The present disclosed subject matter generally relates to the field of ROVs (Remotely Operated Vehicles) and the use of such ROVs in subsea applications.
With reference to
One challenge facing offshore oil and gas operations involves insuring the flowlines and fluid flow paths within subsea equipment remain open so that production fluid may continue to be produced. The produced hydrocarbon fluids will typically comprise a mixture of crude oil, water, light hydrocarbon gases (such as methane), and other gases such as hydrogen sulfide and carbon dioxide. In some instances, solid materials or debris, such as sand, small rocks, pipe scale or rust, etc., may be mixed with the production fluid as product travels through the flowline. The same challenge applies to other subsea flowlines and fluid flow paths used for activities related to the production of hydrocarbons. These other flowlines and flow paths could be used to, for example, service the subsea production system (service lines), for injecting water, gas or other mixture of fluids into subsea wells (injection lines) or for transporting other fluids, or hydraulic control lines operating equipment that come in direct contact with production fluids and causing a potential contamination of control fluids (control lines) should seal barriers degrade.
Problems encountered in the production of hydrocarbon fluids from subsea wells are often multi-faceted where blockage may form in a subsea flowline or in a piece of subsea equipment from a variety of causes from hydrate formation to coagulation or precipitation of byproducts from different fluids coming in contact with one another. In some cases the blockage can completely block passageways (flowlines or control/service lines) while in other cases there is only partially blockage to the flowline/equipment which thereby degrades performance or throughput. However, as used herein, the term “blockage” should be understood to complete or partial blockage of a passageway. For example, solid materials entrained in the produced fluids may be deposited during temporary production shut-downs, and the entrained debris may settle so as to form all or part of a blockage in a flowline or item of production equipment. As another example chemical reactions between two (normally separate) fluids may result in an unwanted precipitate or byproduct that could create a blockage.
In general, hydrates may form under appropriate high pressure and low temperature conditions. As a general rule of thumb, hydrates may form at a pressure greater than about 0.47 MPa (about 1000 psi) and a temperature of less than about 21° C. (about 70° F.), although these numbers may vary depending upon the particular application and the composition of the production fluid. Subsea oil and gas wells that are located at water depths greater than a few hundred feet or located in cold weather environments, are typically exposed to water that is at a temperature of less than about 21° C. (about 70° F.) and, in some situations, the surrounding water may only be a few degrees above freezing. Although the produced hydrocarbon fluid is relatively hot as it initially leaves the wellhead, as it flows through the subsea production equipment and flowlines, the surrounding water will cool the produced fluid. More specifically, the produced hydrocarbon fluids will cool rapidly when the flow is interrupted for any length of time, such as by a temporary production shut-down. If the production fluid is allowed to cool to below the hydrate formation temperature for the production fluid and the pressure is above the hydrate formation pressure for the production fluid, hydrates may form in the produced fluid which, in turn, may ultimately form a blockage which may block the production fluid flow paths through the production flowlines and/or production equipment. Of course, the precise conditions for the formation of hydrates, e.g., the right combination of low temperature and high pressure is a function of, among other things, the gas-to-water composition in the production fluid which may vary from well to well. When such a blockage forms in a flowline or in a piece of production equipment, either a hydrate blockage or a debris blockage or a combination of both, it must be removed so that normal production activities may be resumed.
When a hydrate blockage does form in the flowline 22 or the production equipment 18, 20, the only recourse is to do one or more of (1) reducing the pressure on one (or both) sides of the hydrate blockage restriction; (2) warm the surrounding equipment; and/or (3) introduce chemicals to change phase properties to melt the hydrate blockage so as to re-open the flowline or equipment. These hydrate remediation tasks are often time consuming and, depending on where the hydrate blockage forms, it may be more problematic to remove. The remediation process also requires a high degree of pressure integrity, i.e., insuring the absence of spurious or extraneous small leak path sources associated with intervention hardware and conduits. Otherwise diagnosing and monitoring desired changes and rates in pressure, temperature, chemical treatment rates, and avoidance of water or other contaminating sources ingress may hamper or thwart attempts to remove the blockage. With reference to
In any event, when production is lost due to the formation of a hydrate blockage, the operator's revenue stream is curtailed and the only option may be to bleed off pressure downstream of the hydrate blockage to a pressure that is less than the hydrate formation pressure. In some cases, this means a large portion of the equipment infrastructure must be shut in and hydrocarbons vented so that the hydrate blockage can slowly sublimate from the depressurize side of the blockage. Eventually the blockage melts a sufficient amount such that it frees itself from the sides of the bore in the flowline/equipment. At that point the trapped higher pressure behind the remaining portion of the blockage may send all or part of the blockage hurtling down the bore in the flowline/equipment until it can be stopped and allowed to melt the rest of the way. Some hydrate blockages may be of sufficient mass that, when they are initially “freed” they can travel at speeds that could pose an issue as it relates to the damage of downstream flowline/equipment hit by the released blockage.
In some cases, the hydrate remediation process may involve bleeding off pressure on the upstream side of the blockage until such time as there is a vacuum (or lower pressure below the hydrate formation pressure) in the bore of the flowline/equipment on the upstream side of the blockage. As the hydrate blockage melts, it sublimates back to its water and natural gas constituents thereby slowly rebuilding the pressure on the upstream side of the blockage. The remediation equipment, e.g., the equipment on the hydrate remediation skid 32, is then used to remove, via the hot-stab 40, the sublimated constituents of the blockage to maintain the lower pressure environment on the upstream side of the blockage such that the melting process continues. However, this continual draw down process has its share of technical problems as fluids/gases are withdrawn and pressure is kept below the hydrate formation pressure.
In general, the hydrate remediation equipment in the hydrate remediation skid 32 is somewhat removed distance wise from the access point 23 in the flowlines 22 and/or the equipment 18, 20 that contains the hydrate blockage. For example, in some applications, the umbilical between 44 between the hot-stab 40 may be about 2-3 meters in length. In practice the umbilical 44 may comprise a plurality of lengths of flexible hose that are coupled together using various connections so as to establish a fluid tight conduit through which liquids may flow. Thus, as the length of the umbilical 44 increases, there are more potential leakages sites in the various hose connections that are used to make-up between the hot stab 40 and the remediation skid 32, which increases the likelihood of putting more mechanical strain on these connections as operations take place, possibly loosening these connections. Examples of potential leakage sources include, but are not limited to, leakage around the remediation skid's 32 internal hardware/plumbing, leakage around the internal seals within its pumping equipment and leakage at the site of the connection to the ROV hot stab access point 40 itself, etc. Specifically identifying when leakages occur and where the leakage sites are located in the overall remediation skid hardware 32 and/or the umbilical 44 in real-time and determining the leakage rate (as well as increases or decreases in the leakage rate) can also be problematic. The location of the pumps, hardware piping and sump hardware in the remediation skid 32 that may be positioned relatively far away from the access point can reduce draw down efficiency and lengthen the duration of the remediation process activities. For example, in the case where production fluid is removed from the flowlines 22 and/or the equipment 18, 20 via the hot-stab 40 so as to create a relatively low pressure on one side of the blockage, leakage in the umbilical 44 can result in water from the surrounding environment entering the umbilical 44 if the hydrostatic pressure is greater than the reduced pressure in the umbilical 44. In addition, since the gauges or sensors that are used to monitor and record conditions during the hydrate remediation activities are located in the remediation skid 32, the readings obtained by these gauges or sensors may not accurately reflect the actual process conditions at or near the hydrate blockage or within the flowlines 22 and/or the equipment 18, 20 because of a variety of factors, such as expansion of the umbilical 44, fluid flow friction losses and the further cooling of the fluid in the umbilical 44 (due to the cold sea water environment) as it travels from the access point 23 to the remediation skid 32, making it difficult to monitor hydrate sublimation.
The present application is directed to a unique ROV hot-stab with at least one integrated sensor and methods of using such an ROV hot-stab that may eliminate or at least minimize some of the problems noted above.
The following presents a simplified summary of the subject matter disclosed herein in order to provide a basic understanding of some aspects of the information set forth herein. This summary is not an exhaustive overview of the disclosed subject matter. It is not intended to identify key or critical elements of the disclosed subject matter or to delineate the scope of various embodiments disclosed herein. Its sole purpose is to present some concepts in a simplified form as a prelude to the more detailed description that is discussed later.
The present application is generally directed to a unique ROV hot-stab with at least one integrated sensor. In one example, the ROV hot-stab comprises, among other things, a hot stab body having a flow bore that is adapted to receive a fluid, a housing that is operatively coupled to the hot stab body, and at least one fluid inlet/outlet defined in the housing. In this illustrative example, the device also includes an isolation valve that is at least partially positioned within the housing wherein the isolation valve is adapted to, when actuated, establish fluid communication between the bore of the hot stab body and the at least one fluid inlet/outlet and at least one sensor positioned at least partially within the housing wherein the sensor is adapted to sense a parameter of the fluid.
Certain aspects of the presently disclosed subject matter will be described with reference to the accompanying drawings, which are representative and schematic in nature and are not be considered to be limiting in any respect as it relates to the scope of the subject matter disclosed herein:
While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific 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 disclosed subject matter to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosed subject matter as defined by the appended claims.
Various illustrative embodiments of the disclosed subject matter are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.
The present subject matter will now be described with reference to the attached figures. Various structures, systems and devices are schematically depicted in the drawings for purposes of explanation only and so as to not obscure the present disclosure with details that are well known to those skilled in the art. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the present disclosure. The words and phrases used herein should be understood and interpreted to have a meaning consistent with the understanding of those words and phrases by those skilled in the relevant art. No special definition of a term or phrase, i.e., a definition that is different from the ordinary and customary meaning as understood by those skilled in the art, is intended to be implied by consistent usage of the term or phrase herein. To the extent that a term or phrase is intended to have a special meaning, i.e., a meaning other than that understood by skilled artisans, such a special definition will be expressly set forth in the specification in a definitional manner that directly and unequivocally provides the special definition for the term or phrase.
One illustrative example of a novel ROV hot-stab 100 with at least on integrated sensor disclosed herein will now be described with reference to the attached drawings. In one illustrative embodiment, the ROV hot-stab 100 comprises a hot stab body 102 having a fluid flow bore 102A, a valve body 103 and actuator housing 104 that is operatively coupled to the hot stab body 102 and an ROV handle 101. An endcap 105 is removably coupled to the main housing 104 by a plurality of threaded fasteners. As shown in, for example,
With reference to
In one illustrative embodiment, the isolation valve element 106 may take the form of a two-position, three-way ball valve that is positioned in the valve seat 107. The concentric inlet bore 103A of the valve 103 protrudes into the hot stab body 102 so as to enable fluid communication with flow bore 102A of the hot stab body 102. In the depicted example, the first and second fluid inlet/outlets 104A/104B take the form of threaded openings that are defined in the housing 104. A threaded plug 108 with an opening 108A defined therein is threadingly coupled to the opening 104A. Additionally, a threaded sealed plug body 109 is threadingly coupled to the opening 104B so as to block fluid flow through the second fluid inlet/outlet 104B. Of course, if desired, a threaded plug 108 (with the opening 108A formed therein) may also be positioned within the second fluid inlet/outlet 104B depending upon the particular application, as depicted in
In general, the isolation valve 103 may be at least partially positioned within the housing 104 and the isolation valve 103 is adapted to, when actuated, establish fluid communication between the bore 102A of the hot stab body 102 and at least one fluid inlet/outlet, e.g. the first fluid inlet/outlet 104A and/or the second fluid inlet/outlet 104B, depending upon how the ROV hot-stab 100 is configured. The isolation valve 103 may be actuated by any means e.g., mechanical, electrical, hydraulic, etc., and such an actuator that may be positioned (in whole or part) internal or external to the housing 104. In the depicted example, the ROV hot-stab 100 comprises an electrical actuator 130 that is positioned within the housing 104. More specifically, in the illustrative embodiment disclosed herein, the actuator 130 may take the form of a flat plate electric stepping motor that is adapted to actuate the isolation valve element 106 from a fully closed position to a fully open position with the further capability of incrementally moving the element 106 from the fully closed position to the fully open positioned (or vice-versa). For example, in the case where the actuator is a stepping motor, the actuator 130 may be used to move the illustrative valve element 106 in angular increments from its fully closed position to its fully open position such that the valve 103 may be used as a throttling device. Of course, the isolation valve 103 may take other forms, e.g., a two-position three-way valve to divert the fluid outlet to a third port (not shown) in the housing 104 that could lead to another component such as, for example, a fluid sampling chamber, etc.
Power and control utilities may be provided to the actuator 130 via an opening 105A defined the back cover plate 105 of the housing 104. Terminal leads (not shown) may pass through the opening 105A in the form of a bulkhead connection that allow power and data telemetry to pass to the actuator 130. In another embodiment, where the actuator is in the form of a hydraulically powered actuator, the openings 105A/104C may function as hydraulic inlet and outlets for internal fluid power and control of the actuator 130. The various lines for the utilities for powering and communicating with the actuator 130 the sensor(s) 114 may be part of an umbilical (not shown) that is operatively coupled to the ROV hot-stab 100 and an ROV (not shown). Such an umbilical would also include at least one fluid flow line to allow fluids to be inserted into or removed from the flowline or equipment into which the hot stab body 102 of the ROV hot-stab 100 is inserted. The size of these various lines or cables may vary depending upon the size and type of actuator 130, the number and type of sensor(s) 114 and the manner nature of the fluids to be injected into and/or removed from the flowline or equipment. As will be appreciated by those skilled in the art after a complete reading of the present application, in some embodiments, depending upon the capabilities of the ROV, the illustrative ROV-mounted remediation skid 32 described in the background section of this application may be omitted. For example, if the ROV has on-board pumping and valve capabilities, the ROV hot-stab 100 may be controlled and operated using only the ROV's control system when performing at least some activities.
The unique ROV hot-stab 100 may be configured and operated in several ways depending upon the particular application. For example, with the embodiment depicted in
As will be appreciated by those skilled in the art after a complete reading of the present application, positioning the at least one sensor 114 in the ROV hot-stab 100 may provide several advantages as compared to prior art ROV hot-stabs. For example, in the case where the ROV hot-stab 100 is used in hydrate remediation processes, the sensor(s) 114 is positioned such that it has access to the bore 103A (via the lines 116) at a location upstream of the isolation valve element 106. Accordingly, the sensor(s) 114 may be used to monitor the hydrate's sublimation process unabated, i.e., with the valve 103 in the closed or open position. Since the sensor(s) 114 is physically closer to the hydrate blockage than prior art sensors on the hydrate remediation skid 32 discussed in the background section of this application, the readings obtained by the sensor(s) 114, e.g., temperature and/or pressure, are more likely to reflect the true temperature and pressure of the sublimation process. For example, by positioning the sensor(s) 114 in the ROV hot-stab 100, changes in the temperature of the process fluid is sensed before it loses temperature to it surrounding environment, e.g., the surround water, which was the case with prior art temperature sensors positioned on a prior art ROV mounted remediation skid. Similarly, by positioning a pressure sensor in the ROV hot-stab 100, the pressure of the fluid or equipment is sensed without have to account for any pressure drop associated with flowing the fluid to a relatively remotely placed ROV-mounted remediation skid that contains a pressure sensor. By positioning the sensor(s) 114 in the ROV hot-stab 100 worries about errors in the measured parameters of the fluid due to leaks in the fluid flow lines that extend from the ROV hot-stab 100 to the ROV can be eliminated. Additionally, by use of the unique ROV hot-stab 100 disclosed herein with an integrated sensor(s) positioned within the hot stab itself, one or more of the problems noted in the background section of this application may be eliminated or at least minimized by enabling by isolating the remediation skid equipment 32/44 from the flowline environment 18/22 at the access point 23 interface. By using the ROV hot-stab 100 disclosed herein with the integrated valve 103 and sensor 114, the efficacy of the remediation processes (that may involve pressure drawdown and hydrate sublimation) may be more closely monitored and better controlled as compared to prior art techniques since the novel ROV hot-stab 100 enables one to obtain more accurate information as to the actual process conditions in the flowline adjacent any blockage since the sensor(s) are positioned more closely to the actual environment within the flowline or equipment that needs to be monitored. Additionally, using the ROV hot-stab disclosed herein with the integrated sensor 114 potential leak paths from other sources may be identified, minimized and/or eliminated by locating the necessary sensors and isolation valve as close to the access point as physically possible. Moreover, the isolation valve 103 is adapted to, when actuated, isolates an access point 23 into which the hot stab body 102 is inserted from additional equipment in fluid communication with the hot stab body 102, e.g., the rest of the intervention equipment (such as the remediation skid 32 and the umbilical 44) to thereby minimize extraneous leak paths, and thus improve the monitoring accuracy of the sensor 114.
The particular embodiments disclosed above are illustrative only, as the disclosed subject matter may be modified and practiced in different but equivalent manners apparent to those skilled in the art having the benefit of the teachings herein. For example, the process steps set forth above may be performed in a different order. 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 embodiments disclosed above may be altered or modified and all such variations are considered within the scope and spirit of the claimed subject matter. Note that the use of terms, such as “first,” “second,” “third” or “fourth” to describe various processes or structures in this specification and in the attached claims is only used as a shorthand reference to such steps/structures and does not necessarily imply that such steps/structures are performed/formed in that ordered sequence. Of course, depending upon the exact claim language, an ordered sequence of such processes may or may not be required. Accordingly, the protection sought herein is as set forth in the claims below.
Filing Document | Filing Date | Country | Kind |
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PCT/US2016/584050 | 10/24/2016 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
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WO2018/080421 | 5/3/2018 | WO | A |
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