Downhole electromagnetic telemetry receiver

A method for transmitting data from a downhole tool in a wellbore to a surface location, comprising:

• running a downhole tool into a first wellbore;
• measuring a property using the downhole tool in the first wellbore;
• generating a digital frame, using the downhole tool, wherein the digital frame includes information corresponding to the property;
• encoding the digital frame to superpose the information on a carrier signal;
• converting the carrier signal to a voltage differential that is generated across an insulation layer in the downhole tool, wherein the voltage differential causes a current to flow through a subterranean formation and into a casing in a second wellbore;
• and
• detecting a magnetic flux generated by the current flowing through the casing in the second wellbore using a sensor that is positioned in a bore defined by the casing, in the casing, in a casing shoe that is coupled to the casing, outside of the casing, or outside of the casing shoe.

A method for transmitting data from a downhole tool in a wellbore to a surface location, comprising:

• running a downhole tool into a first wellbore;
• measuring a property using the downhole tool in the first wellbore;
• generating a digital frame, using the downhole tool, wherein the digital frame includes information corresponding to the property;
• encoding the digital frame to superpose the information on a carrier signal;
• converting the carrier signal to a voltage differential that is generated across an insulation layer in the downhole tool, wherein the voltage differential causes a current to flow through a subterranean formation;
• and
• detecting a magnetic flux generated by the current using a sensor that is positioned in a second wellbore that deviates from the first wellbore.

A method for transmitting data from a downhole tool in a main wellbore to a surface location, comprising:

• running a downhole tool into a first wellbore having a first casing positioned therein;
• measuring a property using the downhole tool in the first wellbore;
• generating a digital frame, using the downhole tool, wherein the digital frame includes information corresponding to the property;
• encoding the digital frame to superpose the information on a carrier signal;
• converting the carrier signal to a voltage differential that is generated across an insulation layer in the downhole tool, wherein the voltage differential causes a current to flow through a subterranean formation and into a second casing in a second wellbore;
• detecting a magnetic flux generated by the current flowing through the second casing using a sensor that is positioned at least partially within or at least partially around the second casing;
• transmitting data detected by the sensor to a receiver positioned in or around the first casing in the first wellbore;
• and
• transmitting the data from the receiver to a computer at a surface location using a cable positioned radially-outward from the first casing in the first wellbore.

A system for transmitting data from a downhole tool in a wellbore to a surface location, comprising:

• a downhole tool configured to:
• measure a property in a wellbore;
• generate a digital frame including information corresponding to the property;
• encode the digital frame to superpose the information on a carrier signal;
• and
• convert the carrier signal to a voltage differential that is generated across an insulation layer in the downhole tool, wherein the voltage differential causes a current to flow through a subterranean formation and into a casing above the downhole tool;
• and
• a sensor positioned at least partially within or at least partially around the casing, wherein the sensor is configured to detect a magnetic flux generated by the current flowing through the casing.