Method for drilling wells in close relationship using magnetic ranging while drilling

A method of drilling a plurality of wells, comprising:

• drilling a first well to a target depth with a first drill string;
• leaving the first drill string in the first well;
• drilling a second well with a second drill string configured for magnetic ranging while drilling, 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.

A method of drilling a plurality of wells in a formation in specified orientations relative to one another, comprising:

• producing an electrical current on a bottom hole assembly having an insulated gap, wherein the bottom hole assembly is positioned in a first well;
• introducing the electrical current to a previously positioned drill string via the formation, wherein the previously positioned drill string is in a second well;
• measuring a secondary magnetic field produced by the electrical current on the drill string with the bottom hole assembly;
• and
• calculating a relative position of the bottom hole assembly with respect to the drill string based on values of the electrical current and the secondary magnetic field.