Real-time ranging while drilling

Abstract

Methods and related systems for drilling a subterranean wellbore includes rotating a bottomhole assembly (BHA) to drill the wellbore. The BHA includes a cutting tool and at least one sensor. The at least one sensor is configured to make measurements while drilling. These measurements are processed to compute a magnetic field profile, which is further processed to identify and characterize a signature or pattern in the magnetic field profile that is representative of a target well proximate to the wellbore being drilled. At least one of a distance or a direction to the target well can be computed based on characteristics of the signature or pattern in the magnetic field profile. The computed distance or direction to the target well can be used to control the direction of drilling of the wellbore.

What is claimed is: 
     
         1 . A method for drilling a subterranean wellbore, the method comprising:
 drilling the wellbore by rotating a bottomhole assembly (BHA), the BHA including a cutting tool and at least one sensor;   acquiring measurements with the at least one sensor while drilling the wellbore;   computing a magnetic field profile by processing the measurements acquired with the at least one sensor;   processing the magnetic field profile to identify and characterize a signature or pattern in the magnetic field profile that is representative of a target well proximate to the wellbore being drilled; and   computing at least one of a distance to the target well or a direction to the target well based on characteristics of the signature or pattern in the magnetic field profile.   
     
     
         2 . The method of  claim 1 , wherein:
 the at least one sensor comprises a triaxial accelerometer set and a triaxial magnetometer set.   
     
     
         3 . The method of  claim 2 , wherein:
 the at least one sensor further comprises at least one gyroscope.   
     
     
         4 . The method of  claim 1 , wherein:
 the signature or pattern in the magnetic field profile that is representative of the target well comprises a sinusoidal signature or pattern.   
     
     
         5 . The method of  claim 4 , wherein:
 the distance to the target well is based on magnitude of the sinusoidal signature or pattern in the magnetic field profile.   
     
     
         6 . The method of  claim 4 , wherein:
 direction to the target well is based on wavelength of the sinusoidal signature or pattern in the magnetic field profile.   
     
     
         7 . The method of  claim 1 , wherein:
 the signature or pattern in the magnetic field profile that is representative of the target well is defined by structural features of the target well.   
     
     
         8 . The method of  claim 7 , wherein:
 the structural features of the target well include the body and shoulders of casing joints or liner joints.   
     
     
         9 . The method of  claim 1 , wherein:
 the magnetic field profile is computed from the measurements of the at least one sensor at survey points of varying measured depth in the wellbore being drilled.   
     
     
         10 . The method of  claim 1 , wherein:
 the magnetic field profile includes a plurality of measured magnetic vectors as a function of measured depth along the wellbore axis.   
     
     
         11 . The method of  claim 10 , wherein:
 each measured magnetic vector of the plurality of measured magnetic vectors is represented by a magnitude and an orientation, wherein the magnitude is computed by subtracting contribution of the earth magnetic field from readings of a tri-axial magnetometer set, and wherein the orientation is determined from synchronous readings of a tri-axial accelerometer set.   
     
     
         12 . The method of  claim 1 , further comprising:
 using the computed distance or direction to the target well to control the direction of drilling of the wellbore.   
     
     
         13 . The method of  claim 12 , wherein:
 the direction of drilling of the wellbore is controlled to follow, intercept or avoid the target well.   
     
     
         14 . The method of  claim 12 , wherein:
 the BHA further comprises a rotary steerable drilling tool with a steering element; and   the direction of drilling of the wellbore is adjusted based on the computed distance or direction to the target well and the direction of drilling of the wellbore is controlled by actuation of the steering element of the rotary steerable tool to change direction of drilling.   
     
     
         15 . A system for drilling a subterranean wellbore, the system comprising:
 a bottomhole assembly (BHA) configured to drill the wellbore, wherein the BHA includes a cutting tool and at least one sensor, wherein the at least one sensor is configured to acquire measurements while drilling the wellbore; and   a processor or controller configured to perform operations that include:
 computing a magnetic field profile by processing the measurements acquired with the at least one sensor; 
 processes the magnetic field profile to identify and characterize a signature or pattern in the magnetic field profile that is representative of a target well proximate to the wellbore being drilled; and 
 computing at least one of a distance to the target well or a direction to the target well based on characteristics of the signature or pattern in the magnetic field profile. 
   
     
     
         16 . The system of  claim 15 , wherein:
 the at least one sensor comprises a triaxial accelerometer set and a triaxial magnetometer set.   
     
     
         17 . The method of  claim 15 , wherein:
 the at least one sensor further comprises at least one gyroscope.   
     
     
         18 . The system of  claim 15 , wherein:
 the signature or pattern in the magnetic field profile that is representative of the target well comprises a sinusoidal signature or pattern.   
     
     
         19 . The system of  claim 18 , wherein:
 the distance to the target well is based on magnitude of the sinusoidal signature or pattern in the magnetic field profile.   
     
     
         20 . The system of  claim 18 , wherein:
 direction to the target well is based on wavelength of the sinusoidal signature or pattern in the magnetic field profile.