Tubing conveyed selective fired perforating systems

A select fire sub apparatus, comprising:

• a cylindrical housing having first and second ends;
• said housing having first and second axially extending chambers defined therein communicated with said first and second ends, respectively, and extending axially inward toward each other, said first and second chambers terminating in blind ends separated by a wall of said housing;
• said housing having an actuating pressure supply passage defined therein and extending laterally into said wall between said blind ends of said first and second chambers;
• said first end of said housing including means for communicating said first chamber with a pressure responsive firing head associated with a perforating gun;
• and
• said second chamber including means for receiving an explosive charge for perforating said wall of said housing and thereby communicating said pressure supply passage with said first chamber.

A method of perforating multiple zones in a well, comprising:

• (a) running into said well a tubing conveyed multiple zone perforating string including:
• a tubing string;
• at least a first and a second perforating gun carried by said tubing string;
• and
• at least a first and a second pressure actuated firing head associated with said first and second perforating guns, respectively;
• (b) applying actuating fluid pressure from a source of actuating fluid pressure to said first firing head;
• (c) isolating said second firing head from said source of said actuating fluid pressure during step (b);
• (d) after step (b), firing said first perforating gun and;
• (e) in response to firing said first perforating gun in step (d), communicating said second firing head with said source of said actuating fluid pressure.