Patent ID: 8912915
Filing Date: 2014-12-16
Classification: E21B,G01V

Abstract:
1. A drilling method that comprises: providing at least one reference well having an array of two or more reference nodes, generating or detecting a magnetic field beacon by each of two or more reference nodes in said array to determine a position of a bottomhole assembly in a second well, wherein finding said position of the bottomhole assembly based at least in part on determining distances between the bottomhole assembly and multiple reference nodes in the array; selecting one of the reference nodes in said array with which to establish electromagnetic communication with the bottomhole assembly; electromagnetically communicating information between the selected reference node and the bottomhole assembly; steering the bottomhole assembly based at least in part on said position; and changing which of the reference nodes in said array is selected for communications between a surface facility and the bottomhole assembly as drilling by the bottomhole assembly progresses.