Positioning techniques in multi-well environments

Abstract

A method is provided to determine a distance, a direction, or both between an existing first wellbore and at least one sensor module of a drill string within a second wellbore being drilled. The method includes using the at least one sensor module to measure a magnetic field and to generate at least one first signal indicative of the measured magnetic field. The method further includes using the at least one sensor module to gyroscopically measure an azimuth, an inclination, or both of the at least one sensor module and to generate at least one second signal indicative of the measured azimuth, inclination, or both. The method further includes using the at least one first signal and the at least one second signal to calculate a distance between the existing first wellbore and the at least one sensor module, a direction between the existing first wellbore and the at least one sensor module, or both a distance and a direction between the existing first wellbore and the at least one sensor module.

What is claimed is: 
     
         1 . A method to determine a distance, a direction, or both between an existing first wellbore and at least one sensor module of a drill string within a second wellbore being drilled, the method comprising:
 using the at least one sensor module to measure a magnetic field and to generate at least one first signal indicative of the measured magnetic field;   using the at least one sensor module to gyroscopically measure an azimuth, an inclination, or both of the at least one sensor module and to generate at least one second signal indicative of the measured azimuth, inclination, or both; and   using the at least one first signal and the at least one second signal to calculate a distance between the existing first wellbore and the at least one sensor module, a direction between the existing first wellbore and the at least one sensor module, or both a distance and a direction between the existing first wellbore and the at least one sensor module.   
     
     
         2 . The method of  claim 1 , further comprising controlling the drill string using the calculated distance, the calculated direction, or both. 
     
     
         3 . The method of  claim 2 , wherein the drill string comprises a rotary steerable drilling tool. 
     
     
         4 . The method of  claim 2 , wherein controlling the drill string comprises generating at least one control signal in response to the calculated distance, the calculated direction, or both, and transmitting the at least one control signal to a steering mechanism of the drill string. 
     
     
         5 . The method of  claim 1 , wherein using the at least one sensor module to measure the magnetic field comprises using the at least one sensor module to measure an axial field component of the magnetic field along a longitudinal axis of the second wellbore. 
     
     
         6 . The method of  claim 5 , wherein the axial field component is measured during drilling of the second wellbore. 
     
     
         7 . The method of  claim 1 , further comprising:
 using the azimuth, the inclination, or both with a model of the Earth's magnetic field to estimate a contribution from the Earth's magnetic field to the measured magnetic field;   subtracting the contribution from the measured magnetic field to calculate a corrected measured magnetic field; and   using the corrected measured magnetic field to calculate at least one of the distance and the direction between the existing first wellbore and the at least one sensor module.   
     
     
         8 . A method for controlling a drill string spaced from an existing first wellbore, the drill string drilling a second wellbore, the method comprising:
 receiving at least one first signal indicative of a magnetic field measured by at least a first sensor module of the drill string;   receiving at least one second signal indicative of an azimuth, an inclination, or both measured by at least a second sensor module of the drill string, the second sensor module comprising at least one gyroscopic sensor;   calculating a distance between the existing first wellbore and the first sensor module, a direction between the existing first wellbore and the first sensor module, or both a distance and a direction between the existing first wellbore and the first sensor module; and   generating, in response to at least one of the calculated distance and the calculated direction, at least one control signal to be transmitted to a steering mechanism of the drill string.   
     
     
         9 . The method of  claim 8 , wherein the steering mechanism comprises a rotary steerable tool. 
     
     
         10 . The method of  claim 8 , further comprising transmitting the at least one control signal to a steering mechanism of the drill string. 
     
     
         11 . The method of  claim 8 , wherein the at least one first signal is indicative of a measured axial field component of the magnetic field along a longitudinal axis of the second wellbore. 
     
     
         12 . The method of  claim 11 , wherein the axial field component is measured during drilling of the second wellbore. 
     
     
         13 . The method of  claim 8 , further comprising:
 using the azimuth, the inclination, or both with a model of the Earth's magnetic field to estimate a contribution from the Earth's magnetic field to the measured magnetic field;   subtracting the contribution from the measured magnetic field to calculate a corrected measured magnetic field; and   using the corrected measured magnetic field to calculate at least one of the distance and the direction between the existing first wellbore and the first sensor module.   
     
     
         14 . A method for using a drilling tool to drill a second wellbore along a desired path substantially parallel to a first wellbore, the drilling tool comprising a steering mechanism, the method comprising:
 (a) defining a first target position along a desired path of the second wellbore, the first target position spaced from a current position of the drilling tool by a first distance;   (b) performing magnetic ranging measurements and gyroscopic measurements of an azimuth, an inclination, or both of the drilling tool and using the magnetic ranging measurements and the gyroscopic measurements to determine a second distance between the current position of the drilling tool and the first wellbore;   (c) calculating a third distance between the first wellbore and the desired path of the second wellbore;   (d) calculating a target sightline angle with respect to the desired path of the second wellbore;   (e) measuring a tool path direction with respect to the first wellbore;   (f) calculating a steering angle;   (g) transmitting a steering signal to the steering mechanism to control the steering mechanism to adjust a tool path direction of the second wellbore by the steering angle; and   (h) actuating the steering mechanism to move the drilling tool to a revised current position.   
     
     
         15 . The method of  claim 14 , further comprising defining a second target position along the desired path of the second wellbore, the second target position spaced from the revised current position of the drilling tool by the first distance, and iterating steps (b)-(h). 
     
     
         16 . The method of  claim 14 , wherein the drilling tool comprises a first sensor module and a second sensor module, and the magnetic ranging measurements and the gyroscopic measurements are made using at least one of the first sensor module and the second sensor module. 
     
     
         17 . The method of  claim 16 , wherein the tool path direction is measured using at least one of the first sensor module and the second sensor module. 
     
     
         18 . The method of  claim 14 , wherein calculating the third distance, calculating the target sightline angle, and calculating the steering angle are performed by a computer processor. 
     
     
         19 . A method for gyro-assisted magnetic ranging relative to a first wellbore using a rotary steerable drilling tool to drill a second wellbore, the method comprising:
 (a) steering the drilling tool to a position at which a magnetic field from an electromagnet in the first wellbore can be detected by at least one sensor module of the drilling tool;   (b) performing a multi-station analysis to detect magnetic biases from the drilling tool;   (c) monitoring measurements from a longitudinal axis magnetometer of the at least one sensor module as a drill path of the second wellbore approaches the electromagnet in the first wellbore;   (d) making stationary magnetic ranging survey measurements using the at least one sensor module;   (e) moving the electromagnet to a different position within the first wellbore;   (f) making magnetic ranging measurements and further drilling the second wellbore in a trajectory that is substantially parallel to the first wellbore;   (g) making stationary gyro survey measurements using the at least one sensor module and using the stationary gyro survey measurements to determine a separation and angle of approach of the at least one sensor module to the first wellbore; and   (h) using the stationary gyro survey measurements to compute drilling commands to be performed by the drilling tool and continuing to drill the second wellbore.   
     
     
         20 . The method of  claim 19 , further comprising: (i) iterating steps (f)-(h) until the magnetic field from the electromagnet is again detected. 
     
     
         21 . The method of  claim 20 , further comprising: (j) iterating steps (c)-(h) for drilling subsequent sections of the second wellbore. 
     
     
         22 . The method of  claim 19 , wherein performing the multi-station analysis occurs concurrently with steering the drilling tool. 
     
     
         23 . The method of  claim 19 , wherein monitoring the measurements comprises determining a slant range and a direction of the at least one sensor module with respect to the electromagnet. 
     
     
         24 . The method of  claim 19 , wherein determining the slant range and the direction comprises using the detected magnetic biases. 
     
     
         25 . The method of  claim 19 , wherein making stationary magnetic ranging survey measurements comprises halting drilling of the second wellbore upon the at least one sensor module reaching a predetermined location with respect to the electromagnet. 
     
     
         26 . The method of  claim 19 , wherein making stationary magnetic ranging survey measurements comprises using the detected magnetic biases to correct the stationary magnetic ranging survey measurements.