Patent ID: 8827005
Filing Date: 2014-09-09
Classification: E21B

Abstract:
1. A method of drilling a plurality of wells, comprising: drilling a first well to a target depth with a first drill string without a casing; leaving the first drill string in the first well and exciting a current in the first drill string downhole on an outer drill collar; drilling a second well with a second drill string configured for magnetic ranging while drilling and exciting a current in the second drill string, wherein drilling the second well comprises using the first drill string as a target for magnetic ranging while drilling such that the second well is positioned with a specified orientation relative to the first well; leaving the second drill string in the second well; drilling a third well using a drill string and a bottom hole assembly configured for magnetic ranging while drilling, wherein drilling the third well comprises using the second drill string as a target for magnetic ranging while drilling such that the third well is positioned with a specified orientation relative to the second well.