Electromagnetic wellbore telemetry system for tubular strings

An electromagnetic wellbore telemetry system, comprising:

• a plurality of coaxial transmission lines coupled together in the form of a tubular string for an oilfield operation, each coaxial transmission line comprising:
• an outer conductive pipe;
• an inner conductive pipe disposed coaxially inside an axial bore of the outer conductive pipe;
• a first electrical contact having a first contact face disposed at a first end of the inner conductive pipe;
• a second electrical contact having a second contact face disposed at a second end of the inner conductive pipe, wherein at least one of the first and second contact faces includes at least one slot;
• and
• an insulator disposed between the outer conductive pipe and the inner conductive pipe.

A method of providing communication between a downhole tool in a wellbore penetrating an underground formation and a surface unit, comprising:

• connecting a plurality of coaxial transmission lines together, each coaxial transmission line comprising an outer conductive pipe, an inner conductive pipe disposed coaxially inside an axial bore of the outer conductive pipe, a first electrical contact having a first contact face disposed at a first end of the inner conductive pipe, a second electrical contact having a second contact face disposed at a second end of the inner conductive pipe, and an insulator disposed between the outer conductive pipe and the inner conductive pipe, wherein at least one of the first and second contact faces includes at least one slot;
• coupling the plurality of coaxial transmission lines to the downhole tool;
• and
• establishing communication between the coaxial transmission lines and the surface unit.