Subsea Wellhead Monitoring System

Abstract

A subsea wellbore monitoring system of the present disclosure includes hanger, plug, and monitoring assemblies. The hanger assembly installs on landing in the wellhead, engages the lock profile, and has a hanger seal sealing in the wellhead. The plug assembly is supported in the hanger assembly and has a plug seal to seal in the landing. Ports of the plug assembly communicate with a bore envelope and an annulus envelope. The monitoring assembly has pressure monitors that communicate with the ports and measure pressure measurements related to the envelopes. The hanger and plug seals can be elastomeric and/or metal elements. The hanger and plug seals are preferably expandable or can be energized outward so the seals can pass any shoulders and profiles when installed in the wellbore and can then seal against the internal surfaces.

1 . A system used with a subsea wellhead in a subsea environment, the system comprising:
 an assembly having a hanging portion and a plugging portion,
 the hanging portion being configured to engage on a landing in the subsea wellhead, the hanging portion having a first annular seal disposed thereabout, the first annular seal being configured to seal in the subsea wellhead upbore of the landing, 
 the plugging portion extending at least partially downbore of the hanging portion and having a second annular seal disposed thereabout, the second annular seal being configured to seal in the landing of the subsea wellhead downbore of the first annular seal, 
 the assembly at least defining first and second ports, the first port being configured to communicate with a bore envelope of the subsea wellhead below the second annular seal, the second port being configured to communicate with an annulus envelope between the first and second annular seals; 
   a first pressure monitor configured to communicate with the first port and configured to measure a first pressure measurement related to the bore envelope; and   a second pressure monitor configured to communicate with the second port and configured to measure a second pressure measurement related to the annulus envelope.   
     
     
         2 . The system of  claim 1 , wherein the hanging portion comprises:
 a hanger supporting the plugging portion and having the first annular seal disposed thereabout, the hanger having a landing shoulder configured to install on the landing in the subsea wellhead;   a locking sleeve movably disposed on the hanger; and   a locking ring wedged between the hanger and the locking sleeve and being configured to engage in the subsea wellhead.   
     
     
         3 . The system of  claim 2 , wherein the locking sleeve comprises a retention ring configured to expand into a retention slot defined in the hanger. 
     
     
         4 . The system of  claim 2 , comprising a temporary retainer temporarily retaining the locking sleeve to the hanger. 
     
     
         5 . The system of  claim 2 , wherein the plugging portion comprises a plug supported in a bowl of the hanger, the locking sleeve being movably installed between the plug and the bowl of the hanger. 
     
     
         6 . The system of  claim 5 , wherein the plug comprises:
 a first portion extending at least partially beyond the bowl of the hanger and having the second annular seal disposed thereabout; and   a second portion disposed at least partially in the bowl of the hanger, the second portion having a third annular seal disposed thereabout, the third annular seal being configured to seal with the locking sleeve.   
     
     
         7 . The system of  claim 6 , wherein the second portion of the plug is connected to the first portion at a connection; and wherein at least one intermediate seal is disposed at the connection between the first and second portions and is configured to seal therebetween. 
     
     
         8 . The system of  claim 7 , wherein the first port of the assembly is defined in the plug and is sealed by a first of the at least one intermediate seal at the connection of the first and second portions; and wherein the second port of the assembly is defined in the plug and is sealed by a second of the at least one intermediate seal at the connection. 
     
     
         9 . The system of  claim 2 , wherein the landing shoulder comprises a landing ring being movably biased in biased movement relative to the hanger, the landing ring configured to engage the landing in the subsea wellhead; and wherein the first annular seal is disposed between a first surface of the landing ring and a second surface of the hanger, the first annular seal being energized radially outward in response to the biased movement of the first surface of the landing ring toward the second surface of the hanger. 
     
     
         10 . The system of  claim 2 , wherein the locking sleeve and the plugging portion define first and second chambers sealed therebetween, the first and second chambers defining sealed volumes complementary to one another, whereby an increase in the sealed volume of one of the first and second chambers produces a decrease in the sealed volume of the other of the first and second chamber; and wherein the system comprises:
 a first hydraulic connection being controlled by a first control valve and being configured to communicate with the first chamber; and   a second hydraulic connection being controlled by a second control valve and being configured to communicate with the second chamber.   
     
     
         11 . The system of  claim 10 , comprising a third hydraulic connection being controlled by a third control valve and being configured to test sealing between the hanging portion and the plugging portion. 
     
     
         12 . The system of  claim 1 , wherein the hanging portion comprises a landing ring movably biased in biased movement on the hanging portion and configured to engage on the landing of the subsea wellhead; and wherein the first annular seal is disposed between a first surface of the landing ring and a second surface of the hanging portion, the first annular seal being energized radially outward in response to the biased movement of the first surface of the landing ring toward the second surface of the hanging portion. 
     
     
         13 . The system of  claim 12 , comprising at least one intermediate seal disposed between the plugging portion and the landing ring and being configured to seal therebetween. 
     
     
         14 . The system of  claim 1 , wherein the first annular seal comprises one of:
 at least one elastomeric seal disposed about a circumference of the hanging portion;   at least one metal seal disposed about the circumference of the hanging portion; and   at least one metal C-seal configured to provide a pressure-energized seal between the hanging portion and the subsea wellhead, the metal C-seal having a first side, a second side, an inner dimension, and an outer dimension, the first side being convex, the second side defining an internal cavity, the internal cavity disposed toward the annulus envelope, the inner dimension being free to engage an external surface of the hanging portion, the outer dimension being free to engage an internal surface in the subsea wellhead, each of the inner and outer dimensions respectively engaging with a sealing force increasing with an increase in fluid pressure in the annulus envelope acting in the internal cavity.   
     
     
         15 . The system of  claim 1 , wherein the second annular seal comprises one of:
 at least one elastomeric seal disposed about a circumference of the plugging portion;   at least one metal seal disposed about the circumference of the plugging portion; and   at least one metal C-seal configured to provide a pressure-energized seal between the plugging portion and the subsea wellhead, the metal C-seal having a first side, a second side, an inner dimension, and an outer dimension, the first side being convex, the second side defining an internal cavity, the internal cavity disposed toward the bore envelope, the inner dimension being free to engage an external surface of the plugging portion, the outer dimension being free to engage an internal surface in the landing, each of the inner and outer dimensions respectively engaging with a sealing force increasing with an increase in fluid pressure in the bore envelope acting in the internal cavity.   
     
     
         16 . The system of  claim 1 , wherein the second annular seal is configured to insert past a shoulder of the landing in the subsea wellhead and is configured to expand outward to seal with a surface of the landing in the subsea wellhead; and wherein the first annular seal is configured to insert past a locking profile in the subsea wellhead and is configured to expand outward to seal with a bore of the subsea wellhead upbore of the shoulder of the landing. 
     
     
         17 . The system of  claim 1 , comprising:
 a first hydraulic connection configured to connect the first port and the first pressure monitor; and   a second hydraulic connection configured to connect between the second port and the second pressure monitor.   
     
     
         18 . The system of  claim 1 , comprising a third pressure monitor configured to communicate with the subsea environment and configured to measure a third pressure measurement related to hydrostatic pressure of the subsea environment. 
     
     
         19 . The system of  claim 1 , comprising an interface in electronic communication with the first and second pressure monitors, the first and second pressure measurements being readable via the interface. 
     
     
         20 . The system of  claim 19 , wherein the interface comprises one or more of:
 one or more electronic meters being configured to display the first and second pressure measurements;   memory configured to store the first and second pressure measurements and having a data link being electronically readable; and   a telemetry system being configured to telemeter the first and second pressure measurements.   
     
     
         21 . A method used with a subsea wellhead, the subsea wellhead having a bore with a landing, the method comprising:
 engaging an assembly on the landing of the subsea wellhead by sealing a first annular seal on the assembly in the bore of the subsea wellhead, and sealing a second annular seal on the assembly in the landing of the subsea wellhead;   monitoring, via a first port of the assembly, a first pressure of a bore envelope of the subsea wellhead downbore of the second annular seal; and   monitoring, via a second port of the assembly, a second pressure of an annulus envelope between the first and second annular seals.   
     
     
         22 . The method of  claim 21 ,
 wherein engaging the assembly and sealing the first annular seal comprises:
 inserting the first annular seal past a locking profile in the bore of the subsea wellhead, and energizing the first annular seal outward to seal with the bore of the subsea wellhead; and 
   wherein engaging the assembly and sealing the second annular seal comprises inserting the second annular seal past a shoulder of the landing in the subsea wellhead, and energizing the second annular seal outward to seal with a surface of the landing.