Application of negative-pressure perforation technique with multiple igniters over super-long span in offshore oilfields

Pipe strings for existing multi-stage perforation techniques are characterized by complicated structures, low detonation efficiencies, poor reliability, high operation costs and difficulties in their application in negative-pressure perforation. Consequently, applicability of such pipe-strings in offshore oilfields is limited. In this regard, conventional single-stage perforation devices were modified to develop multi-stage perforation devices. Combined with bypassing joints, hydraulic delayed igniter, RTTS packer and other tools, the negative-pressure perforation technique with multiple igniters over super-long span was developed. Through the integral slid sleeve, the multi-stage perforation device can generate negative pressures after detonation of multiple igniters. In this way, all target intervals can be perforated in one single trip under negative pressure to satisfy demands related to perforation in multiple intervals with significant interval distances (above 500 m). The newly developed device is characterized by simplified structures, safety, reliability. The device has been successfully deployed in 6 wells in Weizhou A Oilfield in western part of South China Sea. These operating time increased by 51.3% and costs decreased by 17.68%.