Automated heave compensation

Abstract

A computer system manages drilling operations in an ocean environment. The system differentiates between nondrilling and drilling states in a closed-loop fluid system on a drilling vessel. In the non-drilling state, where the drillstring is held on the vessel during motion, a “piston effect” can alter downhole pressure. The system adjusts the surface backpressure automatically to counteract this pressure change and maintains the pressure within acceptable limits. The adjustment process incorporates a motion model that predicts the vessel's movement based on environmental factors and the vessel's characteristics. This model uses environmental measurements to calculate the necessary backpressure adjustments, ensuring stable downhole conditions despite the vessel's motion.

1 . A computer-implemented method used with a drilling system on a drilling vessel in an ocean environment to drill a wellbore in a formation, the drilling system being configured to circulate fluid in a closed loop between a drillstring and the wellbore and being configured to regulate a downhole pressure in the wellbore using pressure regulation of the circulated fluid, the method comprising:
 identifying, with a control system, between a non-drilling state and a drilling state of the drilling system, the non-drilling state being indicative of the drillstring being held at the drilling vessel at least during vessel motion, the drillstring held during the vessel motion being expected to produce a first piston effect that changes the downhole pressure in the wellbore, the drilling state being indicative of the drillstring being tripped in the wellbore;   determining, with the control system in response to an identification of the non-drilling state, a first adjustment to the pressure regulation provided by the drilling system, the first adjustment being configured to maintain the downhole pressure in the wellbore; and   counteracting the change to the downhole pressure produced by the first piston effect by automatically adjusting, with the control system, the pressure regulation provided by the drilling system according to the first adjustment.   
     
     
         2 . The method of  claim 1 , wherein to determine the first adjustment, the method comprises:
 obtaining one or more environmental measurements indicative of an influence from the ocean environment on the drilling vessel;   predicting predicted movement of the drilling vessel by motion modelling how the drilling vessel responds to the one or more environmental measurements; and   determining the first adjustment based on the predicted movement.   
     
     
         3 . The method of  claim 2 , wherein predicting the predicted movement of the drilling vessel by motion modelling comprises using transfer function calculations that define how one or more vessel characteristics for the drilling vessel respond to one or more environmental characteristics for the one or more environmental measurements. 
     
     
         4 . The method of  claim 2 , wherein obtaining the one or more environmental measurements comprises at least one of:
 detecting the one or more environmental measurements using one or more first environmental sensors disposed on the drilling vessel;   detecting the one or more environmental measurements using one or more second environmental sensors deployed in the ocean environment in a vicinity of the drilling vessel;   receiving the one or more environmental measurements from one or more external sources;   interrogating an environmental system of the drilling vessel with a request for the one or more environmental measurements;   receiving the one or more environmental measurements automatically from the environmental system of the drilling vessel; and   receiving one or more manual inputs of the one or more environmental measurements.   
     
     
         5 . The method of  claim 2 , wherein the one or more environmental measurements from the ocean environment comprises one or more of: met-ocean data, a meteorological condition, an atmospheric aspect, a speed of wind, a direction of wind, a temperature, a humidity, precipitation, an oceanographic condition, a wave height, a wave period, a surface ocean current, a subsurface ocean current, and a sea surface condition. 
     
     
         6 . The method of  claim 2 , wherein predicting the predicted movement of the drilling vessel by motion modelling further comprises:
 obtaining one or more vessel measurements indicative of a measured movement of the drilling vessel in the ocean environment; and   supplementing the predicted movement of the drilling vessel by using the measured movement of the drilling vessel in the motion modelling.   
     
     
         7 . The method of  claim 6 , wherein:
 obtaining the one or more environmental measurements comprises measuring one or more wave characteristics using one or more environmental sensors deployed in the ocean environment in a vicinity of the drilling vessel;   obtaining the one or more vessel measurements comprises measuring peripheral motion for the measured movement of the drilling vessel using one or more first vessel sensors disposed at a peripheral portion of the drilling vessel, measuring central motion for the measured movement of the drilling vessel using one or more second vessel sensors disposed at a central portion of the drilling vessel, and calculating a difference between the peripheral motion and the central motion; and   supplementing the predicted movement of the drilling vessel in the motion modelling by determining, based on the calculated difference, an influence of the one or more measured wave characteristics on the predicted movement of the drilling vessel in the motion modelling.   
     
     
         8 . The method of  claim 2 , wherein to at least one of: identify between the non-drilling state and the drilling state, predict the predicted movement, and determine the first adjustment, the method comprises using a machine learning model. 
     
     
         9 . The method of  claim 1 , wherein to identify between the non-drilling state and the drilling state of the drilling system, the method comprises:
 detecting the respective state directly using one or more system sensors of the drilling system;   interrogating the drilling system with a request for the identification;   receiving the identification automatically from the drilling system; and   receiving a manual input of the identification.   
     
     
         10 . The method of  claim 1 , wherein identifying the non-drilling state indicative of the drillstring being held at the drilling vessel comprises: identifying a first instance of the drillstring being moved out of the wellbore during first of the vessel motion expected to produce swabbing as the first piston effect decreasing the downhole pressure in the wellbore; and identifying a second instance of the drillstring being moved into the wellbore during second of the vessel motion expected to produce surging as the first piston effect increasing the downhole pressure in the wellbore. 
     
     
         11 . The method of  claim 10 , wherein automatically adjusting, with the control system, the pressure regulation provided by the drilling system according to the first adjustment comprises:
 automatically adjusting, with the control system, the pressure regulation provided by the drilling system according to a downhole pressure increase for the first adjustment in response to the first instance to counteract the change to the downhole pressure produced by the swabbing; and   automatically adjusting, with the control system, the pressure regulation provided by the drilling system according to a downhole pressure decrease for the first adjustment in response to the second instance to counteract the change to the downhole pressure produced by the surging.   
     
     
         12 . The method of  claim 1 , wherein identifying the drilling state comprises identifying a trip of the drillstring being expected to produce a second piston effect that changes the downhole pressure in the wellbore; and wherein the method further comprises:
 determining, with the control system in response to an identification of the drilling state, a second adjustment to a surface backpressure for the pressure regulation provided by the drilling system to maintain the downhole pressure in the wellbore; and   counteracting the change in the downhole pressure produced by the second piston effect by automatically adjusting, with the control system, the surface backpressure according to the second adjustment.   
     
     
         13 . The method of  claim 12 , wherein identifying the trip expected to produce the second piston effect comprises:
 identifying a first instance of pulling the drillstring out of the wellbore that produces swabbing as the second piston effect decreasing the downhole pressure in the wellbore; and   identifying a second instance of running the drillstring into the wellbore that produces surging as the second piston effect increasing the downhole pressure in the wellbore.   
     
     
         14 . The method of  claim 1 , wherein identifying the drilling state comprises identifying a trip expected to produce a second piston effect that changes the downhole pressure in the wellbore; and wherein the method further comprises mitigating a change in the downhole pressure produced by the second piston effect by operating a crown block heave compensator mounted on the drilling system. 
     
     
         15 . The method of  claim 1 , wherein to determine the first adjustment configured to maintain the downhole pressure in the wellbore, the method comprises obtaining, with the control system, a value of the downhole pressure of the fluid in the wellbore. 
     
     
         16 . The method of  claim 15 , wherein obtaining the value of the downhole pressure of the fluid in the wellbore comprises:
 obtaining one or more pressure measurements of the drilling system; and   calculating a bottom hole pressure (BHP) in the wellbore based at least on the one or more pressure measurements.   
     
     
         17 . The method of  claim 1 , wherein determining the first adjustment comprises:
 defining a target for the downhole pressure at a depth in the wellbore as being at least less than one of: (i) a fracture pressure gradient of the formation, and (ii) a pore pressure gradient of the formation; and   setting the first adjustment to effectuate the target for the downhole pressure.   
     
     
         18 . The method of  claim 1 , wherein adjusting, with the control system, the pressure regulation provided by the drilling system comprises at least one of:
 operating, with the control system, a continuous flow apparatus connected to the drillstring to communicate fluid for the pressure regulation into the wellbore through the drillstring in the non-drilling state, and operating, with the control system, at least one choke in fluid communication with flow out of the wellbore in the closed loop to adjust a surface backpressure;   operating, with the control system, at least one choke and a mud pump of the drilling system to pump fluid for the pressure regulation into a riser via a booster line connected to the riser above a wellhead;   operating, with the control system, a booster line connected to the riser above the wellhead to provide a column of fluid for the pressure regulation into the riser; and   operating, with the control system, a subsea pump and a subsea choke to pump fluid for the pressure regulation into the riser via a booster line connected to the riser above the wellhead.   
     
     
         19 . The method of  claim 1 , further comprising monitoring, with the control system, one or more of: a position of at least one choke in fluid communication with flow out of the wellbore in the closed loop; a measurement of a surface backpressure of the drilling system upstream of the at least one choke; a current depth of the drillstring in the wellbore; a current position of a traveling block connected to the drillstring at a rig of the drilling system; and a current end-of-pipe condition on the drillstring in the wellbore. 
     
     
         20 . A computerized method used with a drilling system on a drilling vessel in an ocean environment to drill a wellbore in a formation, the drilling system being configured to circulate fluid in a closed loop between a drillstring and the wellbore and being configured to regulate a downhole pressure in the wellbore using pressure regulation of the circulated fluid, the method comprising:
 storing, with a control system, a motion model modelling movement of the drilling vessel in response to influence from one or more environmental characteristics acting on one or more vessel characteristics of the drilling vessel;   obtaining, with the control system, one or more environmental measurements indicative of the influence from the ocean environment on the drilling vessel;   obtaining, with the control system, a bottom hole pressure in the wellbore;   identifying, with the control system, between a drilling state and a non-drilling state of the drilling system, the non-drilling state being indicative of the drillstring being held at the drilling vessel at least during a vessel motion, the vessel motion expected to produce a first piston effect that changes the bottom hole pressure in the wellbore, the drilling state being indicative of the drillstring being moved in a trip in the wellbore;   determining, with the control system in response to identification of the non-drilling state, a first adjustment to the pressure regulation provided by the drilling system by predicting the movement of the drilling vessel using the one or more environmental measurements in the motion model, the first adjustment being configured to maintain the bottom hole pressure; and   counteracting the change to the bottom hole pressure produced by the first piston effect by automatically adjusting, with the control system, the pressure regulation of the wellbore according to the first adjustment.   
     
     
         21 . The method of  claim 20 , wherein the trip is expected to produce a second piston effect that changes the bottom hole pressure in the wellbore; and wherein the method further comprises:
 determining, with the control system in response to an identification of the drilling state, a second adjustment to a surface backpressure for the pressure regulation of the wellbore provided by the drilling system, the second adjustment being configured to maintain the bottom hole pressure; and   counteracting the change to the bottom hole pressure produced by the second piston effect by automatically adjusting, with the control system, the pressure regulation of the wellbore according to the second adjustment.   
     
     
         22 . A programmable storage device having program instructions stored thereon for causing a programmable control device to perform a method of drilling a wellbore with drilling fluid using a drilling system according to  claim 1 . 
     
     
         23 . A computerized system used with a drilling system on a drilling vessel in an ocean environment to drill a wellbore in a formation, the drilling system being configured to circulate fluid in a closed loop between a drillstring and the wellbore and being configured to regulate a downhole pressure in the wellbore using pressure regulation of the circulated fluid, the computerized system comprising a programmable control device being configured to:
 identify between a non-drilling state and a drilling state of the drilling system, the non-drilling state being indicative of the drillstring being held at the drilling vessel at least during a vessel motion, the drillstring held during the vessel motion expected to produce a first piston effect that changes a downhole pressure in the wellbore, the drilling state being indicative of the drillstring being tripped in the wellbore;   determine, in response to identification of the non-drilling state, a first adjustment to the pressure regulation of the wellbore provided by the drilling system, the first adjustment being configured to maintain the downhole pressure in the wellbore; and   automatically adjust the pressure regulation provided by the drilling system according to the first adjustment to counteract the change to the downhole pressure produced by the first piston effect.