Permanently emplaced electromagnetic system and method for measuring formation resistivity adjacent to and between wells

A method for determining characteristics of geologic formations between wellbores, the method comprising:

• activating a first of a plurality of axially spaced transmitters to generate a first magnetic field, the plurality of transmitters disposed about an external surface of a conductive liner at selected depths in a first wellbore;
• detecting a first formation magnetic field induced by the first magnetic field with a first of a plurality of axially spaced receivers, the plurality of receivers disposed about an external surface of a conductive liner at selected depths in a second wellbore;
• detecting the first formation magnetic field induced by the first magnetic field with a second of the plurality of receivers;
• and
• calculating a first amplitude ratio from the first formation magnetic fields detected by the first and second of the plurality of receivers.

A method for determining characteristics of geologic formations between wellbores, the method comprising:

• activating a first transmitter at a first selected depth to generate a first magnetic field, the first transmitter disposed on a drilling tool disposed at a selected depth in a first wellbore;
• detecting a first formation magnetic field induced by the first magnetic field with a first of a plurality of axially spaced receivers, the plurality of receivers disposed about an external surface of a conductive liner at selected depths in a second wellbore;
• detecting the first formation magnetic field induced by the first magnetic field with a second of the plurality of receivers;
• and
• calculating a first amplitude ratio from the first formation magnetic fields detected by the first and second of the plurality of receivers.

A method for telemetering data between wellbores, the method comprising:

• activating a first transmitter to generate a first magnetic field, the first transmitter disposed on a drilling tool disposed in a first wellbore;
• detecting a formation magnetic field induced by the first magnetic field with at least one receiver, the at least one receiver disposed about an external surface of a conductive liner at a selected depth in a second wellbore;
• and
• determining a drilling tool characteristic from the detected formation magnetic field.

A system for determining characteristics of geologic formations between conductively lined wellbores, comprising:

• at least two axially spaced apart electromagnetic transmitters positioned at selected depths in a first wellbore and disposed about an external surface of a conductive liner;
• at least two axially spaced apart electromagnetic receivers positioned at selected depths in a second wellbore and disposed about an external surface of a conductive liner;
• and
• at least one surface control station operatively coupled to the at least two transmitters and the at least two receivers, the at least one surface control station adapted to selectively activate each of the at least two electromagnetic transmitters to generate first magnetic fields and to selectively activate each of the at least two electromagnetic receivers to detect formation magnetic fields induced by the first magnetic fields.

A system for determining characteristics of geologic formations between conductively lined wellbores, comprising:

• a plurality of axially spaced electromagnetic transmitters disposed about an external surface of a conductive liner at selected depths in a first wellbore, the plurality of electromagnetic transmitters adapted to generate first magnetic fields;
• a plurality of axially spaced electromagnetic receivers disposed about an external surface of a conductive liner at selected depths in a second wellbore, the plurality of electromagnetic receivers adapted to detect formation magnetic fields induced by the first magnetic fields;
• means for calculating an amplitude ratio from the detected formation magnetic fields;
• and
• means for determining a characteristic of the geologic formation from the amplitude ratio.

A system for determining characteristics of geologic formations proximate a conductively lined wellbore, comprising:

• a plurality of axially spaced electromagnetic transmitters disposed about an external surface of a conductive liner at selected depths in a wellbore, the plurality of electromagnetic transmitters adapted to generate first magnetic fields;
• a plurality of axially spaced electromagnetic receivers disposed about an external surface of a conductive liner at selected depths in the wellbore, the plurality of electromagnetic receivers adapted to detect formation magnetic fields induced by the first magnetic fields;
• means for calculating an amplitude ratio from the detected formation magnetic fields;
• and
• means for determining a characteristic of the geologic formation from the amplitude ratio.