WO2020251821A1

WO2020251821A1 - Subsea data acquisition pods

Info

Publication number: WO2020251821A1
Application number: PCT/US2020/035939
Authority: WO
Inventors: Robert Edwin HAHN
Original assignee: National Oilwell Varco, L.P.
Priority date: 2019-06-13
Filing date: 2020-06-03
Publication date: 2020-12-17

Abstract

A data acquisition system for monitoring a subsea BOP stack, the BOP stack including a blue control pod and a yellow control pod for operating the BOP stack, the system including an umbilical having a first end and a second end and a reel on a surface vessel. The umbilical is mounted to the reel and extends therefrom. The data acquisition system further including a subsea instrumentation pod mounted to the BOP stack and a first sensor coupled to the instrumentation pod. A lower end of the umbilical is coupled to the instrumentation pod. The instrumentation pod is spaced apart from the blue control pod and the yellow control pod, and the subsea instrumentation pod is electrically isolated and communicatively isolated from the blue control pod and the yellow control pod.

Description

SUBSEA DATA ACQUISITION PODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. provisional patent application Serial No. 62/861 ,158 filed June 13, 2019 and entitled“Subsea Data Acquisition Pods,” which is hereby incorporated herein by reference in its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not applicable.

BACKGROUND

[0003] This disclosure relates in general to systems and methods for acquiring data subsea. In particular, the disclosure is directed to systems and methods for monitoring and acquiring data relating to subsea equipment such as subsea wellheads, lower marine riser packages, and blowout preventers.

[0004] Subsea wells are typically made up by installing a primary conductor into the seabed and securing a wellhead to the upper end of the primary conductor at the sea floor. In addition, a subsea stack, also referred to as a blowout preventer (BOP) stack, is installed on the wellhead. The BOP stack usually includes a blowout preventer mounted to the upper end of the wellhead and a lower marine riser package (LMRP) mounted to the upper end of the BOP. The primary conductor, wellhead, BOP, and LMRP are typically installed in a vertical arrangement one-above-the-other. The lower end of a riser extending subsea from a surface vessel or rig is coupled to a flex joint at the top of the LMRP. For drilling operations, a drill string is suspended from the surface vessel or rig through the riser, LMRP, BOP, wellhead, and primary conductor to drill a borehole. During drilling, casing strings that line the borehole are successively installed and cemented in place to ensure borehole integrity.

[0005] A subsea control system is used to operate and monitor the BOP stack as well as monitor wellbore conditions. For example, the control system can actuate valves (e.g., safety valves, flow control choke valves, shut-off valves, diverter valves, etc.), actuate chemical injection systems, monitor operation of the BOP and LMRP, monitor downhole pressure, temperature and flow rates, etc. The subsea control system typically comprises control modules or pods mounted to the BOP and/or LMRP. Redundant control pods, typically referred to as the“blue control pod” and the“yellow control pod,” are usually provided to enable operation and monitoring of the BOP stack in the event one of the redundant control pods fails. Electrical power, hydraulic power, and command signals are provided to the blue and yellow control pods from the surface vessel or rig.

BRIEF SUMMARY

[0006] Some embodiments disclosed herein are directed to a data acquisition system for monitoring a subsea BOP stack, the BOP stack including a blue control pod and a yellow control pod for operating the BOP stack, the system including an umbilical having a first end and a second end and a reel on a surface vessel. The umbilical is mounted to the reel and extends therefrom. The data acquisition system further including a subsea instrumentation pod mounted to the BOP stack and a first sensor coupled to the instrumentation pod. A lower end of the umbilical is coupled to the instrumentation pod. The instrumentation pod is spaced apart from the blue control pod and the yellow control pod, and the subsea instrumentation pod is electrically isolated and communicatively isolated from the blue control pod and the yellow control pod.

[0007] Other embodiments disclosed herein are directed to a method, including (a) decoupling an LMRP from a BOP mounted to a subsea wellhead; (b) retracting a marine riser coupled to the LMRP to lift the LMRP and pull the LMRP from the BOP; and (c) separating a male plug and a female receptacle of a wet-mate connector during (b). The male plug is coupled to an instrumentation pod mounted to the LMRP and the female receptacle is coupled to an auxiliary instrumentation pod mounted to the BOP. The auxiliary instrumentation pod remains mounted to the BOP after (c) and the instrumentation pod remains mounted to the LMRP after (c).

[0008] Still other embodiments disclosed herein are directed to a data acquisition system for monitoring a subsea BOP stack, the BOP stack including a blue control pod and a yellow control pod for controlling the BOP stack. The system includes an umbilical having a first end and a second end and a reel on a surface vessel. The umbilical is mounted to the reel and extends from the reel to one of the blue control pod and the yellow control pod. [0009] The system further includes a subsea instrumentation pod mounted to the BOP stack and spaced apart from the blue control pod and the yellow control pod, a cable extending to the instrumentation pod from one of the blue control pod and the yellow control pod, and a sensor coupled to the instrumentation pod. The instrumentation pod is electrically isolated and communicatively isolated from the blue control pod and the yellow control pod.

[0010] Embodiments described herein comprise a combination of features and characteristics intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical characteristics of the disclosed embodiments in order that the detailed description that follows may be better understood. The various characteristics and features described above, as well as others, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes as the disclosed embodiments. It should also be realized that such equivalent constructions do not depart from the spirit and scope of the principles disclosed herein.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] For a detailed description of various exemplary embodiments, reference will now be made to the accompanying drawings in which:

[0012] Figure 1 is a schematic side view of an embodiment of an offshore system for drilling and/or producing a subsea well;

[0013] Figure 2 is a schematic view of the monitoring system of Figure 1 ;

[0014] Figure 3 is a partial cross-sectional side view of the monitoring system of Figure 1 with some components omitted for clarity;

[0015] Figure 4 is a cross-sectional side view of the instrumentation pod of the monitoring system of Figure 3 with the input-output plate removed;

[0016] Figure 5 is a perspective view of an embodiment of an input-output plate for the instrumentation pod of Figure 4;

[0017] Figure 6 is a perspective view of an embodiment of an input-output plate for the instrumentation pod of Figure 4; [0018] Figures 7 and 8 are sequential schematic side views of the offshore system of Figure 1 during an emergency disconnect procedure;

[0019] Figure 9 is a schematic side view of an embodiment of an offshore system for drilling and/or producing a subsea well;

[0020] Figure 10 is a schematic view of the hybrid cable of Figure 9;

[0021] Figure 1 1 is a partial cross-sectional side view of the monitoring system of Figure 9 with some components omitted for clarity;

[0022] Figure 12 is a schematic side view of an embodiment of an offshore system for drilling and/or producing a subsea well; and

[0023] Figure 13 is a schematic side view of the offshore system of Figure 12 during an emergency disconnect procedure.

DETAILED DESCRIPTION

[0024] The following discussion is directed to various exemplary embodiments. However, one of ordinary skill in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment.

[0025] The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness.

[0026] In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean“including, but not limited to... Also, the term“couple” or“couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection of the two devices, or through an indirect connection that is established via other devices, components, nodes, and connections. In addition, as used herein, the terms“axial” and“axially” generally mean along or parallel to a given axis (e.g., central axis of a body or a port), while the terms“radial” and“radially” generally mean perpendicular to the given axis. For instance, an axial distance refers to a distance measured along or parallel to the axis, and a radial distance means a distance measured perpendicular to the axis. Also, as used herein, the term “electrically isolated” may be used to refer to two components or pieces of equipment that do not transfer electrical power to each other, and the term“communicatively isolated” may be used to refer to two components or pieces of equipment that do not communicate data (one-way or two-way) to each other. However, it should be appreciated that“electrically isolated” components may receive power from a common source and “communicatively isolated” components may receive or send data communications to a common component.

[0027] As previously described, conventional subsea control systems include redundant blue and yellow control pods to operate and monitor the BOP stack, as well as monitor wellbore conditions. For example, the blue control pod and the yellow control pods can actuate valves (e.g., safety valves, flow control choke valves, shut-off valves, diverter valves, etc.), actuate chemical injection systems, monitor operation of the BOP and LMRP, and monitor downhole pressure, temperature and flow rates, etc. The blue and yellow control pods receive electrical power, hydraulic power, and command signals from the surface vessel or rig to operate the BOP stack as well as monitor the BOP stack and wellbore conditions. As communication capabilities (e.g., bandwidth) between subsea BOP stacks and surface vessels improve, there has been interest in acquiring additional subsea data and monitoring additional subsea functions. However, many conventional blue and yellow control pods have a limited capacity (e.g., power constraints, data communication limitations, etc.) for accommodating additional sensors and related equipment. Moreover, as the blue and yellow control pods provide particularly established and important functions relating to subsea BOP stack operation, it may not be particularly desirable to further complicate the functions of the blue and yellow control pods or rely on the blue and yellow control pods to provide additional functionality. Accordingly, embodiments described herein are directed to subsea data acquisition systems that provide increased subsea data acquisition functionality independent of and without interfering with the blue and yellow control pods.

[0028] Referring now to Figure 1 , an embodiment of an offshore system 10 for drilling and/or producing a subsea well is shown. In this embodiment, system 10 includes a surface vessel 20, a subsea BOP stack 30 mounted to an upper end of a wellhead 18 at the sea floor 13, and a data acquisition system 100 coupled to BOP stack 30. [0029] Surface vessel 20 is positioned at the sea surface 14, and in general, may be a floating structure (e.g., a ship, semi-submersible platform, etc.) or a bottom founded structure supported by sea floor 13 (e.g., a jackup rig). In this embodiment, surface vessel 20 includes a pair of reels 21 , 22 for storing and deploying (e.g., paying in and paying out) a first umbilical 26, and a second umbilical 27, respectively, that extend from reels 21 , 22 and vessel 20 to BOP stack 30.

[0030] Surface equipment 1 10, which is part of data acquisition system 100, is also disposed on vessel 20. Surface equipment 1 10 includes an instrumentation reel 11 1 , a data logger 1 12, and AC power source 1 13. Data logger 1 12 and AC power source 1 13 are coupled to MUX cable 1 15, which is stored and deployed from instrumentation reel 1 1 1. MUX cable 1 15 extends from instrumentation reel 11 1 and surface vessel 20 to subsea BOP stack 30. Thus, first umbilical 26, second umbilical 27, and MUX cable 1 15 extend from surface vessel 20 to BOP stack 30.

[0031] Referring still to Figure 1 , BOP stack 30 includes a lower marine riser package (LMRP) 31 and a blowout preventer (BOP) 35. LMRP 31 is coupled to BOP 35, which is mounted to wellhead 18. A marine riser 40 is coupled to LMRP 31 and extends to surface vessel 20. Wellhead 18, BOP 35, LMRP 31 , and marine riser 40 are vertically stacked one-above-the-other and arranged such that each shares a common longitudinal or central axis 45, and thus, are coaxially aligned. The position of surface vessel 20 is controlled such that axis 45 is vertically or substantially vertically oriented. In general, surface vessel 20 can be maintained in position over wellhead 18 with mooring lines (not shown) and/or a dynamic positioning (DP) system. However, it should be appreciated that surface vessel 20 may move to a limited degree during normal drilling and/or production operations in response to external loads such as wind, waves, currents, etc. Such movements of surface vessel 20 results in the upper end of marine riser 40, which is secured to surface vessel 20, moving relative to the lower end of marine riser 40, which is secured to LMRP 31. Wellhead 18, BOP 35, and LMRP 31 are generally fixed in position at sea floor 13, and thus, marine riser 40 may flex and pivot about its lower and upper ends as surface vessel 20 moves relative to BOP stack 30. Consequently, although marine riser 40 is shown as extending vertically from surface vessel 20 to LMRP 31 in Figure 1 , marine riser 40 may deviate somewhat from vertical as surface vessel 20 moves along sea surface 14. LMRP 31 includes an upper annular BOP 32, a flex joint 33 coupled to the top of upper annular BOP 32, an upper connector 34a extending upward from flex joint 33, and a lower annular connector 34b extending downward from upper annular BOP 32. The lower end of marine riser 40 is attached to upper connector 34a and lower annular connector 34b is releasably attached to BOP 35. A blue control pod 42 and a yellow control pod 44 are mounted to LMRP 31. Pods 42, 44 are conventional blue and yellow control pods as are known in the art for controlling LMRP 31 and BOP 35. First umbilical 26 extends from reel 21 to blue control pod 42, and second umbilical 27 extends from reel 22 to yellow control pod 44. Umbilicals 26, 27 provide electrical power to pods 42, 44, respectively, communicate control signals to pods 42, 44, respectively, and communicate data (e.g., sensor measurements) from pods 42, 44, respectively, to surface vessel 20. BOP 35 is positioned between LMRP 31 and wellhead 18, and includes a plurality of stacked rams - shear rams 36 and pipe rams 38 in this embodiment. Upper annular BOP 32 and rams 36, 38 are selectively controlled by control pods 42, 44 to close wellhead 18 as needed.

[0032] Referring now to Figures 1 and 2, data acquisition system 100 includes surface equipment 1 10 on surface vessel 20, an instrumentation pod 150 coupled to BOP stack 30, an auxiliary instrumentation pod 200 coupled to BOP stack 30, MUX cable 1 15 extending from surface vessel 20 to instrumentation pod 150, and a wet-mate connector 190 releasably and electrically coupling pods 150, 200. As shown in Figure 1 , in this embodiment, instrumentation pod 150 is mounted to LMRP 31 and auxiliary instrumentation pod 200 is mounted to BOP 35.

[0033] A plurality of sensors 162, 164 are disposed along LMRP 31 and electrically and communicatively coupled to instrumentation pod 150, and a plurality of sensors 210, 212, 214 are disposed along BOP 35 and electrically and communicatively coupled to auxiliary instrumentation pod 200. In general, each sensor 162, 164, 210, 212, 214 can be any type of subsea sensor known in the art including, without limitation, a load cell, pressure transducer, accelerometer, thermocouple, displacement transducer (LVDT), flow meter, acoustic meter, vibration data logger (SVDL), motion reference unit (MRU), ram positon indicator (RPU), cameras, etc.; and further, each sensor 162, 164, 210, 212, 214 can be based on any principle of operation including, without limitation, resistivity, piezoelectric, inductive, magnetometer, capacitive, etc. In this embodiment, sensor 162 is a load cell mounted to lower annular connector 34b, sensor 164 is a vibration sensor mounted to LMRP 31 , sensor 210 is an LVDT mounted to shear ram 36, sensor 212 is a load cell mounted to pipe ram 38, and sensor 214 is a video camera directed toward wellhead 18 and the sea floor 13. Although two sensors 162, 164 are shown electrically and communicatively coupled to instrumentation pod 150 and three sensors 210, 212, 214 are shown electrically and communicatively coupled to auxiliary instrumentation pod 200, in general, any number of sensors can be electrically and communicatively coupled to each pod 150, 200.

[0034] Referring now to Figure 2, surface equipment 1 10 includes instrumentation reel 1 1 1 , data logger 1 12, and AC power source 1 13 as previously described. In addition, surface equipment 1 10 includes network switch 1 14, fiber contacts 1 16, slip ring assembly 118, circuit breaker 122, and brushes 124. AC power source 1 13 (e.g., alternating current of 480 volts) is electrically coupled to slip ring assembly 1 18 via circuit breaker 122 and brushes 124. Slip ring assembly 1 18 is integrated into instrumentation reel 1 11 , while brushes 124 provide electrical conductivity between the contacts of stationary circuit breaker 122 and rotating slip ring assembly 1 18 as MUX cable 1 15 is paid out or paid in by instrumentation reel 1 1 1. Data logger 1 12 (e.g., a computer) is also connected to rotating slip ring assembly 1 18 and to MUX cable 1 15. More particularly, data logger 112 is connected to network switch 1 14, which conditions data signals transmitted therethrough, and then connects to slip ring assembly 1 18 through fiber contacts 1 16. Similar to brushes 124, fiber contacts 1 16 provide connectivity between the stationary contacts of network switch 114 and rotating slip ring assembly 118 as MUX cable 1 15 is paid out or paid in by instrumentation reel 11 1.

[0035] MUX cable 115 houses instrumentation pod fibers 126 and instrumentation pod power lines 128. Fibers 126 communicate control signals from surface vessel 20 to pods 150, 200 and communicate data from pods 150, 200 to surface vessel 20. For example, sensors 162, 164 communicate measured data to pod 150, and sensors 210, 212, 214 communicate measured data to pod 200. The data acquired by pod 200 can be communicated to pod 150 via wet-mate connector 190, and the data acquired by pod 150 from pod 200 and sensors 162, 164 can be communicated to surface vessel 20 via fibers 126. Power lines 128 transfer electrical power from surface vessel 20 to pod 150, which can transfer electrical power to sensors 162, 164 and pod 200, which in turn can transfer electrical power to sensors 210, 212, 214. [0036] Referring still to Figure 2, instrumentation pod 150 includes a network switch 152, a power supply 154, a first circuit breaker 156, a terminal block 158, a signal conditioner 160, and a second circuit breaker 166. Instrumentation pod fibers 126 are connected to network switch 152 (e.g., a multiplexer, switch, router, or modem), which may transmit and/ or condition data signals transmitted therethrough. A first communication line 153a extends from network switch 152 to signal conditioner 160 of pod 150, and a second communication line 153b extends from network switch 152 to wet-mate connector 190. Signal conditioner 160 is coupled to and receives measured data from sensors 162, 164. In addition, signal conditioner 160 may convert the measured data of sensors 162, 164 into another signal which is then communicated to network switch 152 via first communication line 153a. For example, signal conditioner 160 may amplify and/or filer the measured data and may convert the measured data between analog and digital formats. Network switch 152 can then communicate the measured data from sensors 162, 164 to surface vessel 20 via fibers 126. As will be described in more detail below, network switch 152 also receives measured data from sensors 210, 212, 214 via second communication line 153b, and can then communicate the measured data from sensors 210, 212, 214 to surface vessel 20 via fibers 126.

[0037] Power lines 128 of MUX cable 1 15 are connected to power supply 154, which conditions the power provided by AC power source 113 on surface vessel 20. For example in some embodiments, power supply 154 may be an alternating to direct current converter which transitions 480 volts AC into 24 volts DC. Power supply 154 distributes electrical power to terminal block 158 via transmission lines 155, and terminal block 158 distributes electrical power to wet-mate connector 190 via transmission lines 159. First circuit breaker 156 is disposed along lines 155 between terminal block 158 and power supply 154, and second circuit breaker 166 is disposed along lines 159 between terminal block 158 and wet-mate connector 190. Terminal block 158 may provide electrical power (directly or indirectly) to one or more components of instrumentation pod 150, to one or more components of auxiliary instrumentation pod 200 via wet-mate connector 190, to one or more sensors coupled to pod 150, to one or more sensors coupled to pod 200 via wet-mate connector 190, or to combinations thereof. Although one signal conditioner 160 is shown in Figure 2, it should be appreciated that instrumentation pod 150 can include additional signal conditioners (similar to signal conditioner 160) which may support additional sensors (similar to sensors 162, 164).

[0038] Referring still to Figure 2, auxiliary instrumentation pod 200 is coupled to pod 150 via wet-mate connector 190, which supports second communication line 153b from network switch 152 and power transmission lines 159 from terminal block 158. More particularly, wet-mate connector 190 electrically couples transmission lines 159 with transmission lines 198, and couples second communication line 153b with communication line 196.

[0039] Transmission lines 198 couple to circuit breaker 204, and transmission line 205 connects circuit breaker 204 with terminal block 206. Analogously to terminal block 158, terminal block 206 may provide electrical power (directly or indirectly) to one or more components or sensors of auxiliary instrumentation pod 200.

[0040] A communication line 203 extends from network switch 202 to signal conditioner 208. Signal conditioner 208 is coupled to and receives measured data from sensors 210, 212. In addition, signal conditioner 208 may convert the measured data of sensors 210, 212 into another signal which is then communicated to network switch 202 via communication line 203. For example, signal conditioner 208 may amplify and/or filer the measured data and may convert the measured data between analog and digital formats. Network switch 202 can then communicate the measured data from sensors 210, 212 to surface vessel 20 via fibers 196, 126.

[0041] Referring now to Figure 3, data acquisition system 100 is shown in a partial cross-sectional view with surface equipment 1 10 omitted for clarity. The components of instrumentation pod 150 are mounted inside a housing 50, and the components of auxiliary instrumentation pod 200 are mounted inside a separate housing 201. In this embodiment, housing 50 includes a bell-shaped body 51 and a base plate 52 that sealingly engages an annular flange 58 at the lower open end of body 51. Together, body 51 and base plate 52 define a one atmosphere pressure chamber within housing 50. Base plate 52 includes a cylindrical extension 56 extends into and slidingly engages the inner surface of body 51. A plurality of O- rings (not shown) are positioned between extension 56 and body 51 to form pressure seals therebetween.

[0042] As shown in Figure 3, instrumentation pod 150 further includes an input- output (I/O) plate 54, a bottom plate 60, a mounting plate 62, a top plate 64, a plurality of springs 66, and a stop plate 68. Bottom plate 60 is disposed within housing 50 and is mounted to base plate extension 56. Mounting plate 62 extends upward from bottom plate 60 and provides a mounting surface for the electrical components of instrumentation pod 150 such as network switch 152, signal conditioner 160, circuit breakers 156, 166, and terminal block 158 previously described (as shown in Figure 2). Top plate 64 is coupled to the upper end of mounting plate 62. Springs 66 are positioned between top plate 64 and stop plate 68. Power supply 154 is mounted to stop plate 68 and is positioned between plates 64, 68. When installed within housing 50, with flange 58 and base plate 52 in abutting contact, stop plate 68 abuts an annular stop 70 on the inner surface of body 51 and springs 66 are compressed between plates 64, 68. Contact between power supply 154, stop plate 68, annular stop 70, and body 51 allows heat from power supply 154 to be conductively transferred to the seawater surrounding housing 50.

[0043] I/O plate 54 is mounted to of the bottom of base plate 52 outside housing 50 and includes a port 74 that provides a pass through for communication line 153b and transmission lines 159, which extend from mounting plate 62 to wet-mate connector 190.

[0044] Wet-mate connector 190 includes a male plug 192 and a mating female receptacle 194, and provides releasable connectivity between instrumentation pod 150 and auxiliary instrumentation pod 200. Within wet-mate connector 190, transmission lines 159 are electrically coupled with transmission lines 198, while second communication line 153b couples with communication line 196.

[0045] Referring still to Figure 3, auxiliary instrumentation pod 200 includes a housing 201 forming a pressure vessel around network switch 202, circuit breaker 204, terminal block 206, and signal conditioner 208. Additionally, a plurality of ports 203 extend from housing 201 to provide electrical and communication connectivity with wet-mate connector 190 and sensors (not shown in Figure 3), such as sensors 210, 212 shown in Figure 2.

[0046] Referring to Figures 4, 5, and 6, I/O plate 54 of instrumentation pod 150 is shown in more detail. More particularly, Figure 4 shows I/O plate 54 uninstalled from base plate 52 such that I/O plate extension 57 is visible. In some embodiments, I/O plate extension 57 may include O-rings (not shown) such that a pressure seal is formed with base plate 52 as I/O plate extension 57 extends into base plate 52. I/O plate 54 maybe configured with different quantities, types, sizes, and arrangements of ports 74 as needed. Figure 5 shows four ports 74 of the same type and size arranged in a circular pattern, while Figure 6 shows three ports 74 in a linear alignment, with one of the included ports 74 being of a larger size than the other two.

[0047] Referring now to Figures 7 and 8, wet-mate connector 190 enables the subsea decoupling and recoupling of pods 150, 200. This may be particularly advantageous when an emergency disconnection is necessary. For example, in the case of a hurricane, surface vessel 20 may need to decouple from wellhead 18 so that it can move to safer waters and avoid a possible drift off while coupled to wellhead 18. As will be described in more detail below, in this embodiment, the emergency disconnect operation is performed by disconnecting LMRP 31 from BOP 35 to allow surface vessel 20, marine riser 40 hung from surface vessel 20, and LMRP 31 connected to the lower end of marine riser 40 to disconnect and pull away from BOP 35 and wellhead 18, which remain secured to sea floor 13.

[0048] In Figure 7, system 10 and BOP stack 30 are shown in the“connected” positions before an emergency disconnect with pods 150, 200 coupled via wet-mate connector 190 and LMRP 31 coupled to BOP 35 with lower annular connector 34b; and in Figure 8, system 10 and BOP stack 30 are in the“disconnected” positions after an emergency disconnect with pods 150, 200 decoupled and LMRP 31 decoupled from BOP 35. Prior to transitioning from the connected positions to the disconnected positions, shear rams 36 and/or pipe rams 38 are actuated to close and seal wellhead 18, and upper annular BOP 32 (or other valves along marine riser 40) are actuated to close and seal the lower end of marine riser 40. Next, lower annular connector 34b is actuated to disconnect from BOP 35, and then marine riser 40 can be slightly raised by surface vessel 20 to lift LMRP 31 from BOP 35, and simultaneously pull male plug 192 from female receptacle 194, thereby disconnecting wet-mate connector 190 as shown in Figure 8. Disengagement of male plug 192 from female receptacle 194 decouples auxiliary instrumentation pod 200 from instrumentation pod 150. Pod 200 remains stationary and mounted to BOP 35 along with any connected sensors, for example sensors 210, 212, and 214, while pod 150 remains mounted to LMRP 31 along with any connected sensors, for example, sensors 162, 164. This configuration may also be advantageous during the reinstallation of LMRP 31 onto BOP 35 as the mounting positions of male plug 192 and female receptacle 194 enable subsequent reconnection of male plug 192 and female receptacle 194, thereby reconnecting pods 150, 200, concurrent with the reconnection of LMRP 31 and BOP 35 via lower annular connector 34b. In other words, male plug 192 and female receptacle 194 are statically positioned on LMRP 31 and BOP 35, respectively, such that male plug 192 is aligned with and slides into mating female receptacle 194 simultaneous with LMRP 31 being aligned with, lowered onto, and reconnected to BOP 35 with lower annular connector 34b.

[0049] As best shown in Figure 1 , MUX cable 1 15 is physically separate from umbilicals 26, 27, while instrumentation reel 1 1 1 is separate from reels 21 , 22. In some applications, these separations may be advantageous as data acquisition system 100 may be used as a fully standalone system that does not rely on any hardware required to operate offshore system 10. This separation may also be desirable from a retro-fit perspective as data acquisition system 100 may be installed along offshore system 10 without disturbing ongoing production or drilling operations. Additionally, the separation may be useful from a maintenance perspective, as the components comprising data acquisition system 100 may be updated, reconfigured, or otherwise changed, without disturbing ongoing production or drilling operations of offshore system 10.

[0050] As best shown in Figure 2, data acquisition system 100 is also electrically isolated and communicatively isolated from control pods 42, 44, in that data acquisition system 100 does not share electrical power or communicated data to or from control pods 42, 44. As previously described, such separation from control pods 42, 44 may be advantageous in that data acquisition system 100 will not be limited by the bandwidth and power constraints of control pods 42, 44. This separation may enhance the reliability of the data acquisition system 100, which is not dependent on the limitations of control pods 42, 44, and the reliability of control pods 42, 44 may be enhanced as they are not required to operate near their power and bandwidth limits. Additionally, the electrical and communicative isolation of data acquisition system 100 may allow for larger numbers of sensors (such as sensors 162, 164, 210, 212, 214) to be used, may allow different types of sensors to be used which are not compatible with existing control pods 42, 44, and may allow for real time data transmission due to the expanded bandwidth. [0051] Referring now to Figure 9, an embodiment of an offshore system 300 for drilling and/or producing a subsea well is shown. In this embodiment, system 300 includes a surface vessel 20, a subsea BOP stack 30 mounted to an upper end of a wellhead 18 at the sea floor 13, and a data acquisition system 350 coupled to BOP stack 30. Surface vessel 20 and BOP stack 30 are each as previously described. Data acquisitions system 350 is similar to data acquisition system 100 previously described, and thus, components of data acquisition system 350 that are shared with data acquisition system 100 are identified with like reference numerals, and the description below will focus on features that are different. In particular, unlike system 100 previously described, in this embodiment, data acquisition system 350 includes a hybrid reel 302 disposed on surface vessel 20, a hybrid cable 304 extending from hybrid reel 302 to control pod 42, and MUX cable 326 extending from control pod 42 to instrumentation pod 150. Although hybrid cable 304 extends to control pod 42 and MUX cable 326 extends from control pod 42 to instrumentation pod 150 in this embodiment, in other embodiments, hybrid cable 304 extends to control pod 44 and MUX cable 326 extends from control pod 44 to instrumentation pod 150.

[0052] Hybrid reel 302 effectively combines the structure and functionality of reels 21 , 1 1 1 into a single reel, and hybrid cable 304 effectively combines the structure and functionality of MUX cable 1 15 and first umbilical 26 into a single cable.

[0053] Referring still to Figure 9, system 300 includes AC power source 1 13 and data logger 1 12 as previously described, however, despite being coupled to hybrid cable 304, which is coupled to control pod 42, each is electrically and communicatively isolated from control pod 42. In other words, AC power source 1 13 and data logger 1 12 do not transmit power or communicate data to or from control pod 42, despite a common hybrid cable 304, which houses separate power conductors and communication fibers for both control pod 42 and data acquisition system 350. More particularly, as best shown in Figure 10, hybrid cable 304 includes instrumentation pod fiber 310 and instrumentation pod power line 312 for data acquisition system 350, as well as control pod power line 306 and control pod fiber 308 for control pod 42.

[0054] Referring now to Figures 9 and 10, hybrid cable 304 is coupled to control pod 42. Control pod power line 306 and control pod fiber 308 terminate at control pod 42 and provide power and data communication capabilities to control pod 42, while instrumentation pod fiber 310 and instrumentation pod power line 312 effectively split off and pass through control pod 42 to form MUX cable 326, which exits control pod 42 at port 324 and extends to instrumentation pod 150.

[0055] Referring now to Figure 1 1 , data acquisition system 350 is shown in a partial cross-sectional view with surface equipment 1 10 omitted for clarity. In this embodiment, control pod 42 is connected to hybrid cable 304 and mounted on a compensation chamber 322. In general, compensation chamber 322 is a thin walled vessel that provides a mounting structure for port 324, which interfaces with MUX cable 326.

[0056] As previously described, data acquisition system 100 includes wet-mate connector 190 releasably and electrically couple instrumentation pod 150 on LMRP 31 and auxiliary instrumentation pod 200 on BOP 35. However, in other embodiments, different types of connectors may be used to releasably and electrically couple pods 150, 200. For example, referring now to Figures 12 and 13, data acquisition system 100 may also be configured in some embodiments to use a jumper connector 220 instead of wet-mate connector 190 to connect between instrumentation pod 150 on LMRP 31 and auxiliary instrumentation pod 200 on BOP 35. In such embodiments, jumper connector 220 may provide electrical and communicative isolation to data acquisition system 100 in embodiments where wet- mate connector 190 is used for other systems of BOP stack 30.

[0057] In this embodiment, jumper connector 220 may comprise a first receptacle 222 mounted to LMRP 31 , a second receptacle 224 mounted to BOP 35, and a jumper cable 226 extending between and removably coupled to first receptacle 222 and second receptacle 224. In particular, jumper cable 226 extends between receptacles 222, 224 and has a first end releasably connected to first receptacle 222 and a second end releasably connected to second receptacle 224. Thus, jumper connector 220 couples instrumentation pod 150 to auxiliary instrumentation pod 200 in a similar manner as previously described for wet-mate connector 190, as jumper connector 220 electrically couples transmission lines 159 with transmission lines 198, and communicatively couples second communication line 153b with communication line 196.

[0058] Referring still to Figures 12 and 13, jumper connector 220 can be used to electrically and communicatively decouple and recouple pods 150, 200 in the event of an emergency disconnection between LMPR 31 and BOP 35. In Figure 12, system 10 and BOP stack 30 are in the“connected” positions before an emergency disconnect with pods 150, 200 coupled via jumper connector 220 and LMRP 31 coupled to BOP 35 with lower annular connector 34b; and in Figure 13, system 10 and BOP stack 30 are in the“disconnected” positions after an emergency disconnect with pods 150, 200 decoupled and LMRP 31 decoupled from BOP 35. As previously described, prior to transitioning from the connected positions to the disconnected positions, shear rams 36 and/or pipe rams 38 are actuated to close and seal wellhead 18, and upper annular BOP 32 (or other valves along marine riser 40) are actuated to close and seal the lower end of marine riser 40. Next, lower annular connector 34b is actuated to disconnect from BOP 35, and then marine riser 40 can be slightly raised by surface vessel 20 to lift LMRP 31 from BOP 35, and simultaneously applying tension along jumper cable 226, thereby disconnecting jumper connector 220 as shown in Figure 13. Disengagement of jumper cable 226 from second receptacle 224 decouples auxiliary instrumentation pod 200 from instrumentation pod 150, as jumper cable 226 remains attached to LMRP 31 via first receptacle 222. In this embodiment, in the event jumper cable 226 does not release from second receptacle 224, jumper cable 226 is configured to destructively break and pull apart via the forces imparted by the separation of LMRP 31 and BOP 35. Pod 200 remains stationary mounted to BOP 35 along with any connected sensors, for example sensors 210, 212, and 214, while pod 150 remains mounted to LMRP 31 along with any connected sensors, for example, sensors 162, 164. A battery 228 can then be added to BOP 35 via a remotely operated vehicle (ROV) and a replacement jumper cable 226 may be attached between battery 228 and second receptacle 224 to power pod 200. Additional battery backup systems may also be included to provide power to instrumentation pod 150 and/or auxiliary instrumentation pod 200. The battery backup systems may interface, for example, through ports 74 in I/O plate 54 or through additional ports 203 in auxiliary instrumentation pod 200. Alternatively, the battery backups may be housed within instrumentation pod 150 and/ or within auxiliary instrumentation pod 200. It is contemplated that such integrated battery backups within auxiliary instrumentation pod 200 may thus allow data collection along BOP 35 to continue before battery 228 is connected to second receptacle 224 via jumper cable 226 as shown in Figure 13. As MUX cable 1 15 remains attached with LMRP 31 during an emergency disconnect, alternative communications may be established with surface vessel 20 via an ROV or by using an acoustic transducer (not specifically shown). In addition, data may be stored within auxiliary instrumentation pod 200 for latter transfer (e.g., after reconnecting LMRP 31 with BOP 35, via periodic connections with an ROV, after physical retrieval of auxiliary instrumentation pod 200, etc.). The currently disclosed systems will provide sufficient bandwidth for real-time monitoring of multiple data channels without impacting the bandwidth of the control systems of control pods 42, 44, however, it is contemplated that selective transfer of data from instrumentation pod 150 and auxiliary instrumentation pod 200 may also be used. For example, data transfer may be initiated by predefined trigger events, for example when sensor signals are above or below a value, change by a set percentage, or exceed a rate of change. Although jumper connector 220 is shown in connection with system 10 including reels 21 , 1 1 1 and MUX cable 1 15 and umbilical 26, in other embodiments, the jumper connector (e.g., jumper connector 220) is used in connection with hybrid reel 302 and hybrid cable 304 as previously described and shown in Figure 9.

[0059] In the manner described, embodiments disclosed herein include systems for monitoring subsea wellheads and equipment installed on wellheads, such as a LMRP 31 and a BOP 35. Data acquisition systems 100, 350 may be particularly useful for monitoring such equipment as each is electrically and communicatively isolated from control pods 42, 44, thus are not limited by the power or bandwidth constraints of the control pods and don’t interfere with the functionality of the control pods. Additionally, data acquisition system 100, which utilizes a dedicated instrumentation reel 1 11 , may be useful for retrofitting existing offshore systems 10, as each component of data acquisition systems 100 may be installed separately from the hardware needed to operate or control offshore system 10. In other instances, data acquisition systems 350 may offer cost and space advantages over data acquisition system 100, as existing reels 21 , 22 may be utilized rather than requiring a dedicated instrumentation reel 1 1 1.

[0060] One having ordinary skill in the art will appreciate that modification of embodiments of systems disclosed herein are possible without departing from the principles of operation. For example, multiple signal conditioners, similar to signal conditioner 160 as shown in Figure 2, may be added within instrumentation pod 150 and/or auxiliary instrumentation pod 200. Additionally, bell housing 52 and base plate 52 of data acquisition system 100, 350, as best shown in Figures 3 and 1 1 , may be modified to include any geometry and sealing arrangement therebetween. For example a cuboid, cylindrical, or spherical bell housing 52 could be used and base plate 52 may include face sealing O-rings positioned between for example flange 58 and base plate 52. Additionally, metal to metal seals may be useful in some embodiments, for example in high pressure and/or high temperature applications. While exemplary embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the disclosure. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1 ), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.

Claims

CLAIMS What is claimed is:

1. A data acquisition system for monitoring a subsea BOP stack, the BOP stack including a blue control pod and a yellow control pod for operating the BOP stack, the system comprising:

an umbilical having a first end and a second end;

a reel on a surface vessel, wherein the umbilical is mounted to the reel and extends therefrom;

a subsea instrumentation pod mounted to the BOP stack, wherein a lower end of the umbilical is coupled to the instrumentation pod, wherein the instrumentation pod is spaced apart from the blue control pod and the yellow control pod, and wherein the subsea instrumentation pod is electrically isolated and communicatively isolated from the blue control pod and the yellow control pod; and

a first sensor coupled to the instrumentation pod.

2. The data acquisition system of claim 1 , wherein the data acquisition system is configured to acquire measurements from a plurality of sensors coupled to the BOP stack.

3. The data acquisition system of claim 1 , wherein the first sensor is selected from the group consisting of load cell, pressure transducer, accelerometer, thermocouple, displacement transducer, flow meter, acoustic meter, vibration data loggers, motion reference unit, ram positon indicator, and camera.

4. The data acquisition system of claim 1 , wherein the subsea instrumentation pod further comprises:

a housing including a body and a base plate coupled to the body to form a pressure chamber therein;

an input-output plate coupled to the base plate, wherein the input-output plate includes a plurality of ports, wherein each port is configured to allow a power line for transferring power or a fiber for communicating data through the input-output plate.

5. The data acquisition system of claim 4, further comprising:

a mounting plate positioned within the housing and coupled to the base plate; and

a signal conditioner coupled to the mounting plate, wherein the signal conditioner is electrically coupled to the first sensor and is configured to amplify a first signal from the first sensor.

6. The data acquisition system of claim 5, further comprising:

a second sensor electrically coupled to the signal conditioner, wherein the second sensor is of a different type than the first sensor

7. The data acquisition system of claim 1 , wherein the subsea instrumentation pod is mounted on an LMRP of the BOP stack.

8. The data acquisition system of claim 7, further comprising:

an auxiliary instrumentation pod mounted to a BOP of the BOP stack;

a wet-mate connector releasably coupling the auxiliary instrumentation pod to the subsea instrumentation pod; and

a second sensor coupled to the auxiliary instrumentation pod.

9. The data acquisition system of claim 8, wherein the wet-mate connector is configured to disconnect when the BOP and LMRP are separated and reconnect when the lower stack and LMRP are reconnected.

10. The data acquisition system of claim 9, wherein the first sensor is mounted to the LMRP and is configured to remain mounted to the LMRP when the BOP and LMRP are separated.

1 1. The data acquisition system of claim 7, further comprising:

an auxiliary instrumentation pod mounted to a BOP of the BOP stack; a jumper cable releasably coupling the auxiliary instrumentation pod to the subsea instrumentation pod; and

a second sensor coupled to the auxiliary instrumentation pod.

12. The data acquisition system of claim 1 1 , further comprising:

a first receptacle mounted to the LMRP of the BOP stack;

a second receptacle mounted to the BOP of the BOP stack; and

wherein the jumper cable extends from the first receptacle to the second receptacle, and wherein the jumper cable is configured to disconnect from the second receptacle when the BOP and LMRP are separated.

13. The data acquisition system of claim 12, further comprising:

a battery coupled to the BOP of the BOP stack, wherein the battery is configured to be releasably coupled to the second receptacle via the jumper cable, after separation of the BOP and LMRP.

14. A method, comprising:

(a) decoupling an LMRP from a BOP mounted to a subsea wellhead;

(b) retracting a marine riser coupled to the LMRP to lift the LMRP and pull the LMRP from the BOP; and

(c) separating a male plug and a female receptacle of a wet-mate connector during (b), wherein the male plug is coupled to an instrumentation pod mounted to the LMRP and the female receptacle is coupled to an auxiliary instrumentation pod mounted to the BOP, wherein the auxiliary instrumentation pod remains mounted to the BOP after (c) and the instrumentation pod remains mounted to the LMRP after (c).

15. The method of claim 14, further comprising:

(d) reconnecting the LMRP and the BOP after (b) and (c);

wherein (d) comprises:

(d1 ) aligning a connector of the LMRP and the BOP;

(d2) aligning the male plug and the female receptacle during (d1 );

(d3) lowering the marine riser to lower the LMRP onto the BOP; and (d4) inserting the male plug into the female receptacle during (d3).

16. A data acquisition system for monitoring a subsea BOP stack, the BOP stack including a blue control pod and a yellow control pod for controlling the BOP stack, the system comprising:

an umbilical having a first end and a second end;

a reel on a surface vessel, wherein the umbilical is mounted to the reel and extends from the reel to one of the blue control pod and the yellow control pod;

a subsea instrumentation pod mounted to the BOP stack and spaced apart from the blue control pod and the yellow control pod;

a cable extending to the instrumentation pod from one of the blue control pod and the yellow control pod, wherein the instrumentation pod is electrically isolated and communicatively isolated from the blue control pod and the yellow control pod; and

a sensor coupled to the instrumentation pod.

17. The data acquisition system of claim 16, wherein the subsea instrumentation pod further comprises:

a housing including a body and a base plate coupled to the body to form a pressure chamber therein; and an input-output plate coupled to the base plate, wherein the input-output plate includes a plurality of ports, wherein each port is configured to allow a power line for transferring power or a fiber for communicating data through the input-output plate.

18. The data acquisition system of claim 17, further comprising:

a mounting plate coupled to the base plate and positioned within the pressure chamber; and

a signal conditioner coupled to the mounting plate, wherein the signal conditioner is electrically coupled to the first sensor and to a second sensor, wherein the first sensor and second sensors are of different types.