Not Applicable
1. Field of the Invention
The invention relates generally to the field of producing hydrocarbons from subterranean formations below the bottom of a body of water. More specifically, the invention relates to devices capable of providing isolation used to remove liquid from subsea wells.
2. Description of the Related Art
Subsurface valves are often installed in tubing strings between subterranean formations penetrated by wellbores to prevent the escape of fluid, to isolate one producing subsurface formation from another and to isolate the wellbore from the surface. Along with or as part of the subsurface valve, a subsurface safety valve is installed. Typically, the subsurface safety valve is installed in the upper part of the wellbore to provide rapid closure of the producing conduits should there be an emergency. Without a subsurface safety valve, a sudden increase in wellbore pressure can result in catastrophic blowouts of fluids into the ocean or atmosphere.
Two types of subsurface safety valve systems are known in the art: surface-controlled and subsurface controlled. Both types of safety-valve systems are designed to fail-safe so that the wellbore is isolated in the event of any blowout or damage to the surface production-control facilities. Many subsurface safety valves use a flapper-type valve for allowing substantially unrestricted flow when opened, but completely seal off flow when closed. A flapper-type valve typically includes a circular or curved valve disc to engage a valve seat. When engaged, the disc in combination with the valve seat is used to isolate the area above from the area below the flapper in the well. Flapper valve disks are often energized with a spring or hydraulic cylinder. When there is no actuating force applied, the valve remains closed. When the valve is closed, any build-up of pressure from the production zone below the valve will push the valve disc against the valve seat and will strengthen the sealing of the valve as a result. During normal use (as opposed to an emergency condition), the valve disk is kept opened by energizing the spring or hydraulic cylinder. Travel of various devices therethrough is unrestricted in such case.
Certain circumstances arise, for instance, when wells near the end of their productive life require some sort of artificial lift system to ensure sufficient production to remain economically useful. As an example, in gas wells, dewatering may be required to enable gas production to continue at acceptable rates. Such actions may also be required for other fluid producing wells and it may be necessary to be install a pump system downhole. Although the hydrocarbon-producing zone through which the well passes still has hydrocarbon reserves, in some cases the fluid pressure of the hydrocarbon-producing zone is insufficient to overcome the hydrostatic pressure or head of the fluid column in the wellbore. It may also be desirable to install a pump system downhole to periodically introduce particular chemicals into the wellbore to stimulate the production zone to increase the production of hydrocarbons.
In wells where a subsurface safety valve is utilized, a means to maintain a safe automatic well shut-in is required to replace the function of the downhole safety valve if the safety valve is disabled by a retrofit system installed into the existing production tubing. As described more fully below, it may be necessary to install piping or cables through an existing subsurface safety valve, partially or fully disabling the action of the subsurface safety valve. For instance, if subsurface safety valve system contains a flapper-type valve, the piping or cable passing therethrough may obstruct the flapper-type valve and not allow it to fully close.
There have been previous attempts to address similar problems. For instance, for so-called capillary string installations, insert safety valves have been developed. However, these insert safety valves are not suitable for installations where larger diameter equipment must pass through the subsurface safety valve, for example a spooled pipe with signal and power cables.
Accordingly, there exists a need for a relief system that enables fail-safe shut in of a well in which retrofit equipment is inserted through a previously installed subsurface safety valve.
A downhole pump system in one aspect of the invention includes a submersible pump within production tubing for enhancing the flow of fluid, a motor and an internal safety valve. The motor is operably connected to the submersible pump for driving the submersible pump. The internal safety valve is in fluid communication with the submersible pump and is configured to pass substantially all of the fluid capable of passing through the submersible pump. The internal safety valve includes a closure mechanism. The closure mechanism has an open position and a closed position, wherein the closure mechanism allows fluid flow through the internal safety valve when the closure mechanism is in the open position and substantially obstructs fluid flow through the internal safety valve when the closure mechanism is in the closed position. The internal safety valve further includes a biasing mechanism that is functionally connected to the closure mechanism. The biasing mechanism has an energized state and a non-energized state and is configured to move the closure mechanism to the open position when the biasing mechanism is in the energized state. The internal safety valve also includes an actuator. The actuator is configured to change the state of the biasing mechanism from the energized state to the non-energized state.
A method for removing liquid from a wellbore according to another aspect of the invention includes providing a downhole pump system. The downhole pump system includes a motor, a submersible pump mechanically connected to the motor, and an internal safety valve fluidly connected to the submersible pump. The internal safety valve includes a closure mechanism. The closure mechanism has an open position and a closed position wherein fluid flow is possible through the internal safety valve when the closure mechanism is in the open position. The fluid flow has a flow rate. The internal safety valve further includes a biasing mechanism. The biasing mechanism is designed to mechanically connect to the closure mechanism. The biasing mechanism has an energized and non-energized state, and the biasing mechanism is further designed to hold the closure mechanism in the open position when the biasing mechanism is in the energized state. The internal safety valve also includes an actuator, where the actuator is designed to change the state of the biasing mechanism from an energized to a non-energized state. The method further includes disposing the pump system in the production tubing of a wellbore, connecting an umbilical to the pump system, the umbilical having a pressure therein, energizing the biasing mechanism, and activating the pump system to remove liquid from the wellbore, the liquid having a liquid level, through the pump system.
Another example of a pump system for installation disposed in production tubing in a wellbore is disclosed which includes a generally cylindrical housing. The generally cylindrical housing has a circumference and extendable protuberances located along the circumference. The generally cylindrical housing is adapted to fit within a production tubing. The production tubing has landing nipples are disposed along the interior surface of the production tubing which are to receive the extendable protuberances. The pump system further includes an inlet port adapted to allow fluid to enter the generally cylindrical housing, a submersible pump within the generally cylindrical housing in fluid connection with the inlet port, a shaft, the shaft mechanically connected to the submersible pump, a motor, the motor mechanically connected to the shaft, and an internal safety valve. The internal safety valve is disposed within the generally cylindrical housing and is in fluid communication with the submersible pump. The internal safety includes a closure mechanism with an open position and a closed position, wherein fluid flow is possible through the internal safety valve when the closure mechanism is in the open position. The internal safety valve also includes a biasing mechanism designed to mechanically connect to the closure mechanism. The biasing mechanism has an energized and non-energized state and is further designed to hold the closure mechanism in the open position when the biasing mechanism is in the energized state. The internal safety valve also includes an actuator designed to change the state of the biasing mechanism from an energized to a non-energized state.
Other aspects and advantages of the invention will be apparent from the following description and the appended claims.
A more complete understanding of the present disclosure and possible advantages thereof may be acquired by referring to the following description taken in conjunction with the accompanying figures, wherein:
While the present invention is susceptible to various modifications and alternative forms, specific exemplary embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.
The invention enables installation of equipment into existing wellbore tubing wherein it is desirable to maintain the function afforded by a downhole safety valve.
In certain examples, pump systems of the present invention comprise a motor, a submersible pump functionally connected to the motor; and an internal safety valve fluidly connected to the submersible pump. Internal safety valves of the present invention may comprise a closure mechanism wherein the closure mechanism has an open position and a closed position, a biasing mechanism operably connected to the closure mechanism. The biasing mechanism has an energized and a non-energized state wherein the biasing mechanism is adapted to motivate the closure mechanism to the open position when the biasing mechanism is in the energized state, and an actuator configured to change the state of the biasing mechanism from the energized state to a non-energized state.
Pump system (1) is deployed within production tubing (4), typically near the bottom of production tubing (4) and most often below subsurface safety valve (6). Pump system (1) fluidly communicates with wellhead arrangement (12) through umbilical (5). Umbilical (5) connects to pump system (1) through connector (19). The umbilical (5) can also be of a solid type without an inner tube (15) for fluid transport. Such a design can be used where the fluids are produced out of the well in the annulus between umbilical (5) and production tubing (4).
Another non-limiting type of umbilical (5) is shown in
In wellhead system (12) or within tubing hanger (11) it may be necessary to mount one or more barriers (7). Umbilical (5) protrudes through the one or more barriers (7), which act to isolate fluids from within production tubing (4) from the surrounding environment by forming a seal between wellhead system (12) or tubing hanger (11). The type and composition of one or more barriers (7) depends on the geometry of wellhead system (12) and the production fluids themselves.
An additional sealing system (8) can be mounted in or on top of wellhead system (12) in much the same manner described for one or more barriers (7) designed to isolate fluids from exiting wellhead system (12) and entering the surrounding environment. Finally, a sealing and cutting system (13) may be mounted to the top of wellhead system (12). This sealing and cutting system incorporates a cutting system (9) as well as a seal (14) providing a seal against the umbilical (5).
In one example of the present invention, pump system (1) includes an internally mounted safety valve (further illustrated below). The internally mounted safety valve is designed to automatically prevent fluid flow from travelling within umbilical (5) if hydraulic or electric power to pump system (1) is lost, such as from a control system mounted externally on wellhead system (12). In another example of the present invention, the internally mounted safety valve is a flow-operated valve that automatically closes if the fluid flow exceeds a preset maximum flow rate.
Pump system (1) is depicted as including external packing system (2) that fills the annulus between pump system (1) and production tubing (4) and seals against production tubing (4). As will be appreciated by one of ordinary skill in the art, the type of external packing system used, should one be necessary, depends on such factors as the type of pump system (1) employed and the nature of the production fluid, along with such other factors as bottomhole and pump system (1) geometries and operator preference.
In one example of the present invention, external sealing system (2) includes one or more flow ports (20). Flow ports (20) are ports that extend through the upper and lower surfaces of external sealing system (2). It is through these ports that gas may be produced from the formation through the production tubing. Flow ports (20) may include safety valves. The safety valves within flow ports (20) may be designed to work in much the same way as a subsurface safety valve, open during normal production operations and closed in the event of catastrophic failure or a desire to isolate wellhead system (12) from the hydrocarbon-producing formation (not shown).
The present example is related to a gas producing well, where water build-up in the wellbore proximate the reservoir (not shown) prevents or reduces the gas production. However, the system may also be used to lift fluids from a fluid well such as, for example, where the fluid pressure in the reservoir is not sufficient to lift the reservoir fluid to the wellhead system (12). For such an application, pump system (1) can pump the fluids into the annulus between the umbilical (5) and the production tubing (4), and in such applications flow ports (20), as well as any safety valves disposed therein, are optional and not required.
In an alternate installation, the system is installed safely into the well following a well kill operation, where dense fluids (or so called “kill pill” or heavy gel) are placed downhole. When the system has been installed, the dense fluids are pumped out of the well by pumping system (1).
In still another alternative installation method, a downhole check valve mechanism is installed in the wellbore such that that the pump assembly lands into the check valve when lowered into the wellbore. The check valve will be closed until the pump engages into the valve.
Also depicted in the example shown in
In the example shown in
The example of pump system (1) shown in
Closure mechanism (44) shown is a flapper valve and has an open and a closed position. Non-limiting examples of a flapper closure can be found in U.S. Pat. No. 7,360,600 filed Dec. 21, 2005 entitled “Subsurface Safety Valve,” and U.S. Pat. No. 5,862,864 filed Jan. 26, 1999 entitled “Well Safety System.” Note that a ball closure or poppet closure, both well known devices to those of ordinary skill in the art, may also be used as closure mechanism (44). A non-limiting example of each may be found, respectively, in U.S. Pat. No. 4,708,163 filed Jan. 28, 1987 entitled “Safety Valve” and U.S. Pat. No. 4,448,216 filed Mar. 15, 1982 entitled “Subsurface Safety Valve.” When in the open position (as shown in
In the example depicted in
Actuator (40) may be operated by any number of typical means, including remote, manual, and automatic activation. For instance, actuator (40) may be operated from the surface, such as by an operator who desires to stop fluid flow from passing through pump system (1). However, it may be desirable to stop fluid flow from passing through submersible pump (50) due to conditions of pump system (1). For this reason, conditions of pump system (1) may be monitored by sensors (66) that measure various parameters of pump system (1). In various examples of the present invention, sensors (66) may monitor the rate or volume of fluid flow through pump system (1), or the liquid levels within the wellbore. In the event of low or no flow through pump system (1) or high or low liquid levels within the wellbore, actuator (40) may be operated to prevent damage to pump system (1). In some examples of the present invention of pump system (1), a preset upper and/or lower liquid level limit may be established. Then, when the liquid level within the wellbore reaches the upper limit, actuator (40) may be energized, allowing biasing mechanism (42) to hold closure mechanism (44) in the open position and allow fluid flow through pump system (1). Conversely, when the liquid level within the wellbore reaches a pre-set lower limit, actuator (40) may be de-energized, so as to cause biasing mechanism (42) to allow closure mechanism (44) to the closed position and substantially restricting flow through pump system (1). In other various examples of the present invention, sensors (66) may monitor umbilical (5) to determine pressure or breakage of umbilical (5) and operate actuator (40) to de-energize biasing mechanism (42) when umbilical (5) breaks or reaches a certain pre-set high pressure.
The examples disclosed herein have generally been described in the context of a subsea installation. One of ordinary skill in the art with the benefit of this disclosure will appreciate that examples of the present invention would be suitable for surface or land-based installation as well. Additionally, it is explicitly recognized that any of the features and elements of the examples disclosed herein may be combined with or used in conjunction with any of the other examples disclosed herein.
Therefore, the present invention is well adapted to attain the ends and advantages mentioned as well as those that are inherent therein. The particular examples disclosed above are illustrative only, as the present invention may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. Furthermore, no limitations are intended to the details of construction or design herein shown, other than as described in the claims below. It is therefore evident that the particular illustrative examples disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the present invention. Also, the terms in the claims have their plain, ordinary meaning unless otherwise explicitly and clearly defined by the patentee.
Priority is claimed from U.S. Provisional Patent Application Ser. No. 60/947,223 filed on Jun. 27, 2007.
Number | Date | Country | |
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60947223 | Jun 2007 | US |