Closed system. Perforation under drawdown in horizontal well using main and backup hydraulic impact head with delayed actuating time, packer and circulating valve, opened under certain pressure. Use of the spacer (perforator frame without charge between impact head and charged perforator) is required for safe operations.

Production tubing
Shortened connection pipe
Packer
Circulating valve
Shaped charge perforator
Hydraulic impact head with time delay