1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for controlling a subsea tree with controls provided on a blowout preventer stack.
2. Discussion of the Background
During the past years, with the increase in price of fossil fuels, the interest in developing new production fields has dramatically increased. However, the availability of land-based production fields is limited. Thus, the industry has now extended drilling to offshore locations, which appear to hold a vast amount of fossil fuel.
Conventionally, wells in oil and gas fields are built up by establishing a wellhead housing, and with a drilling blowout preventer (BOP) stack installed on top of the wellhead, drilling down to produce the well hole while successively installing casing strings. When the drilling is finished, the well needs to be converted for production. For converting the cased well for production, a tubing string is run in through the BOP and a hanger at its upper end landed in the wellhead. Thereafter the drilling BOP stack is removed and replaced by a Christmas tree having one or more production bores containing actuated valves and extending vertically to respective lateral production fluid outlet ports in the wall of the Christmas tree.
This arrangement has involved problems which have, previously, been accepted as inevitable. Thus, some operations down hole have been limited to tooling which can pass through the production bore unless the Christmas tree is first removed and replaced by a BOP stack. However, this involves setting plugs or valves, which may be unreliable. The well is in a vulnerable condition whilst the Christmas tree and BOP stack are being exchanged and neither one is in position, which is a lengthy operation. Also, if it is necessary to pull the completion, consisting essentially of the tubing string on its hanger, the Christmas tree must first be removed and replaced by a BOP stack. This usually involves plugging and/or killing the well.
Another difficulty that exists in the subsea wells, relates to providing the proper angular alignment between the various functions, such as fluid flow bores, and electrical and hydraulic lines, when the wellhead equipment, including the tubing hanger, Christmas tree, BOP stack and emergency disconnect devices are stacked up. Because there are many different designs and manufacturers for trees and BOPs, ensuring proper alignment of the functions cannot practically be achieved.
As discussed above, when the well is in production, the BOP stack 10 is removed. However, if further work needs to be performed on the well, the BOP stack 10 has to be brought back, which makes the production well not operational for an extended amount of time.
An alternative to using the BOP stack for doing workover is the usage of an Installation WorkOver Control System (IWOC) which is illustrated in
However, for using the IWOC alternative, the operator of the well needs either to rent the IWOC equipment (which today costs in the millions of dollars range) or to own the IWOC equipment (which today costs in the tens of millions of dollars range). These high costs associated with the IWOC equipment are undesirable for the operator of the well. Additionally, many times the IWOC system must be integrated into a BOP systems's LMRP, which entails a great deal of modifications to the BOP when installing and removing. These operations add considerable expense for the operator. Accordingly, it would be desirable to provide systems and methods that are better than the background art.
According to one exemplary embodiment, there is a blowout preventer (BOP) stack configured to provide Intervention WorkOver Control System (IWOC) functionality to a tree attached to a wellhead of a well. The BOP stack includes a lower marine riser package (LMRP) part configured to be attached to an end of a marine riser; a lower BOP part configured to be detachably attached to the LMRP part; a pod extension module attached to the LMRP part or the lower BOP part and configured to receive a fluid under pressure and provide a set of functions to the tree based on the fluid under pressure; and at least a MUX pod attached to the LMRP part or the lower BOP part and configured to receive electrical signals and the fluid under pressure and to transmit required electrical signals to the pod extension module. The set of functions for the tree are different from functions provided to the lower BOP part.
According to another exemplary embodiment, there is a system for controlling a blowout preventer (BOP) stack and a tree attached to a wellhead of a well, the BOP stack including a lower BOP part and a lower marine riser package (LMRP) part. The system includes at least a MUX pod configured to be attached to the LMRP part or the lower BOP part, to receive electrical signals and a fluid under pressure, and to provide a first set of functions to the LMRP part, and a second set of functions to the lower BOP part; a pod extension module configured to be attached to the lower BOP part or the LMRP part, to receive the fluid under pressure from the MUX pod, and to provide a third set of functions to the tree based on the received fluid under pressure; and a control part configured to be attached to the tree and to communicate with the pod extension module. The third set of functions for the tree is different from the second set of functions provided to the lower BOP part.
According to still another exemplary embodiment, there is a method for providing tree control via a lower blowout preventer (BOP) part, wherein the lower BOP part is connected to a lower marine riser package (LMRP) part to form a BOP stack that is attached undersea to the tree. The method includes attaching a pod extension module to the lower BOP part or the LMRP part; hydraulically connecting the pod extension module to a hydraulic supply system; electrically connecting the pod extension module to a MUX pod; attaching a hydraulic connector to the pod extension module, the hydraulic connector being configured to mate with a corresponding connection of the tree; and configuring the pod extension module to provide a set of functions to the tree and to transmit a fluid under pressure from the MUX pod to the tree.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
The following description of the exemplary embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to the terminology and structure of a BOP stack and IWOC systems. However, the embodiments to be discussed next are not limited to these systems, but may be applied to other systems that require to be supplied to with hydraulic pressure and/or electrical signals.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to an exemplary embodiment, a BOP stack and a tree are configured to exchange electrical signals and/or hydraulic functions without the need of a dedicated IWOC system. In other words, existing BOP stacks and/or trees may be retrofitted with appropriated interfaces and/or junction plates and/or pod extension modules for allowing a direct communication (electrical and/or hydraulic) between these two pieces of equipment and for supplying the functionality offered by the dedicated IWOC systems. According to still another exemplary embodiment, a MUX pod may be configured to have an interface that directly communicates with the tree for controlling the tree. According to another exemplary embodiment, new BOP stacks and trees may be directly manufactured to have the capability to communicate with each other and thus, to provide the IWOC functionality.
The term “communicate” is used in the following description as meaning at least transmitting information from the BOP stack to the tree. In one embodiment, the term communicate also includes transmitting information from the tree to the BOP stack. The information may include electrical signals and/or hydraulic pressure. Most of the electrical signal are originally transmitted from the surface, i.e., from the rig or vessel, by the operator of the well. The electrical signals are directed to the MUX POD (see elements 40 and 42 in
According to an exemplary embodiment illustrated in
However, as workover has to be done on the well, the BOP stack 45 is lowered in place and connected to the tree 50 as shown in
The MUX POD 40 (for simplicity the other MUX POD 42 is not discussed here as it acts similar to MUX POD 40) is fluidly connected via one or more pipes to the lower BOP stack 46. These pipes transmit fluid under pressure from the LMRP part 44 to the lower BOP part 46 for executing various functions, e.g., closing or opening the BOPs 47 of the lower BOP part 46. In this regard, it is noted that a set of functions need to be provided to the lower BOP part 46 and this set of functions is achieved either by directly providing the fluid under pressure (hydraulic) to the lower BOP part 46 and/or by transmitting electrical signals from the MUX POD 40 to the lower BOP part 46 for activating these functions. Provisional Patent Application No. 61/329,883 and patent application Ser. Nos. 12/816,901, 12/816,912, and 12/816,923, all assigned to the assignee of the present application and incorporated herein in their entirety by reference, disclose the above noted functions and the communication (hydraulic and electrical) between the LMRP part 44 and the lower BOP part 46.
However, the existing MUX PODs may not be configured to handle and/or control the additional functions associated with the tree. For instance, the functions associated with the LMRP part and the lower BOP part may be different from the functions associated with the tree. Even if the functions are the same (e.g., closing a valve) the pressure or flow rate requirement for closing the valve on the BOP stack or the tree may be different. Thus, the existing MUX POD usually cannot be directly connected to the existing trees as these two elements were not designed to work together. Furthermore, the MUX POD capabilities may be limited for the following reasons. The MUX POD, which is located on the LMRP part 44, is configured to make a mechanical connection to a base plate located on the lower BOP part 46. This mechanical connection has a predetermined number of ports configured to connect corresponding ports from the LMRP part 44 with ports from the lower BOP part 46. In one application, the number of ports is 96. Depending on the manufacturer and the design of the BOP stack, this number can be larger or smaller.
Once all the ports of the MUX POD are used by the functions of the LMRP part 44 and the lower BOP part 46, traditionally, no other functions may be controlled by the MUX POD. Thus, there are situations in which no functions are available on the MUX POD for controlling other devices, e.g., the tree.
However, according to an exemplary embodiment illustrated in
Thus, the PEM 60 that is attached to the lower BOP part 46 has to be configured to fit the existing functions managed by the control part 62 of the tree 50. Therefore, the PEM 60 may be installed on an existing lower BOP part 46 or on new BOP stacks. In one application, the PEM 60 may be installed on the LMRP part 44 to extend the functionality of the MUX POD 40. An advantage of this arrangement is that any lower BOP part may be fitted or retrofitted with the PEM 60 to provide the IWOC functionality and avoids the need of a dedicated IWOC system as shown in
According to another exemplary embodiment illustrated in
According to another exemplary embodiment, the connection between the lower BOP part 46 and the control part 62 of the tree 50 may be achieved using a pod wedge connection as illustrated in
More details are now provided about the MUX pod 40 and the PEM 60. The MUX pod 40 may be fixedly attached to a frame (not shown) of the LMRP part 44 and may include hydraulically activated valves 80 (called in the art sub plate mounted (SPM) valves) and solenoid valves 82 that are fluidly connected to the hydraulically activated valves 80. The solenoid valves 82 are provided in an electronic section 84 and are designed to be actuated by sending an electrical signal from an electronic control board (not shown). Each solenoid valve 82 is configured to activate a corresponding hydraulically activated valve 80. The MUX pod 40 may include pressure sensors 86 also mounted in the electronic section 84. The hydraulically activated valves 80 are provided in a hydraulic section 88.
According to an exemplary embodiment illustrated in
SPM valve 106 is activated by receiving the fluid under high pressure at gate 106g. This fluid is controlled by pilot valve 108 provided in the removable section 110. Pilot valve 108 may have a similar structure as the SPM valve 106 except that an electrical gate 108a is used to activate the valve. The pilot valve 108 may receive the fluid under pressure from the same conduit 132 used by the SPM valve 106 or another hydraulic source. Thus, connections 134a and 134b are implemented on the fixed part 100 and the removable section 110, respectively, for bringing the fluid under pressure to the pilot valve 108. Similar or different connections 136a and 136b are used for providing the fluid under pressure from the pilot valve 108 to the SPM valve 106 when a corresponding electrical signal is received at gate 108a. Thus, when the pilot valve 108 is activated, the fluid from conduit 132 flows via the pilot valve 108 to the gate 106g to activate the SPM valve 106. After the SPM valve gate 106g is activated, fluid from conduit 132 flows via SPM valve 106 to outlet 138 and to the desired function to be controlled.
It is noted that the fluid under pressure entering conduit 132 may be provided either directly from MUX pod 40 along a conduit or from another source, e.g., hot line 144. The fluid may be regulated internally at the MUX pod 40. The hot line 144 may be connected to accumulators or to a conduit that communicates with the ship (not shown) manning the operation of the LMRP.
Similar to the fixed part 100, the removable section 110 may include more than one pilot valve 108. The removable section 110 also includes an electronic part 118 that is electrically connected to the pilot valves for transmitting various commands to them. The electronic part 118 may be connected to power supply lines 140a and 140b that are connected to the MUX pod 40 via the fixed part 100. In addition, the electronic part 118 may include one or more lines 142 (e.g., RS 485 cables) for transmitting various commands from the MUX pod 40 to the corresponding solenoid valves 108 via the fixed part 100. Corresponding wet-mateable electric connectors 145 (e.g., connectors configured to mate/de-mate subsea) may be mounted on the fixed part 100 and the removable section 110 for transmitting the electric power and the commands from one module to the other. Multiple fixed parts 100 and corresponding removable sections 110 may be used on the same subsea structure.
If more than one pilot valve 108 is provided on the removable section 110, the same supply line 146 may be used to supply the fluid under pressure to each of the pilot valve 108. However, each pilot valve 148 would have its own output 150 fluidly communicating with a corresponding SPM valve 152. In other words, for a control module (fixed part 100 and removable section 110) having a predetermined number of functions n (e.g., 8), there are n+1 inlet hydraulic ports, one corresponding to conduit 146 and the others corresponding to outlet ports 150. In one application, the conduit 146 may be connected to another source of fluid under pressure instead of the MUX pod 40 or conduit 144. The removable section 110 may include other elements than those shown in the figures. For example, the removable section 110 may include one or more filtration devices, pressure sensing devices, etc. Similarly, the fixed part may include other devices, e.g., pressure regulators.
If the fixed part 100 and the removable section 110 are disposed on the BOP stack, then the power supply and the communication supply may stay the same, e.g., from MUX POD 40, but the hydraulic supply may provided by a hot line that provides the fluid under high pressure for operating the BOPs of the BOP stack. In one application, the removable section 110 may be fixedly attached to the fixed part 100 so that the PEM 60 is one single component.
According to an exemplary embodiment illustrated in
According to an exemplary embodiment illustrated in
The disclosed exemplary embodiments provide a system and a method for providing IWOC functionality to a tree via a BOP stack. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.