Abstract: A method can include determining that measured outputs of first and second sensors are correlated, calculating a second sensor output based on the measured first sensor output, and in response to a loss of the measured second sensor output or a failure of an item of equipment, controlling a drilling operation based on the calculated second sensor output. A control system can include a statistical model that determines a correlation between measured outputs of first and second sensors, and calculates a calculated second sensor output based on the measured first sensor output, a controller that controls the drilling operation, and a hydraulics model that determines how the drilling operation should be controlled to achieve a desired objective, and determines, based on the calculated second sensor output, how the drilling operation should be controlled, in response to a loss of the measured second sensor output or an equipment failure.

Abstract: Control of a drilling system drilling a wellbore is improved using a hydraulic model corrected for pressure losses. A surface backpressure of the outlet and a standpipe pressure of the inlet are measured with sensors in the system. An estimate of the standpipe pressure is calculated based integrating from the measured surface backpressure back to the inlet in the hydraulics model. The pressure loss increment in the hydraulics model is calculated based on a difference between the measured and estimated standpipe pressures. Meanwhile, a parameter in the drilling system is monitored during drilling so the parameter can be adjusted at least partially based on the hydraulics model corrected for the pressure loss.

Abstract: A system and method are used in drilling a borehole in a formation. A trip to move a drillstring in the borehole is identified, where the trip is expected to produce a piston effect that changes a downhole pressure of the fluid in the borehole. A peak speed to move the drillstring in the borehole is calculated for the trip, and adjustments to a surface backpressure of the drilling system is calculated for the trip at the calculated peak speed to keep the downhole pressure within a tolerance of the formation. The drillstring is moved in the trip according to the calculated peak speed, and the downhole pressure change produced by the piston effect is counteracted by automatically adjusting the surface backpressure according to the calculated adjustments.

Abstract: A system and method are used in drilling a borehole in a formation. A trip to move a drillstring in the borehole is identified, where the trip is expected to produce a piston effect that changes a downhole pressure of the fluid in the borehole. A peak speed to move the drillstring in the borehole is calculated for the trip, and adjustments to a surface backpressure of the drilling system is calculated for the trip at the calculated peak speed to keep the downhole pressure within a tolerance of the formation. The drillstring is moved in the trip according to the calculated peak speed, and the downhole pressure change produced by the piston effect is counteracted by automatically adjusting the surface backpressure according to the calculated adjustments.

Abstract: Control of a drilling system drilling a wellbore is improved using a hydraulic model corrected for pressure losses. A surface backpressure of the outlet and a standpipe pressure of the inlet are measured with sensors in the system. An estimate of the standpipe pressure is calculated based integrating from the measured surface backpressure back to the inlet in the hydraulics model. The pressure loss increment in the hydraulics model is calculated based on a difference between the measured and estimated standpipe pressures. Meanwhile, a parameter in the drilling system is monitored during drilling so the parameter can be adjusted at least partially based on the hydraulics model corrected for the pressure loss.

Abstract: A computerized control is used in controlling a choke when drilling a wellbore with a drilling system. The computerized control obtains a measured value of a parameter in the drilling system and controls the parameter in the drilling system using the choke. The computerized control obtains indications of an error between a set point of the parameter and the measured value of the parameter in the drilling system, a flow coefficient character of the choke, and a current position of the choke. Based on these indications, the computerized control then determines a position adjustment for the choke and adjusting the parameter in the drilling system by applying the position adjustment to the choke.

Abstract: A computerized control is used in controlling a choke when drilling a wellbore with a drilling system. The computerized control obtains a measured value of a parameter in the drilling system and controls the parameter in the drilling system using the choke. The computerized control obtains indications of an error between a set point of the parameter and the measured value of the parameter in the drilling system, a flow coefficient character of the choke, and a current position of the choke. Based on these indications, the computerized control then determines a position adjustment for the choke and adjusting the parameter in the drilling system by applying the position adjustment to the choke.