WO2007143457A2

WO2007143457A2 - Oil and/or gas production system

Info

Publication number: WO2007143457A2
Application number: PCT/US2007/069881
Authority: WO
Inventors: Harald Wahl Breivik; Michael Hosokawa Dupre; Donald Christopher Nelson; Robert Eric Raye; Andrew Vernon Trent
Original assignee: Shell Internationale Research Maatschappij BV; Shell Oil Co
Current assignee: Shell Internationale Research Maatschappij BV; Shell USA Inc
Priority date: 2006-05-31
Filing date: 2007-05-29
Publication date: 2007-12-13
Anticipated expiration: 2008-11-30
Also published as: WO2007143457A3; GB2450665A; GB2450665B; GB0819579D0

Abstract

An oil and/or gas production system, comprising a host in a body of water; a subsea operation in the body of water a distance from the host; an umbilical connecting the host and the subsea operation; a hybrid unmanned underwater vehicle, comprising a communication mechanism to communicate with the host by the umbilical; a propulsion mechanism to transport the vehicle from the host to the subsea operation, and to maneuver the vehicle for intervention activities of the subsea operation; and a power source to power the vehicle for transport from the host to the subsea operation, and for intervention activities of the subsea operation.

Description

OIL AND/OR GAS PRODUCTION SYSTEM

Field of the Invention

This invention relates to oil and/or gas production systems, in particular to oil and/or gas production systems with unmanned underwater vehicles. Background Art

Referring now to Figure 1, there is illustrated a prior art oil and/or gas production system 400. System 400 includes host 402 floating in a body of water. Subsea operation 404 is connected to host 402 by umbilical 406, and subsea operation 408 is connected to host 402 by umbilical 410. Subsea operation 404 and subsea operation 408 may be a large distance from host 402, for example up to about 100 kilometers .

In order to activate, deactivate, maintain, replace components, monitor, troubleshoot, or perform other intervention activities of subsea operation 404 and subsea operation 408 have required the use of an umbilical or direct access with a remotely operated vehicle (ROV) .

ROV 414 is shown accessing subsea operation 404. ROV 414 is supported and controlled from boat 412 by umbilical 416. ROV 422 is shown accessing subsea operation 408. ROV 422 is supported and controlled from boat 420 by umbilical 424.

Cybernetix has developed a vessel named SWIMMER, an AUV/ROV hybrid vehicle in which a standard Work-class ROV is carried by an autonomous shuttle (AUV) from the surface to a subsea docking station installed close to the equipment needing IMR interventions (wellheads, manifolds etc.). The docking station is linked to the surface via a permanent umbilical which provides power and real-time control of the ROV when the AUV shuttle is docked at the subsea station. SWIMMER docks autonomously; its video and sonar images are compared to the docking station image already stored in its processor. Once docked, power and communications are established with the FPSO/platform or even back to an office ashore from which an operator will control the ROV to carry out its task. Its umbilical is paid out and recovered by the Tether Management System carried aboard the SWIMMER shuttle. Once its task is completed, the ROV returns to the SWIMMER shuttle and docks. SWIMMER meanwhile has been recharging its batteries and receiving new instructions to proceed to another docking site in the field to carry out more IRM tasks. It is anticipated that following trials and modifications, the hybrid vehicle will be able to remain on the seafloor for considerable periods and come to the surface only for routine maintenance and when repair. In October 2001, in the Mediterranean offshore Saint Tropez, Cybernetix successfully demonstrated the technology and docking capabilities of SWIMMER (carrying a Phenix WROV) in 100 m (325 feet) of water. The AUV shuttle flew in full autonomous mode down to the subsea station and docked using successively Long Base Line (acoustic) and sonar image 3D processing.

There is a need in the art to perform intervention activities on a subsea operation without the need for an ROV. There is a need in the for an intervention vessel with a sufficient onboard power supply to perform intervention activities on a subsea operation.

There is a need in the for an intervention vessel integrated with a autonomous transport vehicle to perform intervention activities on a subsea operation from a host without the need for an umbilical from the host. Summary of Invention

One aspect of the invention provides an oil and/or gas production system, comprising a host in a body of water; a subsea operation in the body of water a distance from the host; an umbilical connecting the host and the subsea operation; a hybrid unmanned underwater vehicle, comprising a communication mechanism to communicate with the host by the umbilical; a propulsion mechanism to transport the vehicle from the host to the subsea operation, and to maneuver the vehicle for intervention activities of the subsea operation; and a power source to power the vehicle for transport from the host to the subsea operation, and for intervention activities of the subsea operation. Another aspect of the invention provides an intervention method, comprising launching a hybrid unmanned underwater vehicle from a host in a body of water; propelling the vehicle from the host to a subsea operation in the body of water a distance from the host; establishing a communication mechanism for the vehicle to communicate with the host; and performing an intervention procedure on the subsea operation with the vehicle . Brief Description of Drawings

Figure 1 shows an oil and/or gas production system. Figures 2a and 2b show a hybrid unmanned underwater vehicle (HUUV) .

Figures 3-5 show a vehicle assembly building (VAB) and a HUUV.

Figure 6 shows a HUUV handling frame and HUUV. Figure 7 shows a subsea production system.

Figures 8-14 show a HUUV and a subsea facility.

Figure 15 shows an oil and/or gas production system. Detailed Description

Referring now to Figure 2a, there is illustrated an HUUV 101 in accordance with one embodiment of the present invention. HUUV 101 may have a long, tubular shape for improved hydrodynamic purposes. Specifically, the long, tubular shape reduces a coefficient of drag, C_D, on HUUV 101 while traveling through water. The shape of the HUUV determines the stability and maneuverability of the HUUV, in addition to propulsion power required for the HUUV when in motion. With the long, tubular shape, HUUV 101 may sacrifice some maneuverability in exchange for a reduction of the coefficient of drag, C_D.

The coefficient of drag, C_D, is the sum of two main components, skin friction, C₃, and form drag, C_F, as shown below: C_D=C_S+C_F [Equation 1]

Skin friction, C₃, accounts for interaction between the surface of the HUUV with the water. Because the surface of the HUUV may not be completely smooth, the water interacting with the surface of the HUUV may experience a loss of energy, resulting from skin friction, C₃. The magnitude of skin friction, C₃, is dependent on specific properties of the water and the surface of the HUUV, in addition to velocity of the water across the skin surface of the HUUV. Reducing the amount of exposed surface area of the HUUV and maintaining a smooth and polished surface may minimize skin friction, C₃.

Form drag, C_F, accounts for the shape (i.e. form) of the HUUV. The form drag, C_F, is dependent on the ability of the shape of the HUUV to minimize flow separation across the surface of the HUUV. Flow separation on the surface of the HUUV creates turbulence that results in pockets of high and low pressure in the water. This turbulence may be seen as a wake behind the HUUV. A longer and more slender vehicle shapes reduce flow separation, thereby reducing form drag, C_F . An example of a shape for a HUUV 201 that may reduce form drag, C_F, as shown in Figure 2b, would be a design having a diameter gradually increasing from a nose 203 to a mid-section 205 of HUUV 201. The example depicted may sustain laminar flow, resulting in minimal turbulence and flow separation across HUUV 201.

HUUV 101 of Figure 2a is approximately symmetrical in shape, having a cylindrical mid-section 105 and nose caps 103 at the ends. Nose caps 103 are conically tapered cones that are rounded at the ends to reduce form drag, C_F . The torpedo shape has a longer mid-section 105 than mid-section 205 from the laminar flow shape shown in Figure 2b.

The torpedo shape of HUUV 101 is expected to increase the coefficient of drag, C_D, about 30% over the laminar flow shape of HUUV 201 in Figure 2b, but the torpedo shape still maintains a relatively low coefficient of drag, C_D . One advantage of a torpedo shape is increased use of cylindrical mid-section 105 for packing purposes, for example packing instrumentation and payload. Additionally, cylindrical midsection 105 may be lengthened or shortened when necessary for HUUV 101. Furthermore, in some embodiments, HUUV 101 does not have any external control surfaces or propulsion devices (e.g. fins or propellers) to reduce the possibility of mechanical failure and/or interference with HUUV 101. Further, when applicable, the HUUV may be comprised of high density composite materials (e.g. carbon fiber or fiberglass) to reduce the overall weight of the HUUV without sacrificing any strength. Those having ordinary skill in the art will appreciate that while a limited number of shapes are described, other suitable shapes exist and may also be used for the HUUV. Propulsion

Referring still to Figure 2a, cylindrical mid-section 105 of HUUV 101 also includes impellers 107 attached to each end thereof. When in motion, nose caps 103 direct fluid into impellers 107. Impellers 107 are one type of propulsion devices of HUUV 101 that enable HUUV 101 in this embodiment to not have any external control surfaces or propulsion devices (e.g. thrusters). Impellers 107 enable HUUV 101 to have six degrees of freedom of motion: surge, sway, heave, roll, pitch, and yaw. For reference purposes, a three- dimensional coordinate system is located at a center point of HUUV 101 in Figure 2a. As shown, the x-axis of the coordinate system runs along the length of HUUV 101, the y- axis runs out of the side of HUUV 101, and the z-axis runs out of the top of HUUV 101. Each axis is located 90 degrees from one another. Surge refers to displacement along the x- axis, and roll refers to rotation about the x-axis. Sway refers to displacement along the y-axis, and pitch refers to rotation about the y-axis. Further, heave refers to displacement along the z-axis, and yaw refers to rotation about the z-axis .

Preferably, impellers 107 are counter-rotating and have variable-pitch, thus enabling HUUV 101 to be more easily and efficiently controlled within all six degrees of freedom. A counter-rotating impeller refers to two or more impeller disks arranged one behind the other on an axis, rotating in opposite directions within an impeller housing. The turbulence and flow separation created from each of the impeller disks when moving through the fluid may significantly cancel one another out, increasing efficiency of the counter-rotating impeller by reducing the workload of each impeller disk. Also, counter-rotating impeller discs may help reduce any undesired rotational affects (e.g. roll) the spinning impellers may impose on the trajectory of HUUV 101. A variable-pitch impeller refers to an impeller that allows blades on the impeller disk to be rotated. This enables the impeller to control the amount of fluid the impeller may move, thereby controlling an amount of thrust the impeller produces. By selectively controlling direction and thrust, the impellers may enable the HUUV to accelerate and maintain velocity in each of the six-degrees of freedom. Additionally, the impellers may enable the HUUV to hover when in water, for example when in a current. Using the impellers to hover the HUUV when in water may enable the HUUV for use within a wider range of conditions . Payload

When the HUUV is submerged in a fluid, for example water or seawater, a buoyancy force, F_B, pushes the HUUV upward.

This buoyancy force, F_B, is equal to the specific gravity

(density) of the water, P_fi_uld? multiplied by the volume of the water displaced by the HUUV, V_HϋϋV, as shown below:

^F _B = P_βuιd ^V _Huuv [Equation 2] The buoyancy force, F_B, will increase proportionally with an increase in either the fluid density, Pfiuid_? or the volume of the HUUV, V_HUUV- The mass of the HUUV may be selected, in some embodiments, to be substantially equal to the buoyancy force, F_B, thereby allowing the HUUV to be neutrally buoyant when submerged in the fluid. With the HUUV neutrally buoyant, the HUUV will not have any significant gravity resultant forces acting upon it, thus enabling the HUUV to rest in the water without substantially rising or sinking. This may improve the overall efficiency of the HUUV by reducing the amount of power required when submerged.

Further, the HUUV is preferably ballasted such that it remains substantially horizontal when submerged, as shown in Figure 2a. If one of the ends of the HUUV is significantly heavier than the other, the HUUV may have the tendency to rotate with the heavier end being pulled downward by gravity. Thus, even if neutrally buoyant, the HUUV may not be able to remain horizontal unless ballasted properly. When submerged, the HUUV may engage in various activities that may affect the neutral buoyancy and ballasting. Therefore, the HUUV may use various techniques to achieve and maintain neutral buoyancy and proper ballasting when needed. In one technique, the HUUV may be equipped with an active ballasting system to maintain trim. In some embodiments, a weight may be movable throughout the HUUV as needed to maintain the desired trim, for example a weight mounted on a screw. Alternatively, the HUUV may take advantage of the inherent buoyancy of tools used for different tasks the HUUV will perform. By taking advantage of the buoyancy forces of these tools, the HUUV may achieve neutral buoyancy and proper ballasting. Alternatively, the HUUV may use the impellers to compensate and offset imperfections in buoyancy and ballasting. The impellers may have adjustable pitch and/or RPM and/or adjustable impeller intakes and outtakes for buoyancy and ballasting. Those having ordinary skill in the art will appreciate that other techniques may be used, such as redistributing tools and/or payload within the HUUV, when achieving and maintaining desired buoyancy and ballasting. Further, the particular task the HUUV is engaged in may further determine techniques used by HUUV to achieve optimal buoyancy and ballasting. Power As discussed above, the coefficient of drag, C_D, of a HUUV may be partially dependent on its shape. This coefficient of drag, C_D, may be used with a cross-sectional area of the HUUV, A, to calculate a drag force acting on the HUUV. When in motion at a constant velocity, u, the drag force acting on the HUUV is equal to thrust produced by the impellers of the HUUV. These relationships are shown below:

Thrust = Drag = lζp_βmdV²AC_D [Equation 3] With the thrust and velocity of the HUUV known, the power required to move the HUUV at a constant velocity may also be calculated, as shown below:

Power = (Thrust)(Velocity) = [Equation 4]

Thus, power is proportional to velocity cubed, in which power increases drastically with velocity. Doubling the velocity of the HUUV would require eight times more power. This relationship between power and velocity shows that by maintaining a low velocity of the HUUV, significant power may be saved for other activities. In some embodiments, a HUUV will travel at a velocity of about 1.5 m/s to minimize power consumption .

Formerly, ROVs and AUVs have used batteries, such as lead acid batteries, as an energy source due to associated low cost, known performance, reliability, and reasonable life cycle .

In some embodiments, the HUUV may use more than one energy source for power. The HUUV may select from more than one energy source depending on the necessary output of power from the energy source. For example, a battery may be used for powering activities and tasks of the HUUV requiring high bursts of power and because it is easily rechargeable, and a fuel cell may be used for powering propulsion requiring large amounts of energy but at moderate power. Navigation/Survey

An example of a subsea production system is shown in Figure 7. The subsea production system may have subsea facilities 703 on the seafloor arranged radially around a surface support vessel 701. Subsea facilities 703 may be up to about 100 km away from surface support vessel 701. Subsea facilities 703 use flowlines 705 to transport the produced hydrocarbons to surface support vessel 701, and use umbilicals 707, such as electro-hydraulic and/or fiber optic control umbilicals, to transfer data to surface support vessel 701. This allows surface support vessel 701 to monitor and control the production of subsea facilities 703. In some embodiments, a HUUV may be used with these subsea production systems to provide support to the subsea facilities and the surface support vessels through various activities. In some embodiments, support vessel 701 may be replaced with a shore base from which a HUUV may be launched to perform intervention activities on subsea facilities 703, for example up to about 600 km away.

Because the HUUV is autonomous and may be underwater for long periods of time when in use, the HUUV may require a navigation system. Therefore, in some embodiments, the HUUV includes an Inertial Navigation System ("INS") using multiple gyroscopes and/or accelerometers to measure change in direction and acceleration in a three-dimensional coordinate system. This allows the INS of the HUUV to be autonomous and calculate the position of the HUUV relative to a known starting point. In some embodiments, the INS may use landmarks and/or existing infrastructure, such as flowlines, umbilicals, or subsea facilities, to enhance its accuracy. By using known landmarks and/or infrastructure as reference points for the INS when the HUUV is traveling, especially on long endeavors, the accuracy of the INS may be improved by checking the calculated relative position of the HUUV from the gyroscopes and accelerometers with known reference points. Those having ordinary skill in the art will appreciate that the INS accuracy can also be improved by means other than landmarks and/or reference points. In some embodiments, the INS may use artificial monuments, such as strong acoustic reflectors, transponders, and/or visual identifiers, that may be intentionally placed in known locations to aid in navigation. In addition to the INS, the HUUV may also have devices commonly used with AUVs for navigation. These devices may include a gyrocompass, for example a ring laser gyrocompass; a Doppler velocity log; a collision avoidance and high- resolution sonar; and/or cameras, for example CCD color and SIT low light intensity video cameras. Data Transmission and Control

When the HUUV is within a specific range to a subsea facilty, it may require greater accuracy than the INS is able to provide for instruction and navigation. Therefore, for purposes of increasing command and control, the HUUV may communicate with a surface support vessel to transfer large volumes of data, such as a video stream from the video cameras, between the HUUV and the surface support vessel. In some embodiments, the HUUV may not have an umbilical to transmit data, wireless high-speed digital telemetry may be used for communication between the HUUV and the surface support vessel.

In one embodiment, the HUUV may use Free Space Optics ("FSO"), such as modulated blue-green laser light, for wireless high-speed digital telemetry. A Local Area Network using the FSO ("FSO/LAN") may be set up in close proximity to the subsea facilities for the HUUV to transfer data through the FSO/LAN to communicate with the surface support vessel. The use of the modulated blue-green laser light may allow ranges in excess of about 100 meters and data transfer speeds of about 10 Mbps (megabits per second) between the HUUV and the subsea facility. This may enable high-speed transfer of data without the use of an umbilical being connected to the HUUV. In some embodiments, Acquisition, Tracking, and Pointing ("ATP") technology may then be used in conjunction with the FSO/LAN for auto-tracking and positioning of the HUUV within the three-dimensional subsea environment. In some embodiments, when outside of the range of the FSO/LAN, the HUUV may also use an acoustic network when applicable to communicate with the surface support vessel. Current technology enables acoustic communication within about 1000 meters of a host, but does not presently allow such high data transfer speeds as wireless high-speed digital telemetry. The blend of the acoustic network with wireless high-speed digital telemetry may enable high data transfer speeds for the most demanding activities that occur at or in close proximity to the subsea facility, and still have communication capabilities otherwise with the acoustic network when the HUUV is approaching the subsea facilities. When the HUUV is outside of the range of the acoustic network, which may be outside the range of communication altogether, the HUUV may use pre-programmed activities for navigation, thereby functioning in a manner similar to a typical AUV. Then, as the temporarily autonomous HUUV reaches the acoustic network, the HUUV may shift capabilities from an autonomous mode to a remotely operated mode. When the HUUV is in range of the FSO/LAN, the HUUV may then perform in the remotely operated mode because the high data transfer speeds that may mirror the capabilities of an ROV with an umbilical.

When in communication with the HUUV, the surface support vessel may be used to control the HUUV for certain activities. For example, when within the range of the FSO/LAN, real-time information and data from the HUUVs INS, video cameras, and other devices may be sent to the surface support vessel. This information from the HUUV may then be used in a HUUV simulator to run simultaneously with the HUUV. The HUUV simulator may give a three-dimensional view of the HUUV in the subsea environment to an operator or pilot . The simulator may then supply real-time command and control for the pilot or operator for different activities with support from the INS for communication. Docking and Hardware Interface

The HUUV may be equipped with at least one Docking and Hardware Interface Device ("DHID") . The DHID may have a male DHID component and a female DHID component. This will allow for a electro-mechanical connecter interface in the wet environment between the HUUV and the subsea facilities and/or the surface support vessel. In one embodiment, referring to Figure 2a, the ends of nose caps 103 of HUUV 101 may be equipped with a male DHID component. The male DHID component may then connect with the corresponding female DHID component on a subsea facility and/or a surface support vessel to provide an interface. Through this interface, the HUUV may communicate and transfer data with the subsea facility and/or the surface support vessel, in addition to receiving energy, such as recharging batteries . HUUV Design

Preferably, the HUUV will have a modular design to allow for the HUUV to be modified based upon the various activities the HUUV may be performing. In one embodiment, the cylindrical mid-section 105 of the HUUV 101 will have at least one cylindrical segment. The at least one cylindrical segment may be from about 0.1 to about 2 meters in diameter and from about 3 to about 15 meters in length. However, the dimensions of the cylindrical segment may vary based on the specific activities of the HUUV. Further, based on the necessary payload, power, propulsion, and docking interfaces, multiple cylindrical segments may be used to provide extra batteries and/or extra FSO sensors for the HUUV. Launch and Recovery System

As illustrated in Figures 3 and 4, a Launch and Recovery System ("LARS") may be used for launching and for recovering the HUUV. In one embodiment, the LARS may consist of a Vehicle Assembly Building ("VAB") 301, a winch 305, and a HUUV handling frame 303. The VAB 301 may be used to assemble the HUUV 101. The HUUV 101 may be assembled vertically, as shown, to reduce the amount of area occupied by its components (the cylindrical mid-section 105, nose caps 103, and impellers 107) . With the VAB 301, the HUUV 101 may be customized based upon the different activities to be performed. As shown in Figures 5 and 6, the HUUV 101 may be lowered from the VAB 301 using a HUUV handling frame 303 attached to a winch 305. The HUUV handling frame 303, which is designed to securely grasp the HUUV 101, may be lowered by the winch 305 to a depth of about 100 meters when launching the HUUV 101. The HUUV handling frame 303 may then rotate the HUUV 101 from a vertical orientation (Figure 5) to a horizontal orientation (Figure 6) . The HUUV handling frame 303 may include a female docking interface for hardwire communication with the HUUV 101, and the LARS may include a FSO/LAN for wireless communication. Those having ordinary skill in the art will appreciate that the LARS may be used for both launching the HUUV into the water, as shown, in addition to recovering the HUUV from the water. Design Parameters In some embodiments, a HUUV may be capable of a mission depth of about 4, 000 meters of sea water, and an ultimate depth of about 5,000 meters of sea water. The HUUV will typically operate at pressures equal to or below the mission depth, but for safety reasons will be capable of withstanding pressures up to the ultimate depth.

In some embodiments, a HUUV may be capable of a transit range of at least 100 km, so that the HUUV may have the ability to travel at least 100 km without the total loss of power or need for recharging.

In some embodiments, a HUUV may be capable of enduring an ocean current of at least 2.5 kilometers per hour. With its limited power, the HUUV may be capable of enduring an ocean current of 2.5 kilometers per hour without losing any distance in transit range or the need for recharging. In some embodiments, the HUUV may be capable of traveling at speeds up to about 6 kilometers per hour, for example from about 3 to about 5 kilometers per hour.

In some embodiments, a HUUV may be capable of operating in a temperature range from about -2O⁰C to about 8O⁰C. The temperature of the water may decrease in relation to the depth of the water. As the HUUV travels at lower and lower depths within the water, it may be capable of operating at lower temperatures.

In some embodiments, a HUUV may have a dry weight payload of about 500 kg. With a dry weight payload of about 500 kg, the HUUV will also need additional capacity so that it is capable of carrying the necessary energy sources, propulsion devices, and sensors for optimal use when performing subsea activities .

In some embodiments, a HUUV may be capable of autonomous transit. The HUUV may be used to autonomously travel within a subsea production system from the surface support vessel to the subsea facilities.

In some embodiments, a HUUV may be capable of precise navigation. In some embodiments, the INS used for navigation of the HUUV may have less than about 5% error of the traveled distance.

In some embodiments, a HUUV may have a high quality sensor system to be used for surveying. The high quality sensor system, for example, may be capable of side scan sonar and/or bathymetry.

In some embodiments, a HUUV may have an advanced diagnosis and fault recovery system. The diagnosis and fault recovery system may be capable of communicating with the surface support vessel to report State of Health ("SOH") of the HUUV. The SOH may be preprogrammed responses to any system irregularities the HUUV may experience. Therefore, the HUUV may determine its own SOH and communicate the SOH with the surface support vessel.

In some embodiments, a HUUV may be capable of docking autonomously. For example, the HUUV may be capable of autonomously connecting the male docking interface component with the female docking interface component to provide an interface with the HUUV. This interface of the docking interface may then be used to communicate and transfer data with the subsea facility and/or the surface support vessel, in addition to recharging the HUUV.

In some embodiments, a HUUV may be configured with tools to be used during different activities. When the HUUV is being assembled by the LARS, tools, such as a choke or pod, may be supplied to the HUUV based upon the different activities the HUUV may be involved in. When carrying multiple tools, the HUUV may be capable of interchanging amongst the tools while in the subsea production system. The tools may also be powered by the HUUV and may be capable of interacting with standard subsea equipment in the oil and gas industry. The tools the HUUV may be supplied with may enable the HUUV to perform functions such as cutting (e.g. shears, a saw, or a knife) and grabbing (e.g. an attachable arm) .

In some embodiments, a HUUV may have enough stored energy in the energy source for the HUUV to complete a roundtrip between the LARS and a destination site, such as a subsea facility, plus energy to supply activity of the HUUV for about 10 hours at about 3 kW, for example at least about 30 kilowatt hours. This would enable the HUUV to perform activities at the destination site and return to the LARS without risking a total loss of power.

In some embodiments, a LARS may be remotely operated from a host. This may allow the LARS to perform its activities, such as assembling, launching, or recovering the HUUV. The LARS may be used to lower the HUUV to a desired depth, for example in a vertical orientation, then rotate to a horizontal orientation, then launch the HUUV. The LARS may be powered from the host with an armored umbilical.

In some embodiments, a LARS may provide its own power and energy when being used or the LARS may be powered from a host. This would avoid the LARS using any of the stored energy within the HUUV.

In some embodiments, a LARS may be capable of at least withstanding a sea state of 6, as defined by the Pierson- Moskowitz Sea Spectrum. In a sea state of 6, wind speed may reach about 61 kph and waves may reach a height of about 6 m and a length of about 80 m, averaging about 9 seconds between each wave. The LARS may be capable of withstanding wind speeds up to about 130 kph. The LARS may then be capable of mitigating the sea state to allow for a more stable environment for the HUUV when assembling, launching, and recovering . Example

An HUUV 101 may include the following components and characteristics. The shape of HUUV 101 may resemble a torpedo, as shown in Figure 2a. Cylindrical mid-section 105 of HUUV 101 may include six cylindrical segments, each segment being about 1 m in diameter and about 1 m in height. Thus, the total length of cylindrical mid-section 105 may total about 6 m in length. The cylindrical segments may be comprised of carbon fiber and/or fiberglass to reduce weight without sacrificing any strength. Impellers 107 may be attached to the ends of cylindrical mid-section 105. Impellers 107 enable HUUV 101 to have six degrees of freedom of motion, in addition to capable of hovering. In some embodiments, impellers 107 may include two pairs of counter- rotating impellers. In some embodiments, impellers 107 may be variable pitch throughout the rotation. In some embodiments, impellers 107 may have intakes and outtakes that are adjustable to achieve the desired thrust and direction. In some embodiments, suitable impellers are disclosed in U.S. Patent Number 3,101,066, which is herein incorporated by reference in its entirety. Nose caps 105 may be attached to impellers 107. Nose caps 105 may be shaped to reduce form drag and direct water into impellers 107 to increase efficiency of HUUV 101. Nose caps 105 may be comprised of a carbon fiber and/or fiber glass . In some embodiments, HUUV 101 may include an energy source located in cylindrical mid-section 105 for power. The energy source may include a fuel cell and a battery. The fuel cell may be used to power impellers 107 for propulsion, and the battery may be used to power the tools, INS, sensors, radars, and/or activities HUUV 101 may engage in. Preferably, the energy source has a total of at least about 1 X 10⁸ joules of energy to provide for HUUV 101 to travel to and from a site about 100 km away at a velocity of about 1.5 m/s, in addition to provide for HUUV 101 to perform activities for about 10 hours at about 3 kW. An example of a fuel cell that may be used is available from Siemens AG of Hamburg, Germany. Suitable batteries that may be used include lithium, lead acid, and alkaline . In some embodiments, HUUV 101 may include an INS to measure change in direction and acceleration in a three- dimensional coordinate system. The INS may include multiple gyroscopes and/or accelerometers for measurements when calculating the position of HUUV 101 relative to a known starting point. In some embodiments, the INS includes three gyroscopes and three accelerometers, a gyroscope to measure rotation about each axis in the three-dimensional coordinate system and an accelerometer to measure acceleration along each axis in the three-dimensional coordinate system. The INS may further include a clock and a navigation computer. The measurements taken by the gyroscopes and accelerometers may be used by the navigation computer to determine the overall acceleration of HUUV 101 of the INS in the three- dimensional coordinate system. The navigation computer may continuously compute the overall acceleration of the INS at a constant time step calculated by the clock to keep track of the position of the INS relative to a known point. The selection of a gyroscope, an accelerometer, a clock, and a navigation computer is not critical and may be selected from commercially available components used in the AUV and ROV industries. An example of an INS that may be used is TriRate or nIMU available from MEMSense, LLC.

In some embodiments, to enhance the accuracy of the INS, HUUV 101 may be equipped to use existing infrastructure or landmarks as reference points. For example, reference points may be incorporated into a flowline between a surface support vessel and a subsea facility such that emitters in the flowline emit a signal to be received by a receiver in HUUV 101. Each emitter in the flowline may emit a signal that gives the coordinates of the position of the emitter. The INS then may use this information from the emitter to verify this position versus the calculated position of the navigation computer of the INS. In some embodiments, the INS may be equipped with a Global Positioning System ("GPS") as another check to enhance the accuracy of the INS .

In some embodiments, HUUV 101 may include a FSO/LAN for wireless high-speed digital telemetry, enabling HUUV 101 to communicate with a surface support vessel and/or a subsea facility. Specifically, the FSO/LAN may use modulated blue green laser light that may enable ranges of about 100 meters for communication and data transfer speeds of about 10 Mbps . The FSO/LAN may include a receiver installed in cylindrical mid-section 105 of HUUV 101 that is in wireless communication with a router installed at the surface support vessel and/or the subsea facility. Suitable high-bandwidth underwater transceivers that may be used are commercially available from Ambalux Corporation of Tucson, Arizona.

In some embodiments, HUUV 101 may include an acoustic network to communicate with the surface support vessel and/or subsea facility. The acoustic network may be used for positioning and tracking of HUUV 101, for example when outside the range capabilities of the FSO/LAN. HUUV 101 may be equipped with a source that emits an acoustic sound wave. This sound wave may then be identified by one or more receivers within the surface support vessel and/or subsea facility to determine the position of the receiver in HUUV 101. Suitable acoustic transceivers that may be used are commercially available from Benthos, Inc. of North Falmouth, Massachusetts .

In some embodiments, HUUV 101 may be equipped with at least one docking interface. Specifically, the end of nose cap 103 of HUUV 101 may be equipped with a male docking interface component that may connect with a corresponding female docking interface component. Through the docking interface, HUUV 101 may transfer data and/or recharge with the surface support vessel and/or the subsea facility. The selection of the docking interface is not critical. Any commercially available docking interface may be used.

Those having ordinary skill in the art will appreciate that while several examples have been provided and described, the present invention is not limited to these embodiments. For example, the present invention is not limited to a particular number of cylindrical segments, a particular number of tanks and/or pumps for the active ballasting system, a particular location of tanks and/or pumps for the active ballasting system, a particular propulsion system, a particular navigation system, or a particular communication system. HUUV Activities As mentioned above, the HUUV may be used for support of a subsea production system through various activities. Examples of these various activities are as follows :

Visual Monitoring - The HUUV may be used for a visual inspection of the subsea facilities and/or the surface support vessel. For example, the HUUV may be used to survey for post event damages, such as inspecting for damage after a natural disaster.

Pipeline Survey - The HUUV may be used to inspect the flowlines and/or umbilicals that connect the surface support vessel and the subsea facilities. In some embodiments, the HUUV may use cathodic protection surveys to inspect the flowlines. Cathodic protection surveys may be used in subsea pipeline inspection for maintenance and repair. In some embodiments, the HUUV may use Nondestructive Evaluation ("NDE") to inspect the flowlines. NDE refers to techniques that may be used to inspect an object without damaging or destroying the object. Vortex Induced Vibration ("VIV") suppression installation - VIV is potentially damaging vibration caused by currents of deep water that may occur upon a underwater structure. To prevent damage from VIV, suppression devices such as strakes or fairings may be installed on the underwater structure. The HUUV may be used for this type of VIV suppression installation.

Valve Operation - The HUUV may be used to operate valves. Specifically, the HUUV may have a torque tool, such as a flying lead, to operate a valve, or may have an attachment, such as an arm, that may be used to operate the valve .

Choke and/or Pod Replacement - The HUUV may be used for choke and pod replacement for the subsea facilities . Particularly, Figures 8-14 show the HUUV 101 being used to replace an old pod 803 with a new pod 801 at a subsea facility 703.

Hot Stab - The HUUV may be equipped with a hot stab. Typically hot stabs are connectors used by ROVs for easy and reliable connection/disconnection with tools and subsea equipment .

Those having ordinary skill in the art will appreciate that the HUUV may be used for other activities that have been performed with divers, submarines, and/or ROVs. Example HUUV Mission

In some embodiments, the HUUV may be sent on a mission within a subsea production system, as given in an example herein. Initially, the HUUV is assembled and prepared in the VAB of the LARS, in which the LARS may be part of the surface support vessel. When in the VAB, the HUUV may be assembled vertically to save space. Further, the HUUV may be equipped with specific tools based on the specific activities the HUUV will be performing on the mission. For example, if the HUUV will be replacing pods, as shown in Figures 8-14, the HUUV may be equipped with new pods to replace the old pods at the subsea facilities. Further, the HUUV may be supplied with an energy source, such as a fuel cell and/or one or more batteries.

After assembly, the HUUV may be launched into the water. Using the handling frame and the winch of the LARS, the HUUV may be lowered to a depth of about 100 m into the water. Once at this depth in the water, the handling frame may then rotate the HUUV from a vertical orientation to a horizontal orientation. The handling frame may be equipped with a female docking interface to connect with a male docking interface on the HUUV to enable communication with the HUUV during launch. Further, the LARS may be equipped with a FSO/LAN for wireless communication with the HUUV for when the docking interface components of the LARS and the HUUV are no longer connected. This may enable the HUUV to communicate with the surface support vessel, such as reporting the SOH of the HUUV to an operator without the need of an umbilical. Next, after launch, the HUUV may begin its autonomous transit from the surface support vessel to the subsea facility. The transit may be autonomous because the HUUV may have limited communication with the surface support vessel when traveling from the surface support vessel to the subsea facility. Alternatively, this transit may be autonomous because autonomous transit may be programmed to be more power and time efficient than remotely operated transit. During this autonomous transit, the HUUV may be capable of determining its SOH, in which the HUUV may have preprogrammed responses to correct any system anomalies detected in the SOH. The HUUV may then use its impellers to propel itself through the water, ranging from about 5 to about 15 kilometers per hour velocity, and may use its INS for navigation. Further, the INS may use a combination of measuring devices to calculate the position of the HUUV in the three-dimensional coordinate system and use landmarks and/or reference points for verification of the calculated position. Further, the HUUV may have an onboard obstacle avoidance sonar and mission algorithms to sense any potential obstacles, such as rises in the ocean floor or ice floes, that may inhibit the HUUVs autonomous transit and enable the HUUV to maneuver the HUUV to avoid such obstacles. Next, upon arrival, the subsea facility may have an acoustic network and/or FSO/LAN to enable the HUUV to communicate with the surface support vessel. Specifically, when within the range of the FSO/LAN, the operator may take command and control of the HUUV for any activities the HUUV may be used for. During this time, it is preferable that the HUUV have at least enough energy to power the HUUV at about 3 kW for a duration of about 10 hours for the various activities .

Next, upon completion of the of the various activities at the subsea facility, the HUUV may connect with the subsea facility through a docking interface before departure. The subsea facility may have a female docking interface to connect with the male docking interface on the HUUV, in which the docking interface connection may be used to transfer data between the HUUV and the surface support vessel and/or recharge the HUUVs energy source. Preferably, the HUUV has enough energy to make the transit to and from the subsea facility to the surface support vessel, in addition to the energy needed for the various activities, without the need for recharging. However, the subsea facility may be capable of connecting with the HUUV through a docking interface for communication and/or recharging. Next, regardless of whether the HUUV may have connected with the subsea facility to transfer data and/or recharge, the HUUV may begin its autonomous transit from the subsea facility back to the surface support vessel. Alternatively, the HUUV may also begin an autonomous transit to another subsea facility. Assuming the HUUV has enough energy, is equipped with the necessary tools, and is capable of navigating to another subsea facility using its INS, the HUUV may travel to other subsea facilities as needed. Otherwise, when the HUUV arrives at the surface support vessel, the LARS may be used to recover the HUUV from the water. Moving through an analogous reverse movement of launch, the HUUV may connect with the HUUV handling frame through the docking interface, in which the handling frame may then rotate the HUUV from a horizontal orientation to a vertical orientation. The winch may raise the HUUV handling frame with the HUUV out of the water back onto VAB. At this point, the HUUV may then be disassembled and prepared for another mission.

Referring now to Figure 15, there is illustrated oil and/or gas production system 500. System 500 includes host 502 floating in a body of water. Subsea operation 504 is connected to host 502 by umbilical 506, and subsea operation 508 is connected to host 502 by umbilical 510. Subsea operation 504 and subsea operation 508 may be a large distance from host 502, for example up to about 100 kilometers, up to about 50 kilometers, up to about 25 kilometers, or up to about 10 kilometers, and at least about 2 kilometers .

In order to activate, deactivate, maintain, replace components, monitor, troubleshoot, or perform other intervention activities of subsea operation 504 and subsea operation 508, HUUV 514 and HUUV 522 may be used. HUUV 514 is shown accessing subsea operation 504. HUUV 514 is self powered and self propelled and controlled from host 502 by umbilical 506, transceiver 515, and signals 516. Signals may be a laser signal or an acoustic signal as discussed above. HUUV 514 may be provided with a laser and/or an acoustic transceiver in order to communicate with transceiver 515. HUUV may transmit data and receive data to and from host 502.

HUUV 522 is shown accessing subsea operation 508. HUUV 522 is self powered and self propelled and controlled from host 502 by umbilical 510 and umbilical 523. HUUV may transmit data and receive data to and from host 502. Advantages

The invention may have one or more of the following advantages. As discussed above, the HUUV may not require an umbilical to be connected between the HUUV and a surface support vessel. Because of this, the HUUV may be able to travel and survey more remote locations, such as deeper water and under ice applications, than previously completed by ROVs and AUVs. Under ice applications are limited by vertical access at the surface and obstacles such as ice floes. The HUUV may not require vertical access to the surface for support because the HUUV may not have an umbilical, and the HUUV may be equipped with an INS and algorithms to autonomously navigate the HUUV around obstacles. This may enable the HUUV to be used for such remote and demanding applications .

Further, the HUUV may have improved long range capabilities that enable larger transit ranges. With the use of fuel cells and/or batteries as energy sources for the HUUV, the HUUV may be able to preserve energy to be used for propulsion during transit. The INS of the HUUV may also provide improved navigation over previous systems by using known reference points as a confirmation of the INS ' s calculated position.

Further, those having ordinary skill in the art will appreciate that a HUUV in accordance with one or more embodiments of the present invention may be used in other industries besides the oil and gas industry. The present invention may be used in any underwater application that may require autonomous transit and/or remotely operated control of a vehicle when performing various activities, for example servicing seafloor seismic arrays or pressure gauges. Illustrative Embodiments :

In one embodiment, there is disclosed an oil and/or gas production system, comprising a host in a body of water; a subsea operation in the body of water a distance from the host; an umbilical connecting the host and the subsea operation; a hybrid unmanned underwater vehicle, comprising a communication mechanism to communicate with the host by the umbilical; a propulsion mechanism to transport the vehicle from the host to the subsea operation, and to maneuver the vehicle for intervention activities of the subsea operation; and a power source to power the vehicle for transport from the host to the subsea operation, and for intervention activities of the subsea operation. In some embodiments, the hybrid unmanned underwater vehicle further comprising an underwater transceiver. In some embodiments, the underwater transceiver comprises an acoustic transceiver and/or a laser transceiver. In some embodiments, the communication mechanism comprises an umbilical connectable from the hybrid unmanned underwater vehicle to the subsea operation. In some embodiments, the distance from the subsea operation to the host is from 2 kilometers to 100 kilometers. In some embodiments, the subsea operation is at a water depth from 250 meters to 3000 meters. In some embodiments, the subsea operation is selected from one or more of a well head, a tree, a subsea blow out preventer, a vortex induced vibration suppression device, a riser, a flowline, an export line, a separator, an injection well, a production manifold, and a production well. In some embodiments, the propulsion mechanism comprises at least one pair of counter-rotating impellers. In some embodiments, the umbilical comprises a fiber optic communication means. In some embodiments, the power source comprises one or more batteries and/or one or more fuel cells.

In one embodiment, there is disclosed an intervention method, comprising launching a hybrid unmanned underwater vehicle from a host in a body of water; propelling the vehicle from the host to a subsea operation in the body of water a distance from the host; establishing a communication mechanism for the vehicle to communicate with the host; and performing an intervention procedure on the subsea operation with the vehicle. In some embodiments, the vehicle is propelled a distance from 2 kilometers to 100 kilometers. In some embodiments, establishing a communication mechanism comprises activating an underwater wireless acoustic network and/or activating an underwater wireless laser network. In some embodiments, the intervention procedure is at least one of visual monitoring, pipeline survey, VIV suppression installation, valve operation, choke and/or pod replacement, and/or hot stab.

In one embodiment of the invention, there is disclosed a hybrid system of a Remote Operated Vehicle ("ROV") and an Autonomous Underwater Vehicle ("AUV") for use in the oil and gas industry. In some embodiments, there is disclosed a Hybrid Unmanned Underwater Vehicle ("HUUV") combining the autonomous and long range features of the AUV with the maneuverability and manipulative capabilities of the ROV to extend the production of hydrocarbons in the oil and gas industry into greater water depths .

Those of skill in the art will appreciate that many modifications and variations are possible in terms of the disclosed embodiments of the invention, configurations, materials and methods without departing from their spirit and scope. Accordingly, the scope of the claims appended hereafter and their functional equivalents should not be limited by particular embodiments described and illustrated herein, as these are merely exemplary in nature.

Claims

C L A I_ M S>

1. An oil and/or gas production system, comprising: a host in a body of water; a subsea operation in the body of water a distance from the host; an umbilical connecting the host and the subsea operation; a hybrid unmanned underwater vehicle, comprising: a communication mechanism to communicate with the host by the umbilical; a propulsion mechanism to transport the vehicle from the host to the subsea operation, and to maneuver the vehicle for intervention activities of the subsea operation; and a power source to power the vehicle for transport from the host to the subsea operation, and for intervention activities of the subsea operation.

2. The system of claim 1, the hybrid unmanned underwater vehicle further comprising an underwater transceiver.

3. The system of one or more of claims 1-2, wherein the underwater transceiver comprises an acoustic transceiver and/or a laser transceiver.

4. The system of one or more of claims 1-3, wherein the communication mechanism comprises an umbilical connectable from the hybrid unmanned underwater vehicle to the subsea operation.

5. The system of one or more of claims 1-4, wherein the distance from the subsea operation to the host is from 2 kilometers to 100 kilometers.

6. The system of one or more of claims 1-5, wherein the subsea operation is at a water depth from 250 meters to 3000 meters .

7. The system of one or more of claims 1-6, wherein the subsea operation is selected from one or more of a well head, a tree, a subsea blow out preventer, a vortex induced vibration suppression device, a riser, a flowline, an export line, a separator, an injection well, a production manifold, and a production well.

8. The system of one or more of claims 1-7, wherein the propulsion mechanism comprises at least one pair of counter- rotating impellers.

9. The system of one or more of claims 1-8, wherein the umbilical comprises a fiber optic communication means. The system of one or more of claims 1-9, wherein the power source comprises one or more batteries and/or one or more fuel cells .

10. An intervention method, comprising: launching a hybrid unmanned underwater vehicle from a host in a body of water; propelling the vehicle from the host to a subsea operation in the body of water a distance from the host; performing an intervention procedure on the subsea operation with the vehicle.

11. The method of claim 11, wherein the vehicle is propelled a distance from 2 kilometers to 100 kilometers. The method of one or more of claims 11-12, wherein establishing a communication mechanism comprises activating an underwater wireless acoustic network and/or activating an underwater wireless laser network.

12. The method of one or more of claims 11-13, wherein the intervention procedure is at least one of visual monitoring, pipeline survey, VIV suppression installation, valve operation, choke and/or pod replacement, and/or hot stab.

13. The method of one or more of claims 11-14, further comprising establishing a communication mechanism for the vehicle to communicate with the host.