Automated directional drilling system and method using steerable drilling motors

Abstract

A method for drilling a well includes orienting a steerable drilling motor at a selected toolface angle. The steerable drilling motor is connected by a drill string to a surface drilling location. The drill string is automatically rotated at the surface location in a first direction for a first predetermined time interval.

What is claimed is: 
     
         1 . A method for drilling a well, comprising:
 orienting a steerable drilling motor at a selected toolface angle, the steerable drilling motor being connected by a drill string to a surface drilling location; and   automatically rotating the drill string at the surface location in a first direction for a first predetermined time interval:   
     
     
         2 . The method of  claim 1  further comprising automatically reversing direction of rotation of the drill string at the surface location at the end of the first predetermined time interval, the reversed rotation continuing for a second predetermined time interval. 
     
     
         3 . The method of  claim 2  further comprising adjusting at least one of the first and second predetermined time intervals to move a neutral point by a selected longitudinal distance along the drill string. 
     
     
         4 . The method of  claim 2  wherein the first and second predetermined time intervals are adjusted to maintain a value of at least one drilling operating parameter. 
     
     
         5 . The method of  claim 4  wherein the at least one drilling operating parameter comprises a rate of penetration of the drill string into subsurface formations and a differential pressure across the steerable drilling motor. 
     
     
         6 . The method of  claim 1  further comprising measuring torque applied to the drill string at the surface location and automatically rotating the drill string in the first direction until a first measured torque value is reached. 
     
     
         7 . The method of  claim 6  further comprising automatically reversing rotation of the drill string at the first location and continuing rotation in the reversed direction until a second measured torque value is reached. 
     
     
         8 . The method of  claim 7  further comprising switching selection of direction of rotation of the drill string at the surface location between the first and second measured torque values and the first and second predetermined time intervals. 
     
     
         9 . The method of  claim 1  further comprising measuring torque applied to the drill string during rotation of the drill string, determining a time at which the measured torque reaches a first predetermined value and adjusting the first predetermined time interval such that subsequent rotation of the drill string in the first direction for the adjusted first predetermined time interval results in the first predetermined value of torque being applied to the drill string. 
     
     
         10 . The method of  claim 9  further comprising automatically reversing direction of rotation of the drill string at the surface location at the end of the first predetermined time interval, measuring torque applied to the drill string, determining a time at which the measured torque reaches a second predetermined value and adjusting the second predetermined time interval such that subsequent rotation of the drill string in the second direction for the adjusted second predetermined time interval results in the second predetermined value of torque being applied to the drill string. 
     
     
         11 . A system for drilling a well, comprising:
 a steerable drilling motor disposed within a drill string extending into the well;   a surface motor for rotating the drill string from the surface;   a drill string rotation controller in signal communication with the surface motor and operable to cause the surface motor to rotate in a first direction and in a second direction opposite to the first direction;   a timer functionally coupled to the drill string rotation controller, the timer operable to cause rotation of the surface motor in the first direction for a first predetermined time interval.   
     
     
         12 . The system of  claim 11  wherein the drill string rotation controller is operable at the end of the first predetermined time interval to cause the surface motor to reverse rotation of the drill string for a second predetermined time interval. 
     
     
         13 . The system of  claim 12  wherein the drill string rotation controller is operable to automatically reverse rotation of the surface motor at the end of the second predetermined time interval and to repeating rotating the motor in the first direction for the first predetermined time interval. 
     
     
         14 . A method for drilling a well, comprising:
 orienting a steerable drilling motor at a selected toolface angle, the steerable drilling motor being connected by a drill string to a surface drilling location;   automatically rotating the drill string at the surface location in a first direction until a first predetermined measured torque value is reached; and   automatically reversing rotation of the drill string opposite to the first direction until a second predetermined measured torque value is reached, the first and second predetermined torque values initially set by a model.   
     
     
         15 . The method of  claim 14  wherein the initial predetermined first and second torque values are selected to produce a predetermined differential pressure of drilling fluid through the steerable drilling motor and a predetermined weight applied to a drill bit. 
     
     
         16 . The method of  claim 14  further comprising automatically controlling a rate of release of the drill string into the wellbore to optimize a weight applied to a drill bit at a bottom end of the drill string. 
     
     
         17 . The method of  claim 14  further comprising optimizing a rate of release of the drill string based on measurements of at least one of drilling fluid pressure, hookload, and toolface orientation. 
     
     
         18 . The method of  claim 17  wherein the model comprises an empirical model. 
     
     
         19 . The method of  claim 17  wherein the initial model comprises learning software. 
     
     
         20 . The method of  claim 17  further comprising adjusting the initially set first and second selected torque values based on measured drilling fluid pressure.