Exploring, drilling, completing, and operating hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on well access, monitoring and management throughout the productive life of the well. That is to say, from a cost standpoint, an increased focus on ready access to well information and/or more efficient interventions have played key roles in maximizing overall returns from the completed well.
By the same token, added emphasis on operator safety may also play a critical role in maximizing returns. For example, ensuring safety over the course of various offshore operations may also ultimately improve returns. As such, a blowout preventor (BOP), subsurface safety valve, and other safety features are generally incorporated into hardware of the wellhead at the seabed. Thus, production and pressure related hazards may be dealt with at a safe location several hundred feet away from the offshore platform.
In most offshore circumstances, the noted hardware of the wellhead and other equipment is disposed within a tubular riser which provides cased access up to the offshore platform. Indeed, other lines and tubulars may run within the riser between the noted seabed equipment and the platform. For example, a landing string which provides well access to the newly drilled well below the well head will run within the riser along with a variety of hydraulic and other umbilicals.
One safety measure that may be incorporated into the landing string is a particularly tailored and located weakpoint. The weakpoint may be located in the vicinity of the BOP, uphole of the noted safety valve. Therefore, where excessive heave or movement of the offshore platform translates to excessive stress on the string, the string may be allowed to shear or break at the weakpoint. Thus, an uncontrolled breaking or cracking at an unknown location of the string may be avoided. Instead, a break at a known location may take place followed by directed closing of the safety valve therebelow. As a result, an unmitigated hazardous flow of hydrocarbon through the riser and to the platform floor may be avoided along with other potentially catastrophic occurrences.
As with other subsea hardware, over the years, efforts to render the safety valve modular and decrease its overall footprint have been undertaken. Thus, transport, installation time and other costs may be reduced. Of course, with a smaller package and footprint comes the inherent limitation on available modes of actuation. This may be of concern. For example, in certain situations, coiled tubing, wireline or other interventional access line may be disposed through the valve at the time the above tubular separation occurs. When this is the case, the valve may be obstructed and unable to close. Thus, hydrocarbons may continue to leak past the valve and travel up the annulus of the riser to the platform with potentially catastrophic consequences.
Of course, to prevent such hazardous obstructions, the valve may be configured to achieve a cut-through of any interventional access line in combination with closure. So, for example, an internal spring or other valve closure mechanism may be utilized which employs enough force to ensure a cut-through of any obstruction each time that the valve closes.
Unfortunately, where efforts have been undertaken to minimize the footprint of a modular safety valve, ensuring enough force to both close the safety valve and provide any necessary cutting, may be a challenge. A conventional spring-driven mechanical actuator would generally supply sufficient force. However, with the size of the assembly minimized, there may not be sufficient room for such an actuator.
Once more, even when the valve is safely closed to prevent a catastrophic event as described above, there remains the need to re-open the valve in order to complete well-killing operations. That is to say, merely closing a safety valve over an otherwise free-flowing well is insufficient for maintaining long-term control over the well. Rather, at some point in the near term, the need to open the valve, supply kill fluid and take other follow-on remedial measures is necessary. This means that there is the need for yet another actuator capable of providing sufficient force to overcome the force of the initial closing actuator. Conventionally speaking, this would mean including enough space at the assembly for yet another mechanical actuator.
Lower profile, cost-effective, modular safety valves have been developed over the years. However, as a practical matter, the ability to realize the full potential of such valves has been limited due to the required added footspace and design complexity to accommodate actuators with enough actuation forces and capable of providing both “fail-safe” and “pump-through” capabilities, simultaneously. Unfortunately, in many circumstances, these lower profile valves are not even utilized due to the inability to realize any substantial benefit. Instead, high cost, more conventional valve packages are employed.
A fail-safe and pump-through valve arrangement is provided for maintaining well control of a well at an oilfield. The arrangement includes a valve to occupy one of an open position and a closed position in the well. Also included is a first accumulator for actuating the valve to the closed position and a second accumulator for actuating the valve to the open position. The second accumulator is responsive to both a dedicated hydraulic line to surface and a kill fluid through the well for the actuating of the valve to the open position.
In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it will be understood by those skilled in the art that the embodiments described may be practiced without these particular details. Further, numerous variations or modifications may be employed which remain contemplated by the embodiments as specifically described.
Embodiments are described with reference to certain offshore oilfield applications. For example, certain types of subsea blowout isolation assemblies and operations are illustrated utilizing a fail-safe valve. Specifically, assemblies and operations with the isolation assembly disposed over a wellhead and accommodating a coiled tubing conveyance are shown. However, the assembly may be located at various positions, including within a more sophisticated blowout preventer, below the wellhead or elsewhere. Additionally, accommodated conveyances may be wireline, slickline and others. Regardless, so long as the assembly accommodates accumulators for opening, closing and pumping through the fail-safe valve, the profile may be kept to a minimum with appreciable benefit realized.
Referring now to
In the embodiment shown, the overall user-friendly, modular construction of the assembly 101 is further aided by the manner in which the piston 175 is actuated. Specifically, hydraulic arrangements 125, 150 are provided within a modular accumulator housing 192 disposed adjacent the valve housing 190. That is, these are employed rather than utilizing larger physical spring-type actuators which would conventionally assure closure. As detailed further below, the close function hydraulic arrangement 150 provides sufficient force for closure even where closure requires that the piston 175 cut a conveyance such as the depicted coiled tubing 110. Once more, the open function hydraulic arrangement 125 supplies sufficient force for opening the piston 175 as illustrated while also supplying sufficient force for overcoming the close function hydraulic arrangement 150 for re-opening the piston 175 when the time comes.
In the embodiment shown, the assembly 101 is located at a well head 180. However, this hardware may be located in a variety of locations. Similarly, as noted above, the hydraulic arrangements 125, 150 are located in a dedicated accumulator housing 192. However, this is not required. For example, in one embodiment, the valve housing 190 may be enlarged to accommodate the hydraulic arrangements 125, 150 in addition to the associated hydraulics 135, 160 and the noted piston 175. Additionally, the modular concept may be continued into other adjacent equipment housings (e.g. 191). Thus, overall, the entire assembly 101 may be rendered in a cost-effective, user friendly form.
Continuing with reference to
With more specific reference to
Given that the tubular string 260 is structurally guided through a riser 250, added safety features are provided to prevent migration of hydrocarbons through the riser annulus 275 should there be a structural breakdown of the assembly 101. More specifically, as detailed above, where stresses result in controlled separation of a portion of the assembly 101, automatic action, in the form of valve closure with cutting of the coiled tubing 110, may be taken to prevent the noted migration. Thus, personnel at the floor 225 of the platform 220 may be spared a potentially catastrophic encounter with such an uncontrolled hydrocarbon fluid production.
Continuing with reference to
Referring specifically now to
In the embodiment shown, moving from an open position to a closed position or vice versa is achieved by hydraulic interaction with ends 325, 350 of the piston 175. For example, sufficient hydraulic pressure applied to the “open” end 350 of the piston 175 would maintain or shift the piston 175 to an open position as illustrated in
Referring now to
As shown in
In absence of emergency closure or other circumstances likely to present large differential pressure in the channel 115, opening or maintaining the piston 175 in an open position as illustrated in
Referring now to
Continuing with reference to
Continuing now with reference to
The loss of control through line 403 in combination with the introduction of kill fluid into the channel 115 above the closed piston 175, means that from a differential standpoint, pressure is now introduced to the dedicated line above 402 the piston 175. Thus, increasing the kill fluid pressure to be sufficiently higher than the well pressure in line 401 below the piston 175 may ultimately slide the spool valve 407 to the left as illustrated in
Referring now to
The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.
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Number | Date | Country | |
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62680671 | Jun 2018 | US |