While-drilling methodology for determining earth formation characteristics and other useful information based upon streaming potential measurements

A method for investigating an earth formation traversed by a hole during drilling operations, the method comprising:

• a) using at least one sensor located in or about the bottom of the hole while drilling to measure streaming potential voltage signals over a period of time;
• and
• b) processing the streaming potential voltage signals to identify an open fracture in the earth formation based upon at least one of the following:
• i) magnitude of a DC component of at least one streaming potential voltage signal;
• ii) change in magnitude of a DC component of at least one streaming potential voltage signal over time;
• iii) magnitude of an AC component of at least one streaming potential voltage signal;
• and
• iv) change in magnitude of an AC component of at least one streaming potential voltage signal over time.