This section provides background information to facilitate a better understanding of the various aspects of the invention. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
The invention relates to subsea well interventions, and more specifically to hydrocarbon evacuation of the production tubing to perform an environmentally safe well intervention.
Subsea wells are typically completed in generally the same manner as conventional land wells and are subject to similar service requirements as land wells. Further, as with land wells, services performed by intervention can often increase the production from the subsea well. However, intervention into a subsea well to perform the desired services is typically more difficult than for land wells. Conventionally, to perform subsea intervention, the operator must deploy a rig (such as a semi-submersible rig) or a vessel, as well as a marine riser, which is a large tubular that extends from the rig or vessel to the subsea wellhead equipment.
Interventions may be performed for various reasons. For example, an operator may observe a drop in production or some other problem in the well. In response, the operator performs an intervention operation, which may involve running a monitoring tool into the subsea well to identify the problem. Depending on the type of problem encountered, the intervention can further include shutting in one or more zones, pumping a well treatment into a well, lowering tools to actuate downhole devices (e.g., valves), placing the well on secondary recovery (e.g., installing an in-well pump), and so forth.
Performing intervention operations with large vessels and heavy equipment such as marine riser equipment, as conventionally done, is typically time consuming, labor intensive, and expensive. Therefore, a need continues to exist for less costly and more convenient intervention solutions for subsea wells.
A subsea well according to one or more aspects of the invention comprises production tubing having a double barrier positioned downhole from a valve tree, an intervention device deployed in the valve tree, the intervention device comprising a fluid conduit extending to a position within the production tubing, and an isolation plug removably disposed in the fluid conduit.
The intervention device according to one or more aspects of the invention may include a body having a bottom portion sealingly deployed in a tubing hanger and an upper portion sealing disposed through a tree cap. The fluid conduit may include a tubular extending from the body to the position within the production tubing. More than one isolation plug may be disposed in the fluid conduit. In one embodiment, a lower isolation plug is positioned in the fluid conduit between the tubing hanger and the tree cap and an upper isolation plug is positioned in the fluid conduit above the tree cap relative to the production tubing.
A device such as an electric submersible pump (“ESP”) can be deployed in the production tubing between the intervention device and the double barrier, wherein the fluid conduit extends to the position in the wellbore proximate to the ESP.
A method for subsea well intervention according to one or more aspects of the invention includes creating a lubricator section in the subsea well between a double barrier deployed in production tubing and an intervention device deployed proximate a wellhead; connecting coil tubing to the lubricator section through the intervention device deployed in the production tubing proximate to the wellhead; and circulating a clean fluid through the coil tubing and the lubricator section.
The foregoing has outlined some of the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention.
The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.
It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact.
As used herein, the terms “up” and “down”; “upper” and “lower”; “top” and “bottom”; and other like terms indicating relative positions to a given point or element are utilized to more clearly describe some elements. Commonly, these terms relate to a reference point as the surface from which drilling operations are initiated as being the top point and the total depth of the well being the lowest point, wherein the well (e.g., wellbore, borehole) is vertical, horizontal or slanted relative to the surface.
In preparation for performing the intervention a vessel 32, depicted as a light intervention vessel, is deployed at the surface 34 of the water 33. Vessel 32 includes various equipment, such as a deploying devices 36 (e.g., compensated lift crane, winch), coiled tubing 38, pumps 40, liquid storage tanks 42 (e.g., clean fluid, hydrocarbon fluids, etc.), and operational devices 44 which includes for example processor based controllers, electric and hydraulic power sources, and the like. A lubricator 46 comprising a dynamic seal 48 (e.g., traveling barrier) is connected to tree 24. Coiled tubing 38 is deployed through a guide 50 (e.g., riser) from vessel 32 into lubricator 46 for entry into production tubing 20.
The devices of the invention facilitate methods for flushing (e.g., displacing, evacuating) hydrocarbons from production tubing 20 prior to performing the intervention to prevent any unacceptable amount of hydrocarbons to be released into the sea. When double pressure barrier 12 is closed (i.e., lubricator valve 28 and safety valve 30 closed) the upper portion of the production tubing 20 is isolated from the pressure bearing zones 25 for example. When the production tubing 20 is free of installation of any devices, such as an in well pump, access to production tubing 20 can be established using the coil tubing 38 deployed through the guide 50 into the lubricator 46 and into production tubing 20. The bottom end 52 of coiled tubing 38 can be deployed for example proximate the depth of downhole lubricator valve 28 and a fluid 54 can be pumped from vessel 32 through coiled tubing 38 and circulated through the production tubing 20 and returned to vessel 32 through coiled tubing-guide annulus 56. Upon flushing of the hydrocarbons from production tubing 20, the subsea well is accessible through open water 33 so that any equipment can be run in and installed in the tubing, for example as depicted in
Refer now to
Fluid conduit 72 comprises tubular extension 64 which extends below bottom end 70 when installed in the subsea well, thereby extending the length of fluid conduit 72 below body 61. Fluid conduit 72 includes two isolation plug devices 86 providing a fluidic and pressure seal through fluid conduit 72. Isolation plug devices 86 can be removed with conventional intervention techniques, for example using wireline or coiled tubing. Second conduit 74, also referred to a communication conduit in this embodiment, provides a power and communication interface between production tubing and exterior of the well. For example, communication conduit 74 may comprise electrical lines, fiber optics, hydraulic conduits that may be utilized to provide continuity during operations. For example, the electrical lines may extend to the in-well pump 58, the hydraulic lines for chemical injection and/or operating other completion devices (e.g., valves), and fiber optics for example for sensors and communications. Communication conduit 74 is sealed around the electrical, hydraulic and fiber optic lines (see
An embodiment of a segmented intervention device 62 is now described with reference to
As noted above, the number and configuration of interfaces (i.e., conduits) provided by intervention device can vary. Similarly, coiled tubing 38 (
An embodiment of subsea system method is now described with reference to
To flush hydrocarbons from production tubing 20, for example to perform an intervention, downhole double pressure barrier 12 is closed. Coiled tubing 38 can be deployed form a surface vessel 32 and stripped into lubricator 46. Isolation plug device(s) 86 can then be removed and coiled tubing 38 can be deployed and operationally connected, for example at wet-connect 84, to fluid conduit 72 of coiled tubing hanger 62. Fluid 54 can then be pumped down coiled tubing 38, through fluid conduit 72, into production tubing 20 and discharged through production line 100 for example, thereby flushing hydrocarbons from production tubing 20.
The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the disclosure. Those skilled in the art should appreciate that they may readily use the disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the disclosure, and that they may make various changes, substitutions and alterations herein without departing from the spirit and scope of the disclosure. The scope of the invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. The terms “a,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded.
This application claims the benefit of U.S. Provisional Patent Application No. 61/322,205 filed on Apr. 8, 2010.
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