Wellbore communication system

A method of providing downhole information from a downhole evaluation tool located in a wellbore to a surface unit, the wellbore formed by advancing a drilling tool into the earth, the method comprising:

• positioning the downhole evaluation tool in the wellbore, the downhole evaluation tool having an electromagnetic telemetry system adapted to communicate via an electromagnetic field with the surface unit, wherein the electromagnetic telemetry system comprises a pair of collars matingly connected with a non-conductive insulation coating therebetween, the non-conductive insulating coating defining a gap, and wherein the electromagnetic telemetry system further comprises a non-conductive insulation member extending across the gap about one of an inner surface of the collars, an outer surface of the collars and combinations thereof, the insulation member conforming to the shape thereof;
• measuring downhole data using sensors positioned in the downhole tool;
• storing the downhole data in a memory unit positioned in the downhole tool;
• and
• transmitting at least a portion of the downhole data to the surface via the electromagnetic field.

A method of constructing a downhole tool, comprising:

• providing an upper collar member;
• providing a lower collar member;
• applying a non-conductive insulating coating to one of a connector on the upper collar member, a connector on the lower collar member and combinations thereof;
• connecting the upper collar member to the lower collar member such that the non-conductive insulating coating defines a gap;
• and
• applying a non-conductive insulating member about one of the inner surface of the upper and lower collar members, the outer surface of the upper and lower collar members, and combinations thereof, wherein the non-conductive insulating member extends across the gap.

A gap collar for an electromagnetic communication unit of a downhole tool positioned in a wellbore, comprising:

• a first collar having a first end connector;
• a second collar having a second end connector;
• means for electrically insulating the first end connector from the second end connector;
• means for insulating the outer surface of the first and second collar.