. A single door might have any combination of valves, throughput ports, holes, attachment points screens, or flanges. Multiple doors might have any combination of valves, throughput ports, holes, screens, attachment points or flanges.
The doors in
In
This invention helps avoid or eliminate piping or plugging. The doored suction anchor would normally be dropped into the sea floor soil with the top door or doors open. This would cause less friction than open valves in a top plate. Therefore the doored anchor would fall faster and penetrate the sea floor to a deeper depth. If the suction anchor was being used in an area where plugging or piping was a problem, undesirable silt or soil could then be removed from the interior. An ROV could enter the interior of the anchor through a door. It could use a pump to suction or blow out undesirable material. If desirable material had previously been lowered from a surface vessel, It could then replace the undesirable material with desirable material using a pump. Alternately, a surface vessel could lower a clamshell shovel to remove undesirable material from the interior of the suction anchor. An ROV might use its arms to guide the shovel to correct alignment before the shovel was dropped. Or it might communicate with the surface vessel the required corrective movements. If desirable material had previously been lowered, the clamshell shovel could then replace the undesirable material with desirable material.
The benefits of this invention at a wellhead or blowout preventer location are discussed here.
The benefits just mentioned would also apply at a blowout preventer location.
Early in an undersea drilling operation conductor pipe must be installed. Installation of conductor pipe is first discussed here. Conductor pipe has a wide diameter. Imagine a suction anchor similar to
After a well was producing, operators might want to leave the suction anchor in position, as shown in
A spare drill bit or other spare parts could be stored inside the suction anchor. If a drill bit needed to be replaced, the drill string could be raised until the old drill bit was above the BOP but below the top of the suction anchor. The ROV could enter the suction anchor and attach to its side. With another arm or arms it could disconnect the old drill bit and replace it with a new one. This would eliminate the need to bring the whole pipe string to the surface to do this task, saving time and money. The ROV could replace pipe or other parts at the sea floor level as well.
