1. Technical Field
Embodiments of the subject matter disclosed herein generally relate to methods and systems and, more particularly, to mechanisms and techniques for indicating the time elapsed after initiation of an emergency disconnect sequence.
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 increased dramatically. 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.
The existing technologies for extracting the fossil fuel from offshore fields may use a system 10 as shown in FIG. 1. More specifically, a blowout preventer stack (“BOP stack”) 11 may be rigidly attached to a wellhead 12 upon the sea floor 14, while a Lower Marine Riser Package (“LMRP”) 16 may be retrievably disposed upon a distal end of a marine riser 18, extending from a drill ship 20 or any other type of surface drilling platform or vessel. As such, the LMRP 16 may include a stinger 22 at its distal end configured to engage a receptacle 24 located on a proximal end of the BOP stack 11.
In typical configurations, the BOP stack 11 may be rigidly affixed atop the subsea wellhead 12 and may include (among other devices) a plurality of ram-type blowout preventers 26 useful in controlling the well as it is drilled and completed. Similarly, the LMRP 16 may be disposed upon a distal end of a long flexible riser 18 that provides a conduit through which drilling tools and fluids may be deployed to and retrieved from the subsea wellbore. Ordinarily, the LMRP 16 may include (among other things) one or more ram-type blowout preventers 26 at its distal end, an annular blowout preventer 30 at its upper end, and multiplex (MUX) pods 32.
A MUX pod system 40 is shown in FIG. 2 and may provide between 50 and 100 different functions to the BOP stack and/or the LMRP and these functions may be initiated and/or controlled from or via the MUX BOP Control System.
The MUX pod 40 may be fixedly attached to a frame (not shown) of the LMRP and may include hydraulically activated valves 50 (called in the art sub plate mounted (“SPM”) valves) and solenoid valves 52 that are fluidly connected to the hydraulically activated valves 50. The solenoid valves 52 are provided in an electronic section 54 and are designed to be actuated by sending an electrical signal from an electronic control board (not shown). Each solenoid valve 52 may be configured to activate a corresponding hydraulically activated valve 50. The MUX pod 40 may include pressure sensors 56 also mounted in the electronic section 54. The hydraulically activated valves 50 are provided in a hydraulic section 58 and may be fixedly attached to the MUX pod 40.
A bridge between the LMRP 16 and the BOP stack 11 is formed that matches the multiple functions from the LMRP 16 to the BOP stack 11, e.g., fluidly connects the SPM valves 50 from the MUX pod provided on the LMRP to dedicated components on the BOP stack or the LMRP. The MUX pod system is used in addition to choke and kill line connections (not shown) or lines that ensure pressure supply for the shearing function of the BOPs.
The bridge is shown in FIG. 3 and may include a pod wedge 42 configured to engage a receiver 44 on the BOP stack. The pod wedge 42 has plural holes (not shown), depending on the number of functions provided, that provides hydraulic fluids from the LMRP 16 to the BOP stack 11.
In typical subsea blowout preventer installations, multiplex (“MUX”) cables (electrical) and/or lines (hydraulic) transport control signals (via the MUX pod and the pod wedge) to the LMRP 16 and BOP stack 11 devices so the specified tasks may be controlled from the surface. Once the control signals are received, subsea control valves are actuated and (in most cases) high-pressure hydraulic lines are directed to perform the specified tasks. Thus, a multiplexed electrical or hydraulic signal may operate a plurality of “low pressure” valves to actuate larger valves to indicate the high-pressure hydraulic lines with the various operating devices of the wellhead stack.
Examples of communication lines bridged between LMRPs and BOP stacks through feed-thru components include, but are not limited to, hydraulic choke lines, hydraulic kill lines, hydraulic multiplex control lines, electrical multiplex control lines, electrical power lines, hydraulic power lines, mechanical power lines, mechanical control lines, electrical control lines, and sensor lines. In certain embodiments, subsea wellhead stack feed-thru components include at least one MUX “pod” connection whereby a plurality of hydraulic control signals are grouped together and transmitted between the LMRP 16 and the BOP stack 11 in a single mono-block feed-thru component as shown, for example, in FIG. 3.
When desired, ram-type blowout preventers of the LMRP 16 and the BOP stack 11 may be closed and the LMRP 16 may be detached from the BOP stack 11 and retrieved to the surface, leaving the BOP stack 11 atop the wellhead. For example, it may be necessary to retrieve the LMRP 16 from the wellhead stack in times of inclement weather or when work on a particular wellhead is to be temporarily stopped.
To retrieve the LMRP 16 from the wellhead stack, an Emergency Disconnect Sequence (“EDS”) may be initiated. An EDS may include a number of different functions that are to be performed by the LMRP 16 and the BOP stack. The functions of the EDS may be carried out by the LMRP 16 and/or the BOP stack as set forth above via the MUX pod 40 and/or the bridge. A particular EDS may include a predetermined number of functions. For example, one particular EDS may include eighteen (18) functions while another EDS may include twenty-five (25) functions. A particular EDS may take a predetermined period of time to complete. For example, one particular EDS may take 20 (twenty) seconds to complete while another EDS may take 25 (twenty-five) seconds to complete. An EDS may be initiated using an EDS system 60 as shown in FIG. 4. An EDS may be initiated or fired by pressing an EDS button 62 located on a stack controller 64 located on the drill ship 20. Once the EDS is fired, each of the functions included in that EDS may be performed until all of the functions are complete.
An operator may desire to track the progress of the different functions and verify that the EDS is complete. An operator may choose to track the progress of the number of different functions or to verify that the EDS is complete by referring to a document 66 that may constitute one or more EDS charts (called in the art a FAT document). The document 66 may list information about the EDS. For example, the document 66 may list the order, name, and timing of the different functions of each EDS. In the example shown in FIG. 4, the first function is named “A” and occurs during the first three (3) seconds of the EDS, the second function is named “B” and occurs during the 4th through 7th seconds, the third function is named “C” and occurs during the 8th through 10th seconds, and so on in like manner for the total number of functions in the EDS. To track the progress of the functions of the EDS and to verify that the EDS is complete, an operator may take note of the time at which the EDS button 62 is pushed and then refer to the document 66. If, for example, nine (9) seconds have elapsed after the EDS button 62 was pushed, the operator may refer to the document 66 and see that function “C” may be in progress. However, this conventional approach is problematic. For example, if the operator makes an error in noting the time at which the EDS button is pushed, forgets to note the time altogether, or refers to the wrong portion of the document, the operator may not have an accurate measure of the progress of the different functions and may not be able to accurately determine when the EDS completes. This may lead to additional problems such as long wait times to verify that the EDS has completed. Further, this conventional approach is burdensome for the operator in that noting the time at which the EDS button is pushed and referring to the document 66 requires the attention of the operator.
Therefore, it is desired to provide a novel approach for indicating the time elapsed after initiation of an EDS.