System and method for dissolved gas detection

Abstract

A subsea mud evaluation system includes a blowout preventer (BOP), coupled to a wellbore formed in an underground formation, the blowout preventer being positioned proximate a sea floor. The system also includes a riser fluidly coupled to the BOP, the riser extending from the BOP to a sea surface location to transport drilling mud between the wellbore and the sea surface location. The system further includes a dissolved gas detection and mitigation systems (DMS), fluidly coupled to at least one of the BOP or the riser, the DMS receiving a quantity of drilling mud and determining a subsea bubble point of the quantity of drilling mud, corresponding to a pressure where a dissolved gas within the drilling mud is liberated.

1 . A subsea mud evaluation system, comprising:
 a blowout preventer (BOP), coupled to a wellbore formed in an underground formation, the blowout preventer being positioned proximate a sea floor;   a riser fluidly coupled to the BOP, the riser extending from the BOP to a sea surface location to transport drilling mud between the wellbore and the sea surface location; and   a dissolved gas detection and mitigation systems (DMS), fluidly coupled to at least one of the BOP or the riser, the DMS receiving a quantity of drilling mud and determining a subsea bubble point of the quantity of drilling mud, corresponding to conditions where a dissolved gas within the drilling mud is liberated.   
     
     
         2 . The system of  claim 1 , wherein the DMS further comprises:
 a pressure chamber, the pressure chamber receiving the quantity of drilling mud;   a fluid mover, the fluid mover reducing a pressure within the pressure chamber; and   a first sensor, the first sensor detecting the bubble point of the quantity of drilling mud.   
     
     
         3 . The system of  claim 2 , wherein the first sensor is at least one of an acoustic sensor or a volume sensor. 
     
     
         4 . The system of  claim 1 , further comprising:
 a control system, the control system receiving first data from the first sensor and second data from a second sensor arranged at a chamber at the sea surface location, the control system determining a surface bubble point based at least in part on the second data.   
     
     
         5 . The system of  claim 4 , wherein the control system determines a threshold bubble point, based at least in part on a comparison between the subsea bubble point and the surface bubble point. 
     
     
         6 . The system of  claim 1 , further comprising:
 a kill/choke line coupled to the DMS, the coupling receiving dissolved gases from the quantity of drilling mud.   
     
     
         7 . The system of  claim 1 , wherein the DMS further comprises:
 a Venturi tube; and   a fluid mover driving the mud through a reduced diameter portion of the Venturi tube.   
     
     
         8 . A subsea mud evaluation system, comprising:
 a blowout preventer (BOP), coupled to a wellbore at a sea floor;   a riser fluidly coupled to the BOP, the riser extending from the BOP to a sea surface location to transport drilling mud between the wellbore and the sea surface location; and   a dissolved gas detection and mitigation systems (DMS), fluidly coupled to the BOP, the DMS comprising:
 a first pressure chamber; 
 an inlet flow path directing drilling mud from the BOP into the first pressure chamber; and 
 one or more first sensors detecting one or more first properties of the drilling mud in the first pressure chamber; 
   a bubble point analysis system (BPAS), fluidly coupled to the riser, the BPAS comprising:
 a second pressure chamber, the second pressure chamber receiving drilling mud from the riser; and 
 one or more second sensors detecting one or more second properties of the drilling mud in the second pressure chamber; and 
   a control system, communicatively coupled to the BPAS and the DMS, the control system receiving information from the one or more first sensors and the one or more second sensors to determine a difference between a DMS bubble point and a BPAS bubble point.   
     
     
         9 . The system of  claim 8 , wherein the DMS further comprises:
 a fluid mover, the fluid mover lowering a pressure of the first pressure chamber to liberate dissolved gases from the drilling mud.   
     
     
         10 . The system of  claim 8 , wherein the one or more first sensors and the one or more second sensors include acoustic sensors, pressure sensors, temperature sensors, volume sensors, or a combination thereof. 
     
     
         11 . The system of  claim 8 , wherein the DMS is coupled to a kill/choke, the kill/choke line transporting gases from the first pressure chamber. 
     
     
         12 . The system of  claim 8 , wherein the DMS further comprises:
 an outlet flow path, coupled to the BOP, to circulate drilling mud out of the first pressure chamber and back toward the BOP.   
     
     
         13 . The system of  claim 8 , wherein drilling mud in the DMS and the drilling mud in the BPAS is maintained at substantially similar conditions. 
     
     
         14 . The system of  claim 8 , further comprising:
 an alarm system, the alarm system transmitting a signal in response to a determination that a difference between the DMS bubble point and the BPAS bubble point exceeds a threshold.   
     
     
         15 . The system of  claim 14 , wherein the signal initiates an alarm indication, a mitigation event, or a combination thereof. 
     
     
         16 . A method for monitoring drilling operations, comprising:
 obtaining, at a subsea location, a first quantity of drilling mud;   determining, from the first quantity of drilling mud, a subsea bubble point pressure;   obtaining, at a surface location, a second quantity of drilling mud;   determining, from the second quantity of drilling mud, a surface bubble point pressure; and   determining a threshold pressure, based at least in part on a difference between the surface bubble point pressure and the subsea bubble point pressures.   
     
     
         17 . The method of  claim 16 , further comprising:
 determining a riser pressure at a location along a riser;   determining the riser pressure exceeds the threshold; and   providing an alert.   
     
     
         18 . The method of  claim 17 , further comprising:
 in response to receiving the alert, performing one or more mitigation actions to remove a dissolved gas from the first quantity of drilling mud.   
     
     
         19 . The method of  claim 16 , further comprising:
 determining a mud pressure will exceed the threshold; and   shutting a blowout preventer.   
     
     
         20 . The method of  claim 16 , further comprising:
 reducing a pressure of the first quantity of drilling mud;   receiving, from a sensor, information indicative of liberation of the drilling mud; and   determining the information exceeds a second threshold.