Wellbore influx detection in a marine riser

Abstract

Methods and apparatus for managing wellbore influx in a marine riser. In one embodiment, a method for managing wellbore influx includes identifying a difference between measured values provided by a plurality of sensors longitudinally spaced along a riser. Whether the difference between measured values provided by a given pair of the sensors has changed relative to a difference between measured values previously provided by the given pair of the sensors is determined. Whether wellbore influx is present in the riser is determined based on the change in the difference.

What is claimed is: 
     
         1 . A method for managing wellbore influx, comprising:
 identifying a difference between measured values provided by a plurality of sensors longitudinally spaced along a riser;   determining whether a difference between measured values provided by a given pair of the sensors has changed relative to the difference between measured values previously provided by the given pair of the sensors;   determining based on the change in the difference whether wellbore influx is present in the riser.   
     
     
         2 . The method of  claim 1 , wherein the sensors comprise one or more of pressure sensors, temperature sensors, flow rate sensors, resistivity sensors, and acoustic sensors 
     
     
         3 . The method of  claim 1 , further comprising installing the sensors in an interior of the riser after subsea installation of the riser at a wellsite. 
     
     
         4 . The method of  claim 1 , further comprising:
 installing a power transmission system along a length of an exterior of the riser; and   wirelessly transmitting power to the sensors in an interior of the riser through a wall of the riser.   
     
     
         5 . The method of  claim 4 , wherein installing the power transmission system comprises installing the power transmission system after subsea installation of the riser at a wellsite. 
     
     
         6 . The method of  claim 1 , further comprising:
 installing a data telemetry system along a length of an exterior of the riser; and   wirelessly transmitting measurements from the sensors to the data telemetry system through a wall of the riser.   
     
     
         7 . The method of  claim 6 , further comprising transmitting the measurements to a riser monitoring system at the surface. 
     
     
         8 . The method of  claim 1 , wherein the measured values are pressure values and the difference indicates a decrease in pressure between the given sensors. 
     
     
         9 . The method of  claim 1 , wherein the measured values are flow values and the difference indicates an increase in flow between the given sensors. 
     
     
         10 . The method of  claim 1 , wherein the measured values are temperature values and the difference indicates a decrease in temperature between the given sensors. 
     
     
         11 . The method of  claim 1 , further comprising:
 determining a rate of change of the difference;   determining whether fluid flow from the riser will be processed by a mud-gas separator based on the determined rate of change; and   determining whether fluid flow from the riser will be diverted to bypass the mud-gas separator based on the determined rate of change.   
     
     
         12 . The method of  claim 11 , wherein the measured values are pressure values; and further comprising:
 determining that the fluid flow from the riser is to be diverted to bypass the mud-gas separator based on a rate of decrease of the difference being greater than a predetermined pressure threshold; and   determining that the fluid flow from the riser is to be processed by the mud-gas separator based on the rate of decrease of the difference being not greater than the predetermined pressure threshold value.   
     
     
         13 . The method of  claim 11 , wherein the measured values are flow values; and further comprising:
 determining that the fluid flow from the riser is to be diverted to bypass the mud-gas separator based on a rate of increase of the difference being greater than a predetermined flow increase threshold value; and   determining that the fluid flow from the riser is to be processed by the mud-gas separator based on the rate of increase of the difference being not greater than the predetermined flow increase threshold value.   
     
     
         14 . The method of  claim 11 , wherein the measured values are temperature values; and further comprising:
 determining that the fluid flow from the riser is to be diverted to bypass the mud-gas separator based on a rate of decrease of the difference being greater than a predetermined temperature threshold; and   determining that the fluid flow from the riser is to be processed by the mud-gas separator based on the rate of decrease of the difference being not greater than the predetermined temperature threshold value.   
     
     
         15 . The method of  claim 11 , wherein the measured values are acoustic pressure values; and further comprising:
 determining that the fluid flow from the riser is to be diverted to bypass the mud-gas separator based on a rate of increase of the difference being greater than a predetermined acoustic pressure increase threshold value; and   determining that the fluid flow from the riser is to be processed by the mud-gas separator based on the rate of increase of the difference being not greater than the predetermined acoustic pressure increase threshold value.   
     
     
         16 . A system for managing wellbore influx, comprising:
 a riser;   an array of sensors disposed at intervals along the length of the riser, the sensors configured to measure one or more parameters indicative of wellbore influx within the riser; and   influx analysis logic configured to detect wellbore influx in the riser based on a difference in measurement values provided by two of the sensors.   
     
     
         17 . The system of  claim 16 , wherein the influx analysis logic is configured to determine whether the difference in measurement values provided by a given pair of the sensors has changed relative to a previous difference in the measurement values provided by the given pair of the sensors 
     
     
         18 . The system of  claim 16 , wherein the sensors comprise one or more of pressure sensors, temperature sensors, flow rate sensors, resistivity sensors, and acoustic sensors. 
     
     
         19 . The system of  claim 16 , wherein the sensors comprise an optical fiber extending over the length of the riser, the optical fiber configured to measure at least one of temperature, pressure, and acoustics along the length of the riser. 
     
     
         20 . The system of  claim 16 , further comprising a power distribution network disposed on an outside surface of the riser, the power distribution network configured to wirelessly provide power to the sensors in an interior of the riser through a wall of the riser. 
     
     
         21 . The system of  claim 16 , further comprising a data telemetry network disposed on an outside surface of the riser, the data telemetry network configured to:
 wirelessly receive measurements from the sensors in an interior of the riser through a wall of the riser; and   provide the measurements to the influx analysis logic.   
     
     
         22 . The system of  claim 16 , wherein the measurement values are indicative of one of pressure and temperature, and the influx analysis logic is configured to detect wellbore influx based on a decrease in one of pressure and temperature between the sensors. 
     
     
         23 . The system of  claim 16 , wherein the measurement values are indicative of flow and acoustic pressure, and the influx analysis logic is configured to detect wellbore influx based on an increase in one of flow and acoustic pressure between the sensors. 
     
     
         24 . The system of  claim 16 , wherein the influx analysis logic is configured to:
 determine a rate of change in the difference;   determine whether fluid flow from the riser will be processed by a mud-gas separator based on the determined rate of change; and   determine whether fluid flow from the riser will be diverted to bypass the mud-gas separator based on the determined rate of change.   
     
     
         25 . The system of  claim 16 , wherein the influx evaluation system is configured to:
 divert fluid flow from the riser to bypass a mud-gas separator based on a rate of decrease in the difference being greater than a predetermined threshold value; and   apply the mud-gas separator to process the fluid flow from the riser based on the rate of decrease in the difference being not greater than the predetermined threshold value;   wherein the threshold value is one of a pressure threshold value and a temperature threshold value.   
     
     
         26 . The system of  claim 16 , wherein the influx evaluation system is configured to:
 divert fluid flow from the riser to bypass a mud-gas separator based on a rate of increase in the difference being greater than a predetermined threshold value; and   apply the mud-gas separator to process the fluid flow from the riser based on the rate of increase in the difference being not greater than the predetermined threshold value;   wherein the threshold value is one of a flow threshold value and an acoustic pressure threshold value.   
     
     
         27 . The system of  claim 16 , wherein the sensors are magnetically fixed to an interior of the riser. 
     
     
         28 . A marine riser, comprising:
 a plurality of riser tubes connected end-to-end and extending from a blowout preventer to a surface installation;   sensors distributed along at least some of the tubes, the sensors configured to measure a condition of fluid in the tubes; and   a riser monitoring system communicatively coupled to the sensors and configured to:
 collect measurement values generated by the sensors; and 
 detect influx of formation fluid into the riser based on a difference between measurement values provided by two of the sensors. 
   
     
     
         29 . The marine riser of  claim 28 , wherein the sensors comprise one or more of pressure sensors, temperature sensors, flow rate sensors, resistivity sensors, and acoustic sensors. 
     
     
         30 . The marine riser of  claim 28 , wherein the sensors are magnetically fixed to an interior surface of the tubes. 
     
     
         31 . The marine riser of  claim 28 , further comprising a power distribution network disposed on an outside surface of the tubes, the power distribution network configured to wirelessly provide power to the sensors in an interior of the tubes through a wall of the tubes. 
     
     
         32 . The marine riser of  claim 28 , further comprising a data telemetry network disposed on an outside surface of the riser, the data telemetry network configured to:
 wirelessly receive measurements from the sensors in an interior of the riser through a wall of the riser; and   provide the measurements to the riser monitoring system.   
     
     
         33 . The marine riser of  claim 28 , wherein the sensors comprise an optical fiber extending over the length of the tubes, the optical fiber configured to measure one of pressure, temperature, and acoustics along a length of the riser. 
     
     
         34 . The marine riser of  claim 28 , wherein the riser monitoring system is configured to estimate an amount of formation fluid in the riser based on an amount of change in the difference between measurement values provided by two of the sensors over time.