Patent Application
20050217857
The present invention relates to subsea equipment installed on the seafloor and intended for oil production, and which can also be applied to water injection systems in hydrocarbon reservoirs. More specifically, the present invention relates to pumping modules coupled to an intermediate flow inlet on a subsea base, whereby said modules can be installed as well as recovered by cable. The present invention further relates to the method for installing said pumping module.
Offshore oil production requires that subsea wells be drilled and that equipment such as Christmas tree manifolds, oil flow lines, gas injection lines and water injection lines be installed between the wellheads and the processing facilities. These processing facilities may be located on a vessel, platform, or even on land.
Christmas tree manifolds are assemblies of connectors and valves installed at the top of an oil wellhead and are used to block (open and close) and route the flow of fluids produced or injected.
There are two types of wet Christmas tree (WCT) manifolds, depending on how the valves are arranged with regard to the production column hanger inside the well: horizontal and vertical (which is conventional). In some cases, mainly with a vertical wet Christmas tree manifold, additional equipment known as a production adaptor base (PAB) is employed between the WCT and the wellhead. The production adaptor base is mainly intended to support the oil-production and gas-injection lines, as well as the production column. In the latter case, the tubing hanger is attached to the production adaptor base rather than to the WCT. Flow-lines supported by the production adaptor base are connected to the wet Christmas tree, which is in turn connected to the well bottom by the production column.
Inasmuch as producing wells are located at some distance from the processing facilities, sufficient pressure must be maintained at the wellhead so that fluids can flow to the facilities at a reasonable flow rate so as to make the project economically feasible.
Various lifting methods are used to boost flow from the wellhead to the processing facilities. One such method uses pumps, for example centrifugal pumps known as electrical submersible pumps (ESP). Installed at the bottom of oil-producing wells, they are generally driven by an electric motor.
Once the ESP, production column and wet Christmas tree have been installed at the well, maintenance performed on the ESP increases operating costs and risks, involving the equipment as well as the environment.
From time to time it becomes necessary to perform maintenance or repairs on the ESP installed in the well. Removal of an ESP from the subsea well requires an interruption (loss) of oil production for several days, along with the use of additional equipment and vessels equipped with a rig so that the ESP and production column can be removed, resulting in higher production costs.
U.S. Pat. No. 6,497,287 describes how an electrical submersible pump is typically used in the production of offshore oil.
Furthermore, U.S. Pat. No. 5,280,766 shows that an ESP can be installed or recovered from the well bottom without removing the subsea Christmas tree, through flexible steel tubing known as “coil tubing” or “flexi-tubo.”
Based on Applicant's Brazilian Application PI 0301255-7, herein incorporated in full as a reference, it is known that it is possible to use a pumping module installed and retrieved by cable from a nonspecialized vessel. Such a module is comprised of a closed tubular body and a hydraulic connector, whereby said connector is coupled to the mandrel of an intermediate flow inlet (IFI), thus establishing a hydraulic communication between the pumping module and the cavities (holes) in said mandrel, i.e., for pump suction and discharge. Such an application has the disadvantage of requiring changes in the PAB-WCT assembly that alter the manufacturing standard by increasing the weight, size and cost of said assembly. Moreover, when the pumping module is mounted vertically, its upper end extends above the WCT, hampering light activity at these wells due to the need to remove this module to avoid the risk that the completing riser-blow out preventer (BOP) will strike the module during connection for reentry into the well. Another drawback of this system is that it cannot be easily applied to existing wells owing to the need to change the production adaptor base (PAB), in other words, re-completing the well with removal of the production column is required.
U.S. Pat. Nos. 4,900,433 and 6,036,749 show a vertical oil separator system with a pump similar to an ESP, wherein a separator-pump assembly is installed in a dummy well built for the sole purpose of holding the separation-pumping assembly and whose pump is similar to an ESP with rather slender geometry, i.e., thin and long, designed preferably to operate in the vertical position.
Moreover, U.S. Pat. No. 6,688,392 shows that it is possible to install a motor pump assembly, similar to an ESP, hydraulically linked to a dummy well. Nevertheless, this solution presents a number of drawbacks: the dummy well is hydraulically linked to the flow from the oil well, and operates under oil pressure. When the liner of the dummy well corrodes, maintenance becomes difficult because the liner is buried in the seabed and cannot be recovered. Although there is a reference to a bypass, the proposed geometry has no provision or possibility for a pig (i.e., a flow line cleaning device) to pass, a basic necessity to ensure oil well flow. Nor is another lifting method described to maintain production continuity in case the proposed pumping system fails. The dummy well is of conventional construction, i.e., drilled and cemented. In addition, the pump installation method requires a vessel with a coil tubing unit. Connection of the proposed pumping system has no metal-metal seal.
Despite the above developments, there is still a need in the state of art for a cable-based system and method for installing and recovering a centrifugal pumping module that does not have the drawbacks described above.
The present invention overcomes the above drawbacks in the state of art by constructing a pumping module associated with an installation or recovery method by cable, with said module supported by and connected to a base structure on the seabed at a safe distance from the WCT and without interfering with well reentry operations.
Said base structure may simply rest on the seabed, or it may be supported and jacketed (coupled) by a hollow pile, or merely supported on a foundation comprising a pile.
The configuration of a pumping module installed in a hollow pile (which is the preferred embodiment of the present invention) driven into the seabed especially for this purpose, differs from the current state of art whereby a distinguishing feature of the present invention is that the sole purpose of said hollow pile is to support and hold the vertical pumping module, and is not part of the oil flow system. Said hollow pile may be installed by conventional methods such as drilling or blasting, or by torpedo pile (Brazilian Patent Application PI0106461), whereby said pile is raised a certain distance above the seabed then dropped so that it is driven into the bed by the force of the free fall. The oil flow passes through the pumping module, which is hydraulically linked to the producing well. Moreover, the present invention is constructed so that a pig (line-clearing device) can be passed through the flow lines. The pumping module is coupled to the base structure through a connector-mandrel assembly, with metal-metal sealing. Another advantage is the ease of removing the pumping module, using a vessel with a cable, with no need to disconnect the oil flow lines or any other component, thereby reducing the risk of an underwater oil spill. Such a system is described in the text and claims of the present application.
In the alternative configuration that employs this hollow pile, i.e., at a depth of tens of meters, the pumping module is fully or partially contained vertically in this hollow pile, and connected to the oil flow only by the IFI.
By means of a vessel fitted with a winch and cable, this configuration makes it easy to recover the pumping module to perform maintenance on the ESP assembly. Moreover, it is not necessary to use sophisticated vessels such as those outfitted with a rig, and facilitates the use of a longer motor-pump assembly.
In specific situations, the present invention eliminates the need to install an ESP at the bottom of the oil well; consequently, there is no need to work inside the oil well to remove the ESP, thereby substantially reducing production shutdown time (time spent awaiting a rig plus actual work time), as well as cutting costs.
Inasmuch as the ESP of the present invention is positioned outside the oil well, it can be installed or recovered with a cable from a non-specialized vessel, thereby substantially lowering the cost of maintaining the pump.
The system of the present invention also allows for the simultaneous installation of one pump inside and another outside the oil well, one being a backup for the other.
Whenever production or injection without the installed pumping module is desired, a closed cover can be installed on the IFI mandrel to ensure additional (double) blocking of the suction and discharge valves.
The present invention offers the following alternatives for oil production by subsea wells, with lifting through pumping:
by means of a pumping module alone, which can be installed and recovered by cable, with a production line from one or more wells coupled thereto; or
by combining a pump installed at the well bottom and a pumping module, which can be installed and recovered by cable, with a production line from one or more wells coupled thereto. In the latter instance, the pumps will alternate operation, i.e., one pump is a backup for the other, with a subsea electrical switch allowing for remote operation (e.g., from the SPF—stationary processing facility).
The pump to be used in the pumping module in accordance with the present invention can be electrically driven (the preferred embodiment of the present invention) or hydraulically driven.
Furthermore, in accordance with the present invention, the pumping module allows for different types of pumps to be installed. Likewise, the use of electrically driven ESPs—similar to those normally installed at the bottom of oil wells—renders a more advantageous solution feasible, inasmuch as an economy of scale results from using standard manufactured equipment found throughout the oil industry.
The pumping module of the present invention has been developed with use of the ESP in mind, inasmuch as this pump is well known in the state of art as being similar to those installed at well bottoms. Likewise, there is nothing to prevent the development and installation of a more compact pump (not as thin), since by being outside the oil well its diameter can be larger and its height lower.
In a broader sense, the main object of the present invention is to build a pumping module linked to installation and recovery by cable whereby said module is coupled to a base structure that rests directly on the seabed or on a hollow pile, or even on a foundation comprising piles, with said base structure located at a safe distance from the WCT so that it does not interfere with well reentry operations. The pumping module and base structure are coupled through an intermediate flow inlet (IFI) that uses a connector with a metal-metal seal. The metal-metal seal must be used on subsea equipment that remains submerged for long periods of time at high pressures and in contact with corrosive substances generally found in oil.
Said base structure may simply rest on the seabed (similar to a skid), or it may be connected (coupled) to a foundation comprising piles, or can even be supported by and fully or partially inserted into a hollow pile, wherein said hollow pile is made especially for this purpose (in the preferred embodiment).
The pumping module is coupled to the base structure through an intermediate flow inlet comprising two on-off valves and one bypass valve. The base structure rests on the seabed and can be placed anywhere between the producing well and the SPF.
Said pumping module is a tubular structure wherein one or more motor-pump assemblies can be encased, including those of the ESP type. These pumping modules have a hydraulic connector whereby they can be connected to or disconnected from the IFI. If necessary, other components can be incorporated into this same pumping module, such as flowmeters, temperature gauges, pressure gauges, choke valves, and so forth.
In accordance with the present invention, this IFI comprises a cylindrical mandrel with at least two holes (cavities) for oil flow. One hole is interlinked with pump suction flow and the other with pump discharge flow. To render removal of the pumping module easier without causing an oil spill, two on-off valves are installed next to these mandrel holes. By shutting off these valves, suction and discharge flow can be hydraulically isolated, allowing for the pumping module to be installed or removed by cable with no risk of large underwater oil spills. A bypass valve is also installed for rerouting the flow from the pumping module, allowing production to continue whether or not the pumping module is installed and operating.
The following descriptions of the embodiments of the present invention are examples only, and refer to the accompanying drawings. The same numerical references will be used in the attached figures for designating the same or similar parts.
It should be noted that the method for installing the pumping module with regard to the other embodiments of the present invention, i.e., with their base resting on the seabed and a pile, is very similar to the embodiment shown in
The following numbers apply to the description of the embodiments of the present invention:
The following numbers apply to the description of the embodiments of the present invention:
The figures, particularly
A base 15 of the pumping module 1 is interlinked with flow lines by means of devices known as vertical connection modules (VCM), well known in the present state of art. The inlet VCM 12 that receives well production is interlinked with the suction flow from the pumping module pump through a tube wherein a suction on-off valve 3 is installed. Pump discharge is interlinked to the outlet VCM 13 through a tube wherein a discharge on-off valve 4 is installed. A bypass valve 5 allows flow from the module to be rerouted while a pig (a line-clearing device) is passed through whenever necessary. As such, the present invention is built in such a way whereby a pig can be passed through the system when the flow bypasses the mandrel 2 and pumping module 1.
More specifically, said mandrel 2 has an outlet hole and a return hole, whereby a production flow line 8 coming from a well is shunted through the mandrel outlet hole to the pumping module 1. After the oil flow circulates, and accumulates energy (and pressure), in the pumping module 1, the oil flow returns to the mandrel 2 through the return hole, with this flow finally routed through a flow line 9 that interlinks with a processing facility (not shown).
In contrast, for a water injector well, the suction flow and discharge flow are reversed, i.e., the suction flow is fed by the flow line 9 coming from the FPU 1 [flow production unit] and the discharge is interlinked with the flow line 8, which is coupled to a well 17.
When pumping module 1 is not installed, a closed cover 23 is mounted on mandrel 2 for the sole purpose of establishing a second hydraulic barrier to avoid spills into the sea. Two off-on valves, for suction 3A and discharge 4A, should also be installed on the pumping module 1, in addition to the valves 3 and 4 on the mandrel. These valves 3A, 4A block oil leaks from the pumping module 1 while the pumping module 1 is being removed.
With further reference to
Also in accordance with the present invention, the pumping module 1 can be installed and operated separately or associated with another ESP installed at the well bottom. In this case, pumps will be redundant and will operate in an alternating fashion. This concept extends production because the pumping system does not have to shut down to repair the ESP installed at the well bottom, since if one assembly fails, the other can be immediately actuated by remote control using an electrohydraulic switch (not shown) coupled to the WCT. Said electrical switch can be mounted on the WCT or can also be incorporated into the pumping module 1 or the base 15.
With further reference to
As detailed in
When the pumping module 1 is installed vertically, there is a neck type profile 11 at the upper end of the pumping module for connecting a cable installation tool 10 The tool 10 is driven by the ROV. Although the tool 10 is not shown in the subsequent figures, the installation of the neck 11 also pertains to the other embodiments and will not be described again with respect to the remaining Figures.
With current techniques known in the art, ESP applications often require high-flow and high-head (i.e., pressure differential supplied by pump) equipment. However, due to pump construction limitations in geometry whereby there is a small diameter and a long length due to the thin geometry of the oil well, at times these ESP assemblies are mounted with two motors, two protectors and two pumps, all coupled along the same geometrical axis. This type of mounting is performed in order to impart specific flow and head characteristics to the assembly.
In the present invention, because the ESP is installed outside the well; there are no similar geometrical restrictions. However, for economy it is recommended that an ESP of standard manufacture be used.
The present invention suggests that such ESPs be installed inside subsea pumping modules 1. To facilitate the installation and recovery of such modules, preference is given to a geometry with a short length so as to make handling of the module on the vessel and mounting of the module in land-based shops easier.
To circumvent such limitations, according to one embodiment of the present invention, the two motor-pump assemblies are installed on parallel geometrical axes in order to shorten the overall length of the module by around half. This design that can be best visualized in
The pumping assembly of the motor 30 and pump 31 is supported inside the pumping module 1 by the pump support 34.
In
Although the pump motor 30 is shown in the Figures, the pump motor 30 can also be located outside the pumping module in direct contact with the sea water. Whenever the pumping module 1 is lowered and installed horizontally, the neck 11 can be positioned close to the middle of the pumping module 1 and its center of gravity. The pumping module 1 can also be lowered vertically to the bottom, rotated 90 degrees from a support point on the base 15, and then installed horizontally.
Use of the present invention also makes it possible to install two ESPs, one at the bottom of the well and the other on the seabed, and which may operate simultaneously (jointly) or alternatingly, with one serving as a backup for the other in the latter instance.
System Installation Method
The installation steps of the present invention will be described for the embodiment with the hollow pile 20. The installation method of the other embodiments, with the base 15 resting directly on the seabed and the base 15 resting on the foundation comprising a pile 21, will not be described in detail. However, the installations of these embodiments are very similar to the embodiment with the hollow pile and are considered readily apparent to one skilled in the art.
First, a hollow pile 20 is driven (buried) in the sea bed. The inside diameter of the pile is greater than the outside diameter of the pumping module 1. Various techniques can be used to drive in the hollow pile 20, including free fall (similar to the torpedo pile), suction (similar to suction anchoring), blasting (a technique similar to that used to start a subsea well), or simply by drilling with a bit. All of these techniques are well known and mastered in the current state of the art.
If blasting or simple drilling is selected, the hollow pile can be lowered with the base 15 of the pumping module 1 previously connected thereto, saving work time required to lower the base 15 by itself.
After driving in the hollow pile 20, of a length from 15 to 40 meters, and depending on the dimensions of the pumping module 1, a length of around 2 to 5 meters should be left unburied. The function of the unburied portion is mainly to guide and support the base 15 of the pumping module 1.
Next, the base 15 is lowered. The base has a downward-facing funnel 24, which guides the insertion of the hollow pile 20 into the base. Next, the base 15 is attached to the hollow pile 20. Different mechanisms can be employed to make this attachment, including a low-pressure (1500 psi) housing device, or a J slot type system, both of which are well known and used in drilling bases.
After the base 15 of the pumping module 1 has been installed and connected to the hollow pile 20, the flexible lines 8, 9, along with the pumping module 1, are then mounted to the base 15 in any sequence.
The pumping module 1 is lowered until it is fully supported by a shoulder on the base 15. The pumping module 1 is then connected to the mandrel 2 of the base 15 by the connector 6.
The flexible lines 8, 9 are coupled from vertical control modules 12, 13, 14. Depending on the vessel and facilities employed, VCM 12 and its respective base mandrel 15, may not be needed. Instead, a pair of surface-mounted flanges are installed prior to placing the base 15 in the water. In this case, the base 15 can be lowered along with the flexible line 8 mounted on said base 15.
Although the present invention has been described in terms of its preferred embodiments, it is obvious to one skilled in the art that various changes and modifications are possible without departing from the scope of the present invention as set forth in the attached claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| PI 0400926-6 | Apr 2004 | BR | national |
