Drilling system and method using dynamically determined drilling window

Abstract

Control of a drilling system drilling a wellbore is improved using a hydraulics 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.

1 . A method, implemented by a computerized control, for a closed-loop drilling system, the closed-loop drilling system having: a bottom hole assembly for drilling a wellbore in a formation, at least one pump for pumping drilling fluid at an inlet, and at least one choke for choking the drilling fluid at an outlet, the method comprising:
 calculating normal compaction trendlines for intervals of the wellbore to be drilled in the formation;   drilling the wellbore in a drilling operation using the closed-loop drilling system while monitoring inflow at the inlet, monitoring outflow at the outlet, and measuring surface backpressure at the outlet; and   while drilling in the drilling operation, repeatedly:
 defining a dynamic drilling window for the interval of the wellbore being drilled in the formation by using the normal compaction trendline for the interval; 
 estimating a lower boundary for the interval of the dynamic drilling window as an estimated lower boundary by reducing the surface backpressure while simultaneously monitoring the inflow and the outflow until a signature influx is measured; 
 estimating an upper boundary for the interval of the dynamic drilling window as an estimated upper boundary by increasing the surface backpressure while simultaneously monitoring the inflow and the outflow until a signature loss is measured; 
 updating the normal compaction trendline for the interval in the formation ahead of the bottom hole assembly based on the estimated upper and lower boundaries; and 
 adjusting a parameter in the drilling operation to drill at a target bottom hole pressure within the dynamic drilling window. 
   
     
     
         2 . The method of  claim 1 , wherein reducing the surface backpressure comprises stepwise or incrementally reducing the surface backpressure; and wherein increasing the surface backpressure comprises stepwise or incrementally increasing the surface backpressure. 
     
     
         3 . The method of  claim 1 , wherein drilling the wellbore in the drilling operation comprises using a hydraulics model of the closed-loop drilling system drilling the wellbore. 
     
     
         4 . The method of  claim 3 , wherein using the hydraulics model of the closed-loop drilling system drilling the wellbore comprises using one or more of: a trajectory of the wellbore, a measured depth of the wellbore, an inclination of the wellbore, an azimuth of the wellbore, a geometric parameter of the closed-loop drilling system, a geometry of an annulus of the wellbore, a geometry of a drillstring, a fluid property of the drilling fluid, a density of the drilling fluid, a rheology of the drilling fluid, a thermal property for the drilling fluid, a property of the formation, a thermal property of the drillstring, a temperature of the formation in the wellbore, an empirical formula for local pressure loss from a component of the closed-loop drilling system, operational data obtained during drilling, flow rate, rotation rate (RPM), bit depth, and fluid input temperature. 
     
     
         5 . The method of  claim 1 , wherein measuring the surface backpressure at the outlet comprises measuring a value of the surface backpressure with a sensor disposed upstream of the at least one choke. 
     
     
         6 . The method of  claim 5 , wherein the sensor is selected from the group consisting of a pressure transducer, a pressure gauge, a diaphragm-based pressure transducer, and a strain gauge-based pressure transducer, an analog device, and an electronic device. 
     
     
         7 . The method of  claim 1 , further comprising measuring a pressure-while-drilling value indicative of a measured bottom hole pressure at the bottom hole assembly; and wherein adjusting the parameter in the drilling operation comprising adjusting the surface backpressure in the drilling operation to bring the measured bottom hole pressure toward the target bottom hole pressure in the dynamic drilling window. 
     
     
         8 . The method of  claim 7 , wherein measuring the pressure-while-drilling value comprises reading pressure values conducted at full circulation rate by using a Pressure While Drilling (PWD) tool on the bottom hole assembly while estimating the dynamic drilling window. 
     
     
         9 . The method of  claim 1 , further comprising estimating a bottom hole pressure at the bottom hole assembly as an estimated bottom hole pressure; and wherein adjusting the parameter in the drilling operation comprising adjusting the surface backpressure in the drilling operation to bring the estimated bottom hole pressure toward the target bottom hole pressure in the dynamic drilling window. 
     
     
         10 . The method of  claim 1 , wherein estimating the lower boundary comprises estimating a pore pressure gradient by determining, from the signature influx, a pressure value as an estimated pressure value indicative of a current bottom hole pressure, at a current depth of the bottom hole assembly, being equal to or less than a pore pressure. 
     
     
         11 . The method of  claim 10 , wherein estimating the lower boundary further comprises correlating monitored surface parameters including gas-at-surface, flowline pressure, and difference in the inflow and the outflow to evaluate the pore pressure at the current depth. 
     
     
         12 . The method of  claim 10 , wherein updating the normal compaction trendline for the formation ahead of the bottom hole assembly comprises substituting at least the estimated pressure value indicative of the pore pressure back into a calculation of the normal compaction trendline as a function of a measured pressure variable in the closed-loop drilling system, an empirical pressure variable for the closed-loop drilling system, an overburden stress variable, and a drilling exponent variable. 
     
     
         13 . The method of  claim 1 , wherein calculating the normal compaction trendline comprises using a calculation of the normal compaction trendline as a function of measured pressures in the closed-loop drilling system, empirical pressures, overburden stress, and drilling exponent. 
     
     
         14 . The method of  claim 1 , wherein estimating the upper boundary comprises estimating a formation pressure gradient by determining, from the signature loss, a pressure value indicative of a current bottom hole pressure being equal to or greater than a fracture pressure. 
     
     
         15 . The method of  claim 1 , wherein to adjust the parameter in the drilling operation, the method comprises adjusting the at least one choke in communication with the drilling fluid from the wellbore. 
     
     
         16 . The method of  claim 1 , wherein adjusting the parameter in the drilling operation comprises adjusting at least one of: a flow rate of the drilling fluid out of the wellbore using the at least one choke, a pressure of flow of the drilling fluid out of the wellbore using the at least one choke, a current value of the surface backpressure in the wellbore, a mass flow rate of the drilling fluid out of the wellbore, a pressure during make-up of a drillpipe connection while drilling with the closed-loop drilling system, a pressure during a loss detected while drilling with the closed-loop drilling system, or a flow rate during a kick detected while drilling with the closed-loop drilling system. 
     
     
         17 . The method of  claim 1 , further comprising determining an imbalance between the outflow and the inflow as a determined imbalance, wherein adjusting the parameter in the drilling operation is based on the determined imbalance. 
     
     
         18 . The method of  claim 1 , wherein measuring the outflow of the drilling fluid from the wellbore comprise measuring the outflow with a flowmeter in communication with the outflow; and wherein measuring the inflow of the drilling fluid into the wellbore comprise measuring the inflow with a flowmeter in communication with the inflow. 
     
     
         19 . 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 . 
     
     
         20 . A drilling system for drilling a wellbore in a formation with drilling fluid, the drilling system comprising:
 at least one pump disposed at an inlet of the drilling system and operable to pump the drilling fluid into the wellbore when drilling the wellbore with the drilling system;   at least one choke disposed at an outlet of the drilling system and operable to adjust flow of the drilling fluid from the wellbore when drilling the wellbore with the drilling system;   storage storing a hydraulics model of the drilling system drilling the wellbore;   a sensor configured to measure a value of surface backpressure upstream of the at least one choke; and   a programmable control device communicatively coupled to the storage and the sensor, the programmable control device being configured to:
 calculate normal compaction trendlines for intervals of the wellbore to be drilled in the formation; 
 monitor inflow at the inlet, outflow at the outlet, and the value of the surface backpressure during drilling of the wellbore in a drilling operation using the drilling system; and 
 while drilling in the drilling operation, repeatedly:
 define a dynamic drilling window for the interval of the wellbore being drilled in the formation by using the normal compaction trendline for the interval; 
 estimate a lower boundary for the interval of the dynamic drilling window as an estimated lower boundary by reducing the surface backpressure while simultaneously monitoring the inflow and the outflow until a signature influx is measured; 
 estimate an upper boundary for the interval of the dynamic drilling window as an estimated upper boundary by increasing the surface backpressure while simultaneously monitoring the inflow and the outflow until a signature loss is measured; 
 update the normal compaction trendline for the interval in the formation ahead of a bottom hole assembly based on the estimated upper and lower boundaries; and 
 adjust a parameter in the drilling operation to drill at a target bottom hole pressure within the dynamic drilling window.