Magnetic ranging while drilling using an electric dipole source and a magnetic field sensor

Abstract

A system and methods for drilling a well in a field having an existing well are provided. Specifically a method of drilling a new well in a field having an existing well includes drilling the new well using a bottom hole assembly (BHA) having a drill collar divided by an insulated gap, generating a current on the drill collar of the BHA while drilling the new well, and measuring from the existing well a magnetic field caused by the current on the drill collar of the BHA. Using measurements of the magnetic field, a relative position of the new well to the existing well may be determined.

What is claimed is: 
     
         1 . A method of drilling a well comprising:
 drilling a second horizontal well above a first horizontal well using a bottom hole assembly (BHA) having a drill collar divided by an insulated gap;   generating a current along the drill collar of the BHA while drilling the second horizontal well to form an electric dipole over the insulated gap, the dipole having a first pole and a second pole;   calculating a magnetic field strength for the electric dipole for a range of locations;   on the existing well, measuring a magnetic field caused by the electric dipole on the drill collar of the BHA;   comparing the calculated magnetic field strength to the measured magnetic field;   determining a position of the new well relative to the existing well based on the comparing of the calculated magnetic field strength to the measured magnetic field; and   adjusting a trajectory of the BHA such that the second horizontal well will be drilled substantially perpendicular to the first horizontal well based on measurements of the magnetic field.   
     
     
         2 . The method of  claim 1 , further comprising locating in the first horizontal well a point of closest approach between the first horizontal well and the second horizontal well based on measurements of the magnetic field. 
     
     
         3 . The method of  claim 2 , further comprising estimating a distance between the first horizontal well and the second horizontal well at the point of closest approach. 
     
     
         4 . The method of  claim 1 , further comprising estimating a distance between the first horizontal well and the second horizontal well based on a change in magnetic flux as the BHA moves toward or away from the first horizontal well. 
     
     
         5 . The method of  claim 1 , wherein the first horizontal well and the second horizontal well are Cross Well Steam Assisted Gravity Drainage (X-SAGD) wells. 
     
     
         6 . The method of  claim 1 , further comprising deploying a wireline magnetometer into the first horizontal well to measure the magnetic field. 
     
     
         7 . The method of  claim 6 , further comprising measuring the magnetic field with the wireline magnetometer in a variety of locations along the first horizontal well. 
     
     
         8 . The method of  claim 1 , further comprising:
 drilling a third horizontal well before drilling the first and second horizontal wells;   
       adjusting a trajectory of the BHA such that the second horizontal well will be drilled substantially perpendicular to the third horizontal well based on measurements of the magnetic field.